Also when you're on the edge, it's likely you won't get last round bolt open as the gun barely has enough energy to cycle and then as soon as it's a little bit dirty it'll short stroke. My suggestion would be to get a good chrono and work up from 7.2-8.0 and tune the rifle to the load (AGB, Low mass BCG, JP silent with tuning weights, etc) but I'd forget about N105 cycling unsuppressed. It's a recipe to get in trouble and you're not even close to the magic 1050FPS to be subsonic all year. Even at 8.5gr, 225 BTHP and 2.26" you're at 55K PSI. This won't work because at 9.0gr you're already in a 95% fill and you'll be 100% in the danger zone (60K+ PSI according to Quickload). And being coal limited because of the AR15 magazine you'll probably have to load them at 2.25-2.26". And then you'll have 2 MAJOR problems.ġ) To be able to be close to subsonic, you'll need to use a long heavier bullet (225 BTHP, SMK 240, etc). I think to be able to cycle an AR you'll need something like at least 8.5-9.0 gr and then you'll be in the supersonic 1100fps+ range. Even N110 with heavy subs is quite finicky. You could try a CAR buffer but then it doesn't really solve the problem and it'll suck if you shoot super sonic. That being said I doubt N105 would cycle an AR unless you have a suppressor, low weight BCG and JP Silent Captured spring. I also shoot 225 BTHP and 220 ELD-X and they do about 1020 fps 7.3 gr but usually shoot 0.5 mil higher than the 190-208 bullets. It's quickly becoming my favorite bolt gun powder for heavy subs as I'm getting better accuracy and velocity spread than Tinstar.Ģ08 Amax: 2.25 coal - 7.3 N105 - 1035 FPS SD 3.8 (7 shot group)ġ90 SubX: 2.09 coal - 7.3 N105 - No chrono but same drop to 135 yrs so I expect 1020-1040 fps range I absolutely love N105 with my new Defiance anTI 12.5" bolt gun. My other thought is should I start with a mid grain load like 8 grs and vary the depth from 2.25 down to 2.15 in 0.02 increments and do the same tests?Īm I on the right track, am I overlooking anything? Should I start by trying to do a descending powder load or should I target midweight load and vary seating depth? For example my two thoughts either loading up 4 rounds each of 8.5, 8.2, 8.0, 7.7, 7.5 and test velocity, bullet stability, cycle, and BHO. The BTHP bullet is 0.069” longer than the SMK so I should be at a lower pressure at a given COAL. Knowing that my velocity will be lower than listed 225gr BTHP No.9 9.1gr = 1200fps 16” barrel (also a max load for No.9). I see that N105 follows closely with No.9 as a guide but lowered by 0.5 - 0.7gr and the Hornady manual is good guide. I know I need to start mid work down to the min, but also that seating depth will play a large role in velocity / pressure. My question is what is the proper way to work up a subs load. It fully functions currently with factory Winchester 200gr Open Tip Subsonic Whitebox unsuppressed, I have not run them across a chrony though. I plan to test for cycling / bullet stability unsuppressed and my goal would be for full function suppressed. My new endeavor is a 300BLK AR SBR with an 8” barrel with 1:8” twist with a pistol length gas system, H1 buffer with a Geissele Super 42 spring, that I want to work up a subsonic load with N105 & 220gr SMKs. I do have experience loading for what I will call simple wildcats (6x45mm, 250-3000AI) that are pretty easy to extrapolate loads for off published data. I have only been reloading 10 years and mainly been rifle calibers, I have also worked up some pistol loads as well. Been lurking around for a couple years appreciate all the information shared and experience.
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