buffer weight

[Koda]

First post and brand new to the Grendel, I thought I would just dive right in here with a very basic question but first a very quick background.
Built my first AR Grendel, 20in bbl. Still unfired as I wait for the stock to arrive. Use will be deer hunting and I plan to handload for this right from the start. I'm familiar with the AR platform a little bit but never had an adjustable gas block. I ordered a Geissele carbine length buffer tube assembly that comes with an H1 buffer.... but then I wondered if the Grendel gasses more than a standard 223/556....

So my question is there a correct buffer weight to work with the Grendel?

[Harpoon1]

First post and brand new to the Grendel, I thought I would just dive right in here with a very basic question but first a very quick background.
Built my first AR Grendel, 20in bbl. Still unfired as I wait for the stock to arrive. Use will be deer hunting and I plan to handload for this right from the start. I'm familiar with the AR platform a little bit but never had an adjustable gas block. I ordered a Geissele carbine length buffer tube assembly that comes with an H1 buffer.... but then I wondered if the Grendel gasses more than a standard 223/556....

So my question is there a correct buffer weight to work with the Grendel?

Like everything else, “it depends”! If you have an adjustable gas block you can tune it for just about any buffer weight. Fixed gas block, you’ll need to tune it with the buffer weight and/or buffer spring strength.

[LRRPF52]

For buffers and springs, Bill A. said he really wanted people to be able to buy a complete upper from him and drop it onto their existing lower without changing anything, and I can say that every combination I have tested on carbine lowers with 2.9-3.0oz buffers and standard springs has worked when looking at 16” MLGS, 18” MLGS, and 20” RLGS uppers.

I did a test one day where I had built, accurized, and Cerakoted 3 different 20” RLGS set-ups for 3 different friends.

One had a standard carbine RET with 2.9oz buffer, standard carbine spring.

The next had a carbine RET and H2 buffer, standard carbine spring.

The other had a rifle RET, rifle 5.2oz buffer, rifle spring.

I also built a 20” with an A5 RET, A5 mid-weight buffer, and rifle spring.

I didn’t notice too much of a difference between them all in cyclic rate and ejection patterns, but the heavier buffered systems with longer RETs felt smoother.

[Koda]

I'll have to check my settings because I didn't get email notifications.

Appreciate the replies. I kept searching the web and concluded I could run a carbine length buffer assembly with my rifle length gas system. I'm still not certain if the Grendel produces more gas than a 223 but with an adj gas block I don't think it matters. The only downside it I have to remove the mlok forearm to adjust the gas block.
Still unfired but cant wait to play with the new rifle. Today I ordered the bullets I want to hunt with and will get right into load development after they arrive.

[dpete]

The only downside it I have to remove the mlok forearm to adjust the gas block.

Have you looked at using a ball headed allen wrench screwdriver to get at the gas block? You may be able to get it through one of the M-loc slots from the side.

[603Country]

When I bought a Grendel upper from a fellow here, I wanted to use the 5.56 lower I already had. Having the same questions you do, I discussed it with the local and knowledgeable gun shop folks who deal primarily in ARs. They suggested that the 5.56 lower/spring/buffer should work fine, so I tried it. It worked fine. Not exactly a technical answer, but just an experience. I used the Grendel like that till I had a new Grendel lower assembled.

[Koda]

Have you looked at using a ball headed allen wrench screwdriver to get at the gas block? You may be able to get it through one of the M-loc slots from the side.

I have, its too far behind one of the mlok ribs.

[LRRPF52]

I'll have to check my settings because I didn't get email notifications.

Appreciate the replies. I kept searching the web and concluded I could run a carbine length buffer assembly with my rifle length gas system. I'm still not certain if the Grendel produces more gas than a 223 but with an adj gas block I don't think it matters. The only downside it I have to remove the mlok forearm to adjust the gas block.
Still unfired but cant wait to play with the new rifle. Today I ordered the bullets I want to hunt with and will get right into load development after they arrive.

There is a lot more propellant volume in Grendel cases, but there is also a lot more bore volume, so the gas port dimensions actually track right along with 5.56 gas ports in my experience and from what I have seen on barrels that gas properly.

I have seen a few 18” MLGS Grendel barrels cut with .094” gas ports, which don’t work well at all. It’s very difficult to get them to run even with adjustable gas.

[Klem]

Koda,

You could drill a tiny hole in the rib directly above the adjustment screw, no wider than the driver needed to adjust the gas. To conceal the shine tape over or touch it up with paint.

[Koda]

There is a lot more propellant volume in Grendel cases, but there is also a lot more bore volume, so the gas port dimensions actually track right along with 5.56 gas ports in my experience and from what I have seen on barrels that gas properly.

I have seen a few 18” MLGS Grendel barrels cut with .094” gas ports, which don’t work well at all. It’s very difficult to get them to run even with adjustable gas.

This makes sense. Mine is a rifle length system. I'm guessing I wont have any issues but its good to get some confirmation...

[Koda]

Koda,

You could drill a tiny hole in the rib directly above the adjustment screw, no wider than the driver needed to adjust the gas. To conceal the shine tape over or touch it up with paint.

Ive thought about this but decided not to. The handguard has a custom logo and appears to be custom to a custom upper as the geometry lines match. Not that a handguard is that special, but I dont want to modify it since its specific to the build brand.

[rickt300]

I generally set up all my lowers with A4 stocks and of course the rifle buffer set up. No problems ever with any upper so far.

[Bonas]

I use standard carbine buffers. With adjustable blocks, I tune the block with the handgaurd off. The adjustable blocks I use can be adjusted with my handguards on, but it's easier to tune it the first time with them off. I restrict flow on the weakest ammo I'm likely to use until I get a failure to lock back on an empty mag, then open it back up until it locks back. The handgaurd goes back on, and I rarely touch them after that.

[Koda]

I use standard carbine buffers. With adjustable blocks, I tune the block with the handgaurd off. The adjustable blocks I use can be adjusted with my handguards on, but it's easier to tune it the first time with them off. I restrict flow on the weakest ammo I'm likely to use until I get a failure to lock back on an empty mag, then open it back up until it locks back. The handgaurd goes back on, and I rarely touch them after that.

from what Ive read this is what I'll do. I went with a carbine H1 buffer by Geissle.

[Koda]

Update: today I took the new Grendel out for its maiden voyage. I loaded up a pressure ladder of 97gAbsolute Hammers over A2520 powder. I ran 13 rounds getting up to 2788fps safely.

I kept adjusting the gas screw out until it was barely holding on but could not get the bolt to lock back on the empty mag.

Im using a Geissele carbine buffer assembly. I suspect the culprit is their "Super 42" buffer spring, is "15% stronger" than a standard carbine spring.

[montana]

Update: today I took the new Grendel out for its maiden voyage. I loaded up a pressure ladder of 97gAbsolute Hammers over A2520 powder. I ran 13 rounds getting up to 2788fps safely.

I kept adjusting the gas screw out until it was barely holding on but could not get the bolt to lock back on the empty mag.

Im using a Geissele carbine buffer assembly. I suspect the culprit is their "Super 42" buffer spring, is "15% stronger" than a standard carbine spring.

There are many variables that come into play with short stroke or under gas issues..Adjustable gas blocks leak more gas than standard gas blocks and certain adj gas blocks can be more problematic than others..I despise the bleed off types.. If the rifle's gas system runs perfect with a properly fitting standard gas block, using an adj gas block can be problematic.. Adding heavier recoil springs or improperly fitting parts that increase friction will only add to the problem..

[Koda]

There are many variables that come into play with short stroke or under gas issues..Adjustable gas blocks leak more gas than standard gas blocks and certain adj gas blocks can be more problematic than others..I despise the bleed off types.. If the rifle's gas system runs perfect with a properly fitting standard gas block, using an adj gas block can be problematic.. Adding heavier recoil springs or improperly fitting parts that increase friction will only add to the problem..

Im going to order a standard (milspec??) carbine buffer spring and see if that fixes the issue.
I think I have a spare lighter buffer too or I will order one with the spring.

Input welcome on that idea...

I hope I dont need to fix or replace the gas block....

[mtnlvr]

How did you align the gas block?

[Koda]

How did you align the gas block?

I didnt.
I bought the upper as a completed assembly.

[mtnlvr]

I guess I just assumed you biult the upper too. My bad.

There have been reports of undersized gas potrts, misaligned gas blocks, defective gas blocks, etc. You may have to dig into that if the spring doesn't solve it for you.

What brand is the upper?