Modern Sporter builds Q&A

greg olmstead said:
Seems like a buffer tube problem and not a lower problem
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There are three different types of buffer tubes. The standard, Mil-spec or Commercial

.....And the proprietary or what ever some call them which are not manufactured to any spec. These appear to be the third rate OEM Chinese made units that are flooding the market.

If you stick to the real or quality brand mil-spec you will never have any issues.
 
yowski said:
Is anyone having an issue with these RRA LAR-15 10 round mags? They are not properly activating the mag catch and need to be inserted either with the release depressed or with some force in order to seat properly. They are also not releasing properly and require some force to pull out with the release depressed. I have no issue with 5 round rifle mags, in and out very smoothly.

IMG_9686-1-510x517.jpg
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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
 
Sqr said:
There are three different types of buffer tubes. The standard, Mil-spec or Commercial

.....And the proprietary or what ever some call them which are not manufactured to any spec. These appear to be the third rate OEM Chinese made units that are flooding the market.

If you stick to the real or quality brand mil-spec you will never have any issues.
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Stay away from buffer tubes with the little pin notch and the problem won't happen.
 
Cabbose said:
I did run I to an issue with my BCM tube only making it a couple of threads into the receiver. I had a spare Vltor tube that was fine.
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Buffer tube threads can get dingned up at the factory from bumping into other tubes and what not, and prevent smooth insertion. Are the threads nice and sharp/clean all around?
 
I had two tubes I tried. 1 went in with basically size on size fit. It was really tight. I ended up having the chase the thread on the CCS tube I settled on using.
The thread seems needlessly tight.
 
Cabbose said:
I did run I to an issue with my BCM tube only making it a couple of threads into the receiver. I had a spare Vltor tube that was fine.
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greg olmstead said:
I had the same problem with the same tube.
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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.
 
Kratos said:
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.
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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
 
greg olmstead said:
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
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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.
 
Kratos said:
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.
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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.
 
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.
 
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.
 
apex survival said:
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.
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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"
 
apex survival said:
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.
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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.
 
purplezuk said:
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
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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?
 
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