@90yjgimp, if you are feeding them from a magazine then you should not load them "too long" ("too long" means that they won't fit in the magazine at all, or if they do that they might catch up or jam).
There is a standard "maximum COAL" defined for the .308 Win. That number is 2.800". If a .308 rifle magazine won't accept a piece of ammo loaded to 2.800", then it is the rifle that is out of spec not the ammo.
BTW an M305/M14 rifle will absolutely take a 2.800" round (that's where this number came from in fact!)
When loading for your M305, you should load your bullets to 2.775"-2.800" (usually it's not terribly critical), unless you have a good reason to do otherwise. A couple I can think of:
- if you are shooting military style 144 or 147FMJBTs that have a cannelure (crimp groove), you might want to set the bullet seating depth so that the case mouth aligns with the cannelure so you can crimp the case mouth. This is usually not considered necessary but oftentimes a reloader will want to do this, following a sort of belt-and-suspenders logic.
- if you want to play with precision 600 yard slowfire ammo (a la the Yanks), you might consider loading to quite a bit longer than 2.800" (in which case the ammo won't fit in the magazine) and single-loading each round. Unless you have an all-out custom tuned rifle this probably won't buy you a stitch of improvement though.
Take care to make sure your brass is in good shape, your primer pockets are snug and the primers fully seated (below flush). Use mild to medium loads of "the usual suspects" of powders (H4895 and W748 class). Keep your bullets at 2.775"-2.800", tune the load (if you care to) by trying out different powder charges.
Most accuracy potential probably lies in tuning up the rifle before tuning the ammo beyond the starting point of using a good bullet (which you are doing) seated to magazine length with a sensible charge of a standard powder. Look up "Hungry's M14 clinics" and consider attending one....?
