BCM 11.5 w/A5H4 won't lock back or cycle unsupressed.

[Clint]

To answer some questions in the thread (and thanks all for the responses btw)

Factory upper, BCM 11.5 lightweight. However, I installed my own KMR Alpha after chopping down the FSB. I removed the FSB from the rifle and reinstalled it using the same taper pins.

I am using a BCM rifle buffer spring and BCM buffer tube, not a green springco.

Now i'm worried I messed something up when I resembled the upper or lower.
...
Anything I should look for when checking the FSB install job or the buffer retainer pin areas of the rifle?

Just to verify: the longer A5 BCM tube was installed, correct?

Slide off the rail and look for excessive gas residue around the FSB.

[mjpgolf1]

To answer some questions in the thread (and thanks all for the responses btw)

Factory upper, BCM 11.5 lightweight. However, I installed my own KMR Alpha after chopping down the FSB. I removed the FSB from the rifle and reinstalled it using the same taper pins.

I am using a BCM rifle buffer spring and BCM buffer tube, not a green springco.

I am going to shoot the rifle again tomorrow without the can after giving the rifle a really good cleaning. I'll douse it with lube (I have some go juice sitting around) while I am at it.

Now i'm worried I messed something up when I resembled the upper or lower.

I want to make it clear I don't think this is a BCM issue at all, great company.

Anything I should look for when checking the FSB install job or the buffer retainer pin areas of the rifle?

Just installed a G2S trigger in the rifle today, forgot to mention that. Sadly that will be another variable for tomorrow.

Edit 2. Now that I think about it, I never used to have any issues before with the rifle before I started to shoot suppressed 95 percent of the time. I wonder If i'm seriously under lubing now that i'm using a can.

I would also just get a BCM low profile gas block and instal it. They are only about $50 and it will make the entire setup more clean rather than having a chopped down sight post/gas block. Then when you have the rail off you can clean everything up and make sure the gas system is all installed correctly. That is too nice of a setup to have all chopped up and rigged together. Do it the right way my friend.

[jstalford]

Chopped down fsb is still the strongest gas block you can have and then he doesn't have an uncovered hole in the barrel from where the second pin was.

There is nothing "unclean" or "wrong way" about a build with a shaved fsb.


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[Iraqgunz]

If you say so.

Having a gun that only runs on "premium" ammo does not equal a healthy gun. A properly setup rifle should chew up and spit out anything that you throw in it, within reason of course. Especially this platform. Something is obviously not right with this weapon. In a SHTF situation the last thing you want is to have to hunt for the good stuff because your gun will not cycle correctly with your run of the mil target ammo, which will be much more plentiful. Also who the hell wants to go Shooting and blast a bunch of high end ammo down range, unless you're shooting for serious groups. Run and gun and tactical drills are much easier on the wallet when you can shoot cheap stuff. Besides is anyone really using an 11.5" barrel for sub MOA accuracy. That would be a CQB rifle in my eyes so blasting the cheap stuff should be an option for serious practice days when lots of ammo is being shot. Just my 2 cents so take it for what it's worth.

[themonk]

Chopped down fsb is still the strongest gas block you can have and then he doesn't have an uncovered hole in the barrel from where the second pin was.

There is nothing "unclean" or "wrong way" about a build with a shaved fsb.


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OP, jstalford is correct. You do NOT need to purchase a low pro block. Your config is fine with a cut down block. May want to double check but if reinstalled correctly the taper pins will realign the block.

[foxtrotx1]

OP, jstalford is correct. You do NOT need to purchase a low pro block. Your config is fine with a cut down block. May want to double check but if reinstalled correctly the taper pins will realign the block.

the taper pins are in, and I don't see excess powder around the block.

I cleaned the rifle and lubed it up with ALG's new lube. Definately feels smoother, It was pretty dry and the chamber was filthy. The inside of the BCG still had some lube though. I won't get a chance to test till thrursday. If it still won't cycle with Wolf i'll shell out the cash for some XM193 or equiv.

I am using an A5 receiver extension and the gas tube looks to be almost perfectly aligned in the receiver. I took the bolt out and dropped the carrier in a few times at an angle. Zero binding whatsoever. Also checked for wear on the detent pin and the rear of the BCG to see if they were dragging. No wear there.

[firefighter37]

Having a gun that only runs on "premium" ammo does not equal a healthy gun. A properly setup rifle should chew up and spit out anything that you throw in it, within reason of course. Especially this platform. Something is obviously not right with this weapon. In a SHTF situation the last thing you want is to have to hunt for the good stuff because your gun will not cycle correctly with your run of the mil target ammo, which will be much more plentiful. Also who the hell wants to go Shooting and blast a bunch of high end ammo down range, unless you're shooting for serious groups. Run and gun and tactical drills are much easier on the wallet when you can shoot cheap stuff. Besides is anyone really using an 11.5" barrel for sub MOA accuracy. That would be a CQB rifle in my eyes so blasting the cheap stuff should be an option for serious practice days when lots of ammo is being shot. Just my 2 cents so take it for what it's worth.

I would also just get a BCM low profile gas block and instal it. They are only about $50 and it will make the entire setup more clean rather than having a chopped down sight post/gas block. Then when you have the rail off you can clean everything up and make sure the gas system is all installed correctly. That is too nice of a setup to have all chopped up and rigged together. Do it the right way my friend.

I think you should stop giving "advice".

There is nothing wrong with a chopped FSB, its actually the best gas block you can have... especially when the taper pin holes are already in the barrel.

[scooter22]

I would also just get a BCM low profile gas block and instal it. They are only about $50 and it will make the entire setup more clean rather than having a chopped down sight post/gas block. Then when you have the rail off you can clean everything up and make sure the gas system is all installed correctly. That is too nice of a setup to have all chopped up and rigged together. Do it the right way my friend.

I hope that's the most retarded thing I read all day.

[SulzerFirearms]

I didn't see a buffer weight listed. Since it functions fine suppressed (higher pressure) and does not unsuppressed (lower pressure) the first thing I would do would be try a reduced buffer weight. You want to tune the gun so that it functions reliably with the ammo you typically use. Getting it to function with a cartridge with a higher pressure only tells us what we already know from you shooting it suppressed vs. unsuppressed, which is it that it is struggling at a lower pressure. Barring gas leaks, which I doubt you have from what you've said about your setup, this leaves the culprit being a buffer system that is too heavy. The fact that the buffer system has been modified makes this even more likely.

[scooter22]

I didn't see a buffer weight listed. Since it functions fine suppressed (higher pressure) and does not unsuppressed (lower pressure) the first thing I would do would be try a reduced buffer weight. You want to tune the gun so that it functions reliably with the ammo you typically use. Getting it to function with a cartridge with a higher pressure only tells us what we already know from you shooting it suppressed vs. unsuppressed, which is it that it is struggling at a lower pressure. Barring gas leaks, which I doubt you have from what you've said about your setup, this leaves the culprit being a buffer system that is too heavy. The fact that the buffer system has been modified makes this even more likely.

All of this has been covered.

It's an A5H4.

My first post told him to drop down to A5H3.