My primer test results

  • Last Post 30 April 2019
Pentz posted this 29 April 2019

So...I was "called out" on another forum when not subscribing to the proposition that all primers are created equal, in that accuracy was not affected by the brand of primer.  That proposition made it over to this forum, so I am posting here as well.

The test: five, 5-round groups fired at 100 yards from my 1917 Winchester Mod Scope rifle, in a Boyd sporter stock with an Athlon Midas BTR Gen 2  30 mm scope, 4.5-27x.  Powder was 17.5 grains of 2400 weighed, under bullets sorted to 0.5 grain, and cast 22 bhn, from a mold made for my throat and barrel.  The rear band measures .311, the nose .302 that is engraved by the rifling at 3.35 COL when chambered.  The barrel was a virgin 1919 NOS 5-groove when I purchased it and has never seen a jacketed bullet.  The cases are LC 67, weight sorted to within 1 grain, trimmed and neck turned, with reamed flash holes; this lot has been fired 23 times with periodic torch annealing.

Primers tested were Remington 9 1/2 and 9 1/2M, Federal 210, Winchester LR, and CCI 200 seated just below flush with a Frankfort hand primer.  I did not use any large pistol primers.   I used the 27x setting, and fired over a front rest and rear bag with a very hard hold.  Weather was balmy in the low 60s, variable light breezes, and the grass was 2.5 inches high.  I was too lazy to set up my chrony, gonna have to budget a LabRadar some day.

After zeroing, five, 5-round groups were fired, the results are shown on the enclosed target.

Remington 9 1/2    - 2.20" by 1.63" group

Remington 9 1/2M - 2.65" by 1.78" group

Federal 210 -           0.88"  by 0.72" group

Winchester LR -      0.80" by 0.76" group

CCI 200 -                0.69" by 0.29" group ( I pulled the last round at 2clock)

Conclusion:  While this was not a statistician's 100 round group test, I'm not going to cast up 500 weight-sorted bullets to do so - the differences between brands of primers are obvious.  My rifle prefered Remington 9 1/2 primers when using my stash of 4759; grouping went to pot with 2400.  Clearly, I'm using CCI 200s with 2400 for now.


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RicinYakima posted this 29 April 2019

Pentz, I have no heartburn with your five shot groups. The question has always been X brand is better than Y brand. To me, it doesn't work that way. In my one rifle that I have 20 years of experience with, it doesn't matter. BUT that doesn't mean it will always be the result for others. I am down to my last couple of pounds of SR4759, so my A2400 match loads will be with whatever I have. Doesn't mean it will work for you! Ric p.s. My hypotheses is that it has to do with firing pin energy and penetration. I have shortened my '03 striker to stop occluding the flash hole.

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muley posted this 29 April 2019

looks good Pence, I find my scores are sometimes better with cci 400 in 30Br, but no other testing, the other variable being the shooter.

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joeb33050 posted this 29 April 2019


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GWarden posted this 29 April 2019

When the supply of sr4759 runs out, don't overlook Alliant 300mp, on the burn rate chart it is next to 4759. Have used it in 32/40 & 38/55, superior to other tried and true powders for these two. Recently started using in 6mm Rem, and very accurate- best results with LR mag primers.


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Ken Campbell Iowa posted this 29 April 2019

a tiny data dot to add to the mix:

an obsessive but winning mj benchrester mj friend told me that

when using molly'ed bullets he improved groups by going a little bigger on the flash hole sizes. ( already uniforming them, just bigger diameter ) . 

he thought it was because the molly bullet engraved with less resistance.


that was about the time i stopped putting together my br 6ppc kit. still got it, i like to look at it.


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TRKakaCatWhisperer posted this 29 April 2019

A rule of thumb that works for me:  after fine tuning a given load, try EVERY type of primer available to tune it a LITTLE more.


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Pentz posted this 29 April 2019


Joe, the measurements posted and on the target are the axes of the groups, center to center.

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Ken Campbell Iowa posted this 30 April 2019

pentz ... i think joeb is wanting the group size for his stats anal-i-zations, a valuable addition to our attempts to comprehend what is happening to our shots ...

although the x and y axis numbers are valuable, the " group" size can be larger than either of those values.



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tlkeizer posted this 30 April 2019


joeb33050, for your mentioned questioned group sizes, center to center, are you after just the largest spread in the group, or do you also use mean radius?   For my own use I am recording largest spreads for lateral (L), Vertical (V), center to center (CEP)  ((Yeah, I know, not a true CEP but how I keep track of the distance)), and starting to record Mean Radius (MR).  In my logs most of my data is L, V, CEP, sometimes MR.

As for primers, I have gone to CCI 200 for amost everything except 45-70 Black Powder, then I use LRMPs.  Usually CCI 250, but have a couple friends that gave me a few hundred assorted magnum primers, so use them also.  For desired smaller groups chasing accuracy, I use the CCI; others are used as I feel at the time of reloading.  Not very scientific, but the groups are not so affected as to keep from using the loads hunting or practicing, or letting someone try the 45-70 for the first time which is usually a 55 grain FFG load with nominally 420 or 405 grain bullet and not a 500+ bullet pushed by 70 grains of BP, doing that to someone is "not polite".  I do record primer in most recordings of range sessions.


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