Ar15 loads for Bushi DCM upper

[ei276b]

Shoots factory ammo just fine. But when I load 23gr, 23.2gr and 23.4gr of N135 for a 69gr SMKHPBT in a FC 1X fired case and CCI 400 primers the bolt does not go all the way to the rear, about 5/8" short of full open, even with a single round sled for slow fire. No ftf or fte. My plan is to load just enough powder so it cycles the action completely for our 100yd matches and adjust up from there for longer matches. I plan to bring this to the matches I have been shooting with my M1 and M1A. The lower came with a 16" upper from Bushmaster. I was told by BM the buffer should be gtg for the 20" too. I started out with 22grs of N135. Did the same of course. So I started going up in the loads. Am I being too conservative? I was told by another shooter in my club that loading compressed loads in the AR is not unusual. I have always been able to stay away from compressed loads in the M1's. The thought of compressed loads makes me nervous. Should it? Maybe some of you more experienced AR 15 loaders can give me some advice. Thank you in advance.

P.S. Upper has a 1:8 twist in a carbon barrel.

 

[Texas Solo]

I used to shoot a Bushy DCM 20" as well.

First question...why do you want to shoot 69gr Sierras @ 100yds?
That's a real waste of $$$.

FWIW, my 100yd load got me to Master class...
25.0 AA2230, WSR primer, 52gr Sierra BTHP. OAL was 2.220.

It didn't seem to make sense that the lighter bullet shot so well from the 1/8 twist, but it did. 55gr FMJ's also shot really well with the same load data.

Save the 69's for 600 yds.

 

[Bullseye Shooter]

I found a load online from Sierra for that bullet and N135 and their max load was 22.5 grains, so you have something else going on. You might want to check with Bushmaster again.

You'll need a heavier bullet for anything out past 300 yards. I've been loading Nosler 80 grain HPBTs with good results; setting the COAL at 2.245". And with the winds at Mineral Wells and Camp Swift, I've decided to go with a 77 grain bullet for the 200 and 300 yard line. Your 1 in 8 twist will handle both of those.

I'm using a RRA NM A2 with the 1 in 8 twist.