Barrel extension/fork slightly bent

Luddite08 · 04-13-2026, 12:48 AM

Hello all,

I have a 1936 Mauser with a slightly bent in fork. It still cycles okay by hand, I haven't shot it yet. To reinstall the breach block I have to slightly spread the fork. Once installed the breachblock does not slide smoothly, as the bend in the fork pinches it slightly.

I found two great posts on this subject, and am waiting on a caliper to measure the fork and see exactly how it is bent, twisted or misaligned.

I'm wondering if anyone can perform the slight unbending service for me, or if anyone who has had the same issue could share their experience and what they did to resolve the issue.

A Google search suggested using a lapping compound and sliding the breach block in and out of the fork. This seemed like a good idea until I took a look at the breachblock and fork rails, the breachblock rails are not flush with the fork rails.

Thanks to all on the forum, I've learned a lot from reading on here!

Bill_in_VA · 04-13-2026, 08:05 AM

That sounds like a good way to crack it in half.

G.T. · 04-13-2026, 11:28 AM

Hi Luddite08 & Bill, It is a risky repair in that the fork can fail at almost anytime during the straightening proceedure? Usually they have cracked long ago, and break when an attempt to straighten is performed by the next guy!!! I can usually straighten the fork without any special tools, but I do have a mounting and holding fixture for the more severly twisted rceivers? It is not for the faint of heart, and success is not for certain... But usually we can win the battle. Best to you both, til...lat'r...GT

velodog455~ · 04-14-2026, 09:00 AM

I think I speak for numerous forum members here that if you want someone to attempt to correct the bend then G.T. is highly regarded on this forum for his technical proficiency and honesty. He did some work for me that was high quality, quickly done, and reasonably priced. Just sayin'
-Bob

wlyon · 04-14-2026, 10:24 AM

Plus 1 above. Bill

ithacaartist · 04-14-2026, 06:31 PM

I agree that G.T. would do a bang-up job with the least risk.

In case you want to take the plunge yourself, I'll relate how I've straightened the barrel extensions of several early Erma toggle pistols without breaking them. They're made of cast ZAMAK, which is much more brittle than steel.

The idea is to reconcile the sides of the extension to be parallel with the part of it that's the chamber while making certain each one is straight unto itself. I have a 1/2" steel bench, which provides a sturdy, flat surface, so start with a similar surface.

Check with a straightedge to see which, and how far the "legs" are out of true, or if the problem is a bow along either leg's length.

If a leg is straight overall, but bent at its root, where it merges with the body of the chamber area, you'll need a shim, between the latter and the bench, that's slightly more than the offset needed. This allows for spring-back of the material when it's released. I use a C clamp placed perhaps a third of the leg's length away from the chamber area to draw it down towards the bench, tightening in increments and checking after each squeeze. You'll notice that bending it just a hair more than straight actually results in a straight piece once the clamp is let off, that's the material's spring-back.

If one or both legs are bowed, straighten it/them by shimming and squeezing with the clamp. When a leg conforms to the straightedge, *then* you can go ahead and reconcile them to the chamber area.

Go slowly, checking after each increment, and you'll soon enough have straightened your barreled upper! Unless the steel is damaged to begin with, you will succeed just fine. If it can be done with Zamak, it can be done with steel!

Kiwi · Yesterday, 09:30 AM

Read G.T.'s post and understand that the part can break no matter who tries the repair. Do not get upset if G.T. tries and it still breaks.
AND as G.T. said it is probably cracked so even if straightened it is likely to fail when you shoot.

A replacement will be in your future unless you never shoot.

04-13-2026, 12:48 AM	#1
Luddite08 New User Join Date: Mar 2026 Location: United states Posts: 1 Thanks: 0 Thanked 0 Times in 0 Posts	Barrel extension/fork slightly bent Hello all, I have a 1936 Mauser with a slightly bent in fork. It still cycles okay by hand, I haven't shot it yet. To reinstall the breach block I have to slightly spread the fork. Once installed the breachblock does not slide smoothly, as the bend in the fork pinches it slightly. I found two great posts on this subject, and am waiting on a caliper to measure the fork and see exactly how it is bent, twisted or misaligned. I'm wondering if anyone can perform the slight unbending service for me, or if anyone who has had the same issue could share their experience and what they did to resolve the issue. A Google search suggested using a lapping compound and sliding the breach block in and out of the fork. This seemed like a good idea until I took a look at the breachblock and fork rails, the breachblock rails are not flush with the fork rails. Thanks to all on the forum, I've learned a lot from reading on here!

04-13-2026, 08:05 AM	#2
Bill_in_VA Lifer Lifetime Forum Patron Join Date: Nov 2013 Location: Southwest Virginia Posts: 410 Thanks: 823 Thanked 623 Times in 225 Posts	That sounds like a good way to crack it in half. __________________ John 8:32 reive (riːv) vb (Military) (intr) dialect Scot and Northern English to go on a plundering raid [variant of reave] ˈreiver n e.g., " Some view the Border Reivers as loveable rogues."

04-13-2026, 11:28 AM	#3
G.T. Lifer Lifetime Forum Patron Join Date: Jun 2002 Location: Chandler Arizona Posts: 3,542 Thanks: 1,342 Thanked 3,750 Times in 1,021 Posts	fork warp! Hi Luddite08 & Bill, It is a risky repair in that the fork can fail at almost anytime during the straightening proceedure? Usually they have cracked long ago, and break when an attempt to straighten is performed by the next guy!!! I can usually straighten the fork without any special tools, but I do have a mounting and holding fixture for the more severly twisted rceivers? It is not for the faint of heart, and success is not for certain... But usually we can win the battle. Best to you both, til...lat'r...GT

04-14-2026, 10:24 AM	#5
wlyon Lifer 2X Lifetime Forum Patron Join Date: May 2005 Location: Somewhere in Montana Posts: 2,677 Thanks: 3,250 Thanked 2,673 Times in 992 Posts	Plus 1 above. Bill __________________ Bill Lyon

04-14-2026, 06:31 PM	#6
ithacaartist Twice a Lifer Lifetime Forum Patron Join Date: Mar 2011 Location: Atop the highest hill in Schuyler County NY Posts: 3,410 Thanks: 7,584 Thanked 2,660 Times in 1,399 Posts	I agree that G.T. would do a bang-up job with the least risk. In case you want to take the plunge yourself, I'll relate how I've straightened the barrel extensions of several early Erma toggle pistols without breaking them. They're made of cast ZAMAK, which is much more brittle than steel. The idea is to reconcile the sides of the extension to be parallel with the part of it that's the chamber while making certain each one is straight unto itself. I have a 1/2" steel bench, which provides a sturdy, flat surface, so start with a similar surface. Check with a straightedge to see which, and how far the "legs" are out of true, or if the problem is a bow along either leg's length. If a leg is straight overall, but bent at its root, where it merges with the body of the chamber area, you'll need a shim, between the latter and the bench, that's slightly more than the offset needed. This allows for spring-back of the material when it's released. I use a C clamp placed perhaps a third of the leg's length away from the chamber area to draw it down towards the bench, tightening in increments and checking after each squeeze. You'll notice that bending it just a hair more than straight actually results in a straight piece once the clamp is let off, that's the material's spring-back. If one or both legs are bowed, straighten it/them by shimming and squeezing with the clamp. When a leg conforms to the straightedge, then you can go ahead and reconcile them to the chamber area. Go slowly, checking after each increment, and you'll soon enough have straightened your barreled upper! Unless the steel is damaged to begin with, you will succeed just fine. If it can be done with Zamak, it can be done with steel! __________________ "... Liberty is the seed and soil, the air and light, the dew and rain of progress, love and joy."-- Robert Greene Ingersoll 1894

04-14-2026, 09:00 AM	#4
velodog455~ User Join Date: Aug 2023 Posts: 105 Thanks: 30 Thanked 98 Times in 55 Posts	I think I speak for numerous forum members here that if you want someone to attempt to correct the bend then G.T. is highly regarded on this forum for his technical proficiency and honesty. He did some work for me that was high quality, quickly done, and reasonably priced. Just sayin' -Bob

Yesterday, 09:30 AM	#7
Kiwi User Join Date: Mar 2019 Location: Wrong side of the Delaware river Posts: 340 Thanks: 242 Thanked 491 Times in 193 Posts	Read G.T.'s post and understand that the part can break no matter who tries the repair. Do not get upset if G.T. tries and it still breaks. AND as G.T. said it is probably cracked so even if straightened it is likely to fail when you shoot. A replacement will be in your future unless you never shoot.