Gas Gun Seating Depth

[TennJed]

Hi Folks,

Wondering if anyone has tried different seating depths for gas guns (like we do with bolt guns) and what are the results? I know combustion is critical, but again wondering about seating depth, haven't played with it yet. Working on a 6ARC but I don't care what calibers have been used, just looking for real world info from experienced people.

Thank you

 

[Eric H]

Hi Folks,

Wondering if anyone has tried different seating depths for gas guns (like we do with bolt guns) and what are the results? I know combustion is critical, but again wondering about seating depth, haven't played with it yet. Working on a 6ARC but I don't care what calibers have been used, just looking for real world info from experienced people.

Thank you

Currently doing development for a 6MM Predator/Grendel. Looked in Hodgdon load data but nothing for the bullet I'm running. Loaded it to MAG length and went for it. I was already over max pressure when I found a fairly decent group but wanted it closer so started going away from the L/G and groups got better. There was a tradeoff where the further from L/G the.slower the round. Currently at a comfortable .369MOA in 2700's FPS.

 

[C.O. Shooter]

Going through this now. Definitely different than a bolt gun.

 

[Eric H]

Going through this now. Definitely different than a bolt gun.

Just ensure your.pressure is high enough to cycle the spent casing. You gonna go through some brass. ARs are brutal on brass.

 

[C.O. Shooter]

My first 30 new Lapua brass weren't bad at all no issues. All 3pm ejections.

 

[Pdyson]

I definitely do. I start at mag length and work back. Most heavy loads in my ARC perform best very close to mag length. I have to go much shorter with the 75g because they are short and get wonky seated long. I hunt suppressed but for competition shooting the EC tuner brake works like magic.

 

[Pdyson]

I definitely do. I start at mag length and work back. Most heavy loads in my ARC perform best very close to mag length. I have to go much shorter with the 75g because they are short and get wonky seated long. I hunt suppressed but for competition shooting the EC tuner brake works like magic.

By the way you can get false pressure signs with short gas tubes. The bolt unlocks before the pressure falls and the bolt swipes the case head. Rifle + 1 or 2 will reduce the swipes.

 

[TennJed]

Currently doing development for a 6MM Predator/Grendel. Looked in Hodgdon load data but nothing for the bullet I'm running. Loaded it to MAG length and went for it. I was already over max pressure when I found a fairly decent group but wanted it closer so started going away from the L/G and groups got better. There was a tradeoff where the further from L/G the.slower the round. Currently at a comfortable .369MOA in 2700's FPS.

Thank you

 

[TennJed]

Just ensure your.pressure is high enough to cycle the spent casing. You gonna go through some brass. ARs are brutal on brass.

Thank you

 

[TennJed]

By the way you can get false pressure signs with short gas tubes. The bolt unlocks before the pressure falls and the bolt swipes the case head. Rifle + 1 or 2 will reduce the swipes.

Thank you

 

[Bigwilly556]

As previously stated 6 arc is very particular depending on bullet selection. Long heavy will be seated mag length or close to it with some 58-95s will need to be seated much shorter. These weights may be heavily jammed at 2.60. I just finished load development for berger 95 classic hunters in my proof research 6 arc barrel 2.17 OAL was .020 off. I ran some 95 SMK blems to break the barrel in and loaded them @ 2.60 mag length with .030 jump. With my proof 6 arc barrel and the bergers I treated it much like a bolt gun.

 

[Mike D Texas]

Nope. I seat at mag length and let it roll.

 

[Veteran]

All, mechanical and combustion systems have harmonics. The gas gun also has sonic and pressure waves.

It all relates to bullet exit timing and where the tip of the barrel is pointing at bullet exit at the muzzle.

Bullet seating affects both the burn rate, pressure, and therefore bullet exit timing.

So yes, bullet seating can still be a thing on an AR regardless of whether it is gas or mechanically operated.

 

[TennJed]

As previously stated 6 arc is very particular depending on bullet selection. Long heavy will be seated mag length or close to it with some 58-95s will need to be seated much shorter. These weights may be heavily jammed at 2.60. I just finished load development for berger 95 classic hunters in my proof research 6 arc barrel 2.17 OAL was .020 off. I ran some 95 SMK blems to break the barrel in and loaded them @ 2.60 mag length with .030 jump. With my proof 6 arc barrel and the bergers I treated it much like a bolt gun.

Thank you