Backed-out Primers?

[FAsmus]

Gentlemen;

In my recent shooting in 30'06 I have been getting backed-out primers in normal cast bullet loads. The primers, after firing, are as much as 0.015 above the base of the cases.

Why is this happening?

What may be done to avoid it in the future?

Good afternoon,
Forrest

[madsenshooter]

Could be for several reasons. You've pushed the shoulder back when resizing, or, the impact of the firing pin, in combination with the explosive force of the primer has pushed the shoulder of the case forward into the chamber increasing headspace. Your low pressure loads then don't produce enough pressure to move the shoulder forward again. This often happens when shooting low pressure loads in bottlenecked cases, that's why I prefer rimmed cartridges, or keeping pressures up around 35,000psi with non-rimmed cartridges. I'll let some others comment on avoiding the problem, keep my head out of the noose, so to speak, and perhaps learn something. Fixing the cases you've already fired, neck them up to 8mm or 35 cal, then back down to 30 cal a bit at a time, adjusting the sizing die downward, until the bolt will just close on the sized case. If the primers are backed out, chances are the cases haven't stretched in the web yet and will be salvageable.

[Doc Highwall]

I agree with madsenshooter, that the shoulder has been pushed back too far when you sized the cases.

[303Guy]

Yup. As madsenshooter says. If you are going to use those same cases for those same light loads then don't worry about it. If you are worried that the cases might eventually strech in the wrong places (near the web) then lightly lube the cases before firing (quite safe at low pressure). If you want to return the cases to the fold then do as madsenshooter suggests. OR you can use another little trick which fine for moderate pressure loads in a strong rifle - lightly lube the cases before firing. This only works if the chamber is clean and smooth and the brass is clean. At higher pressure it won't work. The case might grip the chamber walls just like a clean dry one will. In anycase, it's considered unsafe to fire lubed high pressure cartridges! (No blobs or droplets of lube allowed and most definately no lube drops or blobs in the bore). It does increase the bolt face thrust by a measureable amount.

[John J]

tell us how your sizeing your brass and what is the load your useing

Iv see this happen before from useing a very light load

John J

[FAsmus]

Gentlemen;

The brass is new unsized goods ~ never saw the inside of a FL die, ever. This brass was purchased for the newly acquired M1917 addressed in the thread down there in the Military Rifle sub-site.

This is the second reload of these cases, neck-sized only in the LEE collet dies

I'm going for the idea of a heavy firing pin fall from this M1917 Enfield as the culprit, combined with the typical low-pressure cast bullet loads that will not expand the case back fully.

I will try the lightly lubed case solution to see if they will expand back to full size. Also, I figure to buy an extra firing pin spring and lighten it up by cutting it off little by little until the problem goes away for good, keeping the original spring in hand for when the rifle is ( if ever ) returned to full-pressure jacketed shooting.

This problem ~ for example ~ has never occurred in thousands of rounds of shooting the same load in a M70.

Good morning,
Forrest

[Freightman]

Did you ck the head space? Had a #. 4 mk 1 Enfield do that the first firing but after adjusting the HS with another bolt head it stopped.

[shotman]

Are you useing a Mauser type bolt ?? Old win 70, o3, a3 If you drop the shell in and close bolt it will not lock in the extractor. need to put in mag and feed that way. The cast load does not have pressure to set primer Jackets will set it back in place but you will see a powder burn past the bottle neck try some by feeding out of mag

[Wayne Smith]

Gentlemen, every time you pull the trigger the primer backs out of the case. This phenomon is so universal that John Garand once designed an automatic/semiautomatic action on the principle. Recoil then re-seats the primer.

Given that it happens each time, the question becomes why isn't the case recoiling enough to re-seat the primer? Not enough recoil, maybe?

[Heavy lead]

Low pressure with excessive head space will cause this. Had it happen before.

[deltaenterprizes]

Call the Sierra Bulletsmiths they explained it to me.

[MtGun44]

Fire the brass with a normal load in your gun. This will fit it to the chamber. Then set up
your resizing die to NOT push the shoulder back, just size the neck.

What is happening is that the firing pin pushes the case fwd until the shoulder hits the end
of the chamber, leaving about .015" clearance (in your gun) between the rear of the cartridge
and the bolt face. The primer is pushed out by pressure until it hits the bolt face.
The brass grips the chamber enough and the pressures are low enough that the
brass does not get forced back against the bolt hard enough to reseat the primer.

A full power load does the same, but the pressure is high enough to stretch the brass and
push the primer back in as the brass is forced to hit the bolt face.

You only see this with significant headspace and low pressure loads.

If you fit your brass to your chamber so that the headspace (gap between the back of the
case and bolt when the brass is full forward) is minimal, the primer protrusion will be
minimal, too.

The new brass is set at minimum length and your rifle's chamber is a bit large. No big
deal, just us once fired and NOT FULLY RESIZED (don't set the FL die down to hit the
shell holder) brass for low pressure loads.

Bill

[FAsmus]

MtGun44;

Bill; Fire the brass with a normal load in your gun. This will fit it to the chamber. Then set up your resizing die to NOT push the shoulder back, just size the neck.

F; I say again - I do not FL size except perhaps every 50 reloads on each case. ~ What do you mean by a "normal" load? Are you referring to a jacketed type loading? Or a typical cast bullet load?

Bill; What is happening is that the firing pin pushes the case fwd until the shoulder hits the end of the chamber, leaving about .015" clearance (in your gun) between the rear of the cartridge and the bolt face. The primer is pushed out by pressure until it hits the bolt face. The brass grips the chamber enough and the pressures are low enough that the brass does not get forced back against the bolt hard enough to reseat the primer.

F: Yes, I got that - I asked how to fix it.

Bill; A full power (jacketed?) load does the same, but the pressure is high enough to stretch the brass and push the primer back in as the brass is forced to hit the bolt face.

You only see this with significant headspace and low pressure loads.

If you fit your brass to your chamber so that the headspace (gap between the back of the case and bolt when the brass is full forward) is minimal, the primer protrusion will be minimal, too.

F: Sure, this is clear. My problem is that I don't intend to buy and shoot jacketed bullets or want anything to do with "full power" loads at all: I've been there, done that.

Bill; The new brass is set at minimum length and your rifle's chamber is a bit large. No big deal, just us once fired and NOT FULLY RESIZED (don't set the FL die down to hit the shell holder) brass for low pressure loads.

F: Again - I do not FL size. I think I may have the die around here somewhere but I'd have to go on a search to find it.

My current fix has been to comply with the suggestion of "303 Guy" who said to try oiling the cases before firing them so as to avoid the cases gripping the chamber walls and thus not backing out to re-seat the primers and also not blowing themselves back out and thus creating excess headspace in a correct ( I checked ) chamber.

This method has worked wonderfully well: Thanks 303 Guy.

Good evening,
Forrest

[Ben]

Fairly common with light cast loads in most all bottle neck rimless cartridges. I've never paid much attention to it. Now.........if you're shooting a 50 K jacketed load and it does that, you better start asking some questions.

Ben

[DIRT Farmer]

I was afraid to touch this, but anyway, I have had this with the 10 grn load of Green Dot in my 03-A3 and 1917, I use seperate brass, and aneal (per what I have been reading here ouer aneal)but have solver the problem by oiling the cases the first fireing after resizingand seating the bullit tight to the lands which also seem to give the best groups and using pistol primers.