M1 Carbine Barrel Question

[cabezaverde]

I have an M1 Carbine that requires not only the slide, but the entire rear sight be moved quite a bit to the left in order to be windage zeroed.

The gun functions fine and is pretty accurate, but one can readily observe that the front sight is off index (to the point where you see lots of hand guard in the peep sight when sighting).

What methods are available to fix this?

[leftiye]

Index barrel correctly? Sounds like barrel is over tightened. It may be possible to loosen the barrel and re-time it without getting too loose. Rear sight is on a tapered dovetail. If you drive it too far it will deform. So long as you don't mind messing up the sight a little, you could file the dovetail.

[cabezaverde]

The way I am seeing it the barrel would need to be tightened. How would you go about filing the dovetail?

[Larry Gibson]

If the rear sight base is centered and the aperture is all the way to the left for zero the barrel is probably turned in to far......if the barrel isn't bent(?). 1st make sure the rear sight base is centered. then check to see if the front sight is vertical. With the action out of the stock place a straight edge under the flats on the bottom of the receiver. Then from the muzzle end (eye about 3 feet away) see if the front sight is perpendicular to the straight edge. If canted to the right (as you're looking at it from the muzzle) then the barrel is screwed in to far. Loosen the barrel and knurl the barrel shoulder or make a very thin shim so the barrel can't be tightened in as much. The front sight should be perpendicular to the straight edge when the barrel is tightened.

Larry Gibson

[cabezaverde]

Thanks Larry.

The aperture is almost all the way left and the base is drifted significantly left.

[cabezaverde]

Looked at it tonight and I agree over tightened is the problem. What tools are needed to loosen the barrel - is an action wrench required?

[Artful]

M1 Carbine Receiver Wrench with Barrel Block Set for barrel removal
http://www.e-sarcoinc.com/m1carbinereceiverwrenchwithbarrelblocksetforbarrel removal.aspx

[cabezaverde]

Will loosening the barrel have a major effect on headspace?

[gussiegoins2]

Is the front site banned? If so you could heat it lightly with a torch and twist it straight, let it cool and it should hold. Worked for me on a barrel banded sling swivel.

[Larry Gibson]

Is the front site banned? If so you could heat it lightly with a torch and twist it straight, let it cool and it should hold. Worked for me on a barrel banded sling swivel.

M1 Carbine front sights are held on via a milled slot with a "key" in it and a pin through the Key and the front sight. They are what they are.

Larry Gibson

[Larry Gibson]

Will loosening the barrel have a major effect on headspace?

None that you will notice.

Larry Gibson

[leftiye]

If the barrel is overtightened, it may be possible to unscrew it some and have it still be adequately tightened. The issue is that the barrel be tight enough to not wiggle loose. Torque can b very tight or quite loose and not affect accuracy. The carbine barrel has slots for the operating rod to travel in. Turning the barrel a lot can affect the operating rod's alignment on the receiver, so watch for this.