Mosin bolt interchangeability

CoverFire said:
Lol I agree, I just read that those gauges being a go gauge, a no go gauge, and a field gauge are just there to see if you can close the bolt fully. With the no to gauge you wont be able to apparently
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Found this.

This is definitely not a recommended practice, but blue 3M masking tape can be used in a pinch and is better than nothing. Strip the bolt.Take a couple rounds of ammo and see if they chamber. If they do, headspace is probably long enough. Next, stick a layer of tape to the rear of the rounds and trim it even with the brass using a razor blade. You want a disc of tape stuck over the primer end of the ammo. See if it chambers now. If it does, add another layer, try again. Eventually the thickness will build up so the bolt only closes with some force. Count the layers. Two random rounds provide an average in case one is slightly out of spec. 1-2 layers, it's probably fine. 3 is probably pushing it and anything more I would definitely get it to a pro with the proper guages.
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CoverFire said:
So what happens let's say if the head gets damaged . How does the owner replace the bolt head and create the appropriate headspace to now shoot safely?
Is this something a gun smith does, can they alter a new or used head to accomadate my barrel /gun ?
It sounds like people are saying you can't use another head not from your gun so the entire barrel is useless without the matching head ?

It kinda sucks having a whole new bolt assembly and having to switch the head over each time. I managed to find a bolt guide which is interchangeable and will replace my bent one shortly but once this new bent handle unit comes in I'd rather keep it as a whole piece and not swap heads. How do I fix this so itll work safely 100% everytime? Gunsmith ?
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If you have headspace gauges, you try multiple bolt heads until one works.
 
OkayShooter said:
Never had a hot knife thru butter, slicker than snot Mosin. Always had some sort of choppiness to the bolt.
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Got to get a Finnish one...you can open the bolt ( empty) , pull the trigger, give it a short sharp jab & watch the bolt glide into the closed ( and fired) position. Trigger is usually better too
 
You should be able to swap out bolt heads and be good. The headspace is dependant on the relationship between the bolt face and the lugs. Keeping the bolt head solves this problem.
 
Perfect. Now I need to find a bolt guide and I have 2 good bolts.

Is there a way to measure the 2 heads and see whats different ? Like is the actual head itself different size or style ? I am reading online trying to understand this topic more but can I not take a micrometer and take critical measurements of the 2 heads to compare?
 
Anybody also know any sites that are reputable ( you guys have used the product) selling headspace gauges. One old fellow who used to make a set for $45 out of stainless passed away and his wife didnt continue the business .
The only site I found was in the states and there 1) $30 per gauge and usually you get the 3 style. Field. No go.. and go. So that's $90!!!! For 1 or 2 times I'll ever have to use it in the guns life and 2) there not shipping to canada due to covid .....
 
CoverFire said:
Perfect. Now I need to find a bolt guide and I have 2 good bolts.

Is there a way to measure the 2 heads and see whats different ? Like is the actual head itself different size or style ? I am reading online trying to understand this topic more but can I not take a micrometer and take critical measurements of the 2 heads to compare?
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So you seem to be lacking a understanding of what determines headspacing.

Headspacing is determined by a couple factors. Basically what you are measuring is the distance between the bolt face and the cut chamber. In the case of a rimmed cartridge it is usually spaced off the rim, which generally means looser tolerances or in the case of a rimless cartridge generally the shoulder of the case.

Since the Mosin Nagant is a rimmed cartridge we shall focus on that. Now there is several factors that come into play, the cut of your chamber, the location your bolt face is in the locked position, where the locked position is in regards to the bolt lugs, and the barrel location.

There are several ways to adjust headspace. The easiest one is changing the bolt head. Depending on where the bolt head locks up and how far forward the face of the bolt head is from the locking lugs, shall adjust the distance between the bolt face and the rim of the cartridge. This shall increase or decrease your headspace accordingly.

Otherways to change your head space are re-cutting the chamber. Re-cutting the chamber and turning a extra thread on the barrel and removing a thread off it. Adjusting the locking recesses on the receiver or barrel (no one does this as it is non-sensical). Adjusting the locking points on the bolt head, and removing material or adding material to the bolt face (these all require re-heat treating and again basically no one does it as it is non-sensical). As you can see by these options the easiest way is to simply change the bolt heads until they work with the gauges.

There is several parts you would have to measure to accurately compare bolt heads, and frankly you can't just measure them with a micrometer. Basically the overall length of the bolt head doesn't really matter for headspace, the distance between the locking lugs and bolt face does. Unlike something like a Lee Enfield which you can simply measure the length of the bolt head (provided you know the measurement required), it doesn't work with a Mosin bolt head due to the recessed face and the locking lugs being on the bolt head as opposed to a Lee Enfield having them on the bolt body.

If your around the Sault Ste. Marie area you can use my set of gauges.
 
Now I understand alot more :) as I said I found a article about this topic I was going to read tonight . Last week was crazy busy, I didnt get a chance too. I appreciate the In depth definition and time spent to type it.
Also I'm located near toronto
 
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