Yesterday at my local gun shop I picked up a 1909 Argentine custom mauser built by Duane Wiebe. I just had to play with it, aim it, dry fire it.
For the first time in my life, I watched a Mauser firing pin fall on an empty chamber and the bolt didn't move. Not even wiggle. Not the cocking piece (after it moved forward of course), not the bolt body or the handle, not the shroud. Nothing. I mean it was dead stable. I've always seen the bolt move when dry firing Mausers, Springfields, Enfields, even Winchesters. But this one was perfect.
So how do you make that happen? Does a rifle with a bolt that moves after the firing pin falls have poorer accuracy?
I just can't get that thing out of my head. Somebody help me before I go and blow 11 large on a gun.

If you care to, please e-mail me at cgrs@earthlink.net.

Look at the bottom of the cocking piece and imagine the things that might cause twist as it moves forward.

More often than not the bolt is not correctly aligned with the firing pin so the camming surface on the firing pin strikes the bolt body causing the bolt to torque. A poorly fitted bolt handle often is the source of bolt movement on firing. I'm confident you'll never seen anything like that on a rifle built by Mr. Wiebe.

Toomanytools...well, thanks for the vote of confidence....never? Oh I dunno!

quote:

Originally posted by Toomany Tools:
More often than not the bolt is not correctly aligned with the firing pin so the camming surface on the firing pin strikes the bolt body causing the bolt to torque. A poorly fitted bolt handle often is the source of bolt movement on firing. I'm confident you'll never seen anything like that on a rifle built by Mr. Wiebe.

Exactly.

As it was explained to me when I was young (and God was still trying to find time to design dirt the inside of a Mauser bolt is engineered so that it cannot fire if the bolt is not completely closed. That was done by putting shoulders on the firing pin and cams on the inside of the bolt. Thus, if the bolt is turned almost but not quite completely closed, the firing pin shoulders will strike the cams and close it the rest of the way before striking the cartridge primer.

Likewise, if through tolerances or poor workmanship (or whatever), the bolt is rotated too far closed prior to firing, then the firing pin will very slightly open the bolt before hitting the cartridge primer.

Either way, the bolt lugs end up where they are intended to be before the cartridge goes "boom".


It may not be correct, but that's the way I've always heard it.

Sounds as if you came upon one where the "tolerance stack"in manufacture puts it in perfect position and alignment when the bolt is closed.

I am no gunsmith but if you ask me, the cocking piece or sear is spring loaded against the trigger, ie the thing that releases the firing pin, this bears ultimately on the bolt, which can be canted and this is why when people convert say a remmy 700 action for bench rest they sleeve the action, this takes the play out between the bolt and the action. so that when the firing pin drops there is no cant or movement in the bolt at the moment of firing that could be a detriment to accuracy. I may be blowing hot air but that is the best answer I can think of

The slop in the rear bridge causes the rear of bolt to drop when the trigger is pulled causing the bolt handle that is closed all the way to lift up a slight amount. If the rear bridge has been welded on then it has shrunk a little minimizing this bolt handle pop. If the handle isn't inlet all the way after customizing then the nose of the cocking piece can contact the helix in the bolt body keeping this from popping up. Usually the handles are inlet until the safety will engage. Another brain teaser is thinking about the direction the main spring is wound. Would it make a difference???

quote:

Originally posted :
I am no gunsmith but if you ask me, the cocking piece or sear is spring loaded against the trigger, ie the thing that releases the firing pin, this bears ultimately on the bolt, which can be canted and this is why when people convert say a remmy 700 action for bench rest they sleeve the action, this takes the play out between the bolt and the action. so that when the firing pin drops there is no cant or movement in the bolt at the moment of firing that could be a detriment to accuracy. I may be blowing hot air but that is the best answer I can think of

Not quite. First of all, Remington triggers and Mauser triggers work in quite different ways.

Remington triggers are basically over-ride triggers. That is, the cocking piece in a Remington bolt pushes down on the sear portion of the trigger assembly. The sear is propped up by a lever so that the cocking piece can't push it down and there isn't enough room for the cocking piece to slide over it and forward. In trying to push the sear down, it does push the cocking-piece (and the back of the bolt) up slightly. The amount depends on the clearance between the bolt exterior and the inside of the action. Pulling the trigger moves the various trigger levers, which removes the prop from under the sear. Then the sear can be pushed down (over-ridden) by the cocking piece, allowing the cocking piece and the firing pin to go forward.

The Mauser, on the other hand, comes with a trigger/sear assembly where the top of the trigger rides on the bottom of the action, not the bolt or the cocking piece. The "bumps" on he top of a Mauser trigger ride on the bottom of the action, not the bolt. The vertical front of the cocking piece is "caught" by the vertical back of the sear. The top of the sear need not touch the bottom of the bolt at all. The trigger, when pulled, acts as a lever which pulls the sear down out of the way of the cocking piece. If the sear is very slightly off vertical towards the rear, it would actually act as a hook and pull the cocking piece very slightly downward as it was being moved down and eventually out of the way of the cocking piece.

Anyhow, for those who want to see a full explanation of what is happening with the Mauser or Springfield type firing pin, and why letting it go forward acts to slightly close or open an action, I suggest turning to Page 44 of "The Mauser Bolt Actions - A Shop Manual" by Jerry Kuhnhausen, available through Brownells and other sources. It explains that the firing pin only lines up perfectly with the inside of the bolt if the bolt is rotated 90 degrees on closure. If the bolt is rotated 85.5 degrees or more, but not a full 90 degrees, the firing pin will close it the rest of the way when it hits the bolt some .010" to .020" before the tip of the firing pin protrudes ANY distance out of the firing pin hole in the bolt face. It will also open the bolt just a hair, to the proper 90 degrees, if it is over-rotated to somewhere between 90 degrees and 94.5 degrees on manual closure.

Best wishes all.

I wish I spoke gunsmith.

So it looks like we now know why it does it but now the question is does it really matter? Any adverse side affects?

til later

I have 6 Winchester Classic Model 70 Rifles. On every single one of them the bolt jumps up when it is fired. And I have looked at countless other Model 70 Classics that do the same thing. I wonder if Winchester made them that way on purpose?

quote:

Originally posted by EP:
So it looks like we now know why it does it but now the question is does it really matter? Any adverse side affects?

til later

Having the bolt handle move slightly up or down when you "drop the hammer" only matters when you are shooting for scores and money. Having one that doesn't move on a custom built gun is a testament to ones skill and attention to detail.

quote:

Originally posted by 22WRF:
I have 6 Winchester Classic Model 70 Rifles. On every single one of them the bolt jumps up when it is fired. And I have looked at countless other Model 70 Classics that do the same thing. I wonder if Winchester made them that way on purpose?

I would guess that Winchester did make them that way on purpose. If I was manufacturing Model 70-type firearms, I certainly would.

First off, let's stipulate that no company making lots of rifles daily is going to make them all perfectly. They will have deviations from perfection as a daily part of life. Acceptably small deviations are what we call acceptable "tolerances".

So, if you are going to have variations from perfection with a bolt holding in a fragile brass vessel which prevents the flow back of 50,000+ p.s.i. of hot gas, powder fragments, and tiny bits of brass, you would probably want to make sure that the bolt always closed a little too far rather than not quite enough. So, probably, did Winchester.

If you over-rotate the bolt closed (close it a little too far), and then the firing pin moves it back to nearly perfect alignment when the pin falls, the bolt handle will jump up. That's because for the bolt to over-rotate closed any at all, the root of the bolt handle has to end up just a hair too far "down" when the bolt is closed by your (or anyone's) hand.

That way too, it IS very safely closed pretty much whenever one shuts the bolt, even if some dirt got in there and kept it from over-rotating.

It's a good compromise. As WestPac so correctly noted, for war or hunting, or even High Power competition, the "jump" either up or down won't materially hurt acuracy for most shooters. And it may contribute to shooter safety if a little over-rotation occurs as a matter of course.

I have seen this happen on many, many bolt guns.
The firing pin drops and goes whack. There is a vibration of the spring and firing pin assembly. If the bolt is closed against the handle the only way for it to move in response to the vibrational energy is to move the handle up.
Check a Lee-Enfield. It has none of the internal shoulders. It is a cock on closing action. When the firing pin slams down there are no cams in contact. The impact vibration just causes the handle to jump up....because it can't go down.

quote:

Originally posted by Mike_Dettorre:
I wish I spoke gunsmith.

I know what you you mean! Best I can tell, the thingy that holds the firing pin has to be in perfect alignment with the other thingy and the firing pin has thingies on it that jolt the bolt if it isn't lined up perfect with the aforementioned firing pin thingies. Right?

I'm with EP.
It appears we've uncovered another one of the many ingenious safety features of the Mauser-based actions.
Now, does it cause problems with accuracy, bolt or action wear, case life, etc.?
My guess is that it would be pretty hard to substantiate anyway.
With regard to making the condition go away, I've just learned in a private message from the gunsmith who made the very rifle over which I was marveling that it can be remedied. In other words, very talented guys can make the bolt not move when the hammer falls.

You remove bolt bounce by adding material to, or removing material from the bottom of the bolt handle where it contacts the receiver. Essentially you are carefully aligning the cocking notch with the "groove" so as to pevent the handle from moving when the cocking piece falls. It's actually a fairly simple procedure in practice, but an often over looked bit of detail when fitting a new bolt handle to a receiver.

It just took 5 layers of electrical tape stuck to the underside of the bolt on my Mod24b Mauser to stop any bolt movement up or down. Not a whole lot of movement to begin with.

til later

tiggertate , I couldn't have said it better myself! That was funny!

Usually this is a problem that does not exist.
We look at it dryfire and worry and scratch our heads.
Insert an empty case, pull the trigger.
This usually gives worried shooters rest and peace.

Tigger,

I have found when my bolt is completed inserted into a thingy and someone trips my trigger, that there is usually a lot of twitching and movement of the bolt going on.

It has never been a problem. As a matter of fact it seems to be quite enjoyable and a condition that I try to repeat often.

Also since, I had the magazine "cut-off" permanently installed it really doesn't matter how accurate I am; I will never score an XX or for that matter an XY again as my gun is now only capable of dry firing.