CAST AFTER JACKETED
From the Cast Bullet Association Forum
Will copper alloy jacketing in the barrel affect the accuracy of cast bullet loads?
Glenn R. Latham posted this 05 January 2019
I did a little test on this back in 1990. I was shooting both jacketed and cast from my Shilen barreled .223 prairie dog gun. I shot 5 rounds with the Hornady 50 gr. SX bullet and 28.0 grs. of T-2208. I then fired two groups with the RCBS 22-055-FN bullet and 13.0 grs. of IMR4227 (2049 fps) which measured 1.58 & 1.51. Cleaned the bore with Sweet's 7.62 Solvent. This was all done at the range of course, and even with Sweet's I find it takes numerous patches over several days to get all the copper out of a barrel. So running a handful of patches thru at the range isn't going to get all the copper out, even from just 5 rounds, but a lot of it came out on the blue patches. Fired another group that went 1.35". Then I cleaned the bore with LBT bore lap, and fired a .78" group. I don't have the patience to do a long, drawn out test, so this was good enough for me. Remember, I did preface this by saying it was "a little test"....
Glenn
Test #1
John Alexander posted this 27 January 2019
I finally got around to loading and shooting a small test today to see if shooting 20 rounds of jacketed bullets degraded CB accuracy afterward and if so how much.
To minimize labor I scrounged around and found 37 left over sized and lubed bullets from a lot that didn't quite shoot up to snuff. Hate to throw things away that take labor to produce. This was enough for three 5-shot groups before 4-5 shot groups of factory level JB and 4 5 shot groups of CBs after. CB load was 85 grain spitzer bullet of 25:1, Remington 71/2 SR primers, and 5 grains of TiteGroup.
For jacketed I found a box of Herter's 55 gr. Semi Pointed World Famous rifle bullets that were more accurate that any other rifle bullet or your money back. Additionally, these had been seasoning for about 60 years.
Resits:
CBs before: .90, .64, and 1.52 MOA -- Average 1.02 MOA
Jacketed : 1.82, 1.68, 1.64, 1.96 MOA -- Average 1,77 MOA
CBs after: 1.06, 0.78, 1.84, 1.86, MOA -- Average 1.38 MOA
This shows an enlargement in groups of 36%. Using Joe's statistical charts for dummies and extrapolating a bit, indicates a confidence level of maybe 75 -- 80 percent. Not a sure thing but a pretty good chance that if we do more testing it will still show a loss of accuracy tending to confirming the conventional wisdom and remarks by Glenn, Brodie, and others.
John
John Alexander posted this 29 January 2019
Hold the conclusions. I'm afraid I have presented the results of a botched test. When I finally got around to cleaning the bore I found it badly leaded. After generous application of steel wool, lead out and elbow grease the bore was clean but what do you do with test reports partially obtained with a leaded bore? Probably do the test again.
I now think that the bullets I dug out of that drawer were probably from a year ago last September when I was bore cleaning after every target card at the 2017 NT to avoiding loss of accuracy. Should have thrown the left over bullets away.
By looking at the group sizes with this new information the two good groups followed by much bigger ones, in both CB strings, take on a different light. Full charge JBs will clean out lead giving the CB string after the JBs a fresh start.
CBs before: .90, .64, and 1.52 MOA -- Average 1.02 MOA
Jacketed : 1.82, 1.68, 1.64, 1.96 MOA -- Average 1,77 MOA
CBs after: 1.06, 0.78, 1.84, 1.86, MOA -- Average 1.38 MOA
If I had only fired two CB groups before the jBs and two CB groups after the results would have looked like this:
CBs before: .90, .64, -- Ave. =.77 MOA
CBs after JBs: 1.06, .78. -- Ave = .92 MOA
Still looks like the JBs didn't improve accuracy, but only 20% worse and based only two 5-shot groups for each condition -- still, a strong hint that accuracy was degraded.
I will find some bullets that fit better and produce strings of groups that don't grow and try again.
John
TEST #2
dbarron posted this 08 February 2019
Well, you aroused my interest. On 6 Feb, a test of whether metal fouling degrades cast bullet accuracy was attempted. The details of the load are irrelevant except to say that before and after were identical. The bullets were all from the same run, and were Accurate 31-215 LG, their version of 311284. Alloy was COWW + 2% SN. Velocity from a 24" barrelled Rem 700V .308 Win was 1600 to 1640 (1640 previously chronographed at about 28 degrees). Range conditions were adequate. It was cloudy, wind 5 MPH or so, blowing directly towards the target. Range temperature was 13 degrees at the start of the test and didn't go up much, if any. Two ten round groups were fired from a squeaky clean barrel, and two from the post-jacket fouled barrel. Twenty rounds of home swaged 180 grain .308 dia bullets were fired between the test loads. These were in commercial jackets of gilding metal. Don’t know what the velocity was as I didn’t chronograph (hey, it was 13 degrees), but they were a near-maximum load of H 4895, so probably 2400 to 2500 FPS. I did not measure the size of the jacketed groups, but just shot them as quickly as possible without over heating the barrel. (again, 13 degrees.) I wazgonna attach a target, but one side of the target has disappeared from the pictures, and now I can't find the hard copy. I am NOT a techie. Nor, apparently, particularly organized. Group sizes, as measured by On-Target were:
Spread Mean Radius
Before
Group 1 1.654 0.641
Group 2 1.388 0.358
Ave 1.521 0.489
After
Group 3 1.436 0.481
Group 4 1.189 0.371
Ave 1.313 0.426
Difference (ave’s) 0.208 0.063
% (After/Before) 86% 87%
The “After” groups were slightly less than 15% smaller than the “Before” groups. Based on this, it would seem that there might be a slight edge to the “After” condition, but I suspect that it’s a non-result. I don’t think the barrel was particularly fouled. I cleaned the crud out with Ed’s Red and a dry patch, added accelerator and soaked with Wipe-Out for two hours. The first patch came out only very faintly blue. Nothing at all thereafter. I’ll plead ignorance on this. Of the heaven knows (I’ll not take the time to count) how many rounds have gone down this barrel in the last seven + years, these are the first jacketed rounds. Apparently, it takes more than this to thoroughly foul the bore. It looks as though this one is going to be time consuming to test, as it would seem that small amounts of fouling don’t have a major effect on accuracy, at least for 1 to 1.5 inch rifles, at frigid temps. Based on this and comments above, it's beginning to look like small amounts of jacket fouling don't really matter for most shooting. The deer would be dead with either condition. While these would not likely win Production class in a local match, it's as likely that they wouldn't finish last.
TEST #3
John Alexander posted this 2 weeks ago
This thread started with the question by max503 – does JB fouling degrade CB accuracy? It has wandered a bit with detours for cleaning elixirs and target cameras but I think the original question is worth working on. This warning of JB fouling is another conventional wisdom “we all know” that is supported by only anecdotal evidence as far as I can find – a very weak stick. In a 1-29-19 post I reported that my first try to test this old rule was questionable because of bore leading and said I would try again with bullets that fit better to avoid leading.
Our local range opened yesterday after a two-week closure by a 30” snow and today I shot another test. The CB load was a different lot of the 85 grain 25:1 spitzer bullets, Mag Tech SR primers, 6 grains of Blue Dot giving approximately the same MV as the earlier load with the same Tikka 223 rifle and no evidence of leading this time. The twenty rounds of jacket bullets were from the same box of Herter 55 grain wonders with the same load as before.
CB 5 round groups starting with a clean bore. -- .97, .84, 1.26, 1.08 moa -- Average 1.04 moa
Jacketed 5 round groups – 2.20, 2.48, 1.34, 1.76 moa – Average = 1.95 moa
CB 5 round groups after JBs -- .46, .80, 1.50, .92 moa – Average = .91, moa
For a person who believes that small differences in even two groups prove things (Joeb’s statistics be damned) this “proves” that a bit of guilding metal fouling improves accuracy of cast bullet loads by 14%.
But usually such conclusions are jumping the gun. It seems to me that these results give a hint, but not much more than a hint, that a bit of JB fouling may improve accuracy (in complete opposition to what most of us have been told). Consulting Joe’s tables this 14% improvement for eight 5 shot groups has a confidence level of much less than 70% -- far from certain. As usual, more groups need to be shot if we want to be more certain.
It would be interesting to see this experiment replicated with other calibers, alloys, muzzle velocities, increased JB fouling, etc. I hope someone will jump in and try it.
John
TEST #4
tlkeizer posted this 5 days ago
Greetings,
Shot some before and after groups Saturday, interesting. A couple comments first. My Savage 99 shoots the cast left of the jacketed (yes, I do fire both in the rifle), and the first shot out of a cold barrel is quite a bit left, then subsequent bullets strike somewhat right of the first shot but left of the jacketed. So, I have to either move sights or put up a siting target. I elected to move the sights on the scope and re-zeroed for jacketed afterwards. My rifle also shot first round left after sitting a bit while resetting targets. I did not include first shots that were definite outliers into the measurements, if the subsequent shots were out a ways I did include them. I cleaned the barrel a couple times before going to the range to let the solvent soak in for copper removal. I had somewhat limited number of rounds, so did not get 3X5-round sets both before and after with the same load. The best group was non-GC's after my comparison was done. I will have to do a run with those sometime. The mold used was a borrowed Lee 170 grain GC mold, and while I had it I cast about 500 bullets so I hope not to run out before the end of summer, batches are segregated. The load was LC82 case, CCI 200 primer, 17 grains IMR 4227, cast and weighed 170 grain, Hornady gas check, SPG lube, .309 sizer. Rifle Savage 99, .308. Weather overcast, 38-43 degrees as day went along, no wind. Shot off bench.
Before: group 3.12 inch mean radius 1.1 inch
group 2.84 inch mean radius 1.0 inch
group 2.42 inch mean radius 0.8 inch
Average MR 0.95 inch
Jacket mean radius 1.0 inch
After group 2.87 mean radius 0.9 inch
group 1.76 mean radius 0.6 inch
Average MR 0.77
Values are rounded off. Granted, a small population, but interesting and a starting point for me adding to the data base.
Just a couple random thoughts: 1. Does copper provide a bearing surface for smoother flight of lead? 2. Does copper microscopically fill in "potholes" allowing for better consistency? I did not have a chance to use the Chronograph to see if before and after groups had varying velocities.
TK
TEST #5
tlkeizer posted this 4 days ago
Greetings,
My error in arithmetic, I used a different number off my working papers. (Besides, I like your numbers better) No, you did not misread; I miscalculated off wrong data.
Now, on to today's results. I shot 25 rounds cast, 12rounds jacketed, then 19 rounds cast (one case was cracked in the neck, so it went into the scrap pile while prepping cases). 5 rounds cast and 2 rounds jacketed were used to adjust scope. Load was LC82 case, Lee 170 grain GC weighed out as 170, CCI 200, 22 grains IMR 4227. Note different charge. Jacketed was 165 Speer BTSP, ADI case, CCI 200, 48 grains H414. Slightly different parameters, but if jacketed before cast improves cast groups, I think it would prove so generally across the board of variables; hence, some different round preparation. Results in inches. Groups for measurement were 5 round groups except for first group after jacketed, that was only 4 rounds. Extra rounds were shot to bring groups near bullseye but not measured. Some numbers rounded.
Results: Before Jacketed After
Group : 3.30, 2.22, 3.49, 3.72 AVE 3.18 3.79, 3.35 3.28, 3.34, 3.04, 2.68 AVE 3.05
Mean Radius: 1.28, 0.79, 1.51, 1.35 AVE 1.23 1.18, 1.19 1.28, 1.07, 1.12, 0.92 AVE 1.09
Results? After the jacketed the cast did better again. Difference in group size was 3.18-3.05=0.13. .13/3.18=.041; 4%
Difference in MR was 1.23-1.09=0.14. .14/1.23=.114; 11%
Hope I got it right this time John, otherwise I may have to stay after school and clean the blackboards.
I find it interesting looking at the group size averages the mean radius averages; looking at the targets there were a couple outliers in the groups that enlarged them, and some after groups had most rounds much closer to each other than before groups. What this seems to indicate to me is that using jacketed bullets just before cast bullets helps groups. Long term, who knows, but in the short run firing 10-15 rounds jacketed before cast would help my scoring slightly. I did not get the 14% mean radius difference, but at 11% that is still significant to me. I think my new motto should be paralysis by analysis as seen in an earlier report in the forum. I do like to work numbers in spite of my arithmetic.
John, hope your trip to the range was as good as mine, especially weather wise.
TK
TEST #6
John Alexander posted this yesterday
Finally got to the range today (March 29) for another try at the accuracy of CB after fouling bore with JB compared to accuracy from clean bore.
Load was the same as before except for a different lot of the same 80 grain spitzer bullets.
Accuracy of four 5-shot groups of CBs starting with a clean copper free bore .84', .70" .88", 1.50" -- Average 0.98"
Accuracy of four 5-shot groups of JBs 1.66, 1.70", 3.00", 1.64" -- Average = 2.0"
Accuracy of four 5-shot groups of CBs .78", 1.24", .42", .96" -- Average = 0.85"
Accuracy of the cast bullet loads were 13% better after fouling the bore with twenty rounds of jacketed bullets.
This result is similar to the previous four similar test results all showing improved accuracy after fouling the bore with 20 jacketed bullet . Groups shrunk by between 13 and 19 percent.
This is of course the exact opposite of what we thought we knew. Every experienced CB shooter knows that jacketed bullet fouling ruins cast accuracy because that's what we have been told. But when five series of groups by three different shooters using five or six different loads all show that 20 rounds of JB fouling improves accuracy an open minded shooter should begin to question the rule that you can't mix cast and jacketed bullets.
Of course these tests so far don't cover all the possibilities. What about the fouling from 50 jacketed bullet loads, 100 loads, 200? Surely gross guilding metal fouling, the kind that we have been told degrades JB accuracy would also degrade CB accuracy. We can guess but at this point we don't know that either.
Anybody have a rifle not cleaned since the last prairie dog shoot that you have a cast bullet load for? Shoot a few groups before cleaning and a few more after cleaning and see what happens.
John
TEST #7
joeb, 4/3/19
M10 Savage, M110 308 HV barrel,
314299, .3095, Lyman Super Moly, 15/A#9 Fired 30 before, 25 after.
Hornady 130 gr sp, 43/IMR4895. Fired 30.
100 yard 5 shot group, inches, in order shot;
Clean barrel, 5 314299 sighters, then
1.625, .8, 1.3, .925, .85,AVG = 1.1 then
130 Hornady, 1.6, .85, .8, 1.4, 1.825 AVG = 1.283, then
314299, 2.9, 1.8, 1.65, 1.1, 1.15, AVG = 1.72
TEST #8
John Alexander posted this 4/6/19
I fired another string in the before and after jacketed fouling test yesterday (4-5-19). The cast bullet load was the same as before but for the jacketed load I dug out some longer bullets (Sierra 69 grain HPBT Matchkings) in hope of reducing the jump short jacketed bullet must make in my Tikka with its eroded throat – same powder and primers. Procedure was the same starting with a clean bore (Sweet’s solvent until no blue green patches) and no cleaning during the test. One fouling shot was fired before each of the 20 shot cast bullet strings. Tikka 223 rifle and no evidence of leading.
CB – 5-shot groups starting with a clean bore. -- .1.36, .88, .50, 1.64 moa -- Average 1.10 moa
Jacketed 5-shot groups – 1.20, .90, .76, 1.28 moa – Average = 1.04 moa
CB 5-shot groups after JBs -- .98, 1.10, .94, .84 moa – Average = .97, moa
Reduction in CB group size after jacketed fouling = 12%
The longer JBs which were seated just off the lands shot as accurately as the CBs.
Cleaning the bore afterwards with Sweets produced patches with a little blue green color.
John
