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MI, USA
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Posted: 3/23/2024 12:09:36 AM EDT
I grabbed one of the 14.7" M4 barrels from Brownells, some alignment shims (plan to buy a Halo or M4SD in not too distant future) and an A2 flash suppressor. I get the muzzle device timed with the shims in preparation to send the barrel off for pinning. I decide to make sure and check, so I fitted a bolt, dropped a cleaning rod down the bore, marked it, and measured.
It came out to be 1/8" shy of 16". I suspect this is because I'm using shims instead of the traditional crush washer. 1.) Are the threads on Brownells barrels sufficiently snug such that the above mentioned cans won't see baffle strikes if I use a crush washer? 2.) I'm assuming the answer to #1 is no. In that case, does anyone make a suitable spacer? Even the Accu-Washers max out at 0.100" and I don't want to stack shims, I need at least 0.125" |
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OH, USA
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Posted: 3/23/2024 12:19:10 AM EDT
[Last Edit: Millennial]
[#1]
You cannot use a crush washer with a suppressor.
I would suggest just use a longer muzzle device and just use a different silencer/mount. There's a lot of cans out there... no need to saddle yourself to things that use an A2 hider. Most cheap A2 hiders are pretty sloppy on tolerances... I wouldn't even trust an A2-pattern unless it was specifically advertised to be fit for suppressor mounting. https://silencerco.com/shop/delta-threaded-rifle-spacer-1-2-28/ https://innovativeindustriesllc.com/1-2-28-200-spacer/ https://www.wojtekweaponry.com/100-Tall-12-28-Barrel-Thread-Spacer_p_820.html |
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PA, USA
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Posted: 3/23/2024 12:33:39 AM EDT
[#2]
Griffin Flashcomp is M4SD compatible and long enough to get a 14.5" over 16". It's even already pre-drilled for the pin.
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MI, USA
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Posted: 3/23/2024 8:12:11 AM EDT
[#3]
This is on a M4gery that I want to keep looking the part as much as possible. Its not so much the mount that bothers me but the suppressors, modern cans all look really busy. The M4SD still looks enough like it did on the original SOPMOD poster, and the GP-NATO is a plain traditional looking can.
The Fallback is to order parts from Otter Creek Labs as I plan to buy a OCM5 later on for my SPR-ish and a planned movie-build Gordon carbine, I've emailed with someone from OCL and they say the flash suppressor is just enough for a 14.5" barrel so I'm confident of it on a 14.7. |
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MT, USA
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Posted: 3/23/2024 9:47:34 AM EDT
[Last Edit: spyderboy03]
[#4]
Quote HistoryOriginally Posted By Millennial: You cannot use a crush washer with a suppressor. @bigbore has shown in a thread pretty recently even, that a crush washer is perfectly fine when installed correctly. |
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Posted: 3/23/2024 9:59:23 AM EDT
[#5]
Quote HistoryOriginally Posted By spyderboy03: Not true. @bigbore has shown in a thread pretty recently even, that a crush washer is perfectly fine when installed correctly. *on a barrel with quality threads. |
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NC, USA
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Posted: 3/23/2024 10:36:15 AM EDT
[Last Edit: lysanderxiii]
[#6]
Quote HistoryOriginally Posted By bigbore: *on a barrel with quality threads. If the pitch diameter of the threads are not concentric with the bore, shims aren't going to magically make threaded things be concentric . . . . |
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Posted: 3/24/2024 11:12:47 AM EDT
[#7]
Quote HistoryOriginally Posted By spyderboy03: Not true. @bigbore has shown in a thread pretty recently even, that a crush washer is perfectly fine when installed correctly. It’s just not great practice. I’ve known people that use them and get away with it, but it’s best to use precision shims or (even better) turn the back of the muzzle device so it indexes when torqued against the shoulder of the barrel. |
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AZ, USA
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Posted: 3/26/2024 2:16:53 PM EDT
[#8]
Adco makes a 0.25" spacer.
https://adcofirearms.com/shop/manufacturer/adco/kac-spacer/ |
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SC, USA
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Posted: 3/26/2024 2:31:21 PM EDT
[#9]
I would get something that uses a better mount than an A2 hider.
But if you must, I would not use a crush washer. In any event, I would get the can and test concentricity before getting a muzzle device pinned, especially if you are going to do any of the above. |
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VA, USA
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Posted: 3/29/2024 11:34:08 AM EDT
[#10]
Years ago I sent my Colt 6721 upper to ADCO to have the barrel chopped and the original A2 FH P/W. I don't know what the barrel came out to be but the end result is legal. Seems like my own calculation was something like 14.73 but each case has to be carefully measured, preferably with the upper and BCG that is going to be used. BTW, the barrel with its new crown actually shot better than before. I have been very happy with this job ever since. With a legitimate company like ADCO, you don't tell them where to cut - you tell them what the desired result should be, and you provide the muzzle attachment you want to use. They are experts at making these things work.
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Posted: 3/29/2024 5:25:43 PM EDT
[#11]
Quote HistoryOriginally Posted By nightshade1: This is on a M4gery that I want to keep looking the part as much as possible. Its not so much the mount that bothers me but the suppressors, modern cans all look really busy. The M4SD still looks enough like it did on the original SOPMOD poster, and the GP-NATO is a plain traditional looking can. The Fallback is to order parts from Otter Creek Labs as I plan to buy a OCM5 later on for my SPR-ish and a planned movie-build Gordon carbine, I've emailed with someone from OCL and they say the flash suppressor is just enough for a 14.5" barrel so I'm confident of it on a 14.7. Get an A2x from BCM. You get the aesthetics of the A2 with the length necessary to get to 16”. And it’s pre drilled for P&W https://bravocompanyusa.com/bcm-a2x-extended-a2-flash-suppressor/ |
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MI, USA
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Posted: 3/30/2024 9:57:40 PM EDT
[Last Edit: nightshade1]
[#12]
Originally Posted By Luny421: Get an A2x from BCM. You get the aesthetics of the A2 with the length necessary to get to 16”. And it’s pre drilled for P&W https://bravocompanyusa.com/bcm-a2x-extended-a2-flash-suppressor/ Go back and re-read the OP. 
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MI, USA
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Posted: 3/30/2024 10:08:22 PM EDT
[#13]
Quote HistoryOriginally Posted By 1saxman: Years ago I sent my Colt 6721 upper to ADCO to have the barrel chopped and the original A2 FH P/W. I don't know what the barrel came out to be but the end result is legal. Seems like my own calculation was something like 14.73 but each case has to be carefully measured, preferably with the upper and BCG that is going to be used. BTW, the barrel with its new crown actually shot better than before. I have been very happy with this job ever since. With a legitimate company like ADCO, you don't tell them where to cut - you tell them what the desired result should be, and you provide the muzzle attachment you want to use. They are experts at making these things work. https://i.imgur.com/iThFskx.jpg Probably would have been the better thing to do. Might even help how overgassed this old(old) CL PSA barrel is. And I could still do that, this 14.7 was originally bought for a M727ish build but since then I decided I'm just going to buy a pre-made Gordon-style 12.5 barrel assembly, so I've got this barrel to use. I see the spacer ADCO sell, but its twice as long as needed and I'm (likely irrationally) paranoid about it not looking like it should. Others have suggested abandoning the idea of abandoning the A2-compatible suppressors and I am starting to lean that way (Otter Creek/Opsinc items, confirmed from a tech at OCL that their brake/FH make a 14.5" legal) but still on the fence. |
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Posted: 3/31/2024 4:17:01 PM EDT
[#14]
Quote HistoryOriginally Posted By nightshade1: I see the spacer ADCO sell, but its twice as long as needed and I'm (likely irrationally) paranoid about it not looking like it should. For me personally, sandpaper+flat surface+elbow grease. Same way I time/clock all my muzzle devices on all my rifles. Seems like that might be the only way if you're dead-set on that particular combo. |
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Posted: 3/31/2024 7:16:12 PM EDT
[#15]
Quote HistoryOriginally Posted By Dragynn: For me personally, sandpaper+flat surface+elbow grease. Same way I time/clock all my muzzle devices on all my rifles. Seems like that might be the only way if you're dead-set on that particular combo. I wouldn't recommend. The result is not going to be square no matter how flat the surface is. |
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