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DC, USA
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Posted: 3/25/2021 6:24:33 PM EDT
[#1]
The Dissipator became popular after the introduction of the early M855 ammo.
The original A1 carbines weren't as reliable as the full length A1 rifle with M193 ammo, but they were considered reliable enough. When the A2 carbine came out, M855 ammo wasn't in full production and not much changed. When M855 ammo came out, it used the same powder as M193 ammo and combined with the heavier bullet, wasn't as reliable in the A2 carbines as M193 ammo, but worked acceptably in the full length A2 rifles. Colt then came up with several modifications to the carbine to get it more reliable with M855 ammo and got the Army to call it the M4. The M4 mods were patented by Colt and the aftermarket was flush with standard carbine components, such as feed ramps, carbine buffers and extractor springs. In an effort to come out cheap and reliable with what they had, the Dissipator started being sold with a full length gas system. This was tuned for and worked well with M855 ammo, but lighter bullet ammo struggled to cycle the action. M855 ammo really overpowered 16" barrel carbines. Then Bushmaster came up with moving the gas port on a 16" barrel a similar amount as the difference between a 14.5" barrel and a 16" barrel in length. This solved the overgas problem with M855 ammo in a 16" barrel and allowed using lighter weight bullets. The Colt M4 has feed ramp mods, chamber mods, extractor spring mods, buffer weight mods and the gas port size was changed from the A2 carbines. Later the powder was changed to a cooler burning powder in M855 ammo, but the newer powder reduced the muzzle velocity in an M4, even though it produced the desired velocity from a 20" test barrel. Instead of improving the NATO spec M855 again, money was spent developing, non-NATO standard M855A1 ammo and powder, optimized for the M4 barrel length. M855A1 ammo produces higher gas port pressure, so the buffer weight was increased again to the H2 buffer. |
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Posted: 3/25/2021 11:38:32 PM EDT
[Last Edit: isullivan]
[#2]
Quote HistoryOriginally Posted By edwin907: I loved those dissipator setups. Here was my girlfriend's old rifle including the cool custom bayonet. https://i.imgur.com/uon2zkB.jpg https://i.imgur.com/aH4sQLU.jpg https://i.imgur.com/pAxTOjo.jpg Edwin, Good to see you are still around. Your SPR’s always gave me inspiration! I bought MR-10 for a MK12 build recently.  Attached File |
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Posted: 4/8/2021 7:48:12 AM EDT
[#3]
Quote HistoryOriginally Posted By Air_Soft_Contractor: ... Then Bushmaster came up with moving the gas port on a 16" barrel a similar amount as the difference between a 14.5" barrel and a 16" barrel in length. ... Bushmaster originally coined the term "Dissipator", using a shaved-down FSB for the gas block at normal carbine gas length on a 16" barrel with a dummy FSB at the rifle length for sights only. Simply a carbine with an extra FSB for sights pinned up front. |
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Posted: 4/8/2021 10:29:14 AM EDT
[#4]
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Posted: 4/8/2021 10:42:15 AM EDT
[#5]
Quote HistoryOriginally Posted By p229s: Bushmaster originally coined the term "Dissipator", using a shaved-down FSB for the gas block at normal carbine gas length on a 16" barrel with a dummy FSB at the rifle length for sights only. Simply a carbine with an extra FSB for sights pinned up front. Quote HistoryOriginally Posted By p229s: Originally Posted By Air_Soft_Contractor: ... Then Bushmaster came up with moving the gas port on a 16" barrel a similar amount as the difference between a 14.5" barrel and a 16" barrel in length. ... Bushmaster originally coined the term "Dissipator", using a shaved-down FSB for the gas block at normal carbine gas length on a 16" barrel with a dummy FSB at the rifle length for sights only. Simply a carbine with an extra FSB for sights pinned up front. Correct. Funny how you managed to say that without a pompous monologue LOL! Bravo! |
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Posted: 4/8/2021 10:43:32 AM EDT
[#6]
Quote HistoryOriginally Posted By beitodesstrafe: https://www.ar15.com/media/mediaFiles/138374/20210407_180216-1896817.jpg That is awesome Beito! Looks like it should be in Fallout! |
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Posted: 4/8/2021 10:45:21 AM EDT
[#7]
Quote HistoryOriginally Posted By E4W: That is awesome Beito! Looks like it should be in Fallout! Quote HistoryOriginally Posted By E4W: Originally Posted By beitodesstrafe: https://www.ar15.com/media/mediaFiles/138374/20210407_180216-1896817.jpg That is awesome Beito! Looks like it should be in Fallout! Thanks man! It's my newest... just wrapped ir up this week. I'll get a pic of all my dissys together later today. 
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Posted: 4/8/2021 11:47:36 AM EDT
[#8]
Rifle length gas system. Barrel work done by Retro Arms Works. Gas port opened, chopped, crowned, MD P/W, FSB installed.
 
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Posted: 4/8/2021 3:10:58 PM EDT
[#9]
9mm version
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Posted: 4/8/2021 3:55:00 PM EDT
[Last Edit: beitodesstrafe]
[#10]
Quote HistoryOriginally Posted By beitodesstrafe: Thanks man! It's my newest... just wrapped ir up this week. I'll get a pic of all my dissys together later today. Quote HistoryOriginally Posted By beitodesstrafe: Originally Posted By E4W: Originally Posted By beitodesstrafe: https://www.ar15.com/media/mediaFiles/138374/20210407_180216-1896817.jpg That is awesome Beito! Looks like it should be in Fallout! Thanks man! It's my newest... just wrapped ir up this week. I'll get a pic of all my dissys together later today. All 3 different dissys  Top: PSA midlength gas Middle: WW carbine gas Bottom: Colt rifle gas 
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Posted: 4/26/2021 6:14:24 PM EDT
[#11]
This is my setup today (minus a few minor tweaks), but I’m considering making changes.
Has anyone mounted a 12” ALG EMR on their dissipator? I’d appreciate any pics. I know there would be a small gap behind the FSP, but I don’t think it would be too bad and I don’t want to trim down the 13” due to interference with the M-Lok slots. I think I’m going to move the ACOG to a different rifle and put the H-1 back on this one but in a Unity FAST mount with their flip up 3x mag mount behind it. I’d like to get back functionality of the FSP that the mounted ACOG eliminates.  Attached File |
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KY, USA
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Posted: 4/26/2021 10:45:58 PM EDT
[#12]
 Brownells 605 1:12 twist barrel KP15 lower Recently took it out to a class and ran drills from 5 yards to 260 yards. Truly a dream to shoot and handle. |
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Posted: 4/26/2021 11:54:46 PM EDT
[#13]
Quote HistoryOriginally Posted By Dragoon_89: https://i.imgur.com/wcmtA4l.jpg Brownells 605 1:12 twist barrel KP15 lower Recently took it out to a class and ran drills from 5 yards to 260 yards. Truly a dream to shoot and handle. Nice. That must feel light as a feather. Kudos. Best, JBR |
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AZ, USA
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Posted: 4/27/2021 7:51:46 PM EDT
[#14]
 Had to give my Dissy upper a turn on my KP-15 after I gave it a once over with some rattlecan. |
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Posted: 4/27/2021 9:58:01 PM EDT
[#15]
Quote HistoryOriginally Posted By Dragoon_89: https://i.imgur.com/wcmtA4l.jpg Brownells 605 1:12 twist barrel KP15 lower Recently took it out to a class and ran drills from 5 yards to 260 yards. Truly a dream to shoot and handle. So what are these KP-15 slick side dissy's running weight wise? |
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Posted: 4/27/2021 10:44:00 PM EDT
[#16]
Quote HistoryOriginally Posted By mike_nds: So what are these KP-15 slick side dissy's running weight wise? A4 lower 2.625 lbs M4 lower 2.012 lbs (with carbine buffer) KE15 lower 1.704 lbs (with carbine buffer) Dissy barrels are pretty heavy though. |
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TX, USA
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Posted: 5/24/2021 5:53:36 PM EDT
[#17]
Quote HistoryOriginally Posted By Air_Soft_Contractor: The Dissipator became popular after the introduction of the early M855 ammo. The original A1 carbines weren't as reliable as the full length A1 rifle with M193 ammo, but they were considered reliable enough. When the A2 carbine came out, M855 ammo wasn't in full production and not much changed. When M855 ammo came out, it used the same powder as M193 ammo and combined with the heavier bullet, wasn't as reliable in the A2 carbines as M193 ammo, but worked acceptably in the full length A2 rifles. Colt then came up with several modifications to the carbine to get it more reliable with M855 ammo and got the Army to call it the M4. The M4 mods were patented by Colt and the aftermarket was flush with standard carbine components, such as feed ramps, carbine buffers and extractor springs. In an effort to come out cheap and reliable with what they had, the Dissipator started being sold with a full length gas system. This was tuned for and worked well with M855 ammo, but lighter bullet ammo struggled to cycle the action. M855 ammo really overpowered 16" barrel carbines. Then Bushmaster came up with moving the gas port on a 16" barrel a similar amount as the difference between a 14.5" barrel and a 16" barrel in length. This solved the overgas problem with M855 ammo in a 16" barrel and allowed using lighter weight bullets. The Colt M4 has feed ramp mods, chamber mods, extractor spring mods, buffer weight mods and the gas port size was changed from the A2 carbines. Later the powder was changed to a cooler burning powder in M855 ammo, but the newer powder reduced the muzzle velocity in an M4, even though it produced the desired velocity from a 20" test barrel. Instead of improving the NATO spec M855 again, money was spent developing, non-NATO standard M855A1 ammo and powder, optimized for the M4 barrel length. M855A1 ammo produces higher gas port pressure, so the buffer weight was increased again to the H2 buffer. Huh? |
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Posted: 5/24/2021 9:49:42 PM EDT
[Last Edit: 762wolverine]
[#18]
Quote HistoryOriginally Posted By Dragoon_89: https://i.imgur.com/wcmtA4l.jpg Brownells 605 1:12 twist barrel KP15 lower Recently took it out to a class and ran drills from 5 yards to 260 yards. Truly a dream to shoot and handle. Very nice and with the 1/12. What is the unloaded weight? |
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Posted: 6/13/2021 6:56:57 PM EDT
[#19]
Bttt
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KY, USA
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Posted: 6/16/2021 9:28:58 PM EDT
[Last Edit: Dragoon_89]
[#20]
Quote HistoryOriginally Posted By 762wolverine: Very nice and with the 1/12. What is the unloaded weight? 5.6 pounds with sling (added after pic was taken) and JP silent captured spring. |
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Posted: 6/19/2021 12:54:04 AM EDT
[#21]
Quote HistoryOriginally Posted By Dragoon_89: 5.6 pounds with sling (added after pic was taken) and JP silent captured spring. Quote HistoryOriginally Posted By Dragoon_89: Originally Posted By 762wolverine: Very nice and with the 1/12. What is the unloaded weight? 5.6 pounds with sling (added after pic was taken) and JP silent captured spring. That is a very nice dissipator. Unfortunately Brownells no longer sells that upper. It just looks so well balanced. |
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KY, USA
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Posted: 6/21/2021 5:11:55 AM EDT
[Last Edit: Dragoon_89]
[#22]
Quote HistoryOriginally Posted By 762wolverine: That is a very nice dissipator. Unfortunately Brownells no longer sells that upper. It just looks so well balanced. It is sad that Brownells stopped selling those parts. I got just the barrel for $180 something as part of their retro clearance sales. The rifle is indeed very well balanced. Balances on the slip ring. |
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CA, USA
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Posted: 7/6/2021 9:01:41 PM EDT
[Last Edit: mrbieler]
[#23]
Spikes/AIM Surplus GMP Dissipator upper in the Exchange. Not mine.
Spikes/AIM dissipator |
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Posted: 7/7/2021 5:12:52 PM EDT
[#24]
Quote HistoryOriginally Posted By mrbieler: Spikes/AIM Surplus GMP Dissipator upper in the Exchange. Not mine. Spikes/AIM dissipator Gone |
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Posted: 7/7/2021 6:07:12 PM EDT
[#25]
I've got one of those barrels on my 601/605-ish build.
So much lighter than the PSA Dissy barrel on my other rifle. |
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GA, USA
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Posted: 7/7/2021 7:25:06 PM EDT
[#26]
Iam about to have my first Dissy. Yep from PSA’s 4th of July sale ......Wish me luck and all advice welcome thanks
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Posted: 7/7/2021 10:35:35 PM EDT
[#27]
Quote HistoryOriginally Posted By exile72: Iam about to have my first Dissy. Yep from PSA’s 4th of July sale ......Wish me luck and all advice welcome thanks
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Posted: 7/9/2021 9:12:13 AM EDT
[Last Edit: Trumpet]
[#28]
So, where to find a 1:7, mid-length dissipator barrel with FSB?
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GA, USA
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Posted: 7/9/2021 8:00:24 PM EDT
[#29]
I was tired of waiting on BCM to stock their Kino upper so I had one made
 So here’s my Mini Mock Dissipator Build. Carbine gas FSB at Midlength 
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Posted: 7/9/2021 8:26:22 PM EDT
[#30]
Quote HistoryOriginally Posted By Dingo-Dog: I was tired of waiting on BCM to stock their Kino upper so I had one made So here's my Mini Mock Dissipator Build. Carbine gas FSB at Midlength https://i.imgur.com/UVMYFpW_d.webp?maxwidth=640&shape=thumb&fidelity=medium I have one Kino, a CMMG, and wouldn't mind another. |
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GA, USA
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Posted: 7/9/2021 8:37:54 PM EDT
[Last Edit: Dingo-Dog]
[#31]
@packinheavy here ya go:
Milspec Upper Toolcraft nitride BCG BCM delta ring and barrel nut Bootleg Ind 12.5 nitride 5.56 barrel Geissele gas block pinned F marked FSB pinned and BCM end cap Midwest Ind rear sight Had an awesome internet stranger pinned the FSB and gas block. Haven’t got to shoot it yet. I had a BCM Kino prior but I put a Larue quad and it was way to front heavy with a pistol lower. So this one is staying as is, well I’ll add a light soon. |
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Posted: 7/9/2021 8:58:48 PM EDT
[#32]
Quote HistoryOriginally Posted By Dingo-Dog: @packinheavy here ya go: Milspec Upper Toolcraft nitride BCG BCM delta ring and barrel nut Bootleg Ind 12.5 nitride 5.56 barrel Geissele gas block pinned F marked FSB pinned and BCM end cap Midwest Ind rear sight Had an awesome internet stranger pinned the FSB and gas block. Haven't got to shoot it yet. I had a BCM Kino prior but I put a Larue quad and it was way to front heavy with a pistol lower. So this one is staying as is, well I'll add a light soon. 
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GA, USA
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Posted: 7/9/2021 9:10:05 PM EDT
[#33]
Took me forever to find a 12.5 barrel that didn’t step down until the very end of the barrel
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AZ, USA
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Posted: 7/15/2021 6:34:52 PM EDT
[#34]
Had to change out my handguard on my Dissy, no longer looks as retro inspired, but definitely more functional now.
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Posted: 7/20/2021 1:33:34 PM EDT
[#35]
The Dissipator that never was.... My unicorn. The BCM Dissipator. A few examples were made to see if anyone wanted them, and then they never made it into production. I know where a couple of them are, but unfortunately they are not in my safe. This was a good looking rifle. (Picture by Stickman)
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Posted: 7/20/2021 1:34:04 PM EDT
[#36]
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Posted: 7/20/2021 9:37:53 PM EDT
[Last Edit: Balloo]
[#37]
Quote HistoryOriginally Posted By Lancelot: The Dissipator that never was.... My unicorn. The BCM Dissipator. A few examples were made to see if anyone wanted them, and then they never made it into production. I know where a couple of them are, but unfortunately they are not in my safe. This was a good looking rifle. (Picture by Stickman) https://www.ar15.com/media/mediaFiles/668/bcm_dissy_22-2021410.jpg When it first came out they were talking about making them, SWAT magazine had an article showing a class that the author was taking. In the background there was a guy running the BCM Dissy. Then there were the adds from BCM that featured a Dissy mixed in with several other rifles. |
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Posted: 7/21/2021 10:29:48 AM EDT
[#38]
It was a lightweight midlength with a pinned gas block.
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Posted: 7/22/2021 10:35:38 PM EDT
[Last Edit: PilatusTurbo]
[#39]
New to the forum, but been lurking and learning for years. Didn't Figured all the build threads I've searched for and learned from, I should finally jump in, become a real member and jump in. Got thick skin, I do White Knight for Taurus from time to time, and generally build poverty ponies.
Also love me some Glocks. I recently was inspired by my buddy to build a faux dissipator. Always wanted to do one, so I finally did. Took the M5 he gave me to position the front sight block, and it really worked well. Set screws through sling gas port machining hole and through bayonet lug, and where taper pins once were. Carbine length lo pro under the M5. I know it ain't much, but it's really the neatest build I've done, out of many over the last few years. I've drilled and pinned an FSB before, but I've found the set screw method with both bottom set screws dimpled into the barrel is pretty solid. Anyway, glad to finally be here. I did look, but unless I missed it, I didn't see anything in COC or rules about where to make welcome post. So here I am. 
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Posted: 7/22/2021 10:48:30 PM EDT
[#40]
Quote HistoryOriginally Posted By PilatusTurbo: New to the forum, but been lurking and learning for years. Didn't Figured all the build threads I've searched for and learned from, I should finally jump in, become a real member and jump in. Got thick skin, I do White Knight for Taurus from time to time, and generally build poverty ponies. Also love me some Glocks. I recently was inspired by my buddy to build a faux dissipator. Always wanted to do one, so I finally did. Took the M5 he gave me to position the front sight block, and it really worked well. Set screws through sling gas port machining hole and through bayonet lug, and where taper pins once were. Carbine length lo pro under the M5. I know it ain't much, but it's really the neatest build I've done, out of many over the last few years. I've drilled and pinned an FSB before, but I've found the set screw method with both bottom set screws dimpled into the barrel is pretty solid. Anyway, glad to finally be here. I did look, but unless I missed it, I didn't see anything in COC or rules about where to make welcome post. So here I am. https://i.imgur.com/PGfXxFK.jpg 
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MI, USA
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Posted: 7/23/2021 12:14:11 AM EDT
[#41]
Quote HistoryOriginally Posted By PilatusTurbo: Anyway, glad to finally be here. I did look, but unless I missed it, I didn't see anything in COC or rules about where to make welcome post. So here I am. https://i.imgur.com/PGfXxFK.jpg Welcome, and nice rifle. A1 stock? |
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Posted: 7/23/2021 12:21:31 AM EDT
[Last Edit: PilatusTurbo]
[#42]
No, it's A2. I did the best I could with it. Converting the carbine barrel only took a few hours the other night. I'm really happy with it. It's a neat concept having the gas block under the hand guards. I may take the gas block, drill and tap the side of the gas port pipe up the block for a 10-32 set screw and make it adjustable. Done a couple like that.
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Posted: 7/23/2021 12:25:22 AM EDT
[#43]
Quote HistoryOriginally Posted By PilatusTurbo: No, it's A2. I did the best I could with it. Converting the carbine barrel only took a few hours the other night. I'm really happy with it. It's a neat concept having the gas block under the hand guards. I may take the gas block, drill and tap the side of the gas port pipe up the block for a 10-32 set screw and make it adjustable. Done a couple like that. It definitely turned out great. |
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Posted: 7/23/2021 12:32:19 AM EDT
[#44]
Thanks man. I just realized, that this front sight block on the dissipator here, I converted to set screw bottom install was originally on my 10.5", that I made adjustable for it for the shorter barrel. Drill, tap for 10-32 on the side, and tune it and loctite it or center punch the edge of the hole to lock it. Notch the set screw to know how many turns you're at. Did it from stuff I googled and learned here and other places. Also learned to make the set screw FSB from googling and stuff here and other places LOL I like to google how to do my own stuff.
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Posted: 7/23/2021 5:08:21 PM EDT
[#45]
I have several others as well, but this is my favorite due to being an original factory Bushmaster. It's an LE trade in that I had the barrel turned down on to lighten it up. I need to put an A1 length stock on it eventually.
I'll post pics of the others later.  Attached File |
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Posted: 7/23/2021 5:20:21 PM EDT
[#46]
Oh that's NICE. I'm playing with taking the M5 off mine and just throwing the carry handle and A2 handguards on it. It's a rifle stock carbine, but with all the crap I have hanging off of it, it weighs a c-hair under 9 lbs.
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Posted: 7/23/2021 9:15:29 PM EDT
[#47]
CMMG with M5 RAS and MATECH rear BUIS. I had a Leupold 1.5-5 MRT on it, but pulled it off to put on another rifle. I need to put an optic back on it soon.
 Attached File |
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Posted: 7/23/2021 9:31:12 PM EDT
[#48]
Nice, also. How many dissies you got? CMMG .22 or 5.56?
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Posted: 7/23/2021 10:11:40 PM EDT
[#49]
5.56mm
5ish or so. I have a Palmetto upper not on a lower at the moment. But I have several lowers I could put it on. I sold its twin earlier this year. I also have two Voodoo Tactical 16.5" ultralightweight barrels. They have rifle gas systems. One also has a pinned on fron sight. The other has an A.R.M.S. folding front sight gas block. The fixed front sight barrel is on a C7 upper and will be going on a KE Arms OD Green polymer lower when it shows up. It's currently on a metal lower with an A2 stock. The barrel with the folding front sight is on a FDE KE Arms polymer lower. I'll post more pics later. I also have Kino CMMG SBR that is sorta Dissipator-ish. I've always had a bit of a Dissipator fetish. I like flat tops, but the fixed iron sight rifles are what I really prefer in this format. Although as I age, even those might get optics.
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Posted: 7/23/2021 10:19:27 PM EDT
[#50]
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