Bolt Machining

10 fingers · Sep 26, 2022

I will be manufacturing a Mauser style bolt from scratch. Bolt body diameter to slip fit receiver with .001-.002 clearance. Easily achievable with my company's precision tool room machinery. Stumped on how to extend the body diameter axially between the locking lugs. Is this surface broached in production? Please, experienced replies only.

michiganbuck · Sep 26, 2022

QT Op:

(Please, experienced replies only.)
Guess that leaves me out...

wesg · Sep 26, 2022

Me too. Other than several internal action wrenches. I relieved them with a series of flats. Evenly spaced so they look nice ...

If it just HAS to be perfect, dress a wheel and grind it. I've seen it done on punches, but they only had to be dimensionally 'perfect', not cosmetic.

No doubt obvious, but it bears on nothing in the receiver when locked.

michiganbuck · Sep 26, 2022

wesg said:
Me too. Other than several internal action wrenches. I relieved them with a series of flats. Evenly spaced so they look nice ...

If it just HAS to be perfect, dress a wheel and grind it. I've seen it done on punches, but they only had to be dimensionally 'perfect', not cosmetic.

No doubt obvious, but it bears on nothing in the receiver when locked.

Agree wesg, dress a concave radius in a wheel and after milling to near to, go in with that wheel and grind down to a grease pencil mark.
For high production make or buy a female radius cutter to the diameter chosen.

I would question .001" clearance. I have a new condition 98 and know it has more clearance than that. I would not like to be standing in front of a buffalo with .001 or .002 clearance.

10 fingers · Sep 26, 2022

wesg said:
Me too. Other than several internal action wrenches. I relieved them with a series of flats. Evenly spaced so they look nice ...

If it just HAS to be perfect, dress a wheel and grind it. I've seen it done on punches, but they only had to be dimensionally 'perfect', not cosmetic.

No doubt obvious, but it bears on nothing in the receiver when locked.

Thanks for the suggestion. Parallels what I had in mind. After milling flats, may try to blend with suitable files. Then jewel bolt to blend surface finishes. From visits years ago, can't recall how manufacturers machined bolts in production. Measuring multiple samples, tolerance spread surprises me. My intent is unique.

john.k · Sep 27, 2022

Friend of mine who did prototypes was asked to make a missing bolt ,like a Mauser bolt...........anyhoo,I showed him a Mauser extractor ,and he quickly changed his mind and said no................although the extractor is probably the trickiest part.

10 fingers · Sep 27, 2022

john.k said:
Friend of mine who did prototypes was asked to make a missing bolt ,like a Mauser bolt...........anyhoo,I showed him a Mauser extractor ,and he quickly changed his mind and said no................although the extractor is probably the trickiest part.

Some tasks are best left to professionals. Mounting a scope or assembling an AR doesn't make you a gunsmith.

akajun · Sep 27, 2022

Id go higher on the clearance and simply leave the clearance on the bolt where it engages the receiver tight, like .001 aka "borden bumps" even on bolts Ive ordered from ptg if I get them tight, I flute them to give running clearance. Doesn't take much of a piece of dirt or metal flake to bind up a bolt.

michiganbuck · Sep 27, 2022

I have 4 Mauser action guns 3 are 8mm and one O6 and they all crimp down a little on a new bullet case. The 06 is a match-grade gun but I just use it as a shooter.
I can feel a little resistance closing on a fresh new bullet. Putting the bullet in the second time that little resistance diminishes. The locking lugs send the case too tight in the breach so the bolt clearance doesn't matter much at all. Super tight might be a better feel on the bench as long as it did not lock up from heat..out in the bush sloppy is likely better.

akajun · Sep 27, 2022

Sounds like a tight chambered rifle
The tight lockup when closed via Borden bumps does two things
Keeps your case heads square upon firing
And keeps the trigger /sear from pushing the bolt up in the raceway giving more repetitive ignition

wesg · Sep 27, 2022

I have instructions with one of my actions ...

"Do NOT use the action as a sizing die. It WILL gall the lugs. Size the cases to .002 clearance minimum."

Bolt head is 17-4, lug insert is 4340 I think.

The other is: "If the case won't extract, DO NOT beat on the bolt handle, it WILL break off. If it does, send it to me, I can fix it".

Sadly, he no longer can ...

Some of them, Remington coming to mind, the bolt head is a separate piece brazed into the bolt body. So it's machined a tick under and ignored after the fact. Or that's the push feed M-70's? I think one of them is 2 piece, body and handle, and the other 3.

10 fingers · Sep 27, 2022

michiganbuck said:
............................all crimp down a little on a new bullet case.

I prefer to use verified, head space gages. As does any respected gunsmith. May require modification of bolt face, chamber, or barrel shoulder.

shutinlead · Sep 28, 2022

TF,
I have a project in the works right now doing similar to what you are asking about. It's a single shot rf, building it on one of G. Breiling's cut receivers. The bolt is copying features of a 40X, a Vudoo, with some of my ideas thrown in.
The question you ask if I understand correctly is how do you cut the diameter between the lugs? An indexing fixture using either a shaper or vertical slotter was the old school method. I've done that on a couple Mauser bolts in the past. The shaper worked best because of the guide rib and the safety lug - there is a lot of "round" cut that can't be turned. My most recent build was using a dividing head and a small endmill. I machined it close - within about .002 and then used small files and stones to finish the fit, smoking it with a lamp to mark it. I finished the fitting last evening and it won't quite hold back water but it's close. The rest of the bolt body isn't quite as close as I had hoped (the simple part) but it slides together with no binding but not much room for dirt and grime either- it won't be shot in a clean room so I'm sure more clearances will be needed. Be careful on what tolerances you decide on.
I didn't take pictures the other evening when I had it in the mill but I put the semi-finished bolt back in the dividing head to make a point. There's a picture or two of the fitting the bolt and finally of a Mauser bolt I did a few years back.
My 2¢ for what it's worth.
Greg

10 fingers · Sep 29, 2022

shutinlead said:
TF,
I have a project in the works right now........

Greg, Sincere thanks for the helpful reply and photos. Gives me confidence in moving ahead.
For reference, the firearm in question is my deceased father's. Is a magnificent custom he built attending gunsmithing school where he studied under P.O. Ackley. The rife was well used before he modified it and shot a LOT of deer in the many years that followed. The bolt is now so loose in the receiver the sear unreliably engages the firing pin tang. At about 13 years old he entrusted me to carry it hunting. End of day, unloading the rifle it discharged blowing a crater between my feet. Well reinforced Hunter Safety lessons on muzzle control. As manager in a local machine tool company he lacked the personal machery to correct the flaw. I am blessed with owning a company of my own with suitable means, but not the knowledge base of professional gunsmithing. Thanks again. -don

triumph406 · Sep 29, 2022

10 fingers said:
Some tasks are best left to professionals. Mounting a scope or assembling an AR doesn't make you a gunsmith.

10 fingers said:
I am blessed with owning a company of my own with suitable means, but not the knowledge base of professional gunsmithing. Thanks again. -don

Better leave it to the profesionals.......

wesg · Sep 30, 2022

Fix the sear/trigger.

michiganbuck · Sep 30, 2022

I am not a gunsmith but I could likely make any machined gun part in my shop. choosing the materials and heat treat scares me. I think one should apprentice under a gunsmith, or take a gunsmith course before working on other people's guns for other than simple stuff.

deltaenterprizes · Oct 1, 2022

I am working on a similar project but on a smaller scale.
The bolts that I am working on are for a Spanish Destroyer Carbine.
I plan to use a dividing head and an end mill and I have a corner radius cutter to do the finish cuts.
I have a test part blanked out to work out the kinks.
I am making the bolt in 2 pieces, the handle separate from the body and will silver solder them together.

wesg · Oct 1, 2022

My Dad had an AD with a sporterized Swede. It has one of the low profile safeties in it to clear the scope, and a Timney trigger.

He had it loaded, safety on, carrying it at his side, and diddling the trigger for whatever reason. He heard or felt a click, and waited until he met up with his hunting partner before trying to unload it. Pointed in a safe direction, it went off when he flipped the safety off so he could open the bolt.

With the playing around I've done building my own rifles, he suggested I take it and see if I could fix it. I couldn't duplicate what had happened to him.

The safety cams the striker back clear of the trigger. Or it's supposed to anyway. I think there's evidence it had been 'fitted' when it was installed, some filing on the cam surface. So maybe a tick too much, or it wore in a bit. Or maybe some dirt in there that had the trigger loaded.

Anyway, it won't get a rd in it until I figure out what the problem is and fix it.

michiganbuck · Oct 1, 2022

My dad who was a gun trader had at least 3 or 4 guns that would go off with loading or racking through shells. He would take them down and wholesale them to Wessels (in Detroit) where the gunsmith would fix or trash them.

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