12" Grendels x 2, Suppressed with TBAC Utras

[LRRPF52]

Top 12" Grendel on Balios Lite Set
12" Faxon Barrel Forum Group Buy ( I dimpled the gas block journal for one of the set screws)
Bedded gas Aero Lo-Profile gas block, with balanced/optimal gas tube alignment with the carrier key
AA Hard Use bolt with relief-cut lug opposite extractor
TBAC Flash Hider/Suppressor Attach .30 Cal, 5/8x24 Rocksett attached

Balios Lite FDE Receiver Set and handguard with Titanium barrel nut

Bootleg Adjustable Gas Carrier
Strike Industries 7075 T6 FDE anodized charge handle with extended latch

LaRue MBT-2S
Strike Industries Polymer Ejection Port Door, modified to close with the Bootleg carrier
Strike Industries Pivot and Take Down Pins, FDE anodized
Strike Industries Mag release button and catch, FDE anodized
Ergo Tactical Deluxe Suregrip

CMMG LPK - FCG

Maxim PDW Brace, FDE, with 8" 17 coil heavy recoil spring and tiny buffer

LaRue LT-104 VFZ mount with 30mm rings

NightForce NXS 1-8x24 MRAD

ThunderBeast Ultra 7 .30 Cal (9.7oz Titanium can)


Bottom 12" Grendel

12" Group Buy Faxon barrel
Group Buy Monster Logo Bolt
TBAC .30 cal Flash Hider
Lo-Pro gas block, bedded

Alexander Arms M4 upper marked "6.5 GREN", Cerakoted FDE
Some off-brand knock-off handguard that has a heavy barrel nut and sharp rails, FDE Cerakoted
Bootleg ABC
BCM Gunfighter Charge Handle

Precision Firearms Forged Lower with 50˚ mag well funnel
LaRue MBT-2S
Ergo Tactical Deluxe pistol grip
Magpul Winter Polymer Trigger Guard, FDE

FDE Cerakoted Mil-Spec RET
QD sling swivel socket end plate
Franklin Armory increased weight action spring
Standard Carbine 2.9oz buffer

ThunderBeast Ultra 5 .30 Cal Titanium Suppressor, 7.4oz FDE high temp Cerakote

LaRue LT-104 FDE
GRSC 1-4x24 CRS


We took both of them to the range today. I shot multiple 5rd groups into sub-MOA, rapid, with both of these little blasters. I used a lot of the lessons-learned on the 1st one when building the 2nd one with the Balios Lite set.

I like how light and handy the Balios Lite receiver set is and the way their handguard mates with the upper and the Titanium barrel nut.

I really like all the little small parts from Strike Industries. I had to remove a small amount of material on the plunger housing for the ejection port door to get it to close with the Bootleg carrier, but it was no big deal at all.

I used Rocksett this time on the TBAC flash hider since my Red Loc-tite one will float when the can heats up on mine.

I tuned the extractors and ejectors on both.

The barrel install on the Balios Lite was the hardest I've ever experienced. Balios Lite even with the Cerakote layer was right within spec at .995" ID for the extension tunnel.

The barrel extension is 1.005". Yeah, that was fun. It's accurate as hell though and would never really need a barrel nut, it's on so tight.

Both guns are shooters. I finally put some 123gr ELD-M through them both today, then 123gr SMK/8208XBR through the new one.

This was my first group, rapid-fired with 123gr ELD-M from my 12":




Here are the groups from his 12". He was zeroing as you can see. I shot the last 2 bottom groups on the right target. Bottom Right was 5rds rapid. Left was 3rds rapid, 123gr SMK/8208XBR load.

[Bigs28]

Very nice. With the nightforce nx8 having a 1.25 moa aiming dot i found that using the round targets would give me a better point of aim for shooting groups then squares or triangles. Not sure what the reticle is on your nxs mrad.

[Grendeltexashunter]

are you using the pistol buffer in the maxim brace?
nice builds sir

[OpFor1]

Oh man, those are super sweet!

[OpFor1]

AA Hard Use bolt with relief-cut lug opposite extractor

What is a relief cut lug and how does it help?

[BluntForceTrauma]

AA's Hard-Use Bolt has a notch cut into the rear of the lug opposite the extractor to more evenly distribute the load on all the lugs upon firing. In many cases, the back of the lugs is not evenly contacting the barrel extension and this can lead to premature breakage.

[OpFor1]

Thanks for that.
At least you know I really read the spec sheet. LOL.

[snarkscarbine]

Love it! How's the backpressure on those? My SAS Barricade and Ultra-5 both cycle...stoutly...with the Odin Click-adj block turned off. Even have a Tubb Spring and H3 buffer in there.

[LRRPF52]

We have the gas adjusted with the Bootleg Carriers to the suppressed position, so ejection was 4:30 with factory loads.

My buddy's hand load of max published 8208XBR under the 123gr SMK had some 5 o'clock ejections initially. Then went to 4:30 and 3.

[LRRPF52]

are you using the pistol buffer in the maxim brace?
nice builds sir

It comes with its own specific 8" 17 coil stiff action spring and a tiny little 2.9oz buffer.

One of the most positive action springs and return-to-battery strokes I've owned in 30 years of shooting AR15s.

I used one of the Franklin Armory extra power action springs with the standard RET and SBA3 brace to get that same behavior, and it seems to work great using a standard carbine 2.9oz buffer.

[LRRPF52]

My buddy took his to the range today to do load development with the 107gr SMK.

38˚ F

Hornady case
CCI 450
2.275" COL
8208 XBR
107gr SMK

27.0 2192fps 5rd avg
27.3 2242
27.6 2307
27.9 2336
28.2 2369

28.5 2415
28.8 2440
29.1 2453 (slight ejector channel wiping)
29.4 2465 (mild ejector channel wiping)
29.7 2499 (mild ejector channel wiping)

Hodgdon's book max is 29.8C at 2.250" COL, 49,300psi. Ejector channel wiping in this case is from bolt rotation with residual obturation, not excessive pressure.

[Redomen]

Sweet!

[LRRPF52]

Someone asked me about preferences between the 2 different braces, and here is my answer:

For compactness, the PDW. This was a factor in my buddy being able to fit his blaster inside his small weapons case with the can on. If it had the SBA3, the can would have to come off for sure.

For everything else, the SBA3, provided you spring it and buffer it accordingly. I sprung mine harder to get similar performance to the Maxim PDW, which has a nice, stout little action spring in it.

There is definitely a different feel on how the Maxim PDW returns to battery, as it is very positive compared to a lightly-sprung carbine spring in a standard RET.

[LRRPF52]

More reports on the new 12".

In order to get placement for the eye relief, we ended up bridging the upper and handguard slightly, which those of you who know me recognize as something I don't like to do.

He brought the scope and mount back some, since he was getting distracted by the charge handle on his nose, and the vertical dispersion average of his groups shrunk dramatically and demonstrably over many group samples now.

He's shooting the 107gr SMKs still at 2475fps, with some slight ejector swipes.

I recommended going down to 28.8gr and just shooting 2440fps, as there is no real practical performance gain at 2475fps.

I think CLGS suppressed, even with the Gas Regulator in the Bootleg dialed all the way to Suppressed position, is running the cyclic rate a bit faster at 2475fps.

[LRRPF52]

He settled on 29.0gr of 8208XBR under the 107gr SMK at 2.275" COL.

Took it out to 250, 350, and 500yds on ~2.5 MOA plates.

No misses on steel poppers. Shooting steel out to 500yds is boring, and you can actually hear the hits.