So I’m getting set up to reload some 308 for the first time, using 147gr M80 ball, 150gr Hornady SST and 168gr Sierra TMK.
I have read that trim length anywhere between 2.000 and 2.015 is acceptable. Some manuals instruct to trim cases to 2.005, however, many reloaders, especially precision reloaders (eg Ultimate Reloader), recommend the full .015.
I will need every bit of that .015 for the Hornady SSTs, and that may not be enough. When the bullet is seated to 2.800 COAL in a case trimmed to .008, the cannelure is still about .020 above the case mouth.
The M80 ball seems to want a .002 to .005 trim length for the cannelure to line up right. In a .008 trimmed case, the bullet seats at 2.795 with the case mouth biting at the very top of the cannelure.
I have high hopes for the 168gr Sierra TMK. I used TMKs in a .223 load I worked up a couple years ago that produced .30 MOA groups. However, TMKs in 308 do not work the same as 223. This is a long bullet with a secant ogive and it seats deep with just .050 of bearing surface (no cannelure) to grab onto.
I’ll be working up loads with three powders, Varget, CFE-223, and H335.
If you have reloaded any of these bullets for 308, let me know how they worked out for you.
You can ignore the cannelure, you are not going to crimp anyway. I just reloaded some 150gn heads with the cannelure with 44 grains of Varget and even though the book calls for a 2.800 COAL, I read several posts where, with the same charge of Varget, they used 2.78 COAL and centered the top of the neck to the cannelure center. I chose that length since I am way to anal not to center on that point! You are going to be packing down the Varget either way, regardless of that slight difference. As for my cases, if they are below 2.015 after resizing, I don’t touch them, when I do trim, I trim to 2.000. I also loaded 100 Hornady 168gr ELD Match to 2.800 with the same 44gn charge of Varget. The range for both of those heads was 42 to 46gns and many posts I read said 44 grains of Varget was their sweet spot load for the best groups so being a lazy ass, I just started at that 44 mark.
I also have the CFE-223 but there just seems to be a great love for Varget over the CFE-223 due to CFE-223 being effected by temperature with the Varget more stable. This is my first time reloading .308/7.62x51 rounds as well, so don’t go by me. I will probably blow up my guns!
I do crimp actually. After cases have been trimmed, or deemed in spec, I ream and debur each case mouth. I set the crimp depth vey shallow, just enough to make contact with the bullet, but not so much that it digs in.
Most of the unfired brass (PPU 145gr Rangemaster & PPU 168gr OTM) measured 2.002 before the freedom seed was liberated. Most of the fired brass dialed in around .006 and .008, they are faily consistant so I’m only gonna trim any that are ,015 and over, down to ,012, and then ream the case mouth to help facilitate bullet insertion.
It’s just my reloading specific OCD kicking in, but I like a nice smooth transition from neck to bullet. I fiddled with case mouth prep for days before I got it worked out to where the crimp was just so.
I also will eventually run a few dummies with a snug but movable bullet semi-seated, into the chamber to figure out distance to lands. I will also measure my mags to see if there is any wiggle room above 2.800.
I always thought crimping was unnecessary unless being shot in a semi-auto. Out of curiosity, are you running these in a bolt gun? And if so, why crimp?
Okay that makes sense. I was talking about rifle ammo specifically. I always crimp revolver and semi-auto. I don’t reload for any tube mag guns currently.
