Buffer Spring and Recoil

[Vetman1]

[LRRPF52]

If the thermal is not built to take semi auto recoil and secondary reciprocating mass effects, I would send it back for repair or refund. ATN?

Your pixel distortion is likely cumulative from 300BLK before you placed it on the Grendel.

What I found with my LaRue complete rifle is that it uses a carbine standard buffer and spring.

I was thinking I would change that out until I shot it-smoothest AR I have, even compared to my Lilja build with a JP SCS.

I need to put another spring or use adjustable gas with that set-up because I'm getting insane carrier bounce.

I might need another bootleg carrier for the Lilja 318 build.

Also, the LaRue Tranquillo brake on my Stealth 2.0 is very pleasant to shoot-no perceived obnoxious muzzle blast typical of a lot of other brakes, at least for the shooter.

I'm sure you could tweak the SCS with the right spring and weight combo to run the LaRue or any other 6.5 Grendel AR smoothly, but I found it to run amazingly well with the standard carbine buffer and spring.

Keep it lubed and run it lightly wet.

[Azgeek]

I was wondering if I should consider this as part of my upcoming upgrade. How often should springs be replaced? Mine is 10 years old. Either way, definitely need to clean and lube.

[LRRPF52]

Spring replacement depends on several factors:

How compressed your shoot schedule is
Quality of springs
Maintenance (corrosion)

Most springs nowadays are pretty corrosion resistant, unless you buy basement-priced garbage from companies who love to whittle away at the margins by attacking the product.

For a high-volume AR15 in 5.56 NATO that is run regularly through a heavy shoot schedule:

Extractor spring every 2000-4000rds

Ejector spring every 2000-4000rds

Recoil spring every 5000-6000rds or when it shortens below the spec.

For a 6.5 Grendel shot maybe 50-100rds per range session, with quality springs, I doubt you'll ever need to change them unless you shoot thousands of rounds every 2-3 months.

[Vetman1]

Lrrp,

Thank you for the reply. The thermal is rated to .375 so it should handle the recoil. With the JP silent Capture spring setup the recoil was sorta jerky and I suspect that uneven recoil was causing the bad pixels.

If I understand your reply correctly, you run the spring and buffer that came with the Larue Ultimate Upper? The way I read your post you would not try to improve on the setup that comes with the Larue UU kit. Am I correct?

I have not tried the buffer and spring that came with the Larue UU kit and plan to try that this weekend. I was waiting on my Larue lower to arrive and have been just using the lowers from my .300 Blackout.

[Kswhitetails]

I will second the smooth operation of the Larue system. There is absolute quiet when charging the system in regards to spring/buffer tube set up. I can't even find the desire to "upgrade" to an SCS in it. Actually, I don't believe it would be an honest upgrade.

As far as the brake, my experience is as LRRPF describes, little or no perceived recoil, and only the guys beside you will notice the blast. I was at a range with 20 feet between us, and they commented about how loud it was, and could feel the blast, but they were impressed rather than upset.

I had a SilencerCo ASR on my last Grendel, and I noticed way more blast at my shooting position, but that is the only other muzzle brake I have experience with. I will say I was pleasantly surprised when I first shot it, and am interested to see what my pistol build is like with the same brake in place this weekend. That build could indeed use an SCS, but It's purpose built to be thrash-able so it seems like an unnecessary step. Perhaps when I have my suppressor in hand and want to further fine tune the system, then I will consider it.

Let us know what you think when you get it all put together. Good quality always shines, even when it's dirty.

[LRRPF52]

Lrrp,

Thank you for the reply. The thermal is rated to .375 so it should handle the recoil. With the JP silent Capture spring setup the recoil was sorta jerky and I suspect that uneven recoil was causing the bad pixels.

If I understand your reply correctly, you run the spring and buffer that came with the Larue Ultimate Upper? The way I read your post you would not try to improve on the setup that comes with the Larue UU kit. Am I correct?

I have not tried the buffer and spring that came with the Larue UU kit and plan to try that this weekend. I was waiting on my Larue lower to arrive and have been just using the lowers from my .300 Blackout.

If someone describes optics being rated to a certain caliber or cartridge, it doesn't address the most challenging aspect of modern optics in semi-auto rifles, which is impact of the bolt and carrier upon the return stroke of the cycle (feeding, chambering).

An AR15 with excessive cyclic rate can be a lot harder on optics than any magnum bolt gun, because the bolt and carrier slam into the breech and extension with each firing other than last round.

Most optics are not designed for semi auto rifle actions, so they break. AR10s are especially brutal on optics because of the mass and velocity of the carrier slamming back home.

It's a deceptive practice to tell a customer that "this optic is rated for huge magnums" knowing that many people are mounting optics on modern rifles with self-loading actions.

This is one of the reasons you see low priced optics, versus expensive optics. There are additional processes in the mounting of critical components inside the optics to insulate them from bi-directional G forces or impulses on higher end optics, including thermals.

I was going to tinker with my LaRue until I shot it. It convinced me very quickly to just leave it alone due to how smooth it cycled. I haven't experienced an 18" MLGS 6.5 Grendel that runs that smoothly with a standard buffer and spring before.

[98Z]

I had a standard AR15 cabine recoil system in mine for the first sight-in range outing. The Grendel recoil is definitely different than other calibers I've got in the AR15 platforms. For mine, 5.56 is the baseline "recoil" when I'm comparing my other rifle-based cartridges. I don't count 9mm and .45ACP in there, because they're blowback operated pistol cartridges, and there's very little recoil in them anyway, with the right buffer weight. The 300BLK I'm loading is 150gr Hornady FMJBT for common ammo, and the recoil is about the same as 5.56. The 25-45 Sharps recoil is actually softer than 5.56. The Grendel is definitely more recoil, sharper, in a way. Not bad, not heavy, just different.

So, out with the AR15 carbine recoil system. Didn't even try different buffers. In went the VLTOR A5 buffer system, with their H1 buffer (4.56oz). That's about the same as an AR15 Carbine H2 buffer. Shoots MUCH different now. Feels more like 5.56 recoil. If I needed to change it up even more, the VLTOR A5 buffers run from H0 to H6, all the way up to 6.8oz. I might try the A5 H2, but the A5 H1 is getting it done right now.