Originally Posted by
45B20
Hylander
Or if you insist on doing it yourself, here is some help on installing a new issue barrel on an 03 receiver, remember this is not everything and I am sure you will encounter something I do not cover.
1 Inspect the supplied new barrel, check for straightness (in your case, the shank from a 19/64“ dill will
work), throat and muzzle wear, check the barrel over to see if it has been installed before. Make sure the
shoulder is smooth and that the chamber is smooth.
2 Inspect the supplied rifle, especially the receiver. I check the headspace with a Field Test Bolt.
Disassemble the rifle, remove the old barrel and then really clean and inspect the receiver, if the receiver
is acceptable go ahead with the project.
3 Assemble the barrel and receiver. Then check headspace with bolt
supplied and then, if needed, extend chamber until the bolt will just close on the Go Gage.
4 Assemble the entire rifle and test fire.
Now,, during any of these steps if I encounter a question, I contacted the customer. In this case, you are your own customer and will have to take the responsibility.
As to step 1, I see if a chamber reamer will fully seat in the barrel’s chamber. I do this to make sure the bore is concentric with the chamber. If the reamer meets resistance I usually stop the project. You do have a chamber reamer, right?? And a reamer holder that will extend thru the receiver. You can deepen the chamber with the barrel NOT installed on the receiver but that is iffish.
As to step 2, One of the thing I really check is the bolt lugs seating area to see if there is any indications of set back. I use a depth micrometer. I also make sure the front of the receiver ring is smooth. If the receiver has been drilled and tapped that is usually no problem, however A3/4 receivers are hard, and some people anneal the spot were the hole is to be drilled and use too much heat. If I feel too much heat had been used I would not rebarrel. Or the receiver is one that has had welding done to it, to make it incapable of firing (Drill Rifle). I would take each ‘welded on’ receiver as an individual case, however in today’s legal world I would be very reluctant to rebarrel such a receiver. I will also screw stocking bolts into the receiver and check that the two bolts are both on the same plane. If not, the receiver is twisted. Straight edges on the bottom of the receiver and the tang will do the same test.
As to step 3, You do have at least a Go Gage, right?? This can be done without headspace gages and using only a unfired case but I DONOT recommend it….Make sure the chamber and the receiver’s bolt locking recesses are cleaned each time before checking headspace. With a few new barrels, the bolt will close on a Go Gage (or unfired case) without any chambering work needed, however that is usually not the case. If the bolt will close on an unfired case and that is the ammunition you intend to use, great. However if you change ammunition makes or lots, your bolt may not close on that ammunition. Usually, with a newly installed new barrel, the chamber will need to be deepened/extended. To do this, you will need a chamber reamer (bought/rented). I do the chamber extending by hand, with the barrel installed, cleaning at each step with oil under pressure until the bolt will just close on the Go Gage. You can get a little more leeway as to your ammunition selection by extending the chamber a little more, but as long as the bolt will not close on the NoGo Gage this should not be a problem. You can make your own headspace gages with unfired cases. ASSUME the unfired case to be an 1.938” gage and add a shim for the size gage you wish. Love the word ‘assume’, it leads to so many interesting experiences. After you are finished with barrel installation, clean carefully the bore, chamber and the receiver’s bolt locking recesses.
Each one of these steps entails some cleaning and detail work, I check and clean the threads on both the receiver and the barrel, touch up the barrel threads if needed and I have a barrel tap for Mauser and 03 receivers. I cleaned the barrel after test firing and the cases (5) went with the rifle. I also slugged each barrel I installed and the slug was also given to the customer.
This all went great unless there is a problem with indexing. I like a barrel to hand tighten to no more than about 30 to 40 degrees before indexing. I use a little grease and tighten and untighten several times to seat the threads before I turn the barrel to its final spot. To me a indexed barrel is not one which an index mark meets the mark on a receiver but a barrel who’s front sight is straight up (at 12 0’clock) in relation to the receiver. To correct a barrel that will not index means lathe time. For me that means holding the muzzle in a collet and the chamber with a live center taking a little off the shoulder (0.0003” removed for each degree the barrel is to turn). In practical terms, that about 0.001” for each 5 degrees. I measure, what I remove with a dial indicator while I am cutting. You can set the shoulders back on an barrel with only two files, a course and a fine one, both with a safe edge, a depth micrometer or caliper, and a square AND a lot of patience.
IF, in that rare occurrence that the barrel goes past it’s index,, that is another set of problems. Every complete turn of an 03 barrel moves it 0.1”. With an A3 you do not have to worry about the rear sight interference, but to set a barrel back that far will usually have interference between the bolt and extractor and the barrel. For me, I would just go get another barrel, but for you that may not be possible. Depending on how much overturn you have, ( for me it is no more than 45 degrees) you can peen the shoulder of the barrel . Take your time and keep the strikes close together and it will not look too noticeable. You could use a shim. If you do,, please use shim stock and not a tin can. If over indexing does occur,, I would really suggest another barrel, on in the very worse case,, a new receiver.
I would suggest doing at least one yourself, that way you will not complain about the price, if you decide to have a qualified smith do it.
Good luck
45B20
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