Load Data: Barrel Length and Twist

The rifle for which I will be loading has a 1:10 twist and a 20” barrel. I will also be using a CCI #2 Large Primer.

However, all of the .308 WIN load data for Accurate powder, regardless of bullet type, was formulated for a 24” barrel having a 1:12 twist using a Federal primer.

Is any type of compensation needed and if so, how it is done?

Thanks.

Using the Greenhill formula you could come up with the optimum bullet weight and length for your barrel. but probably the easiest way would be to direct you to what they call the Load tree. Look for threads on that. But basically what you do is start with a projectile and low charge and work up until you find the sweet spot for your rifle. So look for Load tree threads. I know there is one on here

is a load tree the same as a ladder test?

Yes ladder LOL

While your still in the load development stage, don't worry about using a different primer. If you were using an establised load, or a maximum charge that would be a different story.

Also, I find I usually lose about 150 FPS per inch of barrel. If you chronograph your loads you will find that the FPS on your 20" barrel will be less than the load data's 24" barrel.

The 1:10 should allow you to shoot heavier bullets up to 220gr.

The reloading manuels are a good guide to follow but your results will not always be the same as theirs even if you have the same barrel length and twist. I wouldnt be too overly concerned with the barrel twist rate. I have an AR with a 1/8 twist barrel and it should shoot heavy bullets like 75 grains really well but it does the opposite and shoots light bullets like 50 and 52grains in a lot tighter groups.

http://www.browning.com/customerservice/qna/detail.asp?id=107

After ya get your load hammered out , see if this'll tighten up your grouping

The Browning product looks great, but my rifle is a Savage and the web site implies that the BOSS is only for Browning rifles.

I found with that cal. most of the charges work good a 308 has a good case fill on most powder you can use .
I have found on outher cal. that the charges at or max with the shorter barrel 20' has heat problems the barrel heats up very quick and will have some fly aways .
try to find a powder with good case fill with a lower press. to keep your groupe true i use IMR 4064 works good with the short barrel .