M1 Carbine rebarrel

Dyspnea

Dyspnea

CGN frequent flyer
Rating - 100%
72   0   0
Location
Alberta
I bought one of the non restricted citadel barrels from Tradex, right now it is timing at 52 degrees. I want it to hand time at 20 degrees.

If I'm correct I need too have a machine shop remove .00044 from the shoulder to time to 20 degrees.

I'm I correct?
 
I could, but i would rather not remove any material from the receiver, in the event I want to go back to the original barrel.
 
You need to make your calculations from the threads per inch on the barrel tenon. It's pretty simple stuff. Figure out how much linear distance is taken up with one 365 degree rotation of the thread and divide that by 365, then use the result, which will be one degree to figure out how much you need to have removed from the shoulder to properly index the barrel.

What I'm wondering is how you intend to set headspace once you've done this or had it done? IMHO if you haven't got a reamer to cut the chamber to the proper depth and haven't checked the distance from the receiver shoulder to the face of the bolt to do so and still maintain the proper clearance for the lugs not to bind on opening, you should take this new barrel to a smith and maybe get him to show you how to do this.

M1 Carbines are finicky and most of them actually have chambers that are a few thousandths of an inch deeper than specs stipulate. This was done because of the differing lengths of ammo made by different manufacturers which I have found to be not only on the minimum spec length but also on or over the maximum length spec. Usually the extremes are found on surplus brass. I haven't found any on later made commercial ammo.

Another thing with M1 Carbines is the beveled edge on the chamber. If it is cut to shallow there will be constant feed issues. Be careful though because it can also be cut to deep.

Those barrels from Tradex are made in three pieces and care needs to be taken when they are fitted not to cause any misalignment of those pieces. That piston section is just asking for someone to use a wrench on it to tighten the barrel into the receiver. Big mistake if you do. The indexing has to be close to perfect if you want the op rod/bolt to function properly as well. A few degrees off and binding will occur. Also, those barrels are "short chambered." This means the chamber needs to be cut for each receiver and believe me, not all M1 Carbine receivers are identical. They are a bit more involved in doing a proper job than bolt action rifles but not enough to stop someone that has a good grasp of what is needed.

Get in touch with a CGN member that goes by the handle of PURPLE. He loves the M1 Garand systems and likely the M1 Carbine system. I have seen his work on Garand M1 rifles and it is excellent. Beg, plead barter with him to mentor you on this if you insist on doing it yourself or maybe better, pay him to do it for you properly the first time.
 
I haven't had headspacing set, my intent for the entire rifle is a complete restoration done in incremental steps. The intent of installing the barrel is to get it timed. So I can deregistered as restricted. Then when I have the funds set aside have it professionally headspaced and restored.
 
Dyspnea said:
I haven't had headspacing set, my intent for the entire rifle is a complete restoration done in incremental steps. The intent of installing the barrel is to get it timed. So I can deregistered as restricted. Then when I have the funds set aside have it professionally headspaced and restored.
Click to expand...

I'm not sure how that works. I am sort of on the fence about what is considered restricted as far as components go. Is a receiver without a barrel restricted or does it only become restricted when a barrel under the limit is installed???? Anyway, I see where you're coming from.
 
Gunsdora, I made up a very similar wrench but without the dog leg. I can see how that would come in handy.

One thing about that wrench is that the commercially available units are to thin IMHO. It is possible to damage the op rod return spring well with this wrench due to its lack of coverage. This is only on certain receivers. Most are not tight in any way with only a very few degrees of take up to index point.
 
M1 carbine receivers without barrels are (or are supposed to be) Restricted and therefore required to be registered. If an 18 3/4 to 20" barrel is put on, it can be de-registered. Once this is done, and you remove the NR barrel, and an 18" is put back on, it's now back to Restricted and has to be legally re-registered.

A barrel should clock up by hand with about 1/8 of a turn to go, where a robust receiver wrench has to be used to complete the installation. Threads are 3/4-20 TPI, so 1 rotation is 1/20 or 0.050". 1/8 of a turn is about .006", so if it clocks up by hand to 1/4 of turn, .006 has to turned off the barrel shoulder to get it down to 1/8 turn. If you or a machinist has never done this on a carbine barrel before, then don't attempt it (there's a learning curve). 52 degrees sounds about right for a hand fit up, if I read the OP's numbers right, so 1/8 turn is 365/8 = 45.6 degrees (pretty close to 52).

I've done a number of re-barrellings/chamber reamings, and bearhunter is right, they are finicky.
 
Ok I'll leave the barrel alone and see what the final draw is like. My plan is to make a wrench with some 1/4 steel and have a bar welded on for a handle.
 
Thanks Gunsdora, you have a lot of knowledge on the little rifles that pretty much settles it for me as far as its classification goes.

OP, a 1/4 inch bar is not wide enough to guarantee you don't damage the spring well on the side of the receiver. It is the weakest point on the receiver and difficult to fix if you crush it. I would suggest you use a piece of steel bar that is at least 1/2 (1cm) in thickness. Your call, your receiver.
 
You must log in or register to reply here.
Back
Top Bottom