View Full Version : Problem with new upper
Ok, i got this S&W 5.45x39 upper around Christmas time. I took it out then, and shot maybe a mag through it. Everything seemed ok, but the only problem was light primer strikes. Ok, no big problem, just need to put in the new spring. I did that. And before i was able to shoot it again, i got a compact acog. So i put on a different gas block so i wouldnt have the front sight in the scope picture. Ok, so i take it out last month to shoot it again and i had my shells getting stuck in the chamber. I tried pulling the charging handle but the thing wouldnt budge. I had to run a cleaning rod down the barrel to try to get them out. They were in there so tight, i had to hit the handle with a hammer to get the shell knocked loose. So i thought i just didnt clean it good enought the first time. When i got home i cleaned the chamber real good and put it away. So that brings me to this weekend. I go to shoot it again, and the same problem happened. I dont understand what it could be. I never had a problem like this with my 223 uppers. I even put the 5.45x39 on my 223 lower just to make sure i didnt mess something up when i put the new hammer spring in my 5.45 lower. But the same thing happened. So either something is wrong with the bolt/bolt carrier or something is screwed up in the chamber. I really hate to pay to send it back to S&W and have to wait 4 or 5 weeks for them to send it back to me. Could it be possible that there is a spacing problem with the barrel or something? Ive tried everything i can think of. Im fed up with it!
My guess - Your gas block might not be aligned correctly, hence not enough gas pushing through to push the BCG back.
Honestly you could put your old FSP/gas block back on and should really not mess with the scope.
Ok, i wondered if it was a gas block issue. But then i realized, that if the case is in there so tight that i cant yank it out with the charging handle, there is no way that it could be a gas block issue. I mean the extractor held tight,never turned loose, so no extractor problems with it. I had to take a hammer to the cleaning rod handle to get the thing to budge. I have looked at the case, and i dont see anything out of the ordinary with the case. If i can find one of them in the car, i might post a picture of it to see if you guys see something i dont.
Does anyone else have any ideas? Im really starting to think its a chamber issue. I can cycle shells through by hand. And as far as i know its working fine. I dont notice any hang ups.
Are you using brand new unfired brass ? What kind of ammo ?
I've seen a lot of problems solved by switching ammo. I'd pick up a couple boxes of Winchester USA or Remington UMC and see if the problem persists.
They dont make ammo for this upper.
As painful as it sounds, put the original gas block back in it and fire it and see what happens. I have to believe that this new gas block may be the problem if it worked fine with the original block.
Can you post any pics of the upper for us including the block you installed?
Well to give you guys an update, i think i MAY have found the problem. A moderator on ar15.com told me to take the bolt out of the carrier and try sliding it back and forth in the upper to see if there is any place its binding up. And sure enough when it got up to the gas tube i got hard to push the carrier forward. So apparently its an issue with the gas tube not being aligned right. I wont be able to test it again till this weekend. But i really hope this is the problem! Ill post a response this weekend and let you guys know if that was the problem. Thanks for all your help!
Failure2Stop
04-19-10, 16:07
It's the gas block.
Really.
There should be some, as in a small amount, resistance when the slides over the gas tube. If you look at your gas tube protruding through the upper receiver, you'll notice it has a bulbous end to it, which provides a tighter fit between the gas tube and gas key to help seal the gas and direct it into the carrier. The gas tube should be centered left/right and up/down inside the receiver, and you can check this by sighting into the receiver. Unless you gnarled the end of the gas tube or bent it when you changed the gas block, the problem is not the gas tube/gas key fit.
Either you didn't clean it well enough, which probably is not the case given chrome lining, or there is a problem with the gas block.
My recommendation is to switch back to the original pinned FSB and live with the sight picture. What kind of gas block did you use anyway?
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