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Posted: 7/24/2009 4:26:16 PM EDT
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I'm expecting a LMT CQB to arrive in August and have a question. This will be a pistol but will be turned into a SBR (once the stamp arrive). I'm purchasing a 10.5" barrel and a 14.5" barrel. According to LMT, the CQB is designed so that you can change out the barrel and go. HOWEVER, wouldn't you need to change out the bolt also?
Another question, what is the difference btw the LMT Enhanced Bolt Carrier and the Y/M M16 National Match BCG. I only ask b/c I only have Y/M NM BCGs right now and if it is not advised I use it with the 10.5" barrel for safety issues I need to know now so I can order another BCG. Also, this rifle will be suppressed (if that matters). |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? |
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my $0.02 is to forego the enhanced BCG.
A normal LMT is fine, but not as slick as the Chromed Youngs. Technically, using one bolt for bnoth barrels will work, but if you're putting serious miles on either barrel, it would be better to have a matched bolt for both barrels. In that event, why not go ahead and do a separate BCG for each? Do you need it? No. |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? It would be best to swap out bolts when you swap barrels. As also stated your zero will be off as well. |
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I'm expecting a LMT CQB to arrive in August and have a question. This will be a pistol but will be turned into a SBR (once the stamp arrive). I'm purchasing a 10.5" barrel and a 14.5" barrel. According to LMT, the CQB is designed so that you can change out the barrel and go. HOWEVER, wouldn't you need to change out the bolt also? Another question, what is the difference btw the LMT Enhanced Bolt Carrier and the Y/M M16 National Match BCG. I only ask b/c I only have Y/M NM BCGs right now and if it is not advised I use it with the 10.5" barrel for safety issues I need to know now so I can order another BCG. Also, this rifle will be suppressed (if that matters). No you will not need to change your bolt, bolts are caliber specific not barrel length specific. Don't plan on using your 10.5 inch barrel if your going to get the LMT enhanced BCG. The enhanced BCG is for barrel lengths of 14.5 and up only. The standard bolt, whether it be full auto or semi, is best for the MRP. That way you can leave the same bolt in the upper no matter what barrel length you have. |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? It would be best to swap out bolts when you swap barrels. As also stated your zero will be off as well. I'm waiting on a 12" piston version and I'm curious as to why the bolt swap would be recommended if you're using the same caliber? ETA; didn't fully let the post about the enhanced BCG in 14.5 and above barrels settle in before I posted |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? It would be best to swap out bolts when you swap barrels. As also stated your zero will be off as well. I'm waiting on a 12" piston version and I'm curious as to why the bolt swap would be recommended if you're using the same caliber? ETA; didn't fully let the post about the enhanced BCG in 14.5 and above barrels settle in before I posted You wouldn't, and it's not recommended. |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? It would be best to swap out bolts when you swap barrels. As also stated your zero will be off as well. Why would you have to swap the bolt if using the same caliber? That makes no sense what so ever. |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? It would be best to swap out bolts when you swap barrels. As also stated your zero will be off as well. I'm waiting on a 12" piston version and I'm curious as to why the bolt swap would be recommended if you're using the same caliber? ETA; didn't fully let the post about the enhanced BCG in 14.5 and above barrels settle in before I posted Becuase different barrels have different barrel extensions thus when you run one bolt through one barrel the headspacing wears in together. Taking that same bolt and running it on another barrel may cause premature wear and breakage. Thats my understanding of it. You may get by with it for a while but why take the risk. Compared to all the money he is looking to spend what's another $130? |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? No, head spacing adjustment is not an issue with the MRP. You will not have to bother with this, the platform was designed that way. |
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Here is a cut and paste from a tacked thread. Taxasarcher, you could always call LMT and get the final word from them.
Quoted: I hate to change subjects, but... What actually causes a change in headspace value as rifles are used? Is the bolt face wearing down, or does the barrel chamber or extension go through changes over time? And how many rounds can go through an assembled upper before the problem part needs to be replaced? Wear. The bolt's lugs wear on the backside and the extension lugs wear on the front. The bolt face doesn't wear much at all unless primer leakage and that is limited to the primer area. That is HIGHLY apparant. Wear rate depends on a myriad of influences like port pressure/timing, abrasives/lubricant and overall fit of the parts. The majority of wear happens in the first few hundred rounds until all lugs are lapped in and bearing uniformly. Swapping bolts is a sure way to increase wear as the lugs are now bearing with varying loads until lapped in again. |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? It would be best to swap out bolts when you swap barrels. As also stated your zero will be off as well. I'm waiting on a 12" piston version and I'm curious as to why the bolt swap would be recommended if you're using the same caliber? ETA; didn't fully let the post about the enhanced BCG in 14.5 and above barrels settle in before I posted The bolt carrier and bolt are different on an LMT piston vs. an LMT DI gun. The piston carrier has a strike surface where the gas key is and the piston bolt had no gas rings. The interior of the carrier is not machined to use gas rings so you can't add rings your bolt. As an example lets say you had a 16" and an 18" LMT DI barrels for your MRP. If you have very low round counts, you could get away with one bolt between the two barrels. The best scenario would be to buy a second bolt from Bravo or another reputable seller and pair it with your second barrel. You can change bolts out on the same carrier with no problems at all. For another $40-50 you know you will always have proper headspacing on your barrel. |
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You need to change BCG if going to a different caliber. Within the same caliber, use the same BCG. But, keep in mind you do need to re-zero after swapping barrels. Both 556, however would you not have to worry about head spacing when switching out the barrels? It would be best to swap out bolts when you swap barrels. As also stated your zero will be off as well. I'm waiting on a 12" piston version and I'm curious as to why the bolt swap would be recommended if you're using the same caliber? ETA; didn't fully let the post about the enhanced BCG in 14.5 and above barrels settle in before I posted The bolt carrier and bolt are different on an LMT piston vs. an LMT DI gun. The piston carrier has a strike surface where the gas key is and the piston bolt had no gas rings. The interior of the carrier is not machined to use gas rings so you can't add rings your bolt. As an example lets say you had a 16" and an 18" LMT DI barrels for your MRP. If you have very low round counts, you could get away with one bolt between the two barrels. The best scenario would be to buy a second bolt from Bravo or another reputable seller and pair it with your second barrel. You can change bolts out on the same carrier with no problems at all. For another $40-50 you know you will always have proper headspacing on your barrel. Don't have to buy another BCG. I purchased 5 YM NM BCGs right before the craze hit last year. Still got two of them left and one Larue BCG. I think I will just assign one to each barrel. Thanks. |
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