Pinning 1928A1 Cutt's

[Mywifesgunakillme]

New Member on the forum. I apologize up front if this has been discussed in length in the past, but I have been unable to locate any previous discussion in regards to pinning a Cutt's onto a 1928a1 barrel. I bought a new old stock USGI smooth barrel to replace the old worn out one currently on my Thompson. It's a shooter, so I'm not hurting the value by removing the original. Once the barrel was removed, I knocked out the retaining pin on the Cutt's and noticed a groove in the thread area for the retaining pin. The groove looks very clean cut and done at a factory. My new barrel has the threads, but doesn't have the pin groove pre-cut. What is the correct way to reinstall the Cutt's on the new barrel? I can't imagine you'd just beat the pin into the threads until it submits! I have read I need to install the barrel first, then install the Cutts's as the barrel doesn't have specific torque specifications and If you put the Cutt's on first it may not line up correctly once installed. Any advice you guys can give me with this process would be greatly appreciated.

[Mywifesgunakillme]

Also wanted to add that the Cutt's seemed to be a bit difficult to thread onto the new barrel. It is definitely easier to get started by hand and turned a few rotations on the old barrel vise the new one. I don't wan to screw up the threads on either the Cutt's or the barrel. It seems to engage the first thread and go maybe about 1/3 rotation before it starts getting real tight. Putting the Cutt's on the old barrel, I can get a few full rotations before it gets too tight for hand turning. Has anyone experienced this before? All parts are USGI, so no issue between new manufacture items and old surplus.

[Gio]

You want to put the barrel on first getting it tight. Then put some locktight on the threads of Cutts and screw in place and get inline I have used a string to get it inline with the rear site. Let the locktight dry then run a drill through Cutts pin hole. Drilling should be easy as you are drilling mostly threads. Put you pin back in and your done.

 

That is the way I have done them and had good luck. I'm sure their are other ways but I stick with what works for me.

 

Good luck

Frank

[bob241]

I did one the same way that Gio advised in above post, use a .140 drill bit to drill thru the comp. also you probly damaged the threads of the comp when you took it off, some members advise to cut four small slots in the old barrel threads 90 degrees apart from front to rear, this will act ad a tap, then screw to comp back on the old barrel a couple of times, this should clean up the threads , also apply a little lube when threading on the old barrel.

[Mywifesgunakillme]

Perfect, I'll let you know how it works out. Thanks guys!

[mnshooter]

Only one third of a turn isn't much. Don't try to force it.

 

I've tried the use of a scrap barrel with perfect threads, modified as a tap.

 

Maybe worked for others; didn't work for me.

 

Probably depends on how bad the threads are messed up in the tap.

 

As far as the final fit, if you can, get to the range and test fire to determine if you might want the comp

slightly left or right to correct for windage. A tiny bit of turn won't be noticed by most.

Loc Tite in place with the desired correction, then get drilled for the pin.

 

The other option, if you want perfect windage, is to weld in the rear sight notch, and recut with a windage correction.

If you have enough skill to do that, you sure don't need any advice from me.

Edited November 13, 2015 by mnshooter

[Mywifesgunakillme]

The use of the old barrel as a modified tap worked like a charm! It went on with a little bit of extra leverage beyond the use of my hands. I used some Loc Tite to set in place. I eyeballed it into place and it looks good to me. I will let it sit overnight and drill out the pin hole tomorrow. I am really pleased thus far and can't wait to get it out to the range! Thanks for all of the advise! BTW I'm in the market for a nice "L" drum. If anyone has one for sale let me know. Also a vertical foregrip if anyone has a lead on one. I know the foregrips are really difficult to find. I can live with a repro if you have suggestions to the best made out there. Thanks again. I will be a regular here on the forum!

[AlexanderA]

I would disagree with drilling the barrel through the Cutts pin hole. It's very difficult to keep the drill straight from one side to the other. It tends to go up, following the curvature of the threads. What you want to end up with is a notch in the threaded portion.

 

Following my experience, here's what I would recommend: After installing the barrel as tightly as possible in the receiver, screw on the Cutts, with a wrench, as far as possible, then back it off until the sights align. (Hold the barrel with your barrel wrench so it doesn't by chance loosen in the receiver while working on the Cutts.) Then drill slightly from both sides of the Cutts, just to mark where the ends of the notch should be. Remove the Cutts, and cut the notch using a rotary file in a Dremel tool, or simply by using a round needle file. Reinstall the Cutts to the exact same position, and check that there's a clear hole all the way from side to side. Then drive in the retaining pin, making sure it protrudes equally on both sides.

[Mywifesgunakillme]

I had envisioned the same thing happening with the drill as you described (riding high on the threads). I think I will use a small round hand file to get the desired finish. Thanks for all the tips.

[reconbob]

In the course of making the guns here and fitting hundreds of barrels and

compensators Gios recommendation is the way to go. Comp fitted with lock

Title or epoxy and position with the sight at 12 o'clock. Drill thru with a 9/64"

drill - this is easily done with a hand (electric) drill - you put oil on the drill,

the existing hole in the comp acts as a guide. I have never had the drill go

wrong. The exception would be if your new hole is almost exactly where

the previous hole is. In this case you turn the comp on an extra turn or two

so you are drilling more steel and less air.

By attempting to independently cut the 1/2 circle in the barrel to accept

the pin you are setting yourself up for the comp and sight to move one way

or the other unless the recess you make is perfect. You are spending a lot

more time and asking for trouble. However, if you will be more comfortable

knowing that you fussed with this for a hour and that therefore the sight was

fitted as a "craftsman" would then go for it.

 

My $0.02

 

Bob

[AlexanderA]

I tried doing it the simple way -- drilling from side to side -- and it didn't work very well. What you are trying to do is drill a tangent along the edge of a circle, and this is an invitation for the drill to wander. What I did was drill carefully from both sides, hoping to meet in the middle. My hole ended up arched (higher in the middle) and the pin, when driven in, was bent. I redid it, the way I described earlier, using a new pin. This time it worked very well.

[buzz]

I'm a real perfectionist about everything like this.

 

If I couldn't figure out a way to get the sight blade exactly at 12:00 top dead center, I wouldn't do the work.

 

as far as drilling the hole goes, I guess I would try to think of a way to use my drill press and vice

 

probably end up giving it reconbob to do, his shop is only about an hour from me