Mk 262 Mod 1 etc.
It's cool to see that I am not alone in the quest for reproducing this amazing round. I've recently produced a few of my own. I too am using RL-15 and TAC. As these seeem to be the closets powder to what is being used. apparaently RL-15 is acctually specified for the m-118.
my first run of Nosler CChpbt in 77 grain was backed with 23.0 grains of RL-15. I loaded them to a col. of 2.25" the chronographed out of a 16" carbine at 2614 I believe. but, I have changed that recipe and my manufacturing process all together.
I have a dillion RL-550B and a single stsge RCBS for sizing and trinimng with a Dillion rapind trim 1200. It allowed me to get the cases to very tightghtly trimmed tollerances and fast. After trimming then some brass needed primer crimp removal. done, using the Dillion superswage 600. easy. then every case needs to have the case chamfered for theses VLD style bullets. alot of work. But, now I have uniform brass!
So, that brings to me to what I am currently working up.
last night after careful thought of Noslers recipie for the 77 grain CCHPBT and TAC ma charge of 23.5 grains. I chose to back up to 23.2 grains. I am trying to get near the magic velocity of 2750 to 2800 fps. That seems to be the speed where most of the match and sniper ammo is produced.
so: 77 grain Nosler CCHPBT over 23.2 grains of TAC CCI 400 primmer mixed headstamp brass trimmed and chamfered to 1.75" and COL of 2.252 I will let you know how they group and velocity etc.
Next up I am going to losd the Sierra 77 grain MK over 24.5 grains of TAC and same COL.
The Sierra bullet definitely has a different profile so the must be where the difference in speed comes in. Also Ramshot has a recipie list for new NATO pressures above 62350 PSI. Thier max load shows 24.8 grains of Tac. So, I am backing off a half grain. but according to thier recipies I should still get the velocity I am looking for. The Sierras. manual has 24.0 as thier max. So we will see. I like my riffle and don't neccesarily want to be pushing max loads through it all the time.
Anyway good luck. I look forward to hearing which losd works for you. I havn't even touch on the loads I plan on working up for RL-15. the first stuff I made was shootin dme sized 10 shot groups through an ADAMs Arm Carbine upper with a twist rate of 1-7". Can't wait till it is broke in. I think I'll tryu a match.