Modern Sporter builds Q&A

[Kratos]

The actual threads were oversized vs the dd and vltor tube I measured. Plus the bcm tube wasnt machines right in the inside. There was a step about 3/4" from the end that was about an 1/4" smaller inside. Could not use a jp scs in that tube. It's in the parts bin labeled NFG

That’s messed up, I’d contact the vendor and BCM, it’s an inexpensive part but not acceptable. Maybe a run was FUBAR’d.

[greg olmstead]

That’s messed up, I’d contact the vendor and BCM, it’s an inexpensive part but not acceptable. Maybe a run was FUBAR’d.

Already talked to the vendor. Awesome people. And I'm the type of person that doesnt really care about stuff not working I bought 2 years ago that didnt cost much. I was more upset that my Rainier avalanche charging handle latch broke when I was shooting and caught me in the face.

[apex survival]

Both BCM tubes I have fit no problem. Check your threads, I’ve had new tubes show up dinged like Dietz said. A couple minutes with a file and they were good to go.

I used a BCM mil-spec tube as well, threaded right in no issues at all.

[apex survival]

Anybody using a BCM low profile gas block? Mine seems super tight on the journal (haven't actually installed it yet, just tested it and it will not slip on by hand) and will require a persuader to get it on.

[greg olmstead]

The bcm I have never fit right. The end plate slot was wider than normal and let the tube rotate a bit. The castle nut was hard to screw on and off from new. The step inside that wont allow a scs to be used. Just a bad tube from new. Everyone has lemons slip through and I seem to get them all the time. I dont let it discourage me from buying the same thing again.

[greg olmstead]

Anybody using a BCM low profile gas block? Mine seems super tight on the journal (haven't actually installed it yet, just tested it and it will not slip on by hand) and will require a persuader to get it on.

I have one on my rifle. It was a bit tight but didnt require a lot of persuasion to get on the ballistic advantage barrel. A few taps and it was on. .750"

[jiffx2781]

...

[Dietz]

Anybody using a BCM low profile gas block? Mine seems super tight on the journal (haven't actually installed it yet, just tested it and it will not slip on by hand) and will require a persuader to get it on.

Gas block (FSB) and barrels are a zero tolerance fit. BCM (and anyone who knows what they're doing) hand reams the inside diameter to exactly .750", the barrel is supposed to be exactly .750" too.

Warm it up a bit with a propane torch (doesn't take much) and it will slip right on.

[yowski]

I tested those exact mags with multiple mag catches and had no issues in the Sporter. Oddly enough my stag 10 has that issue with the 308 version.
Try a different mag catch of you can

Tried a different mag catch, same issue. Separated the receivers and the both LAR and AR mags catch/release properly. Tried again with the upper attached and BCG out and the problem is still present, seems like some sort of internal clearance issue with the upper receiver?

[Dietz]

Who made the bolt catches?