8.6 Blackout build. First round, no ejection

[Mike6158]

And I do not recommend buying one...but I had to try it.

Agreed.

Mine is sitting in the corner, waiting on it's can to get out of jail. I have "a few" 300gr Berger and SMK's but the latest from a mostly quiet group of 8.6 folks is it needs to shoot solids to shoot supers. I have some. But I have more than enough projects to keep my busy. It'll probably be winter down here in TX before I get to the 8.6 again. I'll use that week to work on it

PS - mines an AR platform. Price of entry was new barrel. Price of exit is a new barrel.

 

[44-40]

Agreed.

Mine is sitting in the corner, waiting on it's can to get out of jail. I have "a few" 300gr Berger and SMK's but the latest from a mostly quiet group of 8.6 folks is it needs to shoot solids to shoot supers. I have some. But I have more than enough projects to keep my busy. It'll probably be winter down here in TX before I get to the 8.6 again. I'll use that week to work on it

PS - mines an AR platform. Price of entry was new barrel. Price of exit is a new barrel.

Yes I got the AR also, and made up hundreds of brass casings, neck turned, and bought large quantities of 300 gr Bergers and 300 gr SMK. The 8.6 Blackout has been a hard caliber to like for me. Did a lot if testing with bullets. And finally warmed up to it a bit with both 300 gr bullets.
The barrel likes 15.8 gr of IMR 4198 300 gr Berger average velocity for 10 shots 1041 fps 9.4 S/D ...low S/D important to longer shots 2.880" COAL. Probably work at 2.8" I have a modified AR 10 will feed 2.940" the first 3 went into .3" at 70 yds the range I randomly chose that day to stay in the shade.
15.8 gr of AA 1680 300 gr SMK 2.750" COAL is also accurate.
1680 gives larger S/D generally.
15.8 grains of AA1680 or IMR 4198 both work with the 300 gr drop to 15 grs for everything in the 250 and under and stay subsonic, depending on a bunch of variables...but these two 300 gr bullets and 2 powders leaning to IMR 4198 are accurate and consistent, work the action and lock back the bolt. I did drill out the gas port.
Copper suppers and subs have not been very accurate and larger S/D and low super velocities were unimpressive. For me its the 300 gr bullets subsonic. Got a bunch loaded to shoot in the next few days.

 

[victor3ranger]

Kind of a long post but I remember better if I write it...

I found the brass from the 3rd test shot. It was a little forward of where I was standing. To me that says the buffer weight is still too high at 3 oz. And... that is apparently wrong.

I found the following in an article found HERE:
The easiest way to know what effect your buffer weight has on the rifle is to look at the ejection pattern:

• Think of your muzzle at 12 o'clock and the buttstock as 6 o'clock.
• If the casings are flying out from the 12 to 3 o'clock positions, likely your firearm is over gassed with too light of a buffer.
• From 3 to 4:30 (about a 45-degree angle from the ejection port) you're good to go.
• Any further back to about the 6 o'clock position, i.e. hitting you, your buffer may be too light or the rifle is leaking gas in which case it cannot fully eject the casing with the proper force and you're soon going to experience feeding issues.
• If you have anything but perfect ejection, the simplest and cheapest method of seeking a correction is to check your AR10 buffer weight, then try a heavier buffer.

I converted all of the grams to oz's. The only reason I used grams was that's what the digital scale I have was set to. I don't mind metric... it's just a number. When all of the buffer weight articles are written with oz's it's time to convert

Aero Precision Buffer weight: 3.8 oz
Geissele Buffer weight: 4.3 oz
Removing the lightest weight in the Geissele (makes it rattle): 3.07 oz

I haven't tried the lightened Geissele buffer. I think I'll wait for the Odin Works adjustable buffer to get here or put the Geissele back to where it was. Either way I'll install the adjustable gas block.

These are the two commonly supplied buffer weights. The Geissele buffer that I bought is an H2 and that's typical for a carbine length AR10.

The following info was found HERE:

Heavy or H1:
Consists of one tungsten and two steel weights. Weighs around 3.8 oz.

H2:
Typically composed of two tungsten and one steel weight and weighs about 4.6 oz.

H3:
Normally uses three tungsten weights to weigh around 5.6 oz.

Rifle buffer:
Weighs around 5.0 oz and uses five steel weights and a steel spacer.

Configurable:
You can use different combinations of the included parts to tune your buffer weight to your needs.

If I understand all of this right, the original Geissele buffer, which was the heaviest of the buffers that I have on hand, and an adjustable gas block to let me adjust the amount of gas, should get ejection where it needs to be. This is why I prefer bolt guns

The optimal ejection for any AR platform should be at the 4:00 position. When building my AR10 243 it would pull the fired case only about a half inch out of the chamber.
So I went into full blown check everything mode. Rings on the bolt-lined up correctly, buffer and spring-good, gas tube was shorter than I thought it should be so I replaced it. Same problem. Checked gas block and all was good. Last piece was the gas port in the barrel. Sure enough the hole was too small. Drilled it out until I got the 4:00 ejection. After that I sighted in and ran her out to 500 yards.

 

[Ikeman83]

I'd wait to manipulate your gassing on a gun with a cartridge that is intended to be run suppressed 100% of the time until your can arrives. You might have a perfect setup already and be dooming yourself to further struggle.