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1/5/2026 8:25:02 PM EDT
[#1]
Grabbed one for around $350 about six months ago.
1/10/2026 7:56:34 PM EDT
[#2]
Just started a regional swat build and I’m trying to see what info there is on optics. I keep seeing mostly aimpoint T1/T2 and Eotech XPS3-0. What optics are considered clone correct?
1/11/2026 4:29:34 AM EDT
[Last Edit: YukonBoy03][Edited] [#3]
Originally Posted By Womtade:
Just started a regional swat build and I’m trying to see what info there is on optics. I keep seeing mostly aimpoint T1/T2 and Eotech XPS3-0. What optics are considered clone correct?
View Quote



T1/T2/H1/H2
The American assembled Sig Romeo (can't remember which one)
The RDS and MRO are also approved

Also. the Unity mounts are becoming a lot more common.
1/17/2026 12:38:29 AM EDT
[#4]
Quote History
Originally Posted By 3ACR_Scout:

I'm a bit late, haven't been on this thread in a while. Forum member hrt4me posted photos of his duty weapon used on one of the HRT's vehicle teams a couple years back. It used a regular Colt LE6920 lower, right down to the shaved selector stops and everything. Apparently select fire lowers aren't that common on FBI weapons, so commercial Colt lowers are good for these clones.

If I ever come across one, I'd like to use one of these old Rock River lowers, before they changed their roll mark. These are what the FBI used before switching to Colt. It would be interesting and different to built a clone on one of these lowers, to represent one that was upgraded with the Geissele rail and Colt barrel later in life.

https://www.ar15.com/media/mediaFiles/27888/RRA_LAR-15_Cleveland_IL_6_jpg-3606218.JPG
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By 3ACR_Scout:
Originally Posted By Fence_Post:
I've sourced everything needed except for a colt lower.  What markings on the Colt lower(s) are correct for the FBI clone?

I'm a bit late, haven't been on this thread in a while. Forum member hrt4me posted photos of his duty weapon used on one of the HRT's vehicle teams a couple years back. It used a regular Colt LE6920 lower, right down to the shaved selector stops and everything. Apparently select fire lowers aren't that common on FBI weapons, so commercial Colt lowers are good for these clones.

If I ever come across one, I'd like to use one of these old Rock River lowers, before they changed their roll mark. These are what the FBI used before switching to Colt. It would be interesting and different to built a clone on one of these lowers, to represent one that was upgraded with the Geissele rail and Colt barrel later in life.

https://www.ar15.com/media/mediaFiles/27888/RRA_LAR-15_Cleveland_IL_6_jpg-3606218.JPG


always to be found on GB, theres a varmint and this one 1149190523
2/6/2026 4:13:41 AM EDT
[#5]
Need some help, I've been trying to shore up the "near clones" I've managed to build over the years, I built an "FBI" back when the first short rail green Mk4s came out on the Geissele website, before a lot of info came to light in this thread and I got a few things wrong I'm trying to fix. I had a couple of questions on "clone correct" for a regional rifle:

  1. I know that the 6933 profile barrel with 0.750 GB journal is correct. Are all of these barrels undrilled before they get the Geissele GB pinned, or are there any that are FSB take offs? (I currently have a Colt HRT profile with a shaved FSB, which while plausible seems to not be really correct for anything). Do these ever come in stock anymore as a stripped undrilled barrel?

  2. Is the silver/stainless Geissele gas block still correct? Pinned and set screwed? Looks like you guys said the FBI ones are reduced port size 0.067/0.068 but I've got a silver commercial one from years ago, I'm assuming they look identical from the outside.

  3. It used to be that all the regional rifles I saw photos of had A2 flashhiders. Were there any that ran Surefire cans, and if so what are the right cans and mounts? Currently I have a SF closed tine. I saw photos with SF3P but I believe those were HRT.

  4. It looks like there's a bunch of photos with Huxworx now as well, I could go that way but I'm not really into the Huxworx ecosystem. Is it the right one the Flow 556K FDE with the "FLASH HIDER-QD 556 1/2X28"? Those are on the regional rifles? Would that even be right on a gun with the first gen rail or have they moved onto the new design with the longer bottom rail?

  5. I saw a couple of photos with a team running Unity FAST, which is great (part the reason I rarely shot this gun was lower 1/3 was too low for me on a red dot gun). Ya'll know what color mount they're using, can't tell if its black or green, definitely doesn't look tan.

Appreciate the help, pic of how it's looked for many years now (ignore the AUG):

2/6/2026 1:21:47 PM EDT
[#6]
I guess this is kinda close then?
11.5 Colt Heavy/HRT barrel
Geissele rail
T2
Colt BCG
Surefire Scout
I guess the KAC micros instead of Troys is a ding against.


3/4/2026 1:49:17 PM EDT
[#7]
Quote History
Originally Posted By Slu54:
Need some help, I've been trying to shore up the "near clones" I've managed to build over the years, I built an "FBI" back when the first short rail green Mk4s came out on the Geissele website, before a lot of info came to light in this thread and I got a few things wrong I'm trying to fix. I had a couple of questions on "clone correct" for a regional rifle:

  1. I know that the 6933 profile barrel with 0.750 GB journal is correct. Are all of these barrels undrilled before they get the Geissele GB pinned, or are there any that are FSB take offs? (I currently have a Colt HRT profile with a shaved FSB, which while plausible seems to not be really correct for anything). Do these ever come in stock anymore as a stripped undrilled barrel?

  2. Is the silver/stainless Geissele gas block still correct? Pinned and set screwed? Looks like you guys said the FBI ones are reduced port size 0.067/0.068 but I've got a silver commercial one from years ago, I'm assuming they look identical from the outside.

  3. It used to be that all the regional rifles I saw photos of had A2 flashhiders. Were there any that ran Surefire cans, and if so what are the right cans and mounts? Currently I have a SF closed tine. I saw photos with SF3P but I believe those were HRT.

  4. It looks like there's a bunch of photos with Huxworx now as well, I could go that way but I'm not really into the Huxworx ecosystem. Is it the right one the Flow 556K FDE with the "FLASH HIDER-QD 556 1/2X28"? Those are on the regional rifles? Would that even be right on a gun with the first gen rail or have they moved onto the new design with the longer bottom rail?

  5. I saw a couple of photos with a team running Unity FAST, which is great (part the reason I rarely shot this gun was lower 1/3 was too low for me on a red dot gun). Ya'll know what color mount they're using, can't tell if its black or green, definitely doesn't look tan.

Appreciate the help, pic of how it's looked for many years now (ignore the AUG):

https://i.postimg.cc/L4jFRmdG/signal-2026-02-05-234549-002.jpg
View Quote


The colt barrels its both new and take off FSB barrels.  It all depends on how the barrels came and if Quantico was running short on funds.  I have seen one that had a shaved down FSB but that was at Quantico.
4/3/2026 2:55:14 PM EDT
[#8]
Makes sense, thanks.

I've got a spare new undrilled cage marked 6933 bbl if anyone's looking for one
4/5/2026 1:13:36 PM EDT
[#9]
@Slu54

Sent you an IM regarding the barrel.
4/6/2026 2:20:27 PM EDT
[#10]
Finally got around to posting my build. Only deviations are the Romeo5 on the Larue LT660 and the Larue Apeg and Texas BCG that I had laying around. Fun gun to say the least. Attached File
Attached File
Attached File
4/6/2026 9:32:37 PM EDT
[#11]
Quote History
Originally Posted By freefaller1985:
Finally got around to posting my build. Only deviations are the Romeo5 on the Larue LT660 and the Larue Apeg and Texas BCG that I had laying around. Fun gun to say the least. https://www.ar15.com/media/mediaFiles/474620/20260406_125112_jpg-3742244.JPGhttps://www.ar15.com/media/mediaFiles/474620/20260406_125133_jpg-3742245.JPGhttps://www.ar15.com/media/mediaFiles/474620/20260406_125205_jpg-3742246.JPG
View Quote
The red white and blue index clips are a great throwback to old arfcom, I need to track down a pack of those at some point. They only have black and tan now
Collector, historian, and enthusiast of A.R.M.S. rails, mounts, and accessories.
4/6/2026 9:45:18 PM EDT
[#12]
Quote History
Originally Posted By thatARMSguy:
The red white and blue index clips are a great throwback to old arfcom, I need to track down a pack of those at some point. They only have black and tan now
View Quote


Ha, love that someone else has them!  Can’t remember where I got mine. People ask about them all the time.

Pic thread….

Attached File
4/6/2026 10:10:47 PM EDT
[#13]
Quote History
Originally Posted By seand1111:


Ha, love that someone else has them!  Can’t remember where I got mine. People ask about them all the time.

Pic thread….

https://www.ar15.com/media/mediaFiles/24834/IMG_1615_jpeg-3742496.JPG
View Quote

Larue Tactical
4/6/2026 10:14:15 PM EDT
[#14]
Quote History
Originally Posted By freefaller1985:

Larue Tactical
View Quote


Yeah, but I don’t recall how or why. I never ordered a set like that from what I can recall.  But I am old… I’ve forgotten more than I can remember at this point!
4/10/2026 12:53:29 PM EDT
[Last Edit: mbinky][Edited] [#15]
Well, finally got to put it together.  Form 1'd my Colt 6720 last summer.  The Colt 11.5" stripped barrel I backordered last August just came in a month ago.  Sent it to Adco to pin the Geissele gas block.  I cal it "FBi-ish" lol.  Now to start shopping for a can.



4/10/2026 1:43:09 PM EDT
[#16]
Going rate for a new Gen 1 Mk4 rail? I've been holding parts now for a better part of 3 years and I don't think I'm gonna get to this build.
4/15/2026 3:28:34 PM EDT
[Last Edit: Grey_Company][Edited] [#17]
is this the correct barrel for 11.5 HRT setup?

https://www.specializedarmament.com/%E2%80%94-barrel-assemblies-parts/barrel-assy-11.5-inch-r0933hb-commando/
4/24/2026 3:26:47 PM EDT
[#18]
Concerning the old Troy Alpha uppers, I'm almost certain they were all using 10.5 barrels, not 10.3s, and occasionally 11.5s. This means they were almost certainly not Colt uppers although Colt lowers can be seen. Could they be factory Troy uppers with Troy barrels? They just did a "limited" drop of Alpha 10.5 uppers on their site using the current Alpha 9 rail (not TRX Extreme). No info on the barrel other than the length so far. Pretty in the weeds about a niche build but if the barrel is a mystery, then I'd consider getting a nicer 10.5.
4/30/2026 5:09:22 AM EDT
[#19]
Tried to go through 90 pages of the most current builds information, since this thread started in 2018 and much has been learned, etc. Any chance there is a cleaner page with some current information out there? Seems Ronin's Grips has a really detailed list of FBI firearms here: https://blog.roninsgrips.com/the-fbis-hostage-rescue-team-small-arms-overview-for-2024-2025/

HRT used Tan and not Green, but they did use Green but or Black. Regionals did this and didn't do that. I feel like even the FBI probably doesn't even know what their Quartermaster was dishing out at this point.
4/30/2026 5:11:55 AM EDT
[#20]
Quote History
Originally Posted By thatARMSguy:
The red white and blue index clips are a great throwback to old arfcom, I need to track down a pack of those at some point. They only have black and tan now
View Quote


Send me a DM with your shipping information and I'll mail you a pack with one each of the red/white/blue clips.
4/30/2026 7:56:15 AM EDT
[#21]
Quote History
Originally Posted By colexnin:
Tried to go through 90 pages of the most current builds information, since this thread started in 2018 and much has been learned, etc. Any chance there is a cleaner page with some current information out there? Seems Ronin's Grips has a really detailed list of FBI firearms here: https://blog.roninsgrips.com/the-fbis-hostage-rescue-team-small-arms-overview-for-2024-2025/

HRT used Tan and not Green, but they did use Green but or Black. Regionals did this and didn't do that. I feel like even the FBI probably doesn't even know what their Quartermaster was dishing out at this point.
View Quote

Believe the original post was updated with comments from someone in the FBI with exactly what the colors mean.
4/30/2026 4:07:40 PM EDT
[#22]
Thank you. I'll keep looking around. I'm guessing it was a more recent post, like in the high 70's and up?
4/30/2026 7:03:34 PM EDT
[#23]
Quote History
Originally Posted By colexnin:
Thank you. I'll keep looking around. I'm guessing it was a more recent post, like in the high 70's and up?
View Quote

No. It's on the first post of Page 1, the last quote in that post. I'm copying it here for you.

A black rifle can be completely clone correct, it would just represent a regular agent's rifle, not HRT or Regional SWAT. This thread started as a result of the interest in the green Geissele Mk4 handguards that showed up on Regional SWAT rifles, but all four Geissele colors are in use by the FBI. People are just (understandably) a bit fixated on the green ones because they look great. That's led to what a lot of people are doing, which is combining the features of the HRT and SWAT rifles into a mixed clone (SWAT green handguard and CTR stock, HRT heavy barrel, and Spuhr HRT Aimpoint mount).

I think it would be great if @ARogueNinja could update the original post to reflect the four FBI variants that are out there (these details are incomplete and could be a little off):

HRT: DDC Mk4 handguard, 11.5" Colt HRT heavy barrel, Aimpoint T-2 on Spuhr mount (not sure about the stock), black or FDE(?) CTR or Colt stock

Regional SWAT: OD Green Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Aimpoint T-2 on Daniel Defense mount, OD green CTR or Colt stock

Vehicle Teams: Grey Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Sig Romeo, FAB Defense PTK AFG, Maxim Defense collapsible stock

https://www.ar15.com/media/mediaFiles/1182/green___grey_M4_carbines_jpg-1584398.JPG

Field Agent: Black Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Aimpoint T-2 on Daniel Defense mount or Sig Romeo, black CTR or Colt stock

I think this is a grey Mk4 issued to hrt4me but is (I believe) representative of the standard agent rifle configuration. I don't recall seeing any photos in this thread of a regular agent's carbine:

https://i.imgur.com/A6UVttH.jpg
5/1/2026 7:10:53 PM EDT
[#24]
Quote History
Originally Posted By colexnin:


Send me a DM with your shipping information and I'll mail you a pack with one each of the red/white/blue clips.
View Quote
Appreciate the offer, another user already sent me a couple though
Collector, historian, and enthusiast of A.R.M.S. rails, mounts, and accessories.
5/3/2026 5:06:58 PM EDT
[#25]
@mdavis. It’s been added to OP
5/21/2026 7:08:51 AM EDT
[Last Edit: aftac][Edited] [#26]
Well finally finished.

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5/21/2026 8:04:29 AM EDT
[#27]
Hello!

Which of the following 11.5" Colt barrels should I go with for my FBI/HRT/Regional Swat clone?

1. https://coltparts.com/colt-m4-commando-11-inch-556-barrel-assembly-fbi-hrt-profile/

2. https://coltparts.com/colt-m4-commando-11-5-inch-5-56mm-heavy-barrel/

3. Another option?

Thank you for your guidance!



5/21/2026 8:41:15 AM EDT
[#28]
Quote History
Originally Posted By Hylomorphism:
Hello!

Which of the following 11.5" Colt barrels should I go with for my FBI/HRT/Regional Swat clone?

1. https://coltparts.com/colt-m4-commando-11-inch-556-barrel-assembly-fbi-hrt-profile/

2. https://coltparts.com/colt-m4-commando-11-5-inch-5-56mm-heavy-barrel/

3. Another option?

Thank you for your guidance!



View Quote

Assume you mean an upper with the green rail? If yes, the #1 barrel.
5/21/2026 8:21:11 PM EDT
[Last Edit: Hylomorphism][Edited] [#29]
Quote History
Assume you mean an upper with the green rail? If yes, the #1 barrel.
View Quote


That is correct! I'll be using an ODG Geissele FBI Handguard. Now, isn't barrel #1 a mere "government profile"? The fact that it's demarcated as an "FBI HRT Profile" really confused me.

Please clarify and advice. Thank you!
5/31/2026 10:45:06 PM EDT
[#30]
Sexy asf
6/27/2026 6:08:24 PM EDT
[#31]
I might be stricken down for blasphemy but I'm seriously considering a Rhodie 6 for this build with a comparable looking flash hider on a Plan B. Wouldn't be as nice as the surefire QD, but they're apparently an incredible can.
7/2/2026 3:16:03 PM EDT
[Last Edit: Jrwebb][Edited] [#32]
Hey everyone
Those that have the FBI heavy barrel, what ammo do you find is best?
7/4/2026 11:09:22 PM EDT
[#33]
They just got a new contract for Federal’s 64-grain Premium Tactical Bonded  for their duty rounds.
7/5/2026 1:49:16 AM EDT
[#34]
Quote History
Originally Posted By shane01:
They just got a new contract for Federal's 64-grain Premium Tactical Bonded  for their duty rounds.
View Quote


Curious to see what kind of performance that round brings
"Do you want to know who you are? Don't ask. Act! Action will delineate and define you." - Thomas Jefferson
VCDL Member
Volunteer Firefighter/EMT and damn PROUD to be! : Arfcom Callsign "Bucket 2"
7/7/2026 9:01:25 PM EDT
[#35]
Quote History
Originally Posted By shane01:
They just got a new contract for Federal’s 64-grain Premium Tactical Bonded  for their duty rounds.
View Quote


Probably the same round they've always had just renewed.  We have the same rounds, we just buy off CBP's massive contract instead of doing our own.
7/10/2026 12:06:55 PM EDT
[#36]
Quote History
Originally Posted By cone256:


Probably the same round they've always had just renewed.  We have the same rounds, we just buy off CBP's massive contract instead of doing our own.
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By cone256:
Originally Posted By shane01:
They just got a new contract for Federal’s 64-grain Premium Tactical Bonded  for their duty rounds.


Probably the same round they've always had just renewed.  We have the same rounds, we just buy off CBP's massive contract instead of doing our own.


Isn’t this the new FBI T4 ammo? Current being the FBI T3 62 grain bonded soft point.
"I do what I want" - Abu Hajar
7/27/2026 9:40:16 AM EDT
[#37]
Came across this picture on the internet. Had never seen Aimpoint Comp M4S optics before on what appears to be old Mark Brown Custom CQB rear sight riser mounts. I guess those predate the Dominator mounts?

Anyways, cool to see these older 11.5 carbines with PEQ2s and aimpoints.

Attached File
"I do what I want" - Abu Hajar
8/9/2026 10:28:55 AM EDT
[#38]

8/14/2026 4:37:45 AM EDT
[#39]
Quote History
Originally Posted By modelbuilder56:
https://i.imgur.com/2CPJoKzh.jpg
Not 100% correct, kinda close....
View Quote


How do you like the Mini 2 on there?
8/22/2026 10:48:46 PM EDT
[Last Edit: 5RWill][Edited] [#40]
Finished the HRT upper today. Had to put it on the pistol forgot my keys to get to my sbr lower. Still have some things to get.



Mainly gotta get Troy MBUIS, Romeo 4XT, AFG and finish some ceramide on the lower to match the rail. Then I’m gonna dye thr bcm grip to match as well.

8/24/2026 5:40:13 PM EDT
[#41]
Quote History
Originally Posted By 5RWill:
Finished the HRT upper today. Had to put it on the pistol forgot my keys to get to my sbr lower. Still have some things to get.

https://www.snipershide.com/shooting/attachments/img_0005-jpeg.8998224/
View Quote

Looks good, but HRT uses DDC handguards. Green is Regional SWAT. Here’s the breakdown of variations again (I know some details have evolved, but this is where they started).

HRT: DDC Mk4 handguard, 11.5" Colt HRT heavy barrel, Aimpoint T-2 on Spuhr mount (not sure about the stock), black or FDE(?) CTR or Colt stock

Regional SWAT: OD Green Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Aimpoint T-2 on Daniel Defense mount, OD green CTR or Colt stock

Vehicle Teams: Grey Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Sig Romeo, FAB Defense PTK AFG, Maxim Defense collapsible stock

Field Agent: Black Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Aimpoint T-2 on Daniel Defense mount or Sig Romeo, black CTR or Colt stock
8/27/2026 6:38:56 PM EDT
[Last Edit: 5RWill][Edited] [#42]
Quote History
Originally Posted By 3ACR_Scout:

Looks good, but HRT uses DDC handguards. Green is Regional SWAT. Here’s the breakdown of variations again (I know some details have evolved, but this is where they started).

HRT: DDC Mk4 handguard, 11.5" Colt HRT heavy barrel, Aimpoint T-2 on Spuhr mount (not sure about the stock), black or FDE(?) CTR or Colt stock

Regional SWAT: OD Green Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Aimpoint T-2 on Daniel Defense mount, OD green CTR or Colt stock

Vehicle Teams: Grey Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Sig Romeo, FAB Defense PTK AFG, Maxim Defense collapsible stock

Field Agent: Black Mk4 handguard, 11.5" Colt LE6933 government profile barrel, Aimpoint T-2 on Daniel Defense mount or Sig Romeo, black CTR or Colt stock
View Quote


Damn wait a minute the whole first page is OD green that's not HRT? Even the videos show OD green MK4s? Those are regional teams on all the videos?

Even then it wont be 100% clone correct. I went geissele for barrel to shed some weight, will be using a different pistol grip. Had a DBAL A2 but sold it. Then I picked up a RC2.

https://www.youtube.com/watch?v=bIKj01KqYtc

If that's the case I guess that's what I'm cloning lol. This was mock up though, I've still gotta get the Romeo 4xt, AFG, and put it on my SBR lower. I just tossed it on my Pistol lower for show with the 515gm.

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