Extruded primers

[DrMLap]

I recently purchased a box of .303 Savage ammo from Graf & Sons. These have 150 gr jacketed RN bullets made by Hornady. I fired them in my son-in-law's Savage '98 which I had had thoroughly inspected by my gunsmith before firing anything in it. It shot just fine with no problems except one puzzling anomaly. Every case I ejected had a slightly extruded primer, about .016" to .020". And, oddly enough, the primers do not look flattened, as would be the case with a too powerful load. Indeed, the recoil of the weapon felt nominal. Other than sticking out a little, the fired primers looked normal.

It is my understanding that the headspace on a rimmed cartridge like the .303 Savage is determined by the gap for the rim measured from the face of the bolt. Thus, if the gap is too large or the rim is too thin, I could conceive of primers backing out. The rims on my cartridges measure about .058". The data I found says it should be .063". That doesn't seem to be sufficient to cause my problem. I have nothing with which I can measure the actual headspace of the rifle. I can only assume my gunsmith did that.

And in case someone should ask, yes, the Savage is chambered for .303 Savage and which is stamped on the gun.

So what could be causing my primers to extrude? Do I need to take the Savage back to the gunsmith? Do I need to avoid Hornady ammo in .303 Savage?

I think this mystery needs to be solved before I start reloading .303 Savage.

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[Velzey]

Please post a photo of your bolt face.

 

[DrMLap]

Bolt face, plus images of a typical case head.

 

[DLS]

This can be caused by a low pressure load. Normally, the firing pin drives the cartridge fully forward in the chamber. Then, as the powder begins to burn and increase pressure the case begins to expand.

The forward portion of the case expands the fastest as it is the thinnest here ... and provides the least resistance to expansion. Once the forward portion of the case has expanded enough to grip the chamber wall and stop expanding, the pressure will continue to expand the rest of the case. This pressure works in all directions.

There are a few micro-seconds during the expansion phase of the firing cycle where the back portions of the case are in effect unsupported. They have yet to expand and stick to the chamber walls. This allows the case to stretch in a rearward direction until it impinges upon the bolt face.

When firing the primer is pushed back out of the primer pocket until it impacts the bolt face. Moments later, as the case stretches rearward the primer is in effect reseated in the pocket.

Your situation could be that the pressures are low enough that you don't get the full rearward stretching of the case, so the primer is never "reseated" in it's pocket. This lack of brass stretch, the slightly thin rim, and the slightly overgenerous headspace can add to a result such as what you are seeing.

I hope this helps.

 

[DrMLap]

Thanks, DLS. That's quite a scenario. So, is it safe? Can I shoot these rounds again? Can you see anything other than the usual risk in reloading for this rifle? My main concern is safety.

 

[ConcernedCitizen]

I agree with DLS. Likely a sign of a low pressure load.

 

[DLS]

Perfectly safe, as long as the bullets makes it out he barrel.

Your brass may last longer and have less development of "incipient head seperation" since is has less stretching than a higher pressure load.

 

[DLS]

... I have nothing with which I can measure the actual headspace of the rifle...

Nothing compares to actual headspace guages and a fully stripped bolt when measuring this vital dimension, but you can approximate it on a lever action with bits of aluminum foil and an empty cartridge case.

Insert the case in the chamber and add a prices of foil cut to just under case head size
Keep adding foil disks until you feel a slight increase in chambering effort. This requires a gentle touch to feel the right spot.

Once there measure the stack of disks for height and add the thickness of your cartridge rim. There's you headspace dimention.
This won't work if you have a spring loaded ejector or the action is too rough to feel the chambering difference. I would never use a method like this to proof an unknown gun, but it can be handy in a pinch when a quick measurement might prove useful.

 

[DrMLap]

In all honesty, I should note that I mistakenly identified my rifle as a Savage 98. There is no Savage 98. It's a Savage 99.

Funny no one called me on that.

 

[Certaindeaf]

Hey, there's no such thing as a Savage 98, bub.

 

[DLS]

LOL,

I was thinking 99 as I was reading 98. So much for attention to detail.