700 and Factory Primer Cratering

[Tamren]

I just went through a Remington 700 armorer's course and learned some interesting tidbits on 2004 and newer 700's.

In the last few years Remington has been designing there 700's to crater primers on purpose. They've added a very very slight bevel to the firing pin hole so that primer cratering occurs during case expansion. This causes the primer metal to drift forward and thicken at the lip of the cratering and the dome of the firing pin strike. The Remington rep said they even have primer cutaways back at the factory that proves it works.

Normally, cratering comes around from having too much pressure in a hand load and when the case contracts, it hits the bolt face hard enough to bounce the firing pin back and material flows into the firing pin hole.

On a side note, which was news to me but might be common knowledge on THR, Remington has started fluting the 700 firing pins to reduce lock time. The rep thought that the new style firing pins would be comparable in weight and lock time to an aftermarket titanium pins.

 

[Beagle-zebub]

So why would they want to cause this cratering?

 

[GooseGestapo]

I have an older Remington Mod-7 that also craters primers. I noticed that it too has a "chamfered" firing pin hole.

I bought it used (its definitely a pre '04) and thought that some previous owner ill advisedly did that not knowing the ramifications.

I'd planned on rebarreling it and altering the bolt to 6mmPPC, but decided that it's fine as it is. (has 18.5"bbl and gets excellent velocities- has taken 2 dozen + deer so far).

Suprisingly though, my '03 production Rem Mod-7 in 7mm08 dosen't have to recessed firing pin hole.....

 

[Bwana John]

Ive cratered a couple of primers in my M700.

So I backed off a grain or so.

 

[Tamren]

The engineered cratering they came up with actually strengthens the primer, it thickens the metal of the primer at it's weakest point during the initial expansion of the brass.

The cratering from hot reloads occurs after the pressure has started to let off and the brass has contracted and been knocked back against the breech and firing pin hole too violently.

The first one helps, the 2nd one means you need ease off your powder load.

I'm not an engineer in metallurgy and thermo dynamics, so I can't really explain it any better then that.

Bwana John, I'm talking about Remington deliberately causing primer cratering on factory ammo, not cratering from hot reloads.

 

[Slamfire]

I heard about this from a Rem 700 owner. His rifle cratered primers, even with mid level loads. So he called Remington and found out it was a design feature.

I just figured that it made the action less prone to leaking gas down the firing pin shaft in an over pressure situation.