View Full Version : BRT OPTIMUM build
BLUF- Very smooth, LW shooter.
Purpose of build- To build a LW rifle from the ground up with smooth function and light weight as a priority.
Concept of parts chosen- The Black River Tactical Optimum barrel piqued my interest. I chose a handful of other parts that are such as the LMT E-Carrier and SLR adjustable gas block after looking at feedback from other shooters.
Build list-
Magpul SL stock-I prefer the negative pitch.
A5 RE/Green Sprinco spring/ A5H2 buffer-go to setup.
Magpul K2 grip-preferred Grip. Haven't experimented much beyond the K2.
Stripped S&W lower-works with PMAGs, available locally.
Sionics LPK- my preferred LPK.
Vltor MUR w/FA- more protection for my face in the event of a kaboom. Possibly more accuracy.
BCM ambi CH- was the go-to at the time I purchased. Currently prefer Radian ambis.
LMT enhanced carrier/Sionics bolt- interested in if this will run noticeably smoother.
BRT OPTIMUM 16" barrel- looking to go LW with the barrel. Interested in the gas system and low weight.
SLR Rifleworks AGB- supposed to be the best AGB
ALG V3 13" DDC- simple, lightweight, economical, and doesn't feel like gripping a pencil.
Forward Control Designs 6315 FH- more of what I like about the A2.
Accu-washer shim set- a simple way to get a MD torqued to 20#
LMT rear sight- I have ample time with A2 rear sights. Like them for what they are.
DD front sight- Looks like an A2 front sight.
VCAS Multicam sling w/ Magpul QD- VCAS is my go to.
Aimpoint CompC3 2MOA RDS- Been using since '08.
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Overall, exceptionally smooth shooter. I shoot from below zero to 100+ degrees, and have had no reliability issues. Round count is now 2686 rounds.
Deleted due to low knowledge base.
I like the thought that went into the build, and I like the build a lot. I am (slowly) building a upper with the Optimum barrel. Mine will have a standard BCG and gas block and I will run a 1-4 optic.
Andy
That should still work great. Pushing the envelope was my interest in seeing "how much of a good thing" I could have. But even with a standard barrel/BCG/GB, it should still make for a great shooter.
Nice rifle, it shares several components with my optimum barrel build. After shooting mine for a bit, I don't thing an agb is beneficial in any way. I'm really happy with the how the gas system feels. It's very similar to my sr-15. Smooth, soft, but not sluggish.
Did you have any issues with the precision armament shim touching the shoulder of the threaded part of the barrel? I had to modify the shim so it wouldn't hit.
Sent from my XT1565 using Tapatalk
Nice rifle, it shares several components with my optimum barrel build. After shooting mine for a bit, I don't thing an agb is beneficial in any way. I'm really happy with the how the gas system feels. It's very similar to my sr-15. Smooth, soft, but not sluggish.
Did you have any issues with the precision armament shim touching the shoulder of the threaded part of the barrel? I had to modify the shim so it wouldn't hit.
Sent from my XT1565 using Tapatalk
I don't remember having to modify the shim, or having to use much force to seat it. I'd like to think I didn't He-Man it.
I'd bet you're right about the gas block, but I was dealing with a couple unknowns as a combination: How would PMC Bronze and the e-carrier add to the extended gas system, and would there be sufficient gas? I decided to have Clint open the gas port, if necessary, to allow this ammo/component combo to work as my minimum gas drive function, to account for how common the ammo is with my shooting group. (My ammo tends to be full powered 223 factory, and reloads of similar pressure.) In retrospect, it was probably an unneeded variable, but it worked out very well, and I don't have any need to adjust it. Two of the aforementioned shooting buddies picked up the blem version of the same barrel, so we'll have plenty of comparison later once the shooting season starts. One will be using Clint's gas block, and pending that working well, so will the other.
Placeholder so I can find this post tomorrow and update this thread. This rifle will pass 7k rounds tomorrow.
I am definitely looking forward to reading the update. I got mine built about 2 years ago but have not fired anything close to 7000 rounds through it.
https://www.m4carbine.net/showthread.php?226177-16-Inch-General-Purpose-Carbine-and-Bonus-Rimfire-Upper&highlight=
Andy
P.S. I guess I could have checked - you saw and commented on the thread already. It is very interesting how similar the builds are. I obviously copied/was inspired by your gun.
I am definitely looking forward to reading the update. I got mine built about 2 years ago but have not fired anything close to 7000 rounds through it.
https://www.m4carbine.net/showthread.php?226177-16-Inch-General-Purpose-Carbine-and-Bonus-Rimfire-Upper&highlight=
Andy
P.S. I guess I could have checked - you saw and commented on the thread already. It is very interesting how similar the builds are. I obviously copied/was inspired by your gun.
Mine was fairly similar, as well.
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Major changes as they occurred:
The rifle started off with BRT Covert Comp, but switched to FCD 6315 after a few K. Tried a Warcomp for 1k or so but went back to the 6315.
SLR AGB broke. SLR immediately replaced it. Decided to try BCM stock. Added Radian ambi safety.
4537 rounds: E-carrier replaced with standard carrier. The bbl is gassed smoothly enough the e-carrier seemed wasted. Detailed cleaning done.
5200 rounds: Approx this round count the gas block came loose, despite red loctite. SLR gas block replaced and pinned by BRT with BRT gas block.
5419 rounds: Replaced Aimpoint with Steiner P4xi 1-4 & and 1.93 ADM mount.
5450 rounds: Replaced Sionics trigger with Larue 2 stage. Felt like the trigger was too light (just under 4# iirc), added heavier spring.
Detailed cleaning around 6k rounds. Added RMR in 1.93 T Rex arms mount a few months ago, as Steiner never comes off 4x.
Added vert grip as a handstop.
Fired two 5-shot groups yesterday to check accuracy.
69gr SMK w/H322: 1.12"
62gr Horn BTHP w/XBR: 1.4"
FWIW, 55gr reloads with hornady bullets typically shoot <2.5moa.
Should probably check velocity.
Current plan is to continue shooting until groups open up. Gunsmith noted the throat is well worn, be interesting to see how much longer I get from it.
68639
Major changes as they occurred:
The rifle started off with BRT Covert Comp, but switched to FCD 6315 after a few K. Tried a Warcomp for 1k or so but went back to the 6315.
SLR AGB broke. SLR immediately replaced it. Decided to try BCM stock. Added Radian ambi safety.
4537 rounds: E-carrier replaced with standard carrier. The bbl is gassed smoothly enough the e-carrier seemed wasted. Detailed cleaning done.
5200 rounds: Approx this round count the gas block came loose, despite red loctite. SLR gas block replaced and pinned by BRT with BRT gas block.
5419 rounds: Replaced Aimpoint with Steiner P4xi 1-4 & and 1.93 ADM mount.
5450 rounds: Replaced Sionics trigger with Larue 2 stage. Felt like the trigger was too light (just under 4# iirc), added heavier spring.
Detailed cleaning around 6k rounds. Added RMR in 1.93 T Rex arms mount a few months ago, as Steiner never comes off 4x.
Added vert grip as a handstop.
Fired two 5-shot groups yesterday to check accuracy.
69gr SMK w/H322: 1.12"
62gr Horn BTHP w/XBR: 1.4"
FWIW, 55gr reloads with hornady bullets typically shoot <2.5moa.
Should probably check velocity.
Current plan is to continue shooting until groups open up. Gunsmith noted the throat is well worn, be interesting to see how much longer I get from it.
Its interesting how similar our paths were. I too: broke an SLR (they sent me a new one immediately), switched from Aimpoint to Steiner, and from single to two stage.
Thank you for the update.
I have not shot mine as much as either of you.
I started with a BRT gas block a machinist at work pinned for me.
I am using the "heavy" spring in my Larue trigger to firm up the reset more than increase trigger pull, but we both arrived at the same point there.
I would be using a BRT Covert Comp on mine but I put it on my 11.3" build and A2 FHs are cheap.
Still running the Trijicon 1-4 Accupower, still not thrilled with it.
Andy
Edit-You may have to click on jpg to see current rifle set up.
Update at 10,104 rounds:
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When I last updated this thread, I took this build out to 600 yards using the 62gr BTHPs. (The scope matched that load well enough, and I had a spotter.) This build is still chugging along great, but it's starting to lose velocity. Around 9200 rounds, it was losing 70 fps to newer barrels.
Changes since last year:
-I dumped the 1.93 Mount. It was good for running and gunning, but I found it a bit much for my neck when prone. About 2/3 of my shooting is prone and kneeling, so I went to a standard height mount.
-Different lower due to troubleshooting another upper. This lower has a Forward Controls Design 2-stage, A5 system with Springco Green/A5H2 buffer, and a Magpul SL Stock, which is my current preference.
-RMR was moved to a different role for a train up with the M17.
-Handguard swapped out for V1(?) version so original handguard can be used on next upper.
-Rifle was used for 3 different train ups and shared the ammo load at about 40/60. The "other" rifle was constantly changing, so this rifle continued to get the brunt of the practice.
-Scope should probably be sent in for service. Windage and elevation don't always seem to track well. While it completed a box drill, it was slightly erratic. I still wish this was an ACOG.
-Rifle still groups sub-2MOA with 77gr ammo, and sub-4MOA with Lake City. Last unsupported group I measured was 5.5" at 195 yards.
This barrel is on borrowed time. Bullet jump to lands is getting enormous, but I'll complete another train up and then run it for a while longer for CQB drills. It's served it purpose well, but it'll be replaced when it no longer holds sub-4MOA groups with training ammo. I wish I had run a Colt barrel concurrent to this one to see how it would handle the same firing schedule.
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