voip-1 wrote:When researching "how far should I seat a bullet" I saw numerous posts by reloading veterans insisting that it is preferable to load the cartridge as close to SAAMI maximums as possible, clearly that is not always the case as was not working out very well with the 110 Nosler bullets.
Seating depth in 300BLK is completely ass backwards from every other cartridge. Probably not a 100% accurate statement as I am not a cartridge expert on the hundreds of different rifle cartridge so I am sure there are other rifle cartridges where seating depth is weird.
Traditionally you are trying to get into the lands(or damn close) to minimize jump and theoretically increase accuracy. Bullets can wobble as they jump and thus not go down the bore truly straight. Some bullets even like to be jammed into the lands(this is SAFE in some setups and done with knowing 100% exactly what you are doing). Some bullets like more of a jump and are VERY jump tolerant. SMK's and the non VLD Bergers are typically very jump tolerant in something like a .308, in fact the Bergers(like the 185 Juggernaut for example) LIKE a jump and shoot better this way. So loading for something like a factory .308 Rem 700 guys typically use a jump tolerant bullet because its almost impossible to get into the lands and still feed from a box mag or the internal mag(I think on my Rem 700 308 AAC-SD I would have to load to something like 2.950 to get into the lands, where as 2.820 is about as long as I can reliably feed from AICS mags, so I need a jump tolerant bullet).
In 300BLK we are using bullets that arent designed for 300blk, they are designed for .308. There are only a handful of 300BLK spec bullets right now(designed to seat at 2.260 or very close) like the 110g Barnes black tips or the 125g SMK. In a 300BLK bolt, you are only limited by having enough bullet in the case to keep it from falling out, a lot of people say this is at a minimum .308 of the bullet in the case. In an AR you are limited by 2 things: mag length obviously and getting the .250 measurement portion of the OGIVE lined up with the rib in the mag. The second "limitation" is more a feeding thing than anything. This causes us to be loading bullets WAY deeper than the 2.260 SAAMI spec. Something like an ultra long 208g AMAX could be loaded to 2.260 and be completely safe, but you will have feeding issues(the bullet will most likely impact the barrel extension between the feed ramps) so its seated to something like 2.120 to aid in feeding, then we throw a powder charge to correspond with this increased seating depth. If I was loading 208g AMAX strictly for a bolt I would load that sucker LONG LONG LONG to get into the lands and increase accuracy. So with 300BLK you will see recommended seating depths that are SHORT from 2.260 usually for feeding from AR mags.
Once you get deeper into reloading and understand seating depth in relation to pressure and feeding and what not, you can start to tweak. Until then I wouldnt deviate from either published book values or if you see 50 guys loading a 208g AMAX(just using an example) to 2.120 instead of 2.260, you can bet that thats "a clue" on where you should be. Another example would be the 150g FMJ pulls which are typically seated to 2.150 which is obviously short of the 2.260 mag limit. SOME reloading guides simply state all 300BLK was tested at 2.260, which sucks because most of the bullets they are talking about will NEVER feed from an AR mag loaded to 2.260 so you end up "on your own" as far as powder charge and seating depth, which is why this forum is such a GREAT resource for this information. I would bet most .308 bullets have been tested by somebody on this forum so data SHOULD be available for most .308 bullets. If you dont find info on a .308 bullet and powder charge on here, it might be "a clue" that it wont work well for 300BLK OR you are venturing into new territory and tread lightly, especially if you are new and dont understand all the little intricacies of load development.
Sorry for just writing a novel.