Difference in load data for .308 win.

[BowNut]

Ok my sierra book is older but for Varget powder it shows 40.2 as starting point and 42.2gr as the max load for 168gr bullet. Then I was messing around on the Hodgdon site and Varget starts at 42gr and 46gr for a max load. This seems to be a huge difference. I have seen data very a grain or so but never this much. Not sure which to go by now the bullet manufacture or the powder?

[khmer6]

is it for the same listed bullet or just any 168gr bullet? Size and shape and jacket material can have a huge difference in initial pressures.

[BowNut]

Both are for Sierra 168gr BTHP.

[lancetkenyon]

^ This, Different bullets have different lengths, meaning different case capacity if seated to the same COAL. A Barnes bullet is very long for it's weight, due to all copper. A Berger Hybrid or HVLD is long for it's weight too, due to the long ogive. A round nose is short for it's weight, due to a fast taper and more weight being distributed up front. Boat tails are longer than a flat base of the same length. Etc.

 

But only YOUR gun can tell you what max is. Might be 2 grains less than published, might be 2 grains over. Start low and work up looking for signs of pressure and you will have your max load.

 

Also, different chambers cut in rifles call for different charge weights. Free bore makes a difference I pressure and velocity, so does case capacity and brass content from different manufacturers. Way too many factors make a difference to list all of them.

 

Listed charge weights are given for the specific rifle used in testing. Yours WILL vary.

[khmer6]

strange its the same bullet but it does happen. Usually in a very large cartridge with 80-100 capacity or a cartridge like 308 where there are just sooooooo many applications and rifles. off the top of my head I dont know how each one tested, whether it was a real rifle with a pressure sensor or using a multical receiver with very tight tolerances.

work low and start your way up just like any load. Some books don't list pressure either which i really dislike.

I can run some quickload data if you want. 308 WIN 168gr Sierra BTHP with Varget. These are the SMK right?

[khmer6]

also forgot to note. POWDERS DO CHANGE. not sure how old the book is compared to the new data but you notice it a lot in some really old Alliant or hercules data :-)

[STOMP442]

Also check that the test rifle criteria is the same. One load may have been done in a 26" barrel and another in a 22" barrel.

[khmer6]

running Hodgdon max load thru quickload it shows 64,141 PSI. thats about 4k over max for the cartridge. I would start with sierra's data with 1gr increment ladders. get to max and do .3 or .5 ladder until you need to back off. Of course depending on how many bullets and time you got always fine tune!

[BowNut]

Sorry for being slow at responding. Just got to Vegas with the wife. Don't have the Sierra load data but this is from the powder manufacturer. My sierra manual is the 50th year addition.

Thanks for the replies guys. Learning a lot.

[khmer6]

I think Sierra stopped at their max cuz the load was being compressed? Its right abound 100% case load. Another thing to consider is case head stamps. Soooooo many 308/7.62x51 case manufacturers. Some might be more roomy than others. I usually find book max loads are entirely different from me. Some are lower, others I can push higher just like lancet said. Work up your loads slow and take note of case head stamps, oal and all the little variance once you are getting to the very top. Primer can also make a difference. For me I like magnum primers usually, make sure all that powder burns :-p

[maximus]

308 Winchester continued

#2200 .308" 168 gr. HPBT

MatchKing

C.O.A.L. 2.800"

Powder /Velocity 2400 2500 2600 2700

RE-7 32.5 34.9

IMR-3031 36.3 37.9 39.5 41.1

Benchmark 36.9 38.4 39.9 41.4

748 41.9 43.4 44.8

BL-C(2) 42.7 44.5

AA-2460 38.1 40.0 41.9

H335 40.3 41.5 42.6

TAC 38.8 40.4 42.0

H4895 37.3 38.6 39.9

AA-2495 37.7 39.7 41.7

IMR-4895 38.2 39.8 41.3

Varget 38.7 40.3 41.9 43.5

IMR-4064 37.8 39.7 41.5 43.4

AA-2520 36.9 38.7 40.4 42.2

IMR-4320 39.6 41.4 43.1

Viht N140 38.9 40.6 42.3

RE-15 38.8 40.4 42.0 43.6

H380 42.5 44.4 46.3 48.2

760 44.2 45.9 47.5 49.2

Viht N150 38.9 40.7 42.5 44.3

Viht N550 42.1 43.6 45.0 46.5

IMR-4350 44.5 46.0 47.4

Energy/ft.lbs. 2148 2331 2521 2719

Accuracy Load RE-15 42.0 2600 2521

Sierra does not recommend MatchKing bullets for hunting applications.

Powder Grains Velocity Ft. lbs.

Bownut,

this is what i have with the recent manual, i'm in vegas too but leaving today.

goodluck.