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michael1778

Different weight BCGs for different 308 AR uses?

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When considering larger frame ARs for 308 and similar calibers, the 3-gun focused recommendation has always been to go for lower reciprocating mass internals to reduce recoil and disturbance from the carrier moving. OK, got that. Makes perfect sense and if I shoot Heavy Metal that's absolutely the way I will go. However, in other places (not around BE.com) I have seen people discuss using full mass carriers to help with long range precision AR work. They make comments about trying to extend lock up while shooting. I wasn't clear if it was for accuracy or trying to work the brass less. These aren't fast double taps like in close range 3-gun but instead single long range precision shots.

Is there any merit to using a full-mass carrier for a large frame AR upper dedicated to precision shooting? Seems like the recoil would be more pronounced. Thanks for sharing your thoughts.

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Older thread, but yes, I got much better accuracy out of my 6.5 Grendel when I moved from a low mass carrier to a full mass carrier, but it got even better when I added a Tubbs carrier weight. I still use an adjustable gas block and tune the gas accordingly. Usually not shooting this offhand and can't really tell any difference in the recoil.

You can tell the bolt stays locked longer. I can't rechamber fired brass from the low mass carrier, but it rechambers just like it was fired from a bolt gun now.

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Thank you very much for that confirmation.

:cheers:

I'll take this into consideration as I build out my rifle collection.

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I just learned that lock time isn't only effected by bolt mass.... long story aside, the actual gas system length effects how long it takes before gas hits your bolt. The longer the gas system the longer the lock time....

Also adjustable gas, preventing over gassing which can effect bolt velocity and lock time... You want the least amount of gas needed to get the gun to run reliably and repeatable.

Then you bolt+carrier mass and the spring tension behind it... object in motion stays in motion and object at rest stays at rest...

I'm not the best at articulation, so maybe someone can explain it a little better than I just did.

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I just learned that lock time isn't only effected by bolt mass.... long story aside, the actual gas system length effects how long it takes before gas hits your bolt. The longer the gas system the longer the lock time....

Also adjustable gas, preventing over gassing which can effect bolt velocity and lock time... You want the least amount of gas needed to get the gun to run reliably and repeatable.

Then you bolt+carrier mass and the spring tension behind it... object in motion stays in motion and object at rest stays at rest...

I'm not the best at articulation, so maybe someone can explain it a little better than I just did.

Certainly that wouldn't be the only factor, no. Gas system length is definitely a big factor, then other system factors to a lesser extent. I appreciate the comments. Thank you.

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In the scenario I mentioned above, the constant was the rifle length gas system and the buffer weight and spring tension. The variables were the carrier mass and adjusting the gas to suit the carrier mass/ buffer weight/ spring tension. Basically isolating for what difference carrier mass can make to lock time while all else remained the same and the results I had were significant.

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In the scenario I mentioned above, the constant was the rifle length gas system and the buffer weight and spring tension. The variables were the carrier mass and adjusting the gas to suit the carrier mass/ buffer weight/ spring tension. Basically isolating for what difference carrier mass can make to lock time while all else remained the same and the results I had were significant.

Understood. Thank you. This has been very informative and helpful.

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Years ago the AMU tried Tubb CWS in their service rifles. The found that they did nothing so i'm skeptical about accuracy increases and my own use was similar, my guns shot the same. What the heavy mass of a carrier does do is retard bolt velocity. In an AR platform, if you run the bolt too fast you can get extractor marks on the brass or even tear the rims off when pressures get high. Or to state it another way, in an AR the bolt speed becomes the limiting factor before the primers start to go. As such, if you can slow the bolt down a little, the cases handle pressure better.

When you compare one carrier to another its a little bit of an apples to oranges unless your using the same bolt.

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Years ago the AMU tried Tubb CWS in their service rifles. The found that they did nothing so i'm skeptical about accuracy increases and my own use was similar, my guns shot the same. What the heavy mass of a carrier does do is retard bolt velocity. In an AR platform, if you run the bolt too fast you can get extractor marks on the brass or even tear the rims off when pressures get high. Or to state it another way, in an AR the bolt speed becomes the limiting factor before the primers start to go. As such, if you can slow the bolt down a little, the cases handle pressure better.

When you compare one carrier to another its a little bit of an apples to oranges unless your using the same bolt.

Seems like it just lets the case pressure reduce some amount more before the extraction process begins. That's all that I'm hearing from users.

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