New rifle reloads

[wolfen1960]

First off I appologize if this gets lengthy! I just picked up my new Remington 7600 in .308. 22" bbl with 1-10 twist. I have reloaded for years for a few different calibers.
I have 6 books from different bullet manufacturers to get info. from, but the load differences seem a bit odd (at least in one case).
I will shoot a 150gr Hornady SST if I can get it to shoot from this rifle, and this is where I find the strange fact.
Hornady lists (from the powders I have available) Varget from 35.9-44.9 grains with this bullet and a test BBL of 22" BUT a 1-12 twist!
Hodgdon lists Varget to 47 gr. max with a Nosler 150gr Balistic tip with a 24" bbl and ?twist.
Speer lists 43-47gr of Varget from a 22" bbl and 1-10 twist.
Barnes (not really applicable with the different construction of bullet) 43.5-47.5gr of Varget from a 24" bbl and Twist?
Lyman has 42.5-47gr of Varget with the Hornady 150gr. SP (very much the same as the SST) from a 24" bbl and 1-10 Twist.
My question is this...Why is the Hornady load ending (max) about where the others begin? Does the twist affect the pressure? It has the lowest max grains, but also has the slowest twist (1-12 as opposed to 1-10 from all the other test bbls).
No matter the answer I will be developing this load from a SAFE low to a Safe high with accuracy as #1.
The two books that I will be loading by are the Hornady and the Lyman as they both use the Hornady 150gr.
Is there another powder recommendation that anyone out there will share with me? Varget is the only one I have on hand that is a recommended powder for the .308 as my other main rifles are a 300 wsm and a Ruger in 260, both of which are using substantially slower powders.

 

[hs4570]

Depending on what year your reloading manual came out usually governs what the max. loads are for any given powder. My 1960's and up to early 1980's manuals have a higher max than newer ones with the same powder and the same bullets.
Its about liability issues concerning reloaders...."lawyer Loads"

My .308s' useing a 150 gr. Hornady Flat base or Boatail prefer Imr 3031 and Alliants' .. Reloder 15. as do my Hornady 165 /168 s' and in 175 SMK can add Imr 4895 to the accuracy list .

 

[Ganderite]

Twist has nothing to do with pressure. But each rfle is different, so the books reflect the rifle they had . Some develop pressure more than others.

150 gr bullets and Varget are well suited. I would start at 44 gr and if that went well, move up in half grain increments. If you see any pressure signs, back off a full grain. You don't want any extraction problems in a pump rifle. A bolt can be hammered but a pump is more difficult.

At one time the books were based on their test expereince in their pressure guns. Pressure barrels are made to very exacting SAAMI standards and are supposed to be identical. Then they got complaints and started to test in a selection of "real" rifles and discovered they were different than SAAMI spec rifles. Your Remington, for example, has a much deeper chamber throat than a SAAMI miminimum spec chamber. Other rifles could have a shorter throat.

The published results do not have a "safety" factor. They are based on the worst case example that lab happens to have. Some of my rifles have much tighter bores and shorter throats than their worst examples, so published loads are often much too hot for these rifles.

 

[hs4570]

My first 2 reloading manuals were the Vol. #2 Hornady published 1973...Speer # 8 in 1970 and in every instance for every ctg. and bullet weight they tested and with velocities listed ...they quoted the make of rifle and its' brl. length and individual components that were used to achieve said data.

No pressure brls. of any kind were used for this data... just real rifles.

There are people out there who view max loads as safe and start right there at max....have met some that feel that if its in the book it must be ok to start there and maybe a grain or two more is fine too.

I may be wrong but manuals listing 2-4 grains less than the 1970's manuals max loads is a pretty good safety cushion also ..and will for some persons keep them from harm because of the inability of some people to work up loads for their individual rifles .

The only way to keep something foolproof is to keep it away from fools...and in this instance modern Manuals may keep the Darwin contestants a bit safer from themselves.

..merely my 2 cents worth...

 

[wolfen1960]

Oldest

My oldest book is the Speer (13?) followed by the Hornady. Neither have any loads for the short mags, but I forget what issue they are.
The Lyman is the most current as is the Barnes, Nosler and Hodgdon (all show the short mag loads). That's part of the strange load from Hornady since they have the lightest max load of all my manuals.
As I said I have reloaded for years, and will work up a safe load combining the Lyman and Hodgdon manuals. I will start with the Varget since I have it on hand, but will also consider the IMR 3031 as an alternate.
I questioned the twist and effect on pressure since the Hornady book is the only one that I know used a 1-12 twist. In my mind a slower twist would cause a little less pressure since there is less friction (I would suspect that energy is needed to impart rotation on a bullet) and the faster you try to spin the bullet the higher the pressure needed. It is a guess, but even if true then Hornady should have caused less pressure with the slower twist and thus use more powder. No big deal, just wondering where to stop if I see NO pressure signs...at the Hornady max or one of the others? I use a crony to develop loads so I suppose it will be a decision based on velocity and the book max by Lyman.
Thanks for the help.