Protruding primers (.30-06, M1) revisited

[khickey3492]

I took some fresh handloads to the range today to see if careful resizing (measuring headspace for each round) made a difference. Here are the details:

Issue: Primers are "set back" (protruding) about 0.004" to 0.006" on cartridges fired.

Cartridge: Springfield .30-06

Brass:New Winchester
1X fired Remington
Headspace measurement to 0.375" shoulder datum line: 2.043" to 2.045"

Primers:CCI #34
Winchester Large Rifle

Powder charge: 45 grains, IMR 4895

Rifle: 5.6M Series H&R Arms M1 Garand (CMP rifle, headspace is "assumed" to be "good" (based on GO, No-GO and Field gauging at CMP)

The fired brass measures less than 2.040" (Headspace measurement to 0.375" shoulder datum line) after firing, it will also slip easily into the Wilson .30-06 case gauge.The brass shows no external signs of stress, e.g bright line at case base or bulging.

The chamber was cleaned meticulously prior to firing these rounds.

What are your thoughts on the protruding primers? I have tried mil-surp ammo (HXP) and it doesn't show any problem becasue of the primer crimp.

Your input is greatly appreciated!

Kevin

 

[sporter]

Primer crimp(s) on the mil brass keeps this from happening, and is the reason it is there.

Your headspace is fine(in my opinion), the primer backing out is from your op rod starting to disengage the bolt a bit too fast before the end of the powder burn.

If you switched to an adjustable gas plug it might help the issue.

 

[sloughfoot]

I spoke with someone who "knows" this last saturday. He stated that your chamber's headspace can be within limits and that the amount of primer protrusion is the amount your chamber is over minimum dimensions.

So your chamber appears to be .004 to .006 over minimum dimension. Nothing to worry about, just shoot it according to Jerry Johnson.

If you want to talk to him directly about it, PM me and will give you his phone number.

 

[Aszerigan]

As long as your pressures aren't causing a primer to back out, you should be ok. But if you're going to use these in a progressive press, you may have a problem getting them into the shell plate. Good luck.

 

[khickey3492]

I spoke with someone who "knows" this last saturday. He stated that your chamber's headspace can be within limits and that the amount of primer protrusion is the amount your chamber is over minimum dimensions.

So your chamber appears to be .004 to .006 over minimum dimension. Nothing to worry about, just shoot it according to Jerry Johnson.

This actually makes sense, my other Garand doesn't exhibit this behavior, but it also sports a new barrel (installed by Mr. Johnson). I think I'll take his advice,as it shows no sign of high chamber pressure.

But if you're going to use these in a progressive press, you may have a problem getting them into the shell plate.

This was one of my initial concerns, but I have been decapping in a single stage press with a generic decapping die. (Lets me examine the primer pocket prior to cleaning and resizing.)

I ran a few across my RL550 and the protrusion did not create a problem. There was enough slack between the shell holder and the base.

Thanks for all the outstanding advice and commentary!

Kevin