How much do your velocities vary

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  • Last Post 20 January 2013
John Alexander posted this 17 January 2013

I am trying to do a bit of research about how much the muzzle velocities of cast bullet loads vary.

I have a chronograph set up in my tunnel so I measure the velocities of a lot of loads. It is surprising how big the extreme spread in velocities are in some loads that still shoot well. Others with small spreads don't shoot so well. Nevertheless, variations in velocities can't be a good thing, especially at long range, so it would be good if we could reduce the extreme spread (ES) and standard deviation (SD) of our loads.

I would be grateful if those of you that have a chronograph would tell me the average extreme spread of your good cast bullet loads.

To keep it simple please send the ES (and SD if you have it) for ten consecutive shots. Either one ten shot string or the high and low in two five shot strings. If you answer with just the ES number please let me know the average muzzle velocity since I want to convert the ES to percentage of MV. Also please let me know the caliber (308,243, etc.)

PMs are OK but just posting it to this thread so all can see is better.

Thanks for taking the time to look this up and post it.

John

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Lefty posted this 17 January 2013

John I don't keep that data from year to year. I know Tom Acheson does. Perhaps he will contribute. I do have a good memory for numbers however. The load I have been shooting the past two years consistently has a SD in the 12-13 fps range. Extreme spread can vary quite a bit even while the SD remains fairly consistent. It is fairly rare to see anything much over 45 fps with this (or other good) loads in my experience. Up here in Minnesota we have many fans of 4756 for their match loads. It is common to see SD in the 6-8 fps range with this powder. I have had difficulty generating enough velocity with this powder to keep my bullets stable out to 200 yards , however.

I believe it was Ric who said not every load with a low SD is accurate but every accurate load will have a low SD. If I misquote you Ric, I apologize. I do concur with the thought. I rarely use a load with a SD over 16 fps and I really prefer 12. In my experience single digit SD is fairly hard to achieve. Jim

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RicinYakima posted this 17 January 2013

Looking at this question from my viewpoint, a military rifle CB benchrester, there are two counter-acting forces to deal with in extreme spread measurements. One, the slower bullets will far to earth faster so should tend to go low in the group. Two, the slower bullet allows the rifle barrel, via the bore line, to rise up, as the rifle moves from recoil more as the bullet travels the barrel length. This tends to make the bullet go higher in the group. This varies and changes as the bullet shape and length does, wind speed and approach to the speed of sound. Lots of good cast bullets will shoot well at 100 yards, not many at 300 yards. High extreme spreads worsens every factor a shooter must deal with prior to the shot, but low extreme spreads will not make small groups if the other dozen or so factors are not right also.

But, I have done little chronographings since about 1999, takes too much time and I have the basic data I need. The only exceptions is working in the “unknown” data range with low volumne pistol cartridges (32 ACP, 455 Webley) or no modern data available (40/50 Sharps Straight).

30/06, Lyman 311644 cast from Linotype, sized 0.313", weight 192 grains, Hercules 2400 15.2 grains, WLR primer. High 1416 f/s Low 1403 f/s, Ave 1409 f/s.

30/06, Ideal 311284 cast from WW+2% tin, sized 0.311", weight 209 grains, Alliant 2400, 16.0 grains, WLR primer. High 1455 f/s Low 1410 f/s Ave 1440 f/s.

Ric

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PETE posted this 17 January 2013

John,

Lets see if I've got your instruction right. Here's the load for my .30/06 '03 Springfield That I used to win the CBA Season Military Benchrest a few years back.

10 shot 100 yd. groups both loads.

ES - 1.8; SD - 0.6; MV 1669.7 What was really surprising was this particular group went 3 5/16".

Another group, same load:

ES - 17.8; SE - 6.3; MV - 1647.1 Group size - 1 13/16"

I consider the first group a fluke which seems to show up for me once in a while.. The second one was more the norm. The high score for that Postal was a 97-3x.

Pete

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PETE posted this 17 January 2013

John,

Here's two 5 shot 100 yd. .223 groups shot consecutively so you can pair them up for an average if I got your instructions right.

ES - 18.2; SD - 8.2; MV - 2046.7 Group 1 7/8" ES - 5.0; SD - 2.2; MV - 2033.4 Group 2 3/8"

Pete

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John Alexander posted this 17 January 2013

Jim, Ric, and Pete,

Thanks. Most of what you report matches what I see with loads that are shooting well.

Pete, your string with the small ES is a real eye popper. Too bad you can't have it framed to hang on the wall -- or something.

I hope more shooters will chip in with what they have found.

John

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frnkeore posted this 18 January 2013

John, I have a 2” thick, loose leaf binder full of chronograph results so, I'll post the results a few at a time. Unless I indicate it's fixed loads, they will be breech seated @ 100 yds. I'll start with my 22rf. These average 8 chrono shots if thats ok.

1.5 gr B'eye,1208 fps, ES 41, SD 15.8, group .410 (5 shot)

24” barrel, different rifle (all others are 20” bbl)1.8 gr B'eye, 1306 fps, ES 13, SD 5, 1.5 group, 4 in .96

1.8 gr Unique, 1053 fps, ES 53, SD 24.5, 1.5 group

2.3 gr Unique, 1357 fps, ES 76, SD 28.7, 1.31 group

Factory RWS R50 and Eley 10X, 26” bbl, 50 yd 10 shot groups 11 shot chrono

RWS, 1108 fps, ES 22, SD 7.4, .47 group

TenX, 1105 fps, ES 18, SD 5.2, .43 group

Frank

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frnkeore posted this 18 January 2013

XP100, 7mm TCU, Douglas barrel and chamber short throat (not the same as TC).

27.0 gr, 4895, Rem 7 1/2 primer, RCBS 145 (150 gr) 

2091 fps, ES 50, Sd16, 1.44 five shot group, 4 in .67, flier to left

28.0 gr AA2520, same primer/bullet

2152 fps, ES 43, SD 15.9, 1.83 group, 4 in 1.10

 

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frnkeore posted this 18 January 2013

30/40 non std throat, Win HW, 12 twist A&M bbl, small primer 2.8 cc brass case.

BSed 187 gr tapered 20/1 bullet, F100 primer, 4227 powder, 8 shot strings

11.0 gr, 1159 fps, ES 55, SD 20.8, 1.25 group

12.0 gr, 1289 fps, ES 15, 1.0 group 4 in .5

185 gr RCBS gc Spitzer 5% tin/ww, F100, BSed, 8 shot stiring,

14.5 296, 1443 fps, ES 8, SD 2.9, 1.90, 5 shot group, 4 in .56 at 200 yds

160 gr Lee w/gc, BSed, 22/1 F100 primer

8.0 gr Unique, 1323 fps, ES 5, SD 1.9, .330 five shot group, 5 shot string

 

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frnkeore posted this 18 January 2013

Same rifle as above, Std Win case, F210 primer, 190 gr Spreer match, fixed just short of the lands.

45.0 gr H414, 2503 fps, ES 18, SD 6.7, one group .312, one .760 at 100 yards. The .312 is the best group this rifle has fired.

12.5 4759, 1244 fps, ES 57, SD 20, .76 five shot group at 100, 8 shot string.

I have a lot of other info with the stad case but, it's 5 shot groups and 5 shot strings.

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John Alexander posted this 19 January 2013

Frank,

Many thanks. You and others have generously given me enough date to consider for quite a while. I have enjoyed getting a chance to see what others are finding for ES and SD with various calibers and loads.

For some reason velocity variation hasn't been discussed much at least in the stuff that I read. I think it is an eye opener that some accurate loads vary as much as they do. It is also possible to find an occasional load that produces very uniform velocities but subpar accuracy. Such things keep our interest up.

John

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argie1891 posted this 19 January 2013

i am not sure i can really help but have cronograpned a lot of loads. my results have been all over the place from very low extream spread to absoultly awfull looking spread. one thing i soon noticed was that many times the loads with large spreads shot as well and sometimes better than the low spread. as a cast bullet shooter one thing seems to come true. fast power in large cases gave me better results than slower powders at the same velosity. what i mean is if you want a load to produce about 1500 fps normally i get much lower extream spreads with unique or some other powder in the same range than a powder like 4198 or rl7. most of my loading is done at the lower end between 1250 and 1600fps. dont know if others have had the same results. argie1891

if you think you have it figured out then you just dont understand

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frnkeore posted this 19 January 2013

Here is a enteresting one, show what primers alone can do (primers are very important).

45/70 1878 Sharps Borchardt, 31.5 Douglas bbl, 409 gr BSed spitzer bullet, 24/1.

Both 8 shot strings and 5 shot groups at 100 yds.

10.0 gr Unique

F150, 971 fps, ES 19, SD 6.9, group .84, four in .48

F210, 965 fps, ES 20, SD 6, group 1.02

Another interesting load in this rifle but, only 5 shots recorded,

Smokeless duplex, 15 gr 296, 27.5 gr 4831, F210 primer

1473 fps, ES 10, SD 4, group .60

Frank

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Ken Campbell Iowa posted this 19 January 2013

as long as we all are punishing our brains over the high/low sd puzzle ...

( here we go ) ...what good would excellent ignition ( low sd 's ) do you if your barrel is not tuned ..... as in ..  adjustable .... tuner/barrel tensioner/weight/ugly thingamajig /// ... ?

i quit rimfire because ( ok, partly ) the tuner weights made my beloved 40x look like a toilet plunger...

sorry i brought this up ...maybe the visual horror of tuners would be penance for our greediness wishing for better groups ...

think i will start buying larger bean cans ...

ken

ps ...the tuners worked ( sigh  )

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John Alexander posted this 19 January 2013

Ken,

Ken, we depend on you to introduce rich new concepts into shooting discussions on the forum such as punishing our brains, bigger cans of beer as shooting aids, and penance for our various lusts.

I would just as soon you go easy on the penance since I have a backlog of sins that haven't had the proper application of penance and I would rather talk about ES, or about anything else.

As to your question-- What good is low SD without tuners? I always assumed that what reloaders were really doing while finding the load that gave the best accuracy by varying velocities (or other stuff) was finding one of the optimum barrel times for that barrel.

This would be sort of the same thing that the rimfire folks are doing with tuners. They have to use tuners because they can't vary the MV of Tenx -- at least except for the folks that are now reloading rimfire cases.

We vary the barrel time. They change the barrel's characteristics.

So if we can find a low SD and the right barrel time that should be a good thing -- at least theoretically .

An article in the newest Fouling Shot seemed to throw cold water on this possibility by citing three shots of which only one hit the X-ring and the other two missed because one was 4fps too slow and the other was 3fps too fast. This horror was caused by a .2 grain difference in the offending bullets' weights. It was not clear however if the “shots” involved lead bullets or Quickload bullets. So there may still be hope if those “sweet spots” are a little more tolerant.

John

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John Alexander posted this 19 January 2013

Frank,

Three of the loads you have reported have had an ES of 10 or less. I sometimes also get ES below 10 in a string but they are rare events for me and I have no load that will do it consistently or even a good fraction of the time. Will any of the three loads cited produce ESs that low frequently?

John

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John Alexander posted this 19 January 2013

Argie,

I too have seen loads with low ES that wouldn't shoot. I get great uniformity with Trail Boss for instance but haven't found an accurate load.

John

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RicinYakima posted this 19 January 2013

Professionally, I worked with computer modeling of chemical releases for up to 100 kilometers from point of release. The professional programers where always asking me about what happens “in real life". That is because like Quick-Load it has all of the prejudicies of the programers when they develope the formulae and write the code. It can be very accurate, like 90% plus. But it is not 100% accurate.

If you want to shoot small groups, the process is in the shooting of groups, not the theorizing of what a couple of measureable data points are doing.

Shooting cast bullets is an art form, and the science is only in how we approach the shooting.

IMHO, Ric

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Wineman posted this 19 January 2013

When I was in college and took Statistics, there was one overriding theme “Liars figure and figures lie". While most chronographs have good data collection abilities, the small sample size really limits the usefulness of the data. The ES is only two numbers, whether you shoot two or 100 shots so it really does little good. The SD (measure of how the population varies from an average value) tends to be more useful.

The main problem is that the number of variables that contribute to a small group is much larger than just the velocity and its spread. There are a host of other statistical tests to show if the data you have collected is really different and one I am familiar with is Analysis of Variance (ANOVA). Twenty five years ago we needed a mainframe computer to run it, today I bet there is an I-Phone app (not really sure). This could take into account, the weather, shooter, velocity and many other measured variables and tell you if indeed the differences in group size are related to any of the variables. For example if you fired 20 shots a day, of load X for 10 days with the same shooter and rifle, we could tell if the differences in group size were significant for each of the above variables. Now toss in powder and primer lot, alloy, brass type and weight, etc. and you can see that data overload is not too far away.

As Ric has said in MBRS is that any of today's replacement barrels is a huge improvement over any but the most carefully selected As Issued military rifle barrels. If you fired the same load between the two there could be a marked decrease in group size that had nothing to do with ES or the SD of the load.

Dave

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frnkeore posted this 19 January 2013

John,

I only use my chronograph as a tool when working up loads and I'm not caught up in ES & SD numbers. I don't usuaully run strings more that 12 - 13 shots for foulers and the test itself, if the fouler fell within the ES of the rest, I included them but, not if they didn't meet that criteria.

I've always look for target results but, I've never liked nor had faith in a load that had more than about 35 fps ES, plus the lower the velocity the bigger the percentage the ES can effect it. If you check ES's against a external ballistics program, you'll see that in most cases the widest velocity should have a greater vertical despersion than they actually do. A very important aspect in subsonic loads. My 19 fps ES in my 45/70 load shouldn't have allowed me to shoot a .84 group but, there is a effect that I don't think anyone understands or can explain as to why you can shoot good groups with wide ES's. There are to many variables to make a reliable connection.

I always have faith in the saying that “Not every low ES/SD load has target accuracy but and good Target load will have good ES/SD numbers". I have exceptions to that (there is always one of those) such as my BP loads chronogragh better with my smokeless bullet lube but, shoot better with my BP lube (57 smokeless/97 BP fps) it doesn't seem possible but, that's the way it is.

Frank

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John Alexander posted this 19 January 2013

Frank,

The things you mentioned are some of the reasons that cast bullet shooting is endlessly interesting to some of us.

They also make it clear that we can (and should) apply a scientific approach to advancing our knowledge but we are at such a primitive level with so many things we don't fully understand that cast bullet shooting is, in spite of advances, more an art than a science as Ric often reminds us.

That doesn't mean that we have to follow ancient (or new) rules that can be disproven by logical and fair testing, but we aren't going to know everything anytime soon -- sort of like the practice of medicine without the serious outcomes for stupidity.

John

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