Gents:

Can the threads of a MRC be re-cut if they are not right to begin with?

Montana rifle corp???
if so. Sure. But they should be dead nuts perfect.

thanks, KC

I've been wondering the same thing since seeing this on Gunbroker:

http://www.gunbroker.com/Aucti....aspx?Item=178811424

I'd like to know the "real" story.

Seems really fishy. Even if it were cross-threaded or maybe galled, it could be taken apart. In the worst-case senario you could cut the barrel shank off and use a boring bar to remove the stub. If the internal threads are totally ruined they can be recut easy enough. Something very stange about it.

I know this is apples to oranges--

but I recently went through this with a NEW M1A receiver--

the action when barreled was threaded/bored so far off center that the barrel was literally greater than a half inch deflection at the muzzle.

Doesn't happen often-- but when threaded/bored off center it can be a real PITA to fix

The axis of the MRC threads are usually perfectly perpendicular to the receiver face and the inner seat but are co-axial with nothing except by pure chance. It is possible to recut the threads to be co-axial with the bore of the receiver bridge but set up and verification is tricky. Misalignment of the threads in relation to the bore is due to warpage in heat treating the receiver. The receiver is made sloppy at the front and offers no lateral support for the bolt to allow for the warpage.
The worst one I saw was eccentric by .027" (.054 TIR!)as well as as being angled off. Of eight I had in the shop, two were pretty good, four were borderline but usable, and two were unusable without remedial work.
Now, I have heard the problems encountered during heat treating have been addressed and the product is better but I have not seen one of the latest production actions to verify. Regards, Bill.

Bill can you tell me how this would come about in heat treatment please? Is it the way the receiver is cooled?

Cheers, Chris

If in fact it happened they it was described in the add, I have seen this before and isn't for the timid, but can be salvaged. Sounds like their was a friction weld in the threads.

Looks like galled threads to me. Probably the barrel threads weren't quite deep enough. I don't know if it is worth the gamble or not. As stated earlier it may come apart, but worst case would be to cut the barrel off and bore it out until you can cut/collapse the barrel out of the receiver.

ETA: I am trying to be cautious and not start a firestorm, but I recently bought two pre 64 Win 70's from that town in Kansas, and they were the worst two M70's that I ever saw ass far as damage/ poor workmanship. I told the business owner that I didn't know what the heck was going on in that part of Kansas but that I wouldn't buy another gun from them no matter how rare or if a great bargain.

This can happen when you install a stainless barrel in to a carbon steel action. You need to use a thread lube like anti seize or something.

as for the eccentric threads thats possible too. What happens in heat treating is the steel has stress in it from the foundry it came from. then add in the stresses the machining adds and removes in different areas of the action and then stick it in an oven at high temp. 1500 to 1800 degrees F depending on the alloy and the action will unkink and stress relieve it self and sometimes warp big time. 4130 and 4140 are better suited to being resistant to warping but they still can.

.027" eccentric is not a heat treat problem though that was a set up error. or at least it should have been. If that material is moving that much during heat treat and tempering that is some crap steel.

No, the ecentricity in that case was not a set up problem but a heat treat problem just as on every warped action which came out of that shop.
If you read carfully, you will note that I said the threads were eccentric to the bore of the receiver bridge. Since the bore of the action is not machined anywhere else, the bridge is the only bore which can be used as a reference. I'm quite sure the action was reasonably straight subsequent to machining but prior to heat treating but this was most assuredly not the case after treatment. Most of these receivers are visibly bowed out on the left wall.
As I said before, the bore of the receiver ring is deliberately cast large to simplify bolt fitting. In addition, the clearance between the bolt and the bridge is quite generous.
Rockdoc,
Such warpage is usually caused during the quench. Pieces which are complex in shape and which vary in thickness are more difficult to treat than a simple shaft or bushing.
When a piece warps as a result of heat treating, it stays that way even if it is annealed. At least this has been my experience. I was once brought a high quality single shot action which had warped badly when it was color case hardened. I was asked to anneal it in hopes that it would "relax". I soaked it at 1450 degrees for a couple hours and left it packed to cool overnight. It was dead soft but just as crooked as when it went into the oven.
Galling usually occurs when the joint is tight, dry, and the two pieces are of similar hardness. Some materials show a real affinity for themselves and galling is an ever-present threat. Stainless actions with stainless bolts are a classic example. Forget to lube the lugs on your new BAT and galling is almost garanteed. Regards, Bill

What Bill said.
Regards, Joe

Hell, I aint scared. I'm high bid. Proably threads turned with an out of alignment tailstock. I build a dozen of these and they are good actions and I have a sweet short action pattern stock and a hankering for a new .400 Whelen.

I purchased the action on Gunbroker, here is the rest of the story from looking at it when I received it today.

Like usual, only part of the story was told. The barrel is stainless, siezed into a stainless receiver. The threads that can still be seen are very rough and poorly cut. Could be galling, or could be poor dimensions, or both.

Hand tightened is how the barrel was described. That may have been so the first time, but someone really tried to get this back off. The barrel has scars all over it from where it turned numerous times in a barrel vise. It also has pipe wrench marks on it. None of this was described in the ad, but I expected it.

Luckily, the action hasn't been damaged. Cut off the barrel with a hacksaw, center it in the lathe and bore it out, and chase the threads if needed. Should be an easy job.

The barrel is a Shilen Match grade and still long enough to rethread and make a 26" barrel after cutting an inch at the muzzle. I'll send it off to Montana Rifleman or McGowen to be recontoured first, and that will get rid of the removal marks.

Should make a nice rifle. I just wish the pieces were cro-moly instead.

dave

Well, the final outcome is here:

Cut off the barrel, bored out the receiver, picked out the threads, one thread at the front of the receiver was galled. The picked out pieces showed that the barrel had been very poorly threaded, rough and torn. The galling was primarily caused by the poor threading job, in my opinion. The action was usable without even over-cutting the threads, had to chase them in the galled area. Only about half an inch of thread shows the galled area. Another montana barrel threads right into it, no problems.

dave

Glad it worked out for you. You bought it at a good price and the worst case played out with the bonus of salvaging the barrel for something else. Too bad the barrel needs turned down a bit and wasn't disclosed. You rolled the dice and won.

Glad to hear it worked out without too many problems. Looks like you've ended up with a nice action.

We're all waiting to see what you build on it.