Gas Gun Seating Depth

TennJed said:

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

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C.O. Shooter said:

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

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Pdyson said:

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.

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Eric H said:

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.

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Eric H said:

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

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Pdyson said:

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.

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Bigwilly556 said:

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.

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