Unexpected result using magnum primer

[gunwonk]

.350 Rem., Lyman 350447 (250 gr.), paper patched w/ green bar printer paper, ~21.3 gr H-4198. Mild midrange load, about 1200 fps. Some of my other loads about like this (but with a lighter bullet) were burning a little dirty, so I wondered if using a magnum primer might clean things up a bit. As it happens, this load was pretty clean either way, but ...

Same day, same time, same rifle, same old Oehler 35 gun club chrono --


standard primer, 3 rounds: 1254, 1228, 1238 (avg. 1240 fps)
magnum primer, 3 rounds: 1169, 1219, 1214 (avg. 1201 fps)

Not a typo. The same load with a magnum primer was slower than with a standard primer.

How about that. :)

[Scharfschuetze]

That's not uncommon. I've had it happen a few times when developing various loads. Goes against one's intuition.

[6bg6ga]

I was always taught to lower the load by 1 gr when using a magnum primer in place of a standard primer. I guess there are all kinds of myths.

[tranders]

I would like to hear some more theories on this.

[tazman]

The magnum primer is supposed to give better/hotter ignition. It may cause the powder charge to act as a slightly faster burn rate powder. This would give slightly higher pressure with slightly lower velocities.

[OS OK]

Never have seen anything like this...have seen where a magnum primer would increase FPS only marginally but didn't give it much thought after that.

My first reaction would have been..."How the heck did I mix up the primers, I obviously screwed up somehow!"

[rintinglen]

One of anything proves nothing: Jesus rose from the dead but that is not the statistical average. Three shots don't tell us much more than one.

With only a three shot average, there is not enough difference between the two to definitively state one way or the other. Off the top of my head and without recourse to a TI-83, I think you would need a difference of at least 50 before it becomes significant.

But it still is pretty odd.

[William Yanda]

Throw out the first result for each string and they are a lot closer.

[swheeler]

I would guess the magnum primer is moving the bullet forward enough to increase the combustion chamber size at ignition, lowering pressure slightly.

[tranders]

I would guess the magnum primer is moving the bullet forward enough to increase the combustion chamber size at ignition, lowering pressure slightly.

That makes sense. Some of the inline muzzleloader guys found this out with standard 209 primers.


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[Grmps]

So basically, magnum primers make slow powers faster

[Wayne Smith]

Some possible light on the matter - from John Haviland, Rifle, March 2006 article on the 30-06:

In the past riflemaker Charlie Sisk also thought the problem was a bad scope or a poor barrel. "I can't tell you haw many barrels I've changed over the years when the wrong primer was probably to blame all along for the inaccuracy," he said.

The first sign that primers may be causing the a problem with accuracy is a group looks like two distinct groups with a vertical spread between them. Sisk discovered that when he started using pressure-testing equipment a couple of years ago. A customer's new rifle clustered bullets high and low on a target. Sisk hooked the rifle up to his pressure equipment and found the loads varied up to 12,000 psi in pressure.

"After awhile a pattern emerged and you could predit if a round's pressure was high or low by where a bullet landed on the target or where a bullet hit on the target by looking at the pressure reading", he said. Bullets hit low from loads that developed the highest pressure, while low pressure loads threw their bullets high. Sisk said that there was little difference in velocity between the cartridges that developed high and low pressure. So looking at only the chronograph results indicated the load was a good one, although it's accuracy was dismal. "Those swings in pressure probably changed something in the barrel vibration and caused the inaccuracy", he said.

[Larry Gibson]

gunwonk

What exactly were the Mke/numbers of the primers used?

[gunwonk]

What exactly were the Mke/numbers of the primers used?
Standard primer was Winchester WLR.
Magnum primer was Remington 9 1/2 M.

[Larry Gibson]

Standard primer was Winchester WLR.
Magnum primer was Remington 9 1/2 M.

There in is the probable difference.......

Magnum primers were made to have a higher "brissance" to ignite ball powders and large volume of very slow burning extruded powders. They have harder to ignite retardents on them. The Winchester WLR, while not listed as a magnum prmer, is considered ny many, myself included, to be a magnum level primer as it was developed with a high brissence to ignite Winchesters BR748, BR760 and BR780 ball powders. Thus it is not surprising that it gave higher ignition than the Remington 9 1/2M. I find the WLR to be even a bit hotter than the CCI 250. The Winchester WLRM ranks right up there with Federal's 215M primer. A comparison between the WLR and WLRM or the Remington 9 1/2 and the 9 1/2M would have probably given the results expected.

[Meatpuppet]

Been using Federal Magnum SPP and Federal SPP primers in 9mm for USPSA (heavy 147gr and fast powders). Shooting through my CZ Accushadow, I notice no difference in practical accuracy, a nominal 15-20fps velocity gain, but I notice that the Magnum primers always give me a lower standard deviation over the chronograph. Whatever Federal I can find is what I use. My 2 cents.

[gunwonk]

The Winchester WLR, while not listed as a magnum prmer, is considered ny many, myself included, to be a magnum level primer as it was developed with a high brissence to ignite Winchesters BR748, BR760 and BR780 ball powders. Thus it is not surprising that it gave higher ignition than the Remington 9 1/2M. I find the WLR to be even a bit hotter than the CCI 250. The Winchester WLRM ranks right up there with Federal's 215M primer. A comparison between the WLR and WLRM or the Remington 9 1/2 and the 9 1/2M would have probably given the results expected.

Interesting. Thanks! :)

Dunno whether this has appeared here before, but I once ran across the following table of energy content for CCI primers (might be a pic from a Speer reloading manual):
202191
Do you know of any similar hard information available for other primers?

[TXGunNut]

FWIW the standard primer seems to give the lower ES in your small sample.

[swheeler]

Primer Testing Reference

This testing was done to try and rank primers by power (brisance).

Primer tester1.JPG (43461 bytes) This is the home made tester. The shot is fired against a weight which in turn moves a pointer. The pointer remains at the highest point of the shot.

Primer tester2.JPG (37043 bytes) This shows the pointer after a shot has been fired. In this case, it was a Federal large rifle magnum

NOTE: This data is reference only. This is on a DMS (don't mean squat) scale. It is relative to this set of tests and this tester. Take them with a grain of salt and as a guide only. Most of the tests were of 100 or more primers. A few were of 50 when limited amounts were available.

Ranked in order of power

Large Rifle = LR, Large Rifle Magnum = LRM, Large pistol =LP,

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 1/2 LRM 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

[swheeler]

I still think the higher brissance of the Rem 9.5 primer is moving the bullet forward at ignition. "Most of the tests were of 100 or more primers." I would think this should be a very good indicator of brisance of the various brands, looking at deviation I understand why I don't use Remington primers, like a box of choclates! :-?