Home Forums Reloading Big Game Rifles Reaming primer pockets too deep

I'd like to run something past experienced reloaders who may have seen or heard of this. I used the Sinclair Primer Pocket Uniforming tool to clean up new primer pockets of 300 RUM brass.

http://www.sinclairintl.com/reloadi...-primer-pocket-uniformers-prod34720.aspx

During initial load development with CCI 250's I had several primer hits that did not ignite the powder until the 2nd primer strike.

Once I settled on a powder charge and seating depth, I decided to test other primers; Fed215M, Rem 9-1/2 and WLRM; ten each.

CCI 250 = all fired but several needed 2nd strikes
Fed215M= 100% fired
Rem 9-1/2 = 100% fired
WLRM = 5 would not fire even with multiple firing pin strikes

I tore the bolt apart and all seemed in place with the firing pin protruding about .054".

I sent the rifle to my gunsmith whole built the rifle and his finding on the bolt, headspace were all within spec.

He then primed several dozen virgin, fired or sized cases and got 100% ignition with both CCI and WLRM primers.

He did note that the seated primers measured .085" to .09" below flush.

The only difference we could come up with is I used the Sincliar hand priming tool and he used his Hornady press for priming duties. I'm wondering if the Sincliar tool puts a lot of pressure on the primer, seating with a bit of "crush". Also wondering if the Sinclair primer pocket clean up tool could have somehow reamed out the pockets too deep.

Your experiences please.

Alan

That is kinda deep.

Don't you mean .0085" to .009"? .09" is 3/32", that's nearly double the firing pin projection on most rifles. My Sinclair tool had a depth stop on it, I never measured the depth of seated primers but doubt it was as much as you're getting. If your priming tool were putting so much crush on the primers as you suggest I would expect you'r be getting some detonations while priming. If you exert excessive force when priming, you may be pushing the primer's anvil through the priming compound and up against the inner surface of the priming cup. This could explain your failures to fire. Hope you find the answer to your problem.

I think I have figured it out.

I took some virgin Nosler brass and measured the primer pocket depth = .126" to .127" deep.

I took the brass which had the pockets reamed out using the Sinclair Uniforming tool = .130" to .132"

That means on a worse case scenario the difference is .006" and the best is .003"

When I first started load development with uniformed pockets, I was using the press mounted Forster priming device on top and, I just checked, the primers are .006" deep. I wasn't getting near the ignition failures when thusly seated.

I later received the Sinclair tool, adjusted at the factory, which is seating them .000" or flush.

My gunsmith's priming efforts was bottoming out the primers, 008" to .01" deep. So he was getting the primers down deep, agains the bottom and the primers had no where to go when hit.

I measured some primer heights with the anvils sticking out like they come ready to go and am getting .120" to .129" with the Winchesters (the best primer for accuracy and SD but the worst for ignition) and .126" to .127" for the CCI's (a bit better than the Win primer, but not by much)

I think my problem is with the flush seated primer, the firing pin is having to push the primer "IN" to the pocket, before it bottoms out (with the Winchesters) as much as .012", before it hits bottom and starts to resist any deeper seating and the anvil would crush into the primer mix. Glen Zediker would say that's a lot of "real estate" to cover.

So, i'm guessing the culprit is the Sinclair uniforming tool is reaming the pockets too deep. I suppose it could be used in the future to square up the bottom edges of the pockets but don't use it to deepen them.

Opinions?

Alan

Had the same problem with the Sinclair uniforming tool. The Federal 215's were seating to .008-.010. No misfires, but according to the experts they were to deep. I now just square up the bottom (very light pressure on the tool) and clean with a primer brush after tumbling. the primers seat to ,003-.005 just under flush and everything is good. SD's under 10 fps.

That's a good depth.

Primers are designed so that the anvil is proud of the cup, then when seated, the anvil and cup are flush with each other and in contact with the outer edges of the pocket, the necessary depth to compress the priming compound to 'preload' it is .005" below flush, .003" is minimum contact.
This is why I have NEVER bothered to 'uniform' pockets, they always seem to go too deep and cause issues.
I deburr flash holes, this makes a bigger difference than whether the primer pocket is flat.

Cheers.

Spec for large rifle primer pockets is .128" to .132", so your Sinclair tool seems fine. If you're getting .002" depth differences pocket to pocket, you may want to improve your technique using the tool.

The primer is always to be seated firmly against the bottom of the pocket. With an in-spec pocket and an in-spec primer, .008" depth should not be a problem if the primer is firmly seated in the pocket.

Where you can run into trouble, even with the primer end of things ship shape, is with too much headspace clearance.