Primers...Benchrest, Match, Large Rifle and Magnum...

[Dearhunter61]

Loading for a couple of Magnum rifles...What is the advantage and/or disadvantage to using Benchrest vs Match vs Large Rifle vs Magnum primers.

I have tried Magnum primers with some of my loads and also I have tried Match primers.

I am relatively new to reloading and am not sure what the differences would be or the effect each would have on the accuracy of a round/group.

Thanks,

[saber9]

The magnum primers are designed to give more positive ignition to the large loads of slow burning powders that are commonly used in the magnum cartridges. This is particularly true with ball powders I am told.

I always refer to at least 3 trusted sources of reloading data and follow their recommendations. If you have a favorite load that you worked up using standard primers and decide to use it with magnum primers, it is strongly recommended to reduce the load at first and watch for signs of excessive pressure.

I have very limited experience with large rifle bench rest primers. The few times I used them I experienced an occasional failure to fire with what appeared to be a light primer strike. I have "heard" that bench rest primers have somewhat thicker or harder cup metal than standard primers. If this is the case that would explain the apparent light strikes I encountered.

[Shoney]

Brisance - is a measure of the rapidity with which an explosive develops its maximum pressure

Here are the results of a test done to determine the brisance of primers:

RIfle Primers
Brand/type_________Power Average___Range____Std. Dev
1... Fed Match GM215M___6.12______ 5.23-6.8_____.351
2... Federal 215 LRM _____5.69______ 5.2-6.5 _____.4437
3... CCI 250 LRM_________5.66______ 4.5-7.4_____ .4832
4... Winchester WLRM____ 5.45______ 5.1-6.0 _____.2046
5... Remington 9 1/2M LR _ 5.09 _____ 3.5-6.75 ____.6641
6... Winchester WLR _____ 4.8 ______ 4.1-6.0 _____.4300
7... Remington 9 1/2 LR __ 4.75 _____ 3.7-6.25 ____.5679
8... Fed Match GM210M __ 4.64 _____ 4.0-5.6 ____ .3296
9... Federal 210 LR ______ 4.62______ 3.7-5.5 ____ .3997
10.. CCI BR2 ____________4.37______4.0-5.0 _____.2460
11.. CCI 200 LR _________ 4.28 _____ 3.8-4.8 _____.3218
12.. KVB 7 LR Russian_____ 4.27 _____3.8-4.8 ____ .2213
13.. Rem 91/2 (30 yrs old)_ 4.16 _____ 3.8-4.8 ____.3427
Pistol Primers
14 Rem LP ______________4.47______ 3.2-5.6______.5171
15 KVB 45 LP Russian _____3.89 _____ 3.3-4.2 ______.2232
16 CCI 300 LP___________ 3.18______2.7-3.5 ______.2406
17 Federal 150 LP _______ 3.11 _____2.6-3.5 ______.2090
18 Fed Match GM150M ___ 3.05 _____ 2.6-3.7 ______.2299

[Unclenick]

As an aside, I had a brief e-mail exchange with the author of that information because I noticed an error in the method. He e-mailed back and agreed. He said that when his new site hosting is in order he may revisit the situation.

The error can be corrected from the range numbers he gave. The correcting formula is:

New data= old data*sin(old data*11.25)

For example, he gave the Winchester WLR as having a power range on his arbitrary scale of 4.1 to 6.0 with an average of 5.45. Running the formula on those two numbers gives you 3.0-5.5. The average he gave converts to 4.25, though that will not be precise without having all the original numbers to convert before averaging. Standard deviation would also require all the original data to convert. But putting the average through the formula will come fairly close, especially at the higher numbers. SD won't be meaningful to convert.

What the correction is about is that the mechanism the author used causes the primer to swing a suspended weight forward and up, like a ballistic pendulum. That means the work done by the primer is proportional to the distance the weight is raised from its starting point against gravity. The pivot makes the raising easier when the result is low and harder when it is high. That introduces the non-linearity. The actual effort is proportional to the sine of the angle of the pointer. Even though his 0 to 8 scale is arbitrary, you need to put the numbers through the correction formula for them to be comparable. As originally given, a range of 1.9 represents a bigger force difference when the range is high on the scale than it does when it is low on the scale.

The formula doesn't move numbers much in terms of ranking, but as an extreme example, the Winchester WLR primer for rifle and the Federal 150 pistol primer both show a power range from high to low of 0.9 on the original scale. After using the formula on the range numbers, the WLR has a power range of 1.25 while the 150 has a range of 0.95. Those numbers are comparable (equal arbitrary power units) while the original 0.9's didn't represent equal differences in power.