WEIGHING BULLETS TO REDUCE VELOCITY VARIATION AND IMPROVE ACCURACY

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Last Post 02 February 2018

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joeb33050 posted this 10 January 2018

223, 5.5 gr Titegroup, 40 gr bullet, 2063 fps, 53 gr bullet, 1784 fps, delta fps/gr, 21.5

223, 8.5 gr Titegroup, 40 gr bullet, 2678 fps, 53 gr bullet, 2374 fps, delta fps/gr, 23.4

22-250, 5.5 gr Titegroup, 40 gr bullet, 1857 fps, 53 gr bullet, 1622 fps, delta fps/gr, 18.1

22-250, 8.5 gr Titegroup, 40 gr bullet, 2418 fps, 53 gr bullet, 2137 fps, delta fps/gr, 21.6

The largest delta fps/gr of bullet weight is 23.4; a bullet weighing 1 grain more than another would go 23.4 fps slower.

Weighing, segregating, loading and shooting bullets into .1 grain classes reduces delta fps to 2.34 fps.

In .5 gr classes, delta fps is 14.0 fps.

Weighing bullets and segregating them into small classes won’t improve accuracy.

joe b.

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Larry Gibson posted this 12 January 2018

Larry, I'd be happy to send you, or anyone, all the data. Just ask.

[email protected]

Joe

Thank you for sending me the data. As I mentioned before, you are to be commended for the compilation and correlation of all that data. There certainly was a lot of data!

In your summation you state; "Since I have not been able to find why .22 caliber cast bullets didn’t shoot accurately; I thought I’d find out if jacketed bullets with cast bullet powder charges would shoot accurately, and why."

I am not being critical joe, just trying to help you out. There are three phases to ballistics; the 1st phase being internal ballistics.....that which happens in the barrel. You certainly have compiled a lot of data concerning that phase given the amount of chronographed data. The other phase you cover very well with a considerable amount of data is the 3rd phase which is terminal ballistics. You have that very well covered with a lot of correlated group sizes.

What is missing and why you can't find the answer from all that data to your basic question of; "Since I have not been able to find why .22 caliber cast bullets didn’t shoot accurately" is because you have not addressed the 2nd phase of ballistics.....external ballistics or the flight of the bullet and what happens during that flight. It is within that 2nd phase of ballistics the answer lays.

Take those 55 gr Armcour FMJBTs for example. You can measure them every way from Sunday, you can load them to very low ES and SDs yet they will still not be "accurate". Why Because there is imbalances in the bullets probably caused by jacket thickness that is not uniform throughout each bullet and from bullet to bullet. They are made to atypical military accuracy standards. The Sierra's, Nosler's, Hornady's and other commercial made bullets are held to a much higher standard of manufacture. It is the greater imbalances probably caused by uneven jacket thickness in the Armcour bullets that are adversely affected by the rpm during the bullets flight (external ballistic phase) that is the cause of the inaccuracy. There is a very good chapter in the later Hornady reloading manuals that explains this.

So why can't we shoot cast bullets as consistently well as we do quality jacketed bullets? The answer is because we can't consistently cast bullets as balanced as quality jacketed bullets are balanced. Additionally cast bullets undergo a lot more deformation during the internal ballistic phase than do jacketed bullets. All that means the jacketed bullet exits the muzzle better balanced than out cast bullets. Given that the better balanced jacketed bullet will be less affected during flight by the RPM and thus more accurate.

By weight sorting our cast bullets we are attempting to find the most uniform cast bullets we have. Those will also be the best balanced cast bullets we have to begin with. With the best balanced cast bullets we have a better chance, if we load them correctly, of negating as much of the adverse affect the RPM will have on the bullets. Thus the more accurate on target they will be.

LMG

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Larry Gibson posted this 25 January 2018

Lastly I graphed out the nine 30x60 XCB tests by bullet weight and group size. This gives us a “visual” comparing the group sizes vs. the weight increments. Between the graph and the actual on target performance it is pretty obvious that weight sorting is beneficial to increased accuracy.

Caveat; Many of you think of weight sorting as simply sorting by weight (usually in .1 gr increments) and then shooting those in those weight segregations. The thinking is that accuracy will improve. As most of you know accuracy improves perhaps a little but most often doesn’t using that methodology. The technique I use is to weight sort to eliminate potential flyers by selecting the heaviest bullets of each batch cast. Those are the bullets that are most consistent in fillout and thus the better balanced which gives the best accuracy. These 2 tests demonstrate that.

LMG

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Larry Gibson posted this 30 January 2018

John

I'm sure everyone here knows I have many disagreements with 45 2.1. Many don't pay attention that I also agree many time with him. No I don't care for his continual use of "mythical" shooter examples either and he's well aware of that. However, disregarding that the gist of his post here I do agree with 100%. That gist, especially with joeb's latest testing and statistical analysis, seems to hover around the question as to cast bullet accuracy hasn't really improve (at least according to CBA match results) for many years. Basically does the "average" group size stay around 1moa+?

What I hear 45 2.1 saying is exactly what I've been saying in this thread; if we continue to do what we've always done that moa+ average will never get any smaller. If we simply emulate what the top shooters have been doing for the however many years can we really expect to do better? No we can't. To do better we must think "outside the box". We must find the reasons we aren't doing any better and correct them. That's what I hear 45 2.1 saying and, again, I agree 100%.

For example; on the other thread started by joeb about weight sorting and accuracy he shows us the results of a test he conducted in 2007. He weight sorted his 311299s and the results demonstrate the classic "bell curve" of weights. He then takes what he calls his "best" bullets out of the bottom half of that weight sortment and uses those in his test. He is surprised his "best" bullets didn't perform that well and his final conclusion was weight sorting didn't really improve accuracy. What joe did was what we have all done over the years selecting what he (we) assumed was his "best" bullets" (they weren't) and we get the same results; weight sorting doesn't really provide much improvement in accuracy. I'm not arguing with that and it appears 45 2.1 isn't either.

What I'm saying is that if you cast good bullets and, after weight sorting, the sortment demonstrates a classic "bell" shape the problem is you are not cast bullets of good enough quality. As I posted earlier (graph) a curve of really quality bullets weight sortment will not be a "bell". It will instead have a steady rise with most of the bullets being in the top end (heaviest) weights and will drop to nothing after that. There will not be the same downward curve of different weights as with the "bell" curve. It is when you cast bullets of that quality and weight sort out the lighter bullets that the benefit is derived.

LMG

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Larry Gibson posted this 10 January 2018

I've found absolutely no correlation between accuracy and any SD or ES measurement of 10 shot groups. There is usually as much variation if not more than is mentioned between the SD and ES of identical loads tested with as many as 5 test strings.

I do weight sort in .1 gr segregations with my match and HV cast bullets; the 314299 (188 gr) and the NOE 30 XCB (158 gr) . I also am pretty anal about rejecting any bullet with any kind of visual flaw. These weighed bullets that pass visual screening are sorted into .1 gr tubs. Out of a 400 - 600 bullet batch about 17 - 20% will be sorted out because of visual defect or they weigh to light or to heavy (usually only a few are to heavy. Most will weight sort within .2 to .3 gr +/- of each other which are shooters. Of the .5 to .6 gr spread I only use the top half of the 314299s in CBA Military Rifle matches or the top half of the 30 XCBs for really high velocity loads (2600 - 2900+ fps). The bottom half of the shooters I use as foulers, sighters and practice.

I have shot enough of each to know that the kind of weight sorting I do makes a difference. The last couple years I've taken 1st at every Military match I shot in except one. That one I didn't have any of my weight sorted match shooters left so I went with the low weight end of the foulers and sighters......ended up with too many uncalled 9s and a couple 8s, especially at 200 yards. When you are running cast bullets at 2600 - 2900 fps you are pushing them hard. With the match shooter 30 XCBs at 2900 fps my rifle holds 1 1/2 or better moa at 300 yards. with the fouler/sighter shooters that opens to 1 1/2 to 2 moa.

I've seen the results of not weight sorting too many times to think weight sorting doesn't make a difference \.

LMG

I have found that the best and most consistent accuracy comes

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Larry Gibson posted this 10 January 2018

Joe

Here's the "data" I pay attention to, which in the end is what I believe really counts;

I've won 6 matches with weight sorted bullets and lost one with non-weight sorted bullets. The 314299 in a CBA Military rifle match shooting for score;

Here's the 30 XCB at 2900+ fps shooting for score;

LMG

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Larry Gibson posted this 10 January 2018

Joe

Here's the results of an extended test of the 314299 load demonstrating the need to really use a large enough sample;

Average Velocity, ES and SD Variation

I was testing a new (to me) NOE bullet in my M39 Finn Mosin-Nagant 7.62x54R rifle I use in CBA Military Rifle matches so I thought, since I was shooting five 10 shot test strings of the same load, I would chronograph each 10 shot test string to not the subtle differences in the average velocity, ES and SDs of the same load. Since the CBA matches I attend are for group and for score (using the 100 and 200 yard reduced 600 yard NRA HP target) I shot three of the test strings at 100 yards to also test for accuracy and to confirm the 100 yard zero. I then would shoot the two remaining test strings at 200 yards to confirm the zero.

I had cast the NOE bullets using a 311-205 four cavity aluminum mould out of Lyman #2 alloy. The bullets were very uniform with few rejections during visual inspection and weight sorting. The bullets dropped just over .313 on the bands and .302+ on the nose. I seated and crimped the Hornady GCs and lubed them with 2500+ in a Lyman 450 with .314 H&I die. Fully dressed they weighed in right at 200 grains. I loaded them in NS’d Norma cases over 28.5 gr of milsurp 4895 with a 1 gr dacron filler. WLR primers were used. That is the match load I use with the Lyman 314299 which has won me two state championships and numerous matches. I was hoping the NOE bullet would shoot as well as the Lyman and it did.

Many times we see posted on forum a velocity given as XXXX fps with many, if not most, not understanding that chronographed figure is not an absolute. There always will be some variance in the average fps, the ES and the SD of any test of a lot of ammunition. What the variance can be is not only dependent on the quality of the ammunition but also on the number of shots in the test strings. I consider 3 shot tests as only giving an idea of what may be expected. A 5 shot test gives a better idea but still leaves considerable room for error. The 10 shot test is standard but even that gives an optimistic average, ES and SD fps.

The five 10 shot results;

Average fps, ES fps, SD fps

1813, 34, 12

1817, 25, 7

1812, 39, 10

1826, 42, 13

1821, 41, 13

We see here a total difference in average velocity between each test string of only 13 fps. The ES varied 22 fps and the SD varied, between strings, 6 fps. All of which indicates a very consistent load even considering the differences. However, to get a much better understanding lets look at the figures for the entire 50 shot test.

For the entire 50 shot test the average velocity was 1818 fps. The ES was 52 fps and the SD was 17 fps. Some would not consider those figures to be good yet given the winning record of the load it has proven to be a very good load. Bottom line is to actually have the best idea of a loads potential it pays to test a sufficiently large sample. The smallest 10 shot group was not with the test that gave the smallest SD and ES. This is why I don’t give much credence to less than a 10 shot test and really prefer at least three 10 shot back to back tests to confirm probable ballistics and accuracy potential.

LMG

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TRKakaCatWhisperer posted this 11 January 2018

Let me stir the pot. The single most important thing that has improved the quality of my bullets is to have weighed bullets as they are cast. That has directly indicated behaviors (temperature, timing, techniques) that cause variation (in more than just weight).

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Larry Gibson posted this 11 January 2018

Joe

I'll email you. Would be nice to see it here so all can see it though.

Here's another example of weight sorted 314299s at 100 yards from a CBA Military rifle match;

Shooting for score here so after a few shots in that raged hole at 12 o'clock in the 10 Ring I thought if I could just hold a tudge low I could move them into the X ring.........worked well for that 6 o'clock X but then the next shot dropped out the bottom for that 7 o'clock 10 (just cut the line!).....said heck with that and went back to aiming center and put the last 2 -3 into that ragged hole.

Un weighed bullets just visually sorted will not do that.

LMG

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Larry Gibson posted this 18 January 2018

All ballisticians know and understand the adverse affect an imbalance in a bullet, cast or jacketed, has on the bullet during flight. To provide an example let's look at what Mr. Lilja has to say. Please pay particular attention the bold highlighted 2nd paragraph. Mr. Lilja understands it, all other ballisticians understand it, many shooters understand it, I understand but some do not What is high lighted is a matter of ballistic fact.

A Look at Bullet Imbalance and Twist

By Daniel Lilja

Bullet imbalance--or more correctly, static imbalance--occurs when the axial center of gravity and center of form of a bullet are not concentric. It is easy to visualize the effect of this imbalance. As a bullet travels through a rifle barrel, it is being rotated about its center of form. When it exits the muzzle of the barrel, the center of rotation shifts from the bullet's center of form to its center of gravity. In mechanics the difference between these two centers is known as the radius of gyration. The bullet will travel in a roughly helical course, a corkscrew type path. Naturally the greater the divergence of the two centers, the greater will be the dispersion of the bullet from the point of aim.

As a bullet leaves the muzzle and is free to rotate about its center of gravity, if imbalanced it will diverge from the axis of the barrel at an angle that is dependant on the twist rate of the rifle barrel. The deviation angle = arctan (2e*Pi/T) where: e is the radius of gyration and T is the twist rate.

In the November, 1965 issue of THE AMERICAN RIFLEMAN, author E.H. Harrison describes the effects of this imbalance and its relation to rifling twist rate. In his article he derives a formula that calculates the amount of imbalance that will cause one minute of angle (MOA) target dispersion for a given twist rate. The formula is E=.000046(T), where T is the rifling twist rate and E is the amount of imbalance to cause one MOA divergence.

A computer program in Basic was written using the above formula to calculate the effects of a change in twist rate or the amount of bullet imbalance. The figures in the table are from this program. As can be seen from the table, the faster the rate of twist, the greater is the target dispersion. In this example, the amount of bullet imbalance is .0001". The twist rates are from one turn in 8 inches to one turn in 16 inches in one half-inch increments. These rates will cover 95% of the commonly used twists. The values under the heading "Expected `MOA' Accuracy" are just that. With a bullet with only .0001" imbalance, the best grouping at 100 yards that could be expected are these figures in inches for that given twist rate.

These `MOA' values are directly related to both the twist rate and the amount of imbalance. If either is doubled, the amount of target dispersion will also be doubled. From the chart it can be seen that an eight twist barrel will cause twice the amount of dispersion (.272 MOA) as a 16 twist barrel (.136 MOA). Likewise, if the amount of bullet imbalance were doubled, all the values under the `MOA' column would also be doubled.

It is obvious from this chart that two aspects of shooting are quite important. Namely, that we use high quality bullets and the slowest twist that will adequately stabilize that bullet.

It is easy to specify what twist barrel we want to use. It is more difficult, however, to determine the amount of imbalance our favorite bullet has. An obvious cause that comes to mind, in lead core bullets, is bullet jackets that have runout in the wall. It is not quite that simple, though. Let's take the example of a jacket that has .0003" runout, not uncommon in many jackets meant for benchrest shooting. That amount of runout does not translate into .0003" of bullet imbalance.

If the densities of lead and jacket material were the same, the amount of jacket runout would have little or no bearing on balance. They are not the same, though. The Machinery's Handbook, 22nd edition, lists the specific gravity of copper as 8.89 and that of pure lead as 11.34. Lead, then, is about 28% denser than copper. It follows then, that with a jacket with .0003" runout, the area of the jacket wall, on the thin side, that should have been occupied by jacket material has been increased in density by 28%. This will cause a shift in the bullet center of gravity away from the center of form by .28 x .0003" or .000084" (eighty-four millionths).

The above value is the approximate radius of gyration. This is an over-simplification but is probably a close approximation of the amount of imbalance. There are formulas in mechanics that allow for the calculation of the true amount of imbalance but they would require exacting measurements of each jacket and bullet shape. Obviously, greater amounts of jacket runout would cause a greater shift in the two centers.

It was mentioned above that if the densities of jacket material and lead were the same that it would matter little on the balance of the bullet. This is true as far as it goes, but it is known that when the ogive is formed on a bullet, if the jacket is not uniform, the nose of the bullet will yield to the thinner side causing to some extent static imbalance and irregular geometry.

There are other possible causes for bullet imbalance. When a bullet is fired from the cartridge case, it is under a great deal of pressure. Assuming that the barrel groove diameter is no larger than about .0005" over bullet diameter, the bullet will obturate in the barrel, conforming now to the diameter and geometry of the barrel. In the case of an oversized barrel, the obturation is probably not the full length of the bearing surface of the bullet. With a barrel that is the same size as bullet diameter--or undersized--the obturation will be complete and more of the bullet will assume the geometry of the barrel.

All is fine with this situation as long as the barrel is uniform. If the geometry of the barrel is such that the groove depths are not the same, the bullet has now gained static bullet imbalance from the barrel that it did not previously have. There are other possible causes for static imbalance. The lead core may have a flaw, such as a void or air trapped between the jacket and core during core seating. The results are the same.

Another cause of imbalance is a barrel chamber that is not in alignment with the axis of the barrel. The effect is that the bullet enters the rifling misaligned, cocked in relation to the rifling. Again the bullet has gained imbalance from the barrel. In his article, Harrison lists this cause as "yaw" in the barrel.

Besides the above-mentioned cause for imbalance from jacket wall runout, the bullet can obtain imbalance from a swage die that is not geometrically perfect. The bullet may come out of the die less than round, or with an ogive that is not in line with the rest of the bullet. Harrison lists this type of cause as "dynamic imbalance". It also can cause static imbalance.

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Larry Gibson posted this 18 January 2018

Here is the results of the weight sort. 542 bullets were cast of Lyman #2 alloy and WQ'd. They were then aged about 12 days before I got around to weight sorting. Here is my set up for weight sorting. I visually inspect each bullet for any defect. If any is found that bullet is rejected to be melted and recast at a later casting session. Those that pass my anal visual inspection then have any remnant of the sprue cut off. That is done on the lead block with a sharp blade on the pocket knife. The bullet is then weighed on the Redding balance beam scale. While waiting for the beam to settle I then visually examine and sprue cut another bullet. With the magnifier in front of the scale I can readily and accurately see what the weighed bullets exact weight is. The bullet is then placed in a bin for that weight.

Of the 542 bullets weighed 22 were rejected for a visual defect or because they weighed less than 186.9 gr which means the weighed ones had passed the visual inspection but still weighed way lite. The remaining 520 XCBs were weight sorted into separate bins of .1 gr increment from 186.9 gr to 188.0 gr......a 1.1 gr spread.

Here is the rough graph of the weight sort. As you can see there is no "bell curve". The curve rises from 186.9 gr slowly to 187.5 gr and then rises sharply. The "curve" then plateaus out at 187.7, 187.8 and 187.9 gr with 113, 124 and 110 bullets for each weight. The "curve" then falls sharply to just 9 bullets at 188.0 gr. Of those 9 bullets only 2 actually weighed 188.0 gr. The remaining 7 bullets weighed between 187.9 and 188.0 gr. There were no bullets heavier than 188.0 gr.

What the weight sorting is showing us is the 113 bullets of 187.7 gr, the 124 bullets of 187.8 gr and the 119 bullets (I'll put the 188.0 gr bullets in with those) of 189.9 gr weight had the highest weight/mass of alloy in them. Since the curve dropped off suddenly we see those weight bullets are the most consistent and the best the mould will produce with that alloy. Those 356 weight selected bullets will be used for best accuracy.

The 187.6 gr bullets will be used as fouler/sighters as I expect they will give very good accuracy also given only a .2 gr +/- difference in weight.

Had we lumped all the visually selected bullets into one group 70% would have been with the excellent bullets, Another 15% would have been with the fouler/sighter bullets and the remaining 15% would have been with bullets having a weight/mass difference of 1.1 gr. Now, had I done that I probably would have got nice 1 1/2 moa groups with 7 +/- shots going into moa or less and 2 -3 +/- shots going out of the group in the 1 1/2 moa +/-. How many of you shoot groups like that with bullets only visually sorted?

It is with such weight sorted selected bullets (the 187.7 to 187.9 gr bullets) that I am able to hold moa accuracy to 300 yards and beyond with a 2900+ fps velocity.

That is how I weight sort and why it makes a difference.

LMG

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Starmetal posted this 18 January 2018

Drilling a hole in a bullet and shooting a group with a bunch of them proves only that the rpm from the twist will act upon what is bascially an unbalanced bullet and it will be a negative action. Instead try a test where you removed the same amount of weight as that drilled hole except in the very center of the base of the bullet. Shoot those and see what the group is.

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OU812 posted this 20 January 2018

The true sign of intelligence is not knowledge, but imagination. Albert Einstein

I'm going to work on my bump die.

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Larry Gibson posted this 25 January 2018

Weight Sort Test; 30 XCBs of #2 Alloy

In previous posts I posted the graphed results of weight sorting a recently cast batch of 30 XCBs (NOE 310-165-FN 4 cavity aluminum mould). They were cast of Lyman #2 alloy and were WQ’d out of the mould. These were loaded in the 30x60 XCB cartridge with the standard HV load of 53 gr AA4350. That give 2900 fps out of the test rifle; a 31” Broughten Palma contoured barrel with a 16” twist on a BRNO VZ24 Mauser action. The rifle has a Leupold 6.5x20 target scope on it. This rifle was not made for BR shooting. It was made for HV cast bullet shooting to determine how fast a ternary cast bullet could be pushed while maintaining 2 moa accuracy (10 shot groups) linearly to 300+ yards. That goal was achieved. The rifle with weight sorted select 30 XCB bullets will hold 1 to 1 ½ moa accuracy (10 shot groups) to a tested 400 yards (so far).

Let’s keep in mind before we post I shoulda, coulda, woulda tested this many or that many of this or that using different 5 or 10 shot tests of each, etc. that in this batch of 542 cast XCBs there were just only so many of some weights. The number of each weight is on the previously posted graph and listed in the post. The number of some weights, particularly the lower weights, was finite. There were only so many to test….period. Thus I made some judgments on how many each would be a “group”. I strived for 10 shot groups but that was not possible with some weights.

I use the Lyman lino/lead/tin formula to mix #2 alloy. Since I mix my own #2 alloy I’ve found over casting and weight sorting 5,000+ of the 30 XCBs that different batches of #2 alloy usually produce slightly different weights of bullets. In this test I had used a different source of linotype (a pig bar) from the previous batch made with type. The result is that the bullets in this test weighed and average of 1.5 gr less than the previous batch’s 30 XCBs. There was little difference iif any in accuracy or velocity with the slightly lighter weight new XCBs. The previously used weight sorted select XCBs weighed 164 gr fully dressed while the new ones weighed 162.5 gr.

The test was conducted yesterday at a range of 100 yards. Nine test groups were fired plus a sighter target. The barrel was allowed to completely cool and was cleaned between every 3 test groups. One fouler was shot and then the subsequent shots would “go to group” centered on the CBA target. The “foulers were all shot with the heaviest weight sorted select bullets (157.9 gr.) and since it was obviously zeroed no adjustments were made throughout the test to elevation or windage. Each test group was shot with that zero aiming at the center “X” dot.

The fouler target;

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Larry Gibson posted this 25 January 2018

The next test combined 2 weights (156.9 [X]and 157.0 [O]) as there were only 6 of one and 3 of the other. Each weight was tracked on target and is so marked (“X” and “O&rdquo. The 9 shots went into 1.620”

Again I combined 2 weights as there was only 3 of the 157.1 gr and 4 of the 157.2 gr XCBs. The seven shots went into 1.515”. That gives a fairly good indication that accuracy is improving as the bullets get heavier. Again the different weights were tracked on target with “X” and “O”.

Just when things were going good a guy shows up to test a prototype (they make them here in Lake Havasu) AR in 30-06. It had a 16” barrel with a horrendous muzzle brake. He parked himself on a bench 4 down from me. Every time he shot it felt like a grenade going off next to me. I had to put plugs in my ears plus the muffs over my ears. I tried shooting between his shots but I still managed to flinch off a shot of two as the test progressed. If that happened I called the shot (all went to call) and marked it. Thankfully I had at least 10 shots for the remaining group tests or additional loaded to get a 10 shot group.

The 157.3 weight put 6 of the 10 shots “to group”. There was 1 call in this group. Group size is 1.555” without the call shot.

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Larry Gibson posted this 25 January 2018

The next weight, 157.4 gr, grouped into 1.750” for 9 shots. There was one definite called shot (ok, I flinched it off…&hellip.

As the bullets get heavier and are more completely filled out the groups are beginning to get better and to center back up on target. With the 157.5 gr bullets there was also one call but the rest went into 1.371” with more shots beginning to cluster.

The next test is with a mix of 157.6 gr (3), 157.7 gr (3) and 157.8 gr (4). These are tracked separately on target. Looking back at the graph in the previous post the 157.6 gr were selected to be “foulers/sighters” so I wanted to see how they would hit compared to the “select” weights of 157.7 gr and 157.8 gr. Their impact over lapped the heavier weights. The 10 shots went into 1.267”

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Larry Gibson posted this 25 January 2018

The last test was with the heaviest 3 weights; 157.7 gr, 157.8 gr and 157/9 gr XCBs which I considered my “select” bullets. There were an equal number of each and they were mixed into one “lot”. Thus I did not track each weight but shot straight away. Again there were 2 for sure calls and maybe the low 60 shot but I had sufficient of this load to shoot 3 more shots making the group 10 shots. The 11 shots including the “maybe call” went into 1.304” which is what I recorded. The 10 for sure good shots went into 1.001”……moa. We see here the group has centered back up on target without any flyers.

The next test was with the weight sorted XCBs loaded over my match load in the .308W to test in my M70 Match rifle. This is the rifle I use in the “Commercial Rifle” (CBA BR Matches) matches over at Ben Avery Range with the Phoenix CBA bunch. This rifle also has a Leupold 6.5x20 Target scope on it.

This first target is with a mix of the 3 top weights (157.7 gr, 157.8 gr. 157.9 gr) with 3 each of the first 2 and 4 of the last. This group includes the foulers out of the clean barrel as they go very close to group. The first 3 foulers are marked and shots 4 through 10 then went into one small cluster of .584”. The overall group including the foulers is 1.031”

The scope elevation was then adjusted down 3 moa to get close to the aiming point. The next group was with 4 shots each of the 157.8 gr and the 157.9 gr along with the 2 remaining lighter weight sorted out 157.3 gr XCBs. They were mixed when loaded so the test was “blind” so to speak. The group size was 1.692” with 8 shots going into .892”. Wonder which 2 shots were the lighter weight bullets…..?

Well now, one can’t be sure based on just one test so I conducted a second “blind test. Same 4 each of the heavier bullets with 2 157.4 bullets mixed in so I didn’t know which was which when I shot them. The group size was 1.947” with eight shots going into .615”. Again given the almost mirror image of this group with the last one I wonder which 2 shots were the lighter weight bullets…..?

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R. Dupraz posted this 25 January 2018

Thanks Larry for the interesting information. Nice presentaton. clear, concise, on point.

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John Alexander posted this 28 January 2018

Older members are probably tired of hearing me say it but back when I used to weight sort match bullets I saved all the light and heavy culls and used them for testing.

I fired dozen of groups alternating between groups of weight sorted bullets and groups of mixed light and heavy bullets. After a couple of years and dozens of pairs of groups , I had to admit that I couldn't find the slightest difference in average group size between the carefully sorted and the groups of the most extreme weight spreads of my bullets. I stopped weighing my match bullets at least 25 years ago. in light of Larry's providing an indication that light bullets don't shoot as well as heavy bullets maybe I can find the time to replicate my earlier tests this season.

The question is, why don't my shooting results support Larry's theory that light bullets shoot worse? It may be because of the apples and oranges effect. My bullets were all 22 and Larry's were all 30 and twice as heavy (a principle of casting is that larger casting are more likely to have shrinkage voids.) His muzzle velocity was almost twice mine (deflection due to imbalance in the bullet is directly related to muzzle velocity.) We probably have differences in the way we cast.

I urge others who are interested in winning matches or just trying for the best accuracy to test (with their own equipment and their own casting and shooting abilities) to see if weight sorting shrinks groups for them.

John.

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John Alexander posted this 30 January 2018

45.2.1

Here we go again. I deliberately wrote my post trying to avoid yet another recital about how you, and other unknown individuals shoot much better than CBA match shooters even though none of you ever show up and shoot in front of witnesses at matches. My efforts obviously didn’t work.

With all due respect, it is not very convincing to other cast bullet shooters to hear once again about you and other unnamed phantom shooters, who routinely shoot cast bullet averages under 0.5 moa, with factory rifles, dragged into every discussion.

Until you and these mythical shooters either show up at matches or publish your, hinted at, occult secrets on the internet so others can try to replicate their work, most serious shooters will continue to regard them in the same category as Big Foot.

John

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frnkeore posted this 31 January 2018

Some food for thought:

1. One MOA, will not get you anything in target classes

2. Velocity won't get you anywhere, if you use a low BC bullet. They will counter act, against each other.

3. Well cast bullets will get you more consistent results. In ASSRA matches, most of the top shooter DON'T weigh their bullets and only visually inspect. They consistently shoot a 10 shot average of around .75 MOA @ 200 yards, with a velocity of <1500 fps.

4. The best CBA, GC target rifles, have improved over the last several years, as witnessed by new records set. Mel Harris owns many of them. Granted, records don't come that often but, they are shot with some regularity, as well as "screamers".

5. All match shooters have their up's and down's. What they shoot on any one day, can differ from their best. There are no exceptions to that!

6. There are things about cast bullets that no ONE person can explain.Cast bullets don't "play by the rules" and don't seem to abide by the laws of physic's! We all do our best to improve and most improve by attention to detail.

7. Loading density, seems to help but, in my sport, you can not prove that. Many of our records are held by the, very old 32/40's with ~15.0 gr of dense powder in a 3+ cc case. Loading density make make up for some attention to detail? I don't know!

8. Based on the role that powders play, regarding accuracy, internal ballistics play a part. But, something that no ones addressed here, barrel harmonics, do too, especially lighter barrels, such as the production types. Internal ballistics are what causes barrel harmonics.

9. There are more things but, no one thing is the answer. My opinion is that you need every thing to come together, or at least as many as you think you can control, to improve your accuracy!

Frank

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WEIGHING BULLETS TO REDUCE VELOCITY VARIATION AND IMPROVE ACCURACY

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