123 Lapuas in GAP built AR-10???

[wksinatl]

Hey guys, Noob checkin' in.

I am a regular on the 'Hide and was fortunate enough to get some good info from YO and checked out the site. The guys running this site have done an AWESUM job.

I have a GAP built AR-10 in 260. It shoots 140MK's very well but will NOT shoot 142's,I guess the different ogive really makes a difference). I was wondering if anyone has tried the 123's in a gas gun. I have heard so much good stuff about the 123's but think it was all in bolt guns. Most of my shooting will be under 500-600 yds but want to stretch it out to 1K. Is there and optimum,efficient)velocity I should be looking for? I want one load for all ranges up to 1K. I want to miss the short range load and a different long range load.
My load now is:

Win brass,243 resized)
140MK's
WLR
37.5gr Varget

I installed an adjustable gas tube on it and have shot Varget and H4350 in it and the brass looks almost brand new upon ejection. Without it a varget load would almost destroy the brass. I tried H4350 but don't think I really gave it a fair chance, might try it again and be more methodical with load development. My barrel is a 24", 1-8" Mike Rock.

Any and all opinions/suggestions are appreciated. I don't mind spending the extra money for the Laupas if the make itty-bitty groups. BTW, 120MK's also shoot well but the 107's just looked like a load of buckshot.

I know the 123 Lapua/4350 loads seem to be pretty much the norm.

thanks guys,

Keith

 

[jerryrowe]

I just had a 260 built by JP Enterprises. this on a DPMS lower. I have tried the 123 and the 107 Lapua. I really need to put more work into it but had not the time and the weather has been cold. I noted your comment on the gas. I have the adjustable gas block. When shipped to me it was open too much and I have turned it down a bunch. I was getting preasure way before I was getting speed. the next load that I am going to try when I get the powder this month is N550 with the 123. John Paul at JP sent me this load and is getting 2950 fps out of a 22 inch barrel with good groups. I have been able to get a couple of groups with h414 and the 107 of about 5 inchs at 500. I would like to see it do better then that. I think it will I just have not had the time to spend on it yet.
Jerry

 

[Forum Boss]

I did a lot of load testing with a .260 in the bolt gun. After trying most of the 140gr class bullets, I settled on a load of H4350 with the 123 Scenars, jumped about .018". I used 43.8 gr H4350, but I noted that others needed well over 44.0 to reach the same velocities. Groups were tight and ES/SD was VERY low with H4350, Fed 210m, and the 123s.

Given Lot variations, I'd start at 43.0 and work up. Something in the 2930-3000 fps range should work well.

Like you, I could never get the 107s to work very well from my .260.