Cycling problem are almost always related to the gas not flowing properly to the BCG. Is you gas block well installed in line with you gas port? Is your gas block or gas tube obstructed? If it’s an ajustable gas block, open it up more. And lastly, it could be a too heavy buffer or buffer spring. Cheers!
Modern Sporter - Build Discussions
- Thread starter ATRS Shaun
- Start date
Cycling problem are almost always related to the gas not flowing properly to the BCG. Is you gas block well installed in line with you gas port? Is your gas block or gas tube obstructed? If it’s an ajustable gas block, open it up more. And lastly, it could be a too heavy buffer or buffer spring. Cheers!
Thanks ! Yes your right! the gas block is well installed, i tried 2 aluminum block + 1 ajustable, nothing is obstructed, it's all new parts from TNA, it's a .300 blackout..I tried 2 different barrel, 2 different bcg, the only thing i didnt try is to change on the gas system is the gas tube, i was wondering if my carbine buffer tube could be a problem, ill try to find more informations here, thank you!
- Location
- northern BC
Is it a pistol length gas system?
300 blackout can be a tricky caliber to get to function reliably. If the gas system isn’t a pistol length, it’s huge problem. If you’re trying to cycle subsonic, it’s tricky..
if you’re using tna branded parts, you’ll have issues.
Some details on the barrel, bcg, and buffer/spring would be helpful in order to assist with troubleshooting
if you’re using tna branded parts, you’ll have issues.
Some details on the barrel, bcg, and buffer/spring would be helpful in order to assist with troubleshooting
Thanks sir! yes the gas tube is pistol lenght, only supersonic ammo..
Parts of the gas system :
- bcg from TNA (cheap one) - i also tried one from a bcl coyote (no changes)
- 2 different Barrel one from tna with an oversized gas port and one from atrs with a small gaz port
- 1 aluminum gas block from TNA, 1 ajustable gb from tna and one gas block from maple ridge armory
- pistol Gas tube from TNA
- tapco ajustable stock with carbine buffer tube
Thanks for your time!
How heavy is the buffer?
Does it cycle at all, or try to? Has it yet to cycle a new round or just super unreliable?
You may need to lighten the buffer and double check your spring length. Should be about 10.5” long. I’d also consider a lightweight BCG if you can find one.
Is it only subsonic that doesn’t cycle, have you tried different ammo?
Does it cycle at all, or try to? Has it yet to cycle a new round or just super unreliable?
You may need to lighten the buffer and double check your spring length. Should be about 10.5” long. I’d also consider a lightweight BCG if you can find one.
Is it only subsonic that doesn’t cycle, have you tried different ammo?
Thanks Colin,
It's weird because sometimes i can fire 2 rounds with no issue but after that a brass doesnt eject and stays in my upper causing a jam, i think the brass hit the barrel extension and fall in the upper, but i cant understand why, probably undergassed but why it's intermittent... buffer weight is 3oz, the spring is around 10 inches, i just tried supersonic ammo, 2 different brands..
Not sure if this is the right thread for this question, but it is build related I suppose...
I am wanting to purchase a couple .22 conversion kits for my Modern Sporters and am wondering if any AR kit will fit AND if there is one particular kit that runs better with the ATRS MS?
Thanks!
I am wanting to purchase a couple .22 conversion kits for my Modern Sporters and am wondering if any AR kit will fit AND if there is one particular kit that runs better with the ATRS MS?
Thanks!
The CMMG works great, but you’ll need to ask ATRS to modify the back of the bolt because the MS receiver is slightly shorter than an AR.
- Location
- calgary alberta
The modified CMMG kit works the best in our experience. There is a minor modification required to the CMMG carrier required, but it is easily reversible just in the off chance we ever get to use an AR again.
The big problem is getting the CMMG kits past CBSA these days.
mmcintyre1220
CGN frequent flyer
- Location
- Tillsonburg, Ontario
So.. If a regular BCG works fine sticking out slightly due to the shorter upper, why would the CMMG bolt not work? Not trying to be a smart *ss, a truly don't know. I just built my first MS and found it weird the BCG does not sit flush with the back of the receiver.
I believe they shorten the CMMG BCG overall then add a small block to the rear portion which prevents it from going back into the buffer tube. The AR bcg works fine because in an AR it retracts probably 3/8 to a 1/2" behind the ejection port so there is a larger tolerance. In the MS it only clears the ejection port by about 3/16." Maybe someone else can explain more clearly but the ATRS mod on the CMMG kit runs perfect .
