Home Forums Hunting & Shooting Ask The Gunwriters Substituteing primers

Just got back from the range. Beautiful day in central Wyoming. 60' and NO wind. Our range is about 6000' elevation.If this is because of global warming, I love it.--- My question is: One of the guys was short on large rifle primers (aren't we all) so he loaded his 6.5 Creedmoor with H4350 and LARGE PISTOL primers,with 130 grain Hornady ELD-M bullets. The chrno showed 2730 average velocity, which is close to what the Hornady manual says it should be with his amount of powder. Everything went pretty smooth. Maybe it's been brought up before, but have you ever done this or heard of anybody doing it. He said he tried them in his 30-06 also and had no problems.

I think pistol primers have thinner cups and are made for less pressure. Kinda one of those things that works until it doesn’t.

Yep, do believe there is also a difference in height between LR/ LP unlike SR/SP.

I do not substitute primers. Russian roulette is a dangerous game.

Yeah, I wouldn't be doing it. Just me though. Also must just be me that I have quite a few lr primers on hand too. When that guy pierces a thin cup primer and screws up his bolt (or worse) he may think twice.

I THINK Beretz and Swifty are correct. As others have said, I'd not do it. Please set us straight if we're wrong.

Primer pocket dimensions and tolerances

Pocket Type Depth Min Depth Max Diameter Min Diameter Max
Small Rifle/Pistol 0.1170 0.1230 0.1730 0.1745
Large Rifle 0.1250 0.1320 0.2085 0.2100
Large Pistol 0.1170 0.1230 0.2085 0.2100

Primer dimensions and tolerances

Primer Type Height Min Height Max Diameter Min Diameter Max
Small Rifle/Pistol 0.1150 0.1260 0.1745 0.1765
Large Rifle 0.1230 0.1360 0.2105 0.2130
Large Pistol 0.1150 0.1260 0.2100 0.2120

Some guys in the BPCR game do this to get gentler ignition on specific loads but they are dealing with low pressure loads & take steps to accommodate the shorter height of the primer, using a paper shim seated under it. Apparently if this step is not taken the primer gets a running start at the breech face & causes damage. I’ve never messed with it, just read it.

Just a guess, but I suspect there are very good reasons why there are both large rifle and large pistol primers.

Me either. Not worth the chance there.

Pistol primers are shorter but they will work. Ross Seyfried loaded 60,000 PSI loads in 45 Colt brass with large pistol primers with zero issues.
If your firing pin is a few thousandths short you I may have ignition issues would be my only concern

I used about a thousand large pistol magnum primers in my 45-70. I guess that the magnum pistol primers are rated for far higher pressures than I would ever put a 45-70 through and had no issues. Standard large pistol primers are usually used in cartridges that put out less than 40,000 psi. The 6.5 Creedmoor probably works at pressures around a third higher than that. No I would use them for that. As for the cups being shorter that made no difference.

He did? 60,000 psi in the 45 colt case? I wouldn't do that either!

I would and have, that is 454 load pressure in a 454 revolver. Been doing it for years.

I don't care for the small rifle primers.

While you are correct about the primers height, I don't think it makes all that much difference.

I use LPM primers in my 458SOCOM which has LP pockets. Without thinking, I used a large rifle primer pocket uniformer to clean the pockets, presumably making the pockets deeper than intended. I reloaded the brass with LPM primers and had no problems.

Pressure concerns are another issue all together.

I don't even use CCI 400s in any small rifle load over 50,000 psi. Prefer a thicker cup.

The guy would be alot better off switching to a Large rifle mag primer than a pistol primer, he's playing with problems i wouldnt want.

Over the years, I've come across several articles testing pressure changes from primer substitutions. Pressure changes of 15,000 psi with relatively little effect on chronographed velocity have been recorded. There is no way I'd play that game with high pressure loads--unless the rifle you're using is exceptionally strong and with the very best gas venting.

Bullshit. You can't push on a bullet 15KPSI harder with the same powder (so same basic burn curve) and get "relatively little" change in velocity without also changing something else (barrel length, bullet weight etc.). The kinetic energy is simply the pressure times bullet cross section integrated over the length of the barrel. More pressure equals more KE/velocity.

For a lot of hunting configurations, the difference from 15KPSI will be about 200ft/s although obviously that depends on all sorts of factors.

Leave the bullet mass out of that. The integral for the work done is ∫p(v)dv with dv = cross section area * dl.

Now I'll be really nitpicky: What if the difference in p(v) occurs over a stretch of dl of arbitrarily small measure?