Yesterday's Weapons Forums

The primers are being set back with my Chilean 1912 Mauser. Probably all of my reloads and 16 out of 20 new S&B FMJ. Maybe 1 to 2/100ths. This isn't happening in my Ken Ball Custom Mauser, just the Chilean, so I'm thinking it is the gun and not primer pockets wearing away with reloading.

I don't recall this happening when I first got the gun.

One fix suggested was to have a gunsmith reface and re-seat the barrel just that 1 or 2/100ths deeper. (I assume the 'reface' part is because it is eroding over time?) But doesn't the round index on the shoulder? And even if it indexes on the neck/mouth isn't it the chamber that it indexes against, not the barrel? The chamber is part of the action isn't it? Not part of the barrel?

I wondered if the locking lugs could have worn just enough that the bolt doesn't seat properly against the cartridge. Or is it possible to turn the bolt handle 'almost' closed? Maybe on those 4 factory loads that the primer didn't shift I had snugged the bolt tight?

Is it possible to shim/build up just the 3/8" dia. centre of the bolt, just the part that should be pressing against the primer?

Or is 2/100ths too small to worry about? Just keep shooting and see if it grows to 3/100ths or more?

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Before investing big money in a gunsmith, you could try fireforming cases to that specific rifle.

Using the longest bullets available, seat them out to touch the rifling. When you fire, the case will expand to fill the chamber. (Light loads for this!)

You are then in a neck size only situation, though. SW

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The chamber is in the barrel. .020 is a lot of headspace. When you have a barrel set back they usually do a full thread to keep sights in line. Another way in to expand the neck then using your sizer back off a turn and size case neck till the bolt just closes on it Then is is neck size for that rifle only.

Rad

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Rad's way is better. SW

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Slava Ukraini!!

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Expand a case to 8mm. The bolt shouldn't close. Then run the case into the 7mm FL die... a little at a time... until the bolt will barely close.

When you fire, the shoulder will be moved forward to fill the chamber, and headspace will be corrected - for that rifle only. Neck size only for that specific rifle.

My method of seating the bullet out to touch the rifling does the same thing, but Rad's way gives more consistent results.

Further... when the barrel is set back a full thread to keep sight alignment right, it will have to be rechambered. SW

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Slava Ukraini!!

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Them that know, know that they know. Them that don't know don't know they don't know.

In his book 'Modern reloading" (I think that's the title) Richard Lee gives one of the causes of primer backout as being not enough powder in the case. I had this problem in my Arisaka carbine. Added a grain extra powder and the problem went away.
In any event, this isn't a good thing to have going on. A quick resolution is what is needed.

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David

"We are not interested in the possibilities of defeat; they do not exist"
Victoria 1899

Well I finally got some rounds modified and loaded and got out to the range. No primer backout at all. But also no backout on rounds the I had loaded a year ago and didn't go through the expanding the neck and then carefully bringing it back to 7mm. And I really had to eat my Wheaties to seat these primers. They were really tight. I'm now wondering if the problem originally arose from maybe having a different brand of primers, possibly infinitesimally smaller than standard? God knows I've got several different brands coming with an auction lot when I'm bidding on something else in that lot. The ones I used this time were CCI number 200's.

Anyway, it's all good now!

Thanks guys.

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