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Posted: 12/18/2015 12:55:03 PM EDT
| Alright so i had my barrel cut down and a surefire socom brake attached. i stuck a cleaning rod down the barrel with the bolt fully forward it measures 16.3 to the end of the muzzle. the surefire brake is 2.70 according to the website. my question is could i change out the surefire brake for AAC 51t that measures 2 1/2 and still be at the legal 16 length? Did i measure the barrel correctly? |
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This will put you at 16.1" very very close to the legal limit for a PINNED AND WELDED barrel. It's still legal but barely. Most prefer to be on the + side of the limit by .500" Full disclosure: I've built a 14.7" with a pinned BCM MOD 0 at 16.125" before. http://i841.photobucket.com/albums/zz336/Dodge223/Arfcom/A37BBB9A-4F56-4C0B-A872-F8BAE40E6B97_zpszgvtx4cd.jpg yeah it would be pinned. |
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Quoted: Alright so i had my barrel cut down and a surefire socom brake attached. i stuck a cleaning rod down the barrel with the bolt fully forward it measures 16.3 to the end of the muzzle. the surefire brake is 2.70 according to the website. my question is could i change out the surefire brake for AAC 51t that measures 2 1/2 and still be at the legal 16 length? Did i measure the barrel correctly? |
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You need to account for the length of overlap between the barrel threads and the flash hider. You can't just add the length of the barrel and the length of the muzzle device because you lose some length with the threads. Typically it's around .700". Quoted:
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Alright so i had my barrel cut down and a surefire socom brake attached. i stuck a cleaning rod down the barrel with the bolt fully forward it measures 16.3 to the end of the muzzle. the surefire brake is 2.70 according to the website. my question is could i change out the surefire brake for AAC 51t that measures 2 1/2 and still be at the legal 16 length? Did i measure the barrel correctly? so then this would not be the legal length? |
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You did measure correctly, most likely. I say that because, although it is minor, was your hammer cocked or dropped? Need to have the hammer cocked, so that the firing pin will retract. A hammer sitting on the firing pin will have the pin protruding from the face of the bolt, however slight.
If you're at 16.3 with the Socom brake attached, you SHOULD be good by .100 with the 2.5 inch hider. Key word being SHOULD. I'd want to install it and verify by your measuring method. On another point. You do know that the hider has to be permanently attached, right? pin/welded |
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Quoted: so then this would not be the legal length? Quoted: Quoted: Quoted: Alright so i had my barrel cut down and a surefire socom brake attached. i stuck a cleaning rod down the barrel with the bolt fully forward it measures 16.3 to the end of the muzzle. the surefire brake is 2.70 according to the website. my question is could i change out the surefire brake for AAC 51t that measures 2 1/2 and still be at the legal 16 length? Did i measure the barrel correctly? so then this would not be the legal length? |
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If the AAC is .2" less than the Surefire, and your barrel measured with the Surefire is 16.3", then it should be okay with the AAC since 16.3"-.2"=16.1" Quoted:
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Alright so i had my barrel cut down and a surefire socom brake attached. i stuck a cleaning rod down the barrel with the bolt fully forward it measures 16.3 to the end of the muzzle. the surefire brake is 2.70 according to the website. my question is could i change out the surefire brake for AAC 51t that measures 2 1/2 and still be at the legal 16 length? Did i measure the barrel correctly? so then this would not be the legal length? I don't agree with that logic. I think someone could potentially take a flash hider off, put it right back on, and come back with a different length. Maybe not by much, but it's hard to believe it will screw back on to the same exact spot with the exact same number of turns. Now consider a different flash hider, from a different manufacturer nonetheless, which could potentially thread differently, have a different length of threads, different timing, fresh crush washer, etc. I'm sure it's close, but I don't think it's sound logic to follow. I think if it was that way, the industry would be shooting for 16.0" and not 16.1", since there would be no margin of error. |
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I don't agree with that logic. I think someone could potentially take a flash hider off, put it right back on, and come back with a different length. Maybe not by much, but it's hard to believe it will screw back on to the same exact spot with the exact same number of turns. Now consider a different flash hider, from a different manufacturer nonetheless, which could potentially thread differently, have a different length of threads, different timing, fresh crush washer, etc. As far as removing and then replacing the same flash hider, you aren't going to change the length (shorten it) by more than about .002, no matter how much you torque it down. I'm sure it's close, but I don't think it's sound logic to follow. I think if it was that way, the industry would be shooting for 16.0" and not 16.1", since there would be no margin of error. Quoted:
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Alright so i had my barrel cut down and a surefire socom brake attached. i stuck a cleaning rod down the barrel with the bolt fully forward it measures 16.3 to the end of the muzzle. the surefire brake is 2.70 according to the website. my question is could i change out the surefire brake for AAC 51t that measures 2 1/2 and still be at the legal 16 length? Did i measure the barrel correctly? so then this would not be the legal length? I don't agree with that logic. I think someone could potentially take a flash hider off, put it right back on, and come back with a different length. Maybe not by much, but it's hard to believe it will screw back on to the same exact spot with the exact same number of turns. Now consider a different flash hider, from a different manufacturer nonetheless, which could potentially thread differently, have a different length of threads, different timing, fresh crush washer, etc. As far as removing and then replacing the same flash hider, you aren't going to change the length (shorten it) by more than about .002, no matter how much you torque it down. I'm sure it's close, but I don't think it's sound logic to follow. I think if it was that way, the industry would be shooting for 16.0" and not 16.1", since there would be no margin of error. How much do you know about thread fits, besides the obvious, little? Muzzle devices don't bottom out on the shoulder at the bottom of the muzzle device, they bottom out on the shoulder of the barrel. Add crush washer, split washer, or shims to time it, and it still buttresses against the barrel shoulder. If a 2.7 inch flash hider yields 16.3 inches overall length (OAL), a 2.5 inch flash hider is going to yield 16.1.......no matter the thread fit, thread timing, length of threads (depth of threaded hole in FH), etc etc etc. |
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<snip> How much do you know about thread fits, besides the obvious, little? Muzzle devices don't bottom out on the shoulder at the bottom of the muzzle device, they bottom out on the shoulder of the barrel. Add crush washer, split washer, or shims to time it, and it still buttresses against the barrel shoulder. If a 2.7 inch flash hider yields 16.3 inches overall length (OAL), a 2.5 inch flash hider is going to yield 16.1.......no matter the thread fit, thread timing, length of threads (depth of threaded hole in FH), etc etc etc. The AAC 51T FH doesn't use shims or a crush washer just an FYI in case you didn't know as you don't time it. |
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The AAC 51T FH doesn't use shims or a crush washer just an FYI in case you didn't know as you don't time it. Quoted:
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<snip> How much do you know about thread fits, besides the obvious, little? Muzzle devices don't bottom out on the shoulder at the bottom of the muzzle device, they bottom out on the shoulder of the barrel. Add crush washer, split washer, or shims to time it, and it still buttresses against the barrel shoulder. If a 2.7 inch flash hider yields 16.3 inches overall length (OAL), a 2.5 inch flash hider is going to yield 16.1.......no matter the thread fit, thread timing, length of threads (depth of threaded hole in FH), etc etc etc. The AAC 51T FH doesn't use shims or a crush washer just an FYI in case you didn't know as you don't time it. So the simple math definitely doesn't work, assuming the surefire does have a crush washer, or something. I know where a flash hider bottoms out, I was making a point that there are too many variables to apply simple math, especially when the law is the issue, and he has a tenth of an inch to spare. Like, for an example, one muzzle device using crush washers and one not.... That would be fun to find out after someone in a forum told you it was all good. |
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Because of this OP will be short. He can extend it with shims though, and pin after he has measured that it's over 16". Quoted:
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Surefire has no crush washer or shims SAY WHAT????!!!! OP said that the barrel PLUS Surefire brake came up to 16.3. Now you are saying he'll be short because he doesn't have shims, etc. Why's that. 16.3 is 16.3. If he uses another flash hider that is 2.5 inches long, where as the SF brake is 2.7, there isn't any way he'll be short. He'll be at 16.1 If he uses a crush washer or not, he'll be at least 16.1, longer if he does use a washer. Where's the reading comprehension??? |
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Quoted: SAY WHAT????!!!! OP said that the barrel PLUS Surefire brake came up to 16.3. Now you are saying he'll be short because he doesn't have shims, etc. Why's that. 16.3 is 16.3. If he uses another flash hider that is 2.5 inches long, where as the SF brake is 2.7, there isn't any way he'll be short. He'll be at 16.1 If he uses a crush washer or not, he'll be at least 16.1, longer if he does use a washer. Where's the reading comprehension??? Quoted: Quoted: Quoted: Surefire has no crush washer or shims SAY WHAT????!!!! OP said that the barrel PLUS Surefire brake came up to 16.3. Now you are saying he'll be short because he doesn't have shims, etc. Why's that. 16.3 is 16.3. If he uses another flash hider that is 2.5 inches long, where as the SF brake is 2.7, there isn't any way he'll be short. He'll be at 16.1 If he uses a crush washer or not, he'll be at least 16.1, longer if he does use a washer. Where's the reading comprehension??? For reference you can see the shims on this mounted surefire brake.  |
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Surefire break is timed with shims. 51T isn't. He will lose the length of the timing shims plus the .2" shorter the 51T mount is. For reference you can see the shims on this mounted surefire brake. http://modernserviceweapons.com/wp-content/uploads/2014/07/photo17-e1405529879607.jpg Quoted:
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Surefire has no crush washer or shims SAY WHAT????!!!! OP said that the barrel PLUS Surefire brake came up to 16.3. Now you are saying he'll be short because he doesn't have shims, etc. Why's that. 16.3 is 16.3. If he uses another flash hider that is 2.5 inches long, where as the SF brake is 2.7, there isn't any way he'll be short. He'll be at 16.1 If he uses a crush washer or not, he'll be at least 16.1, longer if he does use a washer. Where's the reading comprehension??? For reference you can see the shims on this mounted surefire brake. http://modernserviceweapons.com/wp-content/uploads/2014/07/photo17-e1405529879607.jpg My Surefire was timed without shims. |
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Quoted: I have that same surefire brake, and the shims only take up like, MAYBE 0.05" of space. If he was a 16.3 and the new brake itself is .2 shorter, that still puts him over 16 even without the shims |
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It's just going to vary by the barrel. As long as he measures it and confirms it's over 16.0" He's good. Quoted:
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I have that same surefire brake, and the shims only take up like, MAYBE 0.05" of space. If he was a 16.3 and the new brake itself is .2 shorter, that still puts him over 16 even without the shims In agreeance with. 
My BCM 14.5s have been a hair longer than 14.5 so it varies from manufacturer, but OP, even if you're at 16.001 in the end, you're good to go. |
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