Bolt action mechanics


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rockstar.esq
August 17, 2007, 09:45 PM
So this one's been puzzling me for some time. Why is it that the vast majority of bolt actions are configured as cock on open? There are only two bolt actions that I can think of that are cock on close; the Enfield and one of the earlier Mausers. The Enfields that I've played with were exceedingly easy to operate which I think has a bit to do with the leverage associated with bringing the hands together to cock the rifle. I'm hoping that the collective wisdom here could shed some light on this matter since there's just got to be a reason.

Thanks in advance!

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Nameless_Hobo
August 17, 2007, 11:07 PM
The Mauser action is stronger than the Enfield action, and just fine for hunting, as you don't need the speed provided by the enfield-style. To clear it up a bit, this is why most bolts are cock-on-open, they decended from the Mauser action.

But, I agree with you.
The Lee Enfield is a wonderful, accurate action, I'd prefer it over the Mauser for a general purpose rifle, though, I'd want one build like a modern sporting rifle, in .30-06, .308 or .300 WSM, ect.

Ol` Joe
August 18, 2007, 11:18 AM
I "think" the 1892/96 Mauser type cock on closing was dropped because it was found to be easier to work a bolt from the shoulder with a cock on opening feature. The force needed to close a bolt on a possibly dirty cartridge with a dirty/carboned chamber during a battle often caused one to drop the rifle from his shoulder to gain leverage closing the action. (It is easier to pull a bolt against, then push it away from ones shoulder) This slowed the shooter down at a time when he needed all the speed he could muster.
For hunting either type is fine and the cock on closing can be very smooth as noted.

DMK
August 18, 2007, 12:46 PM
I think it has more to do with convention than anything.
The Mauser action is stronger than the Enfield action
Cock on open, vs cock on closing has nothing to do with receiver or bolt strength. If one gun is stronger than the other, it's for other reasons.

It is easier to pull a bolt against, then push it away from ones shoulderI disagree. Pushing is easier for your muscles to do that pulling is. You can lift more weight in a Bench Press than you can in a Row (even bent over using a bench for support).

SlamFire1
August 18, 2007, 01:03 PM
So this one's been puzzling me for some time. Why is it that the vast majority of bolt actions are configured as cock on open?

The actions you reference were military actions. In period source literature, the British are quoted as saying that cock on closing is an advantage with overpressure ammunition, or hot barrels. And having shot some awful Iraqi ball ammo in Lee Enfields, I would have to agree. When you have overpressure ammunition sometimes you have to beat the bolt open. If you also have to overcome the resistance of the mainspring, well fun, fun, fun.

However, the majority of commerical actions have shorter striker falls and very powerful cocking cams. Assuming you are using ammunition which does not cause sticking, a M70 for example, is almost effort less in the bolt lift. The overall cycling of a M70 is very smooth from lift to closure. Cock on closing requires a good push on the bolt and is not as smooth in rapid fire.

Vern Humphrey
August 18, 2007, 01:41 PM
The chief disadvantage of cock-on-closing is sear engagement. In a cock-on-opening action, rotation of the bolt cams the bent back and holds it back until the bolt is fully forward and turned down, more or less gently lowering the bent onto the sear.

This means a cock-on-opening action doesn't need a lot of sear engagement, and it is easier to get a decent trigger pull.

With a cock-on-closing action, on the other hand, the only thing keeping the rifle from firing as you rotate the bolt into locking position is the sear -- which has to have lots of engagement surface for safety purposes.

Nameless_Hobo
August 18, 2007, 05:39 PM
Cock on open, vs cock on closing has nothing to do with receiver or bolt strength. If one gun is stronger than the other, it's for other reasons.

This has what to do with my statement?
I'm saying that the Mauser action is stronger than the Enfields action, not that cock-on-close is inherently stronger.

DMK
August 18, 2007, 06:19 PM
Quote:
Cock on open, vs cock on closing has nothing to do with receiver or bolt strength. If one gun is stronger than the other, it's for other reasons.


This has what to do with my statement?
I'm saying that the Mauser action is stronger than the Enfields action, not that cock-on-close is inherently stronger.You're the one who brought it up. What does strength have to do with the OP's question?

Nameless_Hobo
August 18, 2007, 06:21 PM
He asked why most bolts are cock-on-open. I said that it came from the prevalence of Mauser-style actions, and stated why Mauser-style actions are popular. It's really rather simple.

rockstar.esq
August 19, 2007, 07:49 PM
I really really appreciate all the answers. Vern Humphery's answer seems the most likely reason that newly introduced rifles are set up this way. I have to wonder if anyone ever made a bolt action that half cocked the bolt on open and half cocked on close. Seems like it'd require less effort to operate than either design. I could see that being something of a selling point on rifles designed for small folks or the tactical crowd - high speed low drag and all.

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