11-18-2014, 05:04 PM
LRRPF52 Wrote:Yes, you need to full-length re-size for gas guns as a rule. The shoulder needs to be bumped back enough so that they will actually chamber as well.
What chamber do you have? If it's the compound throat, engagement of the first angle isn't going to spike pressures, since it's only .5 degrees. If you are close to be hard into the 1.5 degree angle of the lands, then you will need to work up from 10% below max loads, using no more than .3gr increments, to find where you are at, with a chronograph at the least. Looking at brass and primers won't tell you much about pressures, until you are way too far.
Do you have the Reloading Handbooks? Your questions and a lot more are covered in them.
I bought and read Vol. 2 a couple times, it's just nice to hear this stuff confirmed by people who are currently working on the guns everyday. They are handy Manuals though, I'll order Vol. 1 when payday rolls around.
I'm not sure which chamber I have. It's an 18" 1-8" AR-Stoner BBL/Bolt combo bought about 2 years ago from Midway. I know there has been some dispute on these barrels around that time-frame but I haven't a clue which one I have.
It chambers resized brass effortlessly, the struggle comes when bullet is seated beyond 2.26". I think it may be engaging the lands at right around 2.255". It almost seems like a moot point because my AA mag won't allow much past that but I was just interested in hearing how tight other's OALs are.
The Grendel is the first gas gun I've had issues with just neck sizing. The .223 barrel that came out of the upper I built the 6.5G on would cycle fire formed and neck-sized reloads all day. Some of that brass got loaded 3-5 times with just neck sizing. The same with SKS and AK. I'm not flattening primers with these 7.62x39/5.56 reloads either, they are reasonable loads for general blasting. I had the mindset that if it worked with the 7.62x39, then it should work for the Grendel (Grendel's Father right?). I'm not real familiar with these steep shouldered rounds and their particular quirks, so finding that fire-formed brass would not fit back into the chamber it just came out of was a bit of a mystery to me. Everything 6.5G gets a full resize now.
So your suggestion is to compare velocities between my gun and known pressure/velocity/bullet combinations from other guns (in the reloading guide of course) to figure out my pressure? I've got a box of 123gr A-Max and a bunch of Nosler 140gr Blems from the 1960's-70's. I would assume I should use the A-Max starting loads (either CFE223, TAC, or IMR4895) and try to get a correlation from that. If I get to 2400 FPS I'm too hot right? Or should the cut-off be lower?