308 Win load help.

[4x4yj]

I have just started reloading 308 for my bolt action, and need some help with how to find my most accurate load for my rifle.

I started my loads using Hornady 9th edition data, Hornady 150gr SST, IMR 4064 powder. I loaded up the first 4 charges as listed by Hornady , just to start low and check for pressure signs as I went up. I was looking for the best group and then planned on working in small increments.

38.4 (2300fps)
40.4 (2400fps)
41.7 (2500fps)
43.3 (2600fps)

100yds

Is it odd that the 38.4 has the best group and is super tight?
The other 3 loads were not even close in group size.
Starting with the 38.4 gr just seems so low to me?
I guess I am getting to hung up on high velocity

 

[jwrowland77]

If it's accurate, speed don't matter unless you plan on shooting a long way off.

With the way you did your work up, you more than likely jumped over other good loads. I mean that's really spread out. At most start at min and go up in .5gr increments. Most the time if you go up in .3gr, you can find more than one good load.

 

[jwrowland77]

Also, Google Ladder test (normally for long distance), and OCW test.

 

[Duvel]

As rowland stated, those are pretty big jumps.

 

[witchhunter]

How many rounds per charge? I load 9 rounds per charge weight and shoot 3 each 3 shot groups and average the groups. I also use .5 grain increments. You will probably see groups getting smaller, then bigger. Then you can fine tune to .1 grain. Then seating depth. Shoot a couple of foulers before you get started.

 

[VoodooMountain]

Accuracy if the gun itself has several factors. Try different bullets and work up again in .5 increments if you want more velocity. You will also find there are certain pressures yourgun will like due to harmonics. Moving to a faster if slower powder can yield a different velocity in that same pressure window(s)

Having said all that, some guns just don't like some bullets. I have a 308 that doesn't like the game kings but loves Speer btsp for the velocity window I want.

If you find your rifle is only accurate with lower pressure loads on a consistent basis, you may have a mechanical issue with the receiver or barrel though this is not common.

 

[jmr40]

My manuals show 43 gr as the starting point with 47.7 as max. I think you need to add a lot more powder. If the load is so light that the powder has lots of room to move around in the case it causes inconsistent ignition. The most accurate loads pretty well fill up the case or are slightly compressed so the powder stays in place. I wouldn't want to go less than about 2800 fps and you should be able to get near 2900 fps with a full charge of 4064 and very good accuracy.

You don't have to use mouse fart loads to get good accuracy. Not 4064, but in the past I've used it with similar results as Varget.

 

[yugorpk]

Seems a bit low for speed. I chrono pretty much everything and i get about the same speeds with 175 grain BTHP and a 20 inch barrel. My favorite 4064 load at 2600 fps uses 42.8 grains of 4064 COAL of 2.800" . Keeps a very tight SD.

FWIW I don't think I could fit 47.7 grains in the case without settling the powder in steps.

 

[MikeInOr]

I found a decent 4064 load for my Rem 700 heavy barrel. I found several very acurate loads with Varget. Once I switched to varget I never look back at the cans of 4064 on my shelf.

 

[4x4yj]

Thanks everyone for the help. I will start at the bottom and work up in .5 increments. Once I find the best group I'll go back and fine tune it.

I have noticed quite a bit of variances between starting and max loads in the different manuals out there. So I am a little unsure as to what load data to begin with. Just slowly work my way up and watch for pressure signs....

 

[Reloadron]

Thanks everyone for the help. I will start at the bottom and work up in .5 increments. Once I find the best group I'll go back and fine tune it.

I have noticed quite a bit of variances between starting and max loads in the different manuals out there. So I am a little unsure as to what load data to begin with. Just slowly work my way up and watch for pressure signs....

The load data in the manuals are based on their test setup and the bullets and seating depths they used. It is normal to see things vary. I load .308 Winchester for several rifles including a bolt gun (Rem 700), AR-10 Armalite, M1A Springfield Armory and based on all of those rifles faster does not always equal more accurate. Just the nature of the beast, barrel. powder burn rate, pressure curve and all the variables.

This past summer I was working a great load for my bolt gun. AA2495 41.0 gr. under a 168 gr, SMK bullet using a BR-2 primer WCC 08 brass. All here nor there. The average velocity in 10 shot groups was 2550 FPS. I really "thought" my best accuracy would be around 2650 plus FPS so go figure.

Just remember the minimum and maximum loads published in any loading manual will always vary based on their test equipment and setup as well as their components used from bullets to primers.

Ron

 

[LiveLife]

Is it odd that the 38.4 has the best group and is super tight?
The other 3 loads were not even close in group size.

Was the barrel allowed to cool between groups?

If not, that could explain the tight first group and subsequent larger groups.

I load .308/.30-06 for auto loading rifles and usually shoot a few rounds to warm up the barrel and allow the barrel to cool until I could touch it before I start my next group. With bolt action rifle, many will use the first shot as "fouling shot" before shooting groups.

308 for my bolt action

If the load is for hunting, what would matter is the first shot cold barrel accuracy.

Here's cold barrel accuracy for hunting vs hot barrel accuracy for auto loading rifle discussion - http://www.thehighroad.org/showthread.php?t=306072

 

[4x4yj]

Hmm. I didn't really let the barrel completely cool down between shots. Just enough time for me to reload and get settled on the cross hairs again.