Discussion in 'Rifle Country' started by MySuomi, Oct 12, 2020.
3 calibers with just a different bolt head? Didn't have to change the barrel? That is a neat trick.
That pic, the round looks like it's been hit hard, was it in the mag like that, as you mean next one up? If so it sure sounds like as another mentioned gas is hitting it. If it looked like that after clambering but not firing? Then it looks like it would be feeding issues. Something certainly hit that round and pushed the slug in further. If it is like that before clambering, it will create more pressure, then if the action is opening before the slug leaves the barrel? That would cause a KB.
Someone always has to pretend to be dumb and not get it I guess. Problem is this just confuses many who can't see that someone is trying to play dumb and or be funny. At least I would hope you are playing but you never know. So just in case, yes, assuming the JRC is the same internally as the TNW look alike you of course get a different barrel for each caliber. The whole selling point of these is you buy one gun, the receiver is serial numbered. Then you can order parts to convert them to .22 LR, 9mm, .40 S&W, .45 ACP, 10mm ect. directly. If the JRC has the same internals they sell you just the bolt head that goes with a two piece bolt. The way a blow back operates is the weight of the bolt and weight of the recoil spring, which in the case of the TNW is a Mil-Spec Buffer Tube and spring. On mine the same buffer and spring works with 9mm, 10MM, and .45. The bolt head they sell is weighted to balance things out with no other changes in the action. I have not handled a JRC so do not know for sure it's the same inside, sure looks like the people who designed both used the same idea though.
So again this was why I asked the OP, did the conversion just come with a new bolt head, and say to use the same buffer spring already there. Reason being it looks like the action was being allowed to open before the round left the barrel which would create a KB.
The conversion kit contained the following:
Recoil spring and new buffer
New mag well
New bolt and carrier.
The buffer is pretty heavy and the bolt seemed to have a little more restricted movement than the 9mm.
Yes they did. It is hard to describe the "funny" sound. They went bang hard and loud. It just sounded a little off. Hard to explain. But they did seem to be working the gun's action.
I inspected the barrel last night. It looks fine. I can see no evidence of a squib round being pushed out.
I am leaning toward the headspace problem or somehow the bullets are getting jammed into the case due to the blowback action. Maybe even some issue with the bolt not behaving correctly.
Here are the barrel pics as best as I could get them:
It will be interesting to see what the manufacturer has to say then, very strange. I would hope they ask for it back and replace it. If they do I hope they tell you what they think went wrong.
THAT is the problem right there. You are already dealing with very high pressure cartridge in 40sw. Bullet set back in these can subsequently DOUBLE the pressure!
A pistol (40S&W)headspaces off of the case mouth, really can’t mess it up, unless the chamber wasn’t machined correctly.
I'd suspect an OOB due to bolt bounce and bullet setback before I even thought about a miscut chamber.
I was trying to rationalize the headspace theory... Finding the round setback in the magazine, is a dead give away in my book.
No. The conversion kit had a clearly marked barrel labelled 40 s&w. And I plunk tested several 40 rounds to make sure they had case support. They did. I would not say perfect case support but it looked adequate. So that is probably not it.
Might be beating a dead horse here, but stamping a barrel .40 S&W doesn't necessarily mean it is. cutting a .40 chamber into a 9mm barrel would allow it to pass a plunk test. I know pictures can be a bit odd, but the one you posted looks like a big step down from the chamber to the barrel - way more than what I see in the 9mm and .45 barrels I just checked.
You would think the bullet would be stuck in the barrel if that were the case.
Shooting a 40 Short and Weak in a 10mm chamber would not cause this blowout. It's the same as shooting a 38 SPL in a 357 Mag.
Take a tight fitting jag and patch and run it through the barrel. Not all bulges will show on the outside. If there are loose spots where the jag and patch move through the barrel you've got a problem.
I would think so too, but I’ve been wrong often enough. And that looks like one heck of a wide shelf at the end of the chamber. Could be an odd photography artifact I suppose.
I did notice that too!
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