Sierra hpbt 190gr with win 748 powder question

[leviathanxx]

I am currently loading some sierra match hpbt 190gr for my .308 with win 748 powder. I had a question regarding how much powder to use. Most records I see online recommend not exceeding 42 gr max load at coal 2.750. However the sierra handbook recommends 42 lowest to 44.5 max load at coal 2.8. Seems like quite a difference just wanted to see if anyone had any opinions or experience with a variance like this. Trying to figure out if the sierra is a safe load....would assume so as its in their manual

[Beelzy]

Sierra is always spot on with their data, you can trust it.

[tyler_sti]

If it's published its safe. Even though I still cross reference and start at the lowest and work my way up until pressure signs. If your short on components I get it, but working a load in general blows through components anyhow. Just do 3 round ladders till you see the velocity you want and adjust accordingly.

[ptmn]

When you are looking at the various published load data, make sure you also look at the casing, primer and coal that the company used for their load data.

Internal case capacities vary greatly with 308 Winchester, which affects pressure. If you review the Lyman Reading manual, it has a section on primer pressure testing. They tested same size primers, large rifle, and just a change in the brand could cause up to a 3,000 cup pressure difference.

Like tyler_sti mentioned, cross reference with several sources.

When you cross reference, check to see what case, primer, coal they are using that is the closest match to what you have, then start low and work your way uo checking for signs of overpressure ( or underpressure)

[DueceMcGurk]

I shoot 175 gr HPBT in 308 over 41.5 gr of IMR 4895. That is within the Sierra recommended load range. Maybe they are right about 748 too.

[LynnJr]

If you read your post it says one manual lists 2.750 as the OAL and the other manual lists 2.800 as the OAL.
If you look at two Sierra manuals for 117 grain 25-06 loads one old and one more recent you will see that the maximum load from one manual is actually less than the begining load from the other manual both using the same exact bullet and powder type and primer and brass and both from Sierra's.
BUT
When you look at the cartridge overall length of the two manuals both from Sierra bullets they are vastly different.
If you call Sierra they will tell you two different Reamers where used and the reamer with the longer freebore gives you a longer COAL and thus more powder is used and subsequently more velocity.
In modern day reloading some of the companies will list a load as a +P load and give a velocity that is in excess of 100 fps faster.
They get that extra velocity because they used a reamer with extra freebore which allows the bullet to be seated further out which creates more case capacity.