m70 chambering issues..weird problem

[wooltie]

This is an odd problem.  I have a model70 post 64, w/bench barrel.

I had the barrel removed, brake installed, then barrel re-attached and headspaced by a qualified gunsmith. 

The problem is that closing the bolt with a handload, factory round, or empty sized brass is very difficult.  I'm not talking about the last bit of closing, I'm referring to the entire cycle of close the bolt -- push the bolt forward to seat the cartridge in the chamber, then begin pushing the bolt handle down, and the entire motion down is difficult.

The bolt closes and cycles just fine with no cartridge.  I can also insert a cartridge into the chamber by hand with no effort.

And yes I've done all this -- removed scope mounts, removed action from stock, measured OAL of a few bullets to determine jump (OAL did not change), sharpied the bullet and case to verify that the cartridge is not too long, brass has been measured and is in spec, tried different types of brass, ran nylon and brass brushes through the bore, talked to the smith (I'm gonna take it back in for evaluation).

The only thing I haven't done yet is cut a cartridge in half to remove the neck and should from the situation, and see if there are issues closing the bolt.

It's like the chamber and bolt are misaligned, or something.

[bobcat]

I would take it back to the gunsmith.

[BULLBLASTER]

 

I would take it back to the gunsmith.

[follow maggie]

Did it do it before the work was done? Either way I think a trip to a good gunsmith is in order.

[Stein]

That is strange and misalignment was what came to my mind too, but as the barrel screws onto the receiver and neither are new, not sure how that could possibly happen. 

Did you inspect receiver to make sure there isn't a big scratch, metal shaving or something like that the cartridge is rubbing on?  Any marks on the cartridge?  I would probably sharpie the whole thing and run it in and out a half dozen times without ejecting.

Only other thing I can think of is the bolt, but again that shouldn't have changed.

[Encore 280]

Wondering if the gunsmith had the bolt out and it got mixed up with a different one.

[wooltie]

I am taking back to the smith later this month. Just trying to avoid another trip.

The barrel was bead blasted before it was reinstalled. So it is possible there is contamination somewhere in the chamber.

But I can fully seat a cartridge just fine manually, with no issues. The chamber is not tight.  But for some reason it doesn’t like the bolt seating the cartridge.

Looking for a hack saw to cut off the case at the shoulder to remove that piece of the puzzle. Or just cut the case in half.

Didn’t record the s/n of the bolt. But what are the odds that another bolt was in the shop and got mixed up.

[BULLBLASTER]

Does the extractor work correctly? Can you put a case under the extractor and feed it into the chamber?

Shoudnt be anything on the barrel if it was just roved and reinstalled with no work on the action end

[wooltie]

Does the extractor work correctly? Can you put a case under the extractor and feed it into the chamber?

Shoudnt be anything on the barrel if it was just roved and reinstalled with no work on the action end

Yes. It’s controlled round feed.

I disassembled the bolt and cleaned it. You unscrew the firing pin assembly and remove it from the bolt. Then you’re left with the bolt and the crf extractor.

Interestingly, the problem did not occur when I chambered a round with just the bolt and the extractor—without the firing pin assembly.

I reassembled the bolt+firing pin assembly and tried again thinking maybe stuff was just dirty, but the problem occurred again when chambering a round or case.

Just don’t know what is different when chambering a round/case vs no round/case...there are no issues with the bolt, firing pin and no round.

It’s like the bolt and chamber are just off, or there’s something I can’t see in the chamber. Need a bore scope.

Need to go back and inspect the action around the firing pin assembly.

[h20hunter]

I would lose my mind...it's likely something so simple and obvious but sends one into a fury of frustration.

[Stein]

I bought this bore scope for $45 on Amazon, works pretty dang good, especially for the money.  It hooks to the USB on a laptop, so you need one of those which is the only drawback.  I think they make other versions with a screen for more money.

https://www.amazon.com/gp/product/B07TTQF24F/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I'm down in Arlington, if you get this way you're welcome to borrow it.

[BULLBLASTER]

I had my pf m70 bolt unscrew a rotation and could not close the bolt years ago. I cant remember how it behaved with or without a case but had to be sire the firing pin assembly was installed correctly. Can you make sure it is threaded in all the way? Not sure how it would be affected with or without a round in that case tho since it shoudlnt matter if its a bolt assembly thing

[BULLBLASTER]

Does it make any difference in feel wether the safety is on or off?

[Caseknife]

Sure sounds like a headspace issue.

[BULLBLASTER]

I wouldnt think headspace since the barrel was just removed and put back in the same place. Since the bolt can lock in at all means that the barrel is in the same spot it was before removal with the crf extractor cut in the barrel.

Probably best to just take it back to whoever did the work.

[TooTallMike]

This is not a chamber issue and has nothing to do with the barrel.

It's your firing pin assembly based on what you last said.

Do you encounter the issue just cycling the action without any ammo?

If so then it's the firing pin assembly. Something is catching or creating resistance within the receiver and causing the bind.

I fixed weapons in the army for a living and if there is one thing I took away is that if you start taking away parts and then somehow the issue is fixed then you focus on that part.

Also when it comes to firearms it's almost always something simple and overlooked. I wish you posted pictures so we can get as good a look without hands on.

Hope you fix it!

[wooltie]

Yea at this point the smith needs to see it.

Problem still happens when the firing pin assembly is removed and just the bolt and extractor are used.

The barrel does not appear to be over threaded or under threaded. The Smith who originally installed the barrel cut it so that you thread the barrel all the way to the shank So that the shank is flush to the receiver.

There are no issues whatsoever cycling the action with no round involved.

There is just a bind somewhere between the chamber the cartridge in the bolt. Seems like somehow those three pieces are misaligned

[OneHoleGun]

Where you located. I'm in Lynden and dont mind taking a look at it with scope if you haven't taken to smith yet

[Jon]

It is a headspace issue. I did the same thing on my first M70 build. The rifling is a far from optimal distance in the M70... probably in the .030+ area. If you hang the bullet out of the case to get the desired distance to the rifling then the round becomes too long for the magazine or mag well. To try and compensate for that I ran my barrel on the tight side of my head space gauge and this was the result. Not being happy with it I purchased an X-caliber pre fit barrel. Probably the best choice I ever made with an M70. I had it perfect within an hour of receiving it.