View Full Version : Anyone able to re-index M1 Carbine barrel?
Anyone have the tools available to do this correctly?
My Carbine shoots way right, so I need to max the sight out to the left to zero it. The index lines do line up, but I 'm hoping a re-index may be able to correct this.
If you had a straightness gauge for a .30 carb, that would be great too.
BPTactical
05-19-2015, 10:56
Bent barrel most likely.
Bring that over when you bring the 1911
Bent barrel most likely.
Bring that over when you bring the 1911
Are bent barrels common on the carbine?
Just curious.
Don't know about how common bent barrels are with the carbine, but shooting to the right with the rear sight centered is a very common ailment many people have with their carbines.
It's been addressed many times on the CMP forums but no one to my knowledge has ever offered up a reason why or a fix. Many just shoot to the right so you need to max out the rear sight to the left.
milwaukeeshaker
11-28-2015, 13:22
Waking up old thread to ask if you ever found anyone to redo your carbine barrel?
It's with Bert at BP. Hopefully he can figure something out.
BPTactical
11-30-2015, 20:45
And what I found with Robb's Carbine is......
Pretty normal for what it is IMHO.
Keep in mind the purpose the M1 Carbine was built for, it was a "support" rifle that really was not destined to be for front line troops. It was more of a cooks, truck drivers etc rifle.
It wasn't a riflemans rifle the way the Garand was.
They were built to "Minute of Man" standards and for all intents and purposes, slapped together so quickly that as long as they could get it on the test target by sliding the sight in the dovetail, it was good enough for a cook or truck driver.
My dad carried one for a brief time in Italy and said he would have had better luck throwing it at somebody.
Barrels were often bent from the factory, receivers not bored square and any other of a myriad of QC issues but it went bang and did what it needed to do. Maybe not pretty but it did the job.
Robb's little Carbine is a neat little piece. It was made late 44-early 45 and the barrel is marked "General Motors 45".
There is a high probability it is the original barrel and the finish on the rest of it matches the receiver and barrel.
It could be very well a relatively unmolested survivor.
The barrel/receiver index marks show the barrel is ever so slightly under timed. It may have a bit of an effect but I don't feel it would be enough to make a marked difference.
The stake marks for the rear sight are heavy and deep, making me think they are original.
One thing to consider on the M1 carbine- the operating system is very sensitive to misaligned components, one thing is a hair off and it may cause reliability issues.
Robb stated that this rifle is 100% reliable and when they were built that was more critical than driving tacks. We change much of anything and it may create more issues than we started with.
I am far from an expert on the platform but I did not see anything that said "This is it, fix me!".
Personally I think it is just the nuances of an old warhorse.
That rear sight being offset like that is one of those little things that doesn't really matter - but aggravates me none the less. But thanks for being willing to look at it and give it a try.
milwaukeeshaker
02-23-2016, 17:02
The index lines on the barrel and receiver must line up correctly. That is probably all that can be done. Does the carbine have a deep, blue sky import stamp on the side of the barrel?
No, it was a CMP rifle, not an import.
milwaukeeshaker
02-25-2016, 10:40
Are the index lines on the barrel and receiver aligned perfectly? The reason I was asking about the stamp was that some of the guns were stamped so deep as to make the barrel be out of round.
I've read that about the import stamps also, but that isn't the case on my rifle, no import stamp exists.
The shooting right issue also affected many of the rifles when the CMP offered them up a few years back. I received both a USGI and then an Italian return, both Inlands, and both with the same issue, as did many many others on the CMP boards. I do not believe the issue is manufacturer specific however.
Had BPTactical take a look and he didn't see any issues.
The tic marks on the bottom of the barrel and the receiver are not perfectly lined up but so close they overlap, they're less than a hairs thickness off. Bert & I felt that just wouldn't account for the rifle throwing rounds off to the right as far as it does. Something else is the issue. I can only assume a tweaked barrel, or maybe the receiver/barrel interface wasn't square, but that's just a SWAG on my part.
I've researched the issue quite a bit, I've done a lot of reading but have never discovered any conclusions about why this affects so many M1 Carbines.
Just found this: http://pacifictoolandgauge.com/bore-straightness-gauge/9206-204-ruger-1975-bore-straightness-gauge.html#/528-gauge_tolerances_-_001/1112-choose_caliber_a_diameter-308_win_762_x_51_2978
It's a bore straightness gauge. Hey Bert, I take it that if this gauge doesn't slide down the bore you use the patented "crook in the tree" or 5lb hammer method to tweak the barrel until it does?
I have access to a good 20 ton press. Just saying.
Sent from my SM-G900P using Tapatalk
FWIW - my Inland and IBM carbines both have to have the rear sight adjusted way to the left.
FWIW - my Inland and IBM carbines both have to have the rear sight adjusted way to the left.
Maybe you want to use my press to straighten those barrels?
[Coffee]
Sent from my SM-G900P using Tapatalk
Maybe you want to use my press to straighten those barrels?
[Coffee]
Sent from my SM-G900P using Tapatalk
Maybe... Just maybe.
milwaukeeshaker
04-19-2016, 14:50
I have over 25 of these carbines and not one of them has this problem. In all my gunsmithing of these rifles I've never had to deal with this problem. Other than the misalignment I could not say what your carbine's problem is. I wish I could help, carbines are great little rifles.
Maybe you want to use my press to straighten those barrels?
[Coffee]
Sent from my SM-G900P using Tapatalk
Hmmm, making a note - "Ray has a press, remember this, I will....."
And FWIW, with my carbines I've always assumed I could just drift the rear sight assembly over a tad in its dovetail to the left, so I could get the windage marks back into the center. Never done it though, it just hasn't bugged me enough yet to do so.
Keep in mind these carbines weren't built with adjustable sights originally, they had 2-position flipper sights and the type 2 & 3 adjustable rear sights were late-war field upgrades. That might have something to do with it too.
BPTactical
04-19-2016, 20:00
10 pound hammer Robb
10 pound hammer Robb
Oh, you gunsmiths - always gotta be so delicate!
http://i18.photobucket.com/albums/b150/rinselman/garage/DSCN1243.jpg
Going to add to a long dead thread.
Visited ChuckinDenver yesterday. He's basically known for milsurp work I believe. He felt the barrels were bent, said he could see it. I couldn't . He chucked them up in a vise and leaned on them, eye'd them, repeated a few times and handed them back to me.
Hopefully that's the answer, haven't shot them yet but I will re-zero and I'll report back.
Powered by vBulletin® Version 4.2.3 Copyright © 2026 vBulletin Solutions, Inc. All rights reserved.