05-02-2020, 12:48 PM
Be aware that tolerance stacking is a thing. I tried to use a Young NM carrier in an SPR build with a 5.56 LaRue 18" Stealth barrel (their bolt, gas and brake) and a BCM upper. Given BCM are made to the minimum internal dimensions and the Young carrier is oversized it wouldn't fully lock back when firing. While the gun did cycle and ejection was at 4 o'clock the bolt would hang on the follower after the last round.
I switched that build to a standard carrier and it worked fine. I moved the Young to a spare PSA upper I had parted out and made into another SPR with a White Oak Mk12 barrel. It worked perfectly there.
An interesting point is both uppers were AH marked Anchor Harvey forgings (new BCM now have their own forge mark though). The difference is clearly in the finish machining and tolerances.
If you watch the John Carlos videos on building/tuning match AR's the over sized carrier or adding set screws to change carrier tilt are more for tuning a specific gun that needs it Vs an item to start with.
For the typical home builder a BCM or Vltor upper is chosen because of the minimum tolerances and undersized opening for the barrel to hopefully allow for thermo-fitting instead of needing to shim. A home builder won't have the luxury of choosing from different sized barrel extensions and assembling their own barrel like a fully equipped gunsmith. This tight fit is usually the biggest return accuracy wise over a different carrier.
Properly aligning the gas tube with the carrier key of any BCG will be your best return for accuracy and wear in that area. A gas tube bender may be needed for final alignment. http://www.m-guns.com/tools.php
I switched that build to a standard carrier and it worked fine. I moved the Young to a spare PSA upper I had parted out and made into another SPR with a White Oak Mk12 barrel. It worked perfectly there.
An interesting point is both uppers were AH marked Anchor Harvey forgings (new BCM now have their own forge mark though). The difference is clearly in the finish machining and tolerances.
If you watch the John Carlos videos on building/tuning match AR's the over sized carrier or adding set screws to change carrier tilt are more for tuning a specific gun that needs it Vs an item to start with.
For the typical home builder a BCM or Vltor upper is chosen because of the minimum tolerances and undersized opening for the barrel to hopefully allow for thermo-fitting instead of needing to shim. A home builder won't have the luxury of choosing from different sized barrel extensions and assembling their own barrel like a fully equipped gunsmith. This tight fit is usually the biggest return accuracy wise over a different carrier.
Properly aligning the gas tube with the carrier key of any BCG will be your best return for accuracy and wear in that area. A gas tube bender may be needed for final alignment. http://www.m-guns.com/tools.php