04-15-2012, 02:43 PM
After many attempts to get full function from the Grendel, with 100% function while maintaining 100% sub sonic performance, I accieved the feat on 4-14 by seating the .267 bullet further down in the converted (fireformed) 7.62x39 WW case to an OAL of 1.794 with 12gr of AA-2015 BR. I reduced the buffer to 3oz and used a full rifle stock spring in a rifle stock. Temprature on this day 82 degrees. The barrel is 16 inches with a CAR gas tube. The load shoots .5 inches at 50 yards. It shoots 1.5 inches at 100 in a fair wind. At 100 with my 1-9 twist gun, the bullets are starting to get unstable and show signs of striking the target just off center, with round holes, but with ΒΌ moon black on one edge of the holes. I sighted in my gun for the load and feel confident in making a neck shot on a hog out to 100. Remember this is a night gun, not a day gun so any day shooting will be with full power loads.
The following is based on a five shot string, the AA-2015 load of 12 gr at 1.794 OAL, deliveres an average velocity of 1054 fps, a SD of 31 fps, a high of 1100.7 fps (my SS break is at 1116 fps), a low of 1024 fps with an ES of 77 fps with a MHD of 22.7 There was no failure to function in my 16 inch barrel with the suppressor attached. All shots were with the can. It was very nice to hear the whap as each bullet hit the cardboard at 100.
As we have gone through this process it has become obvious to me that the subsonic loads are going to have a high ES number regardless of what is done, so the figure you shoul be looking at in your testing is that one shot, that gives you the highest velocity reading. Could you reduce the high fluctiation, yes, and I have done this with bolt guns using spherical buffer. But in a gas gun, in my opinion, based on many years experiance with the use of various buffers, using something that does not burn is a recipe for disaster in the future as whatever you use, will build up in the tube/carrier key. An experiment for another day might be to use a very, very slow burning powder as a buffer.
Regards the soot build up, the neck of the 12gr loaded cartridges seals fairly well, leaving the body of the case only moderately dirty.
ERH
4-15-12
The following is based on a five shot string, the AA-2015 load of 12 gr at 1.794 OAL, deliveres an average velocity of 1054 fps, a SD of 31 fps, a high of 1100.7 fps (my SS break is at 1116 fps), a low of 1024 fps with an ES of 77 fps with a MHD of 22.7 There was no failure to function in my 16 inch barrel with the suppressor attached. All shots were with the can. It was very nice to hear the whap as each bullet hit the cardboard at 100.
As we have gone through this process it has become obvious to me that the subsonic loads are going to have a high ES number regardless of what is done, so the figure you shoul be looking at in your testing is that one shot, that gives you the highest velocity reading. Could you reduce the high fluctiation, yes, and I have done this with bolt guns using spherical buffer. But in a gas gun, in my opinion, based on many years experiance with the use of various buffers, using something that does not burn is a recipe for disaster in the future as whatever you use, will build up in the tube/carrier key. An experiment for another day might be to use a very, very slow burning powder as a buffer.
Regards the soot build up, the neck of the 12gr loaded cartridges seals fairly well, leaving the body of the case only moderately dirty.
ERH
4-15-12