Primer Pocket Leakage

D

deerfarmer

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This has been an on-going pain in the a!@ for me and I'm looking for some opinions here. I have purchased 2 bags of Winchester brass in .270win and both experience gas leakage around primer. This doesn't happen with federal or RP brass that I load - all same charges and projectiles 1 grain below max and all sized the same. The bags of brass were purchased several months apart at different stores so I'm pretty sure they would be different lots. The leakage does happen to varying degrees but the fact that the bolt face is shiny silver makes it very detectable.

I've tried 3 different brands of primers: RP, cci and win
Happens with new full length sized, as well as 1x fired or more, partial full length sized
I normally hand prime, but I've also tried priming in press with same results. Primers seat with normal resistance
Rifle is a Tikka m695. I'm barely bumping the shoulder back in my dies when I re-size if at all.

What gives? Did I get 2 bad bags of brass or is something going on with headspace or something else altogether?

Thanks
 
The primer acts just like the rings on a piston of a internal combustion engine and seals combustion pressure inside the chamber. Your getting blow-by caused by a primer that isn't sealing the primer pocket. If the cases had less internal volume your primers would be flatter from higher pressure "BUT" it doesn't mean the higher pressure would cause the primer to leak around the circumference of the primer.

Photos of the primers would help but it sounds like the primers are too small in diameter or the primer pocket diameter is too large.

Below is what happens when people reload .223 cases with loose primer pockets in their AR15 and they loose the gas seal and have high pressure gas leakage.

coltbolt-1_zpsd2c35141.jpg


You need the primer to provide a good high pressure seal, please notice below how the primer can move when the cartridge is fired. The primer can move to the rear under pressure and is pushed back into contact with the bolt face. Then the chamber pressure builds higher and the cartridge case stretches to meet the bolt face.

HeadClearance_zps03634b1b.gif


You need to find out if the primers are causing the problem or if the primer pockets are defective on your cases.
 
I would start by backing down 3 gn and see if you still have leak. When I shoot hot loads, I can get cases with somewhat loose primer fit, when I check these with pin gauges I find they are 1 thou oversize. With modest loads I never get leak with these cases, despite the sloppy fit. You indicate that the primer fit feels 'Normal' Since your new brass may be stiffer with a smaller internal volume and you are 1gn below max, I would guess your leak is due to high pressure and not an oversized primer pocket.

Source for individual pin gauges:

http://www.meyergage.com/wp-content/uploads/2012/09/Individual-Gage-Pins.pdf

http://www.jamescalhoon.com/primers_and_pressure.php

Large Rifle
Cup Thickness Diameter Height
CCI 200 .027" .2112" .118"
CCI 250 .027" .2113" .118"
Federal 210 .027" .2120" .117"
Remington 9 1/2 .027" .2100" .119"
Winchester LR .027" .2114" .121"

Pocket TypeDepth MinDepth MaxDiameter MinDiameter Max
Small Rifle/Pistol0.11700.12300.17300.1745
Large Rifle0.12500.13200.20850.2100
Large Pistol0.11700.12300.20850.2100
 
bigedp51 said:
The primer acts just like the rings on a piston of a internal combustion engine and seals combustion pressure inside the chamber. Your getting blow-by caused by a primer that isn't sealing the primer pocket. If the cases had less internal volume your primers would be flatter from higher pressure "BUT" it doesn't mean the higher pressure would cause the primer to leak around the circumference of the primer.

Photos of the primers would help but it sounds like the primers are too small in diameter or the primer pocket diameter is too large.

Below is what happens when people reload .223 cases with loose primer pockets in their AR15 and they loose the gas seal and have high pressure gas leakage.

coltbolt-1_zpsd2c35141.jpg


You need the primer to provide a good high pressure seal, please notice below how the primer can move when the cartridge is fired. The primer can move to the rear under pressure and is pushed back into contact with the bolt face. Then the chamber pressure builds higher and the cartridge case stretches to meet the bolt face.

HeadClearance_zps03634b1b.gif


You need to find out if the primers are causing the problem or if the primer pockets are defective on your cases.
Click to expand...






P51, your descriptions and graphics/pics of various reloading topics are incredible! thank you for providing us all with this valuable info.
 
Thanks for all the replies folks - to answer a few questions. I've been measuring the brass and they are at trim to length. I've had leakage with lighter loads as well, and the loads I've been using lately and in past show no sign of pressure. Looking at the chart roberti11 added, I might try the Winchester primers again as it's been a while ... I started a thread a while back regarding having one blow out on me damaging my bolt face. This happened early on in my ownership of the rifle and I've been shy of using them since, but lighting never strikes twice...

http://www.canadiangunnutz.com/forum/showthread.php/917581-Bolt-face-damage-primer-pocket-leak
 
One final point, are your primer pockets 'virgin'? or have you used a uniformer?

I have seen pockets opened up using an out of spec. uniformer or having the uniformer not true to the axis of the case when using it
 
.Ben said:
P51, your descriptions and graphics/pics of various reloading topics are incredible! thank you for providing us all with this valuable info.
Click to expand...

It started thousands of years ago when my ancestors got tired of painting on cave walls and wanted to trade artwork for food and goods.

http://i122.photobucket.com/albums/o254/bigedp51/caveman####_zpscd4a0133.jpg

My wife won't let me trace nude models anymore so now I deal in gun ####. ;)
 
JJ-65 said:
Try a different brand on brass, Winchester has gone for sh!t of late.
Click to expand...

Of late?????

Winchester lost the contract to produce ammunition at Lake City Army Ammunition Plant in 2001. Winchester/Olin sold off its brass manufacturing plant shortly thereafter and its ball powder manufacturing plant to General Dynamics weapons Division. My 30-30 Winchester I bought in 1981 was made by U.S. Repeating Arms Company because Winchester sold the firearms company to the employees. (no one else would buy it)

Today Winchester does make ammunition and someone else makes her brass and powder and Olin also makes chemicals for fertilizer. So you could say the Winchester business has turned to $hit. :rolleyes:
 
Winchester used to be considered about the best of the normal priced brass, but in the last couple of years I have sure heard a lot of complaints about it.
As a point of interest, what are the loads you are using that sometimes leak gas around the primer?
 
H4831 said:
As a point of interest, what are the loads you are using that sometimes leak gas around the primer?
Click to expand...

The testing I've done lately has been done using 110gr vmax's with 58gr of IMR4831. I've had all sorts of projectiles and other powders leak as well at varying pressures. This same load in RP brass is very accurate in my rifle and exhibits no leakage.

I would have bought Remington brass if I could have found it - I really didn't think I'd run into troubles again with win brass to be honest.
 
Dang, I haven't had any problems with my current Winchester brass but based on all these bad reports, I'm afraid to stock up on it. Maybe I'll have to switch to Remington or Federal. (Forget Lapua/Nosler, too much money and I'm cheap)
 
bigedp51 said:
The primer acts just like the rings on a piston of a internal combustion engine and seals combustion pressure inside the chamber. Your getting blow-by caused by a primer that isn't sealing the primer pocket. If the cases had less internal volume your primers would be flatter from higher pressure "BUT" it doesn't mean the higher pressure would cause the primer to leak around the circumference of the primer.

Photos of the primers would help but it sounds like the primers are too small in diameter or the primer pocket diameter is too large.

Below is what happens when people reload .223 cases with loose primer pockets in their AR15 and they loose the gas seal and have high pressure gas leakage.

coltbolt-1_zpsd2c35141.jpg
Click to expand...

That bolt face pic is NASTY!:eek:
 
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