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Primer velocity disparity

This is a discussion on Primer velocity disparity within the Reloading forums, part of the Firearm Forum category; I chrono'ed loads yesterday. I've started shooting IDPA and I was checking my loads against power factor (105 for SSR). With the component craziness I ...


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Old June 29th, 2013, 08:19 AM   #1
 
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Primer velocity disparity

I chrono'ed loads yesterday. I've started shooting IDPA and I was checking my loads against power factor (105 for SSR). With the component craziness I haven't been too particular about primer brand, as long as they touch off. The load was .38 special 158 gr Berry plated RN over W231. I use a Lee Classic Turrent press and was using the 4.0 powder cavity which drops 4.3 gr+/- when using W231/HP38.

I chrono'ed 10 rounds with Federal primers and 12 rounds with Winchester primers. All rounds were loaded in the same session just before going to the range. Temperature was 95 degrees at the range and about that in my garage at the loading bench. The only variable was primer brand. Here are the results shot through a GP100 with 4" barrel ten feet from chronograph.

Fed 624, 698, 745, 612, 735, 688, 658, 706, 676, 689. Low of 612 high of 745
with 8 falling between 624 and 735.

Win 675, 745, 729, 752, 725, 746, 769, 756, 735, 752, 739, 730
Low of 675 and high of 769 with 10 falling between 725 and 756

Chronograph was Competition Electronics Pro Chrono and it was a sunny cloudless sky shot between 4:00 and 5:00 pm. Elevation is approximately 1800 feet above seal level. I'm not trying to make any judgements here. I don't have a brand loyalty and I don't sell reloading components. Just looking for the best load for my gun.

I felt good about the rounds with Win primers. Not so much with the Federals. From your experience, is there typically this much disparity using Federal primers compared to Winchester? Do Fed primers usually give up markedly slower velocities than Winchester. Is this an aberration with the Federals or Winchester? Comment?




Last edited by fastlane604; June 29th, 2013 at 08:25 AM.
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Old June 29th, 2013, 10:07 AM   #2
 
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Each primer brand is different unto itself, and that is why reloading data generally lists the primer used and it is suggested to work back up a load when primers are switched. Each brand has a different hardness (cup thickness) brisance and heat, which is why primers can and do make a difference in accuracy during load development. Often times, especially with revolvers, the hottest, most powerful primer will not be the most accurate or efficient.

Somebody here may have a list of the chart that used to be in Speer manuals that show the primers all compared to each other for pressure and heat.

It all comes down to what is accurate and what you are trying to do. Many IDPA guys will use small rifle primers instead of small pistol for the thicker cups to make power factor for their gun. Again, it all depends on what you are asking the primer to do.
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Old June 29th, 2013, 12:08 PM   #3
 
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Quote:
Originally Posted by fastlane604 View Post
I chrono'ed loads yesterday. I've started shooting IDPA and I was checking my loads against power factor (105 for SSR). With the component craziness I haven't been too particular about primer brand, as long as they touch off. The load was .38 special 158 gr Berry plated RN over W231. I use a Lee Classic Turrent press and was using the 4.0 powder cavity which drops 4.3 gr+/- when using W231/HP38.

I chrono'ed 10 rounds with Federal primers and 12 rounds with Winchester primers. All rounds were loaded in the same session just before going to the range. Temperature was 95 degrees at the range and about that in my garage at the loading bench. The only variable was primer brand. Here are the results shot through a GP100 with 4" barrel ten feet from chronograph.

Fed 624, 698, 745, 612, 735, 688, 658, 706, 676, 689. Low of 612 high of 745
with 8 falling between 624 and 735.

Win 675, 745, 729, 752, 725, 746, 769, 756, 735, 752, 739, 730
Low of 675 and high of 769 with 10 falling between 725 and 756

Chronograph was Competition Electronics Pro Chrono and it was a sunny cloudless sky shot between 4:00 and 5:00 pm. Elevation is approximately 1800 feet above seal level. I'm not trying to make any judgements here. I don't have a brand loyalty and I don't sell reloading components. Just looking for the best load for my gun.

I felt good about the rounds with Win primers. Not so much with the Federals. From your experience, is there typically this much disparity using Federal primers compared to Winchester? Do Fed primers usually give up markedly slower velocities than Winchester. Is this an aberration with the Federals or Winchester? Comment?
My EXCEL spreadsheet gives me this analysis:

Federal
683.1 fps average velocity 42.9 fps standard deviation full dataset
684.2 fps average velocity 33.1 fps standard deviation tossing high and low, 8 datapoints

Winchester
737.8 fps average velocity 23.5 fps standard deviation full datasset
740.9 fps average velocity 10.9 fps standard deviation tossing high and low
741.0 fps average velocity 9.2 fps standard deviation 8 central datapoints

I would be unconcerned about the velocity difference. That can be made up for by adjusting the powder charge. The superior standard deviation of the Winchester-powered loads is what attracts me. How is the grouping on-target for each of these loads?

More to the point, I would load up some Federal-primered loads to achieve 740 fps and Winchester-primered loads to achieve 740 fps and run the test again, recording grouping as well as velocity.

If you get the same velocity, you are likely getting the same pressure. If you get better groups with one primer over the other, use those. If it makes no difference, then either will do.

Thanks for presenting an interesting comparison.

Lost Sheep
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Old June 29th, 2013, 01:21 PM   #4
 
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Lost Sheep,

Thank you for the thoughtful post. I should have made my original post more clear. I too agree that the inconsistency in velocities of the Federal primers is more concerning than lower velocity vs Winchester. I was more concerned with chronographing and recording than I was shooting for and indentifying accuracy, so I do not have an answer on which primer produced better accuracy.

I will do as you suggest and report back by findings. May throw in Remington primers as well, to further confuse the situation.
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Old June 29th, 2013, 01:27 PM   #5
 
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I would suspect the ES comes from the Lee powder measure. I would be quite curious to see the same 10 + 10 strings repeated with weighed charges.
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Old June 29th, 2013, 01:34 PM   #6
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fastlane604, Yes, as 429421Cowboy stated, changing primers may change velocities. Further even if the same brand and type are used, there can be just as much difference from lot-to-lot than brand-to-brand. With the exception of "bench rest" or "match grade" primers that are exceptionally uniform, normal primers don't have perfectly the same mix in each one so there will always be a token amount of velocity fluxuation.

Further, after conducting many tests with as many brands any types of primers as I could find, I discovered another interesting issue ... all brands/types of primers produce more flash when struck harder by the firing pin ... up to a point of course. So ... one brand in one gun may produce a hotter flash than the same brand in another gun. I used a S&W Mod 10 for 38 Special small primer tests where I could back off the strain screw and adjust hammer spring tension. I could get light primer hits where the primer would not detonate and with just a little more tension, the primer would "poof". Still more tension would make the primer "pop", and finally with even more spring tension, the primer would "bang". Once hammer tension made the primer "bang", any additional tension did not increase primer flash. This happens with all brands of primers but not at the same spring tension where some brands/types are more sensitive than others. After spending a lot of time and money with these primer tests, I concluded there wasn't enough change from brand-to-brand to make a notable difference in chamber pressure or velocity, providing the hammer springs were not reduced power and you compare standard to standard or magnum to magnum but not a mix. ... Different? yes, but only slightly and just as noticable from different lots as from different brands.

Chronographs are wonderful tools that provide a host of valuable information if you take the time to analyze the data. Looking at your data ... what jumps off your post is your wild max velocity spreads. This is always an indicator of sub-standard reloading techniques ... not primers. If you look at your data set with Federal primers, you had a low of 612 and a high of 745. This is a whopping 133 fps max velocity spread. The Winchester set has a 94 fps spread ... not quite as bad but still way out of control.

Typical factory ammo has a max velocity spread of 50 fps ... match grade has to be under 25 fps max spread so as you can see, your spreads are double to almost tripple that of acceptable factory ammo limits.

So what causes wild velocity spreads? Four main issues ... none of which involve primers. Powder ... select the right burn rate and proper charge weight. Your W-231 powder is fine for 38 Specials but with one problem ... your charge weight is too low. As you probably know, with a fast burning powder such as W-231, a tenth of a grain will make a very notable difference in pressure and velocity. With factory ammo, manufacturers found through extensive testing that pressure is very important for powder to get a uniform burn. As such, nearly all factory ammo is loaded to pressures right at SAAMI max ratings. For a 38 Special, that would be 17,000 psi. 4.3 gr of W-231 with your bullet produces about 12,000 psi, way too low for a uniform burn. By increasing your powder charge to 4.8gr of W-231, you will still be safely under max pressure @ 16,000 psi and will get a much more uniform burn that will reduce max velocity spreads. Further, even though W-231 drops quite well from a powder measure, it only takes a tiny difference in powder drop to make a notable difference in velocity. Try weighing each charge and trickling up to exact weight ... again it will make a significant difference in max spreads.

Next are the bullets. Two issues here ... weigh each bullet and note the difference between lightest and heaviest. If bullets vary more than a couple tenths of a grain, it will show up in max spreads. The max for non-match grade factory ammo is +or- 1 grain. Along with weights ... bullet seating depth is critical to mimimum spreads. Because pressure increase with deeper seated bullets, you want all bullets to be seated to the same depth ... +or- .002".

Last are your cases. As a case has been reloaded several times, it's neck tension will change do to the brass getting "work hardened". If neck tension is not uniform from case-to-case due to a difference in brass hardness or crimp, the bullet will exit the case at a different time in the powder burn cycle, which can change velocity considerably. Try your test with once fired brass that has been trimmed to the same length for a uniform crimp.

Finally, another issue but this time it is the gun itself. Cylinder throat diameter makes a huge difference in chamber pressure and in turn, chamber pressure will change velocity. The optimum throat diameter for a 38 Special is .358". If throat diameters are smaller than .358", chamber pressure will elevate .. the tighter the throats, the higher the pressure and if all throats are not exactly the same diameter, each one will produce a slightly different velocity. So ... some of your velocity spread issues may be from non-uniform cylinder throats.

My "bench mark" match grade load is similar to yours ... except a 158 gr LSWC and 4.8gr of W-231. I use a file on the base of the bullets and dress them for uniform weight. My max velocity spreads are usually about 12 fps ... even single digits in a S&W Mod 14. You will find the lower your max spreads, the better the potential for accuracy.

Do you need this low level of max velocity spreads? Probably not, but I can assure you ... the above test will be a lot more valid when you get your max spreads under control.

Hope this helps and you weren't offended by my comments.

Last edited by Iowegan; June 29th, 2013 at 10:09 PM.
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Old June 29th, 2013, 01:53 PM   #7
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Just a few more comments ... The most accurate 38 Special I have ever fired is my S&W Mod 52-2. Oddly enough, it's not not a revolver ... rather a semi-auto that was specifically designed for 148gr hollow base wad cutters. A 2.8gr charge of Bullseye with a 148gr HBWC is probably the most accurate load known to man but ... it shoots even better in my 52-2 than any revolver. Why? No cylinder throats. Each cartridge will develop the same chamber pressure (assuming good reloading techniques) and will chronograph with less than 10 fps max velocity spreads.
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Old June 29th, 2013, 02:17 PM   #8
 
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Ah crap..... I have a standard .45 ACP practice load that is accurate in all my guns. Now you guys are going to worry me into chronoing them to make sure the SD is OK!
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Old June 29th, 2013, 08:03 PM   #9
 
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Iowegan,

Not offended. I always appreciate your insight. I have your Gun Guide that I keep under lock and key. I will try the test with once fired brass. These tests were done with mixed cases that have been fired numerous times. I know I have one chamber that is a little tight. I occasionally debate myself on the merits of reaming the chamber throats. I will bump up my powder charge. I was at 4.3 because I knew from past tests that I could make power factor at that charge and have less recoil for follow up shots.

I looked back on some tests that I did in the past with brand new Starline brass in .45 acp with Berry plated 230 gr RN bullets shot from a full size RIA 1911. Max spread on three different tests were all under 50 fps.
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Old June 29th, 2013, 09:18 PM   #10
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fastlane604, It's much easier to get lower velocity spreads with a pistol because you are not dealing with 6 different chambers and throats. I might suggest trying a 10 shot string in your revolver with all rounds fired from the same chamber. If that tightens your spreads (and it probably will), it tells you the gun it at least part of the problem and would likely warrant having the throats reamed.

What I really didn't say in the above post .... if you get your max spreads under control, either primer should work just fine but one brand will likely be a tad higher velocity ... the nature of the beast. The next time you buy primers, it could reverse.

Here's an old post explaining some of my primer tests: Primer Sensitivity by brand
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Old July 16th, 2013, 07:46 PM   #11
 
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After several days of traveling and a few days of catching up, I was able to get back to the range. Following Iowegan's suggestions each round was fired from the same chamber of the GP100. Powder charge was increased to 4.3 cavity which yields 4.65 gr. plus or minus of W231. I did not weigh the bullets. I did not weigh the powder charge after the first three drops. I'm looking for an IDPA load and I won't be weighing bullets or charges when I load them for practice or matches. I did use once fired Federal brass. It was 72 degrees and I began recording speeds at 6:20 pm. The chamber was clean when I started but I did not clean it during the shooting. I shot the loads in this order, Win primer, Fed primer, Rem primer

Here are the results
Winchester primers 10 rounds from 790 fps to 850 fps. 60 fps max spread
Federal primers 10 rounds from 781 fps to 844 fps. 63 fps max spread
Remington primers 10 rounds from 786 fps to 859 fps. 73 fps max spread

Better than the first test, but not quite to the 50 fps max spread of factory loads. I suspect my powder drops are not quite precise enough. However, there was not much difference in speed or max spread between either of the three brands of primers.
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Old July 16th, 2013, 09:17 PM   #12
 
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I'm mostly w/ Iowegan , but with a cpl caveats . I once tested a certain factory load in a certain revolver , 100 fps variation , but six shots into 7/8 in @25yds . I decided results were more important than theory , and declared Victory.

And I have gotten excellent results with lighter charges of 231 in .38spl . ( All refrenced using 158 lead bullets , cast RN and SWC , and Speer swaged. All CCI std SP primers, usually w/ mixed range brass ). 3.2gr gave aprox 700fps 1.0 in groups , and single digit SDs .Increasing to 3.4gr gave aprox 750fps aka match factory std vel loads.

I am getting a sense of very inconsistant ignition ( and while using a fairly easy to ignite powder) . My experiences noted above rule out issues with powder selection or pressure level ( to me , YMMV ) .

Since this is a competion gun , it may have had an overenthuiastic action job to where the hammer strike is so light it barely makes the primers go *bang* , but not hard enough to give consistant ignition.

Widely inconsistant neck tension. This could be really crappy brass , inconsistant crimp application , inconsistant case neck expansion. Case neck expansion not properly matched to bullet dia. Bullet diameter could be widely inconsistant.
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Old July 16th, 2013, 09:30 PM   #13
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fastlane604, Good work!! You are making excellent progress and have cut your max spreads almost in half plus there is very little difference between primers. Next time try all six chambers in your GP-100. If max spreads jump up again, you'll know the cylinder throats need to be reamed. If not, you should be good to go. Being slightly over max spread standards isn't going to affect accuracy that much ... maybe for precision bullseye, but not for IDPA.
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Old July 17th, 2013, 06:37 AM   #14
 
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Bigfoot and Iowegan,
Thanks for the replys. How might I tell if I my hammer strikes are too light to give consistent ignition? The hammer is light, about 7.75 lbs by my gage. But, it touches off the primers each time. Never had a light strike but I have not tried CCI.
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Old July 17th, 2013, 06:56 AM   #15
 
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How about this? All my tests were done D/A. Does not S/A provide slightly harder strikes? If I tested S/A and D/A with the same load and S/A showed tighter spreads it would tell me that D/A is a little light. Correct?

I suppose I could do the same thing by switching out springs, but I'm trying to keep the weather variable at a minimum. Changing springs at the range is doable but inconveinient.

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