What Grain is suitable for 1/15 twist if 308


Well-Known Member
Jul 31, 2010
Unless this thing is being used strictly for target shooting under 300 yards I would suggest you get the gun re-barreled. A 308 that is pretty much limited to 150 grain, and that would be marginal, and under bullets is not my idea of a good setup for hunting. As a specialised target gun, fine but you are stuck with relatively low B.C. bullets..


Well-Known Member
Aug 2, 2007
MN Iron Range
If you are 300yds and under as you stated in post #8, I would use the speer 125gr TNT. My understanding is this bullet is pretty much the front half of a 168 smk. Accuracy is superb and the load of 52gr WIN748 is a known good one. Work up though. I use this for hunting and have had excellent results. I hunt for meat though and I'm choosy about my shots.

J E Custom

Well-Known Member
Jul 29, 2004
Here is my list of recommendations for twist. 308's are at the lower end of the .30 calibers so depending on load pressure and barrel length the twist rates can vary and it becomes a choice you have to make. I would recommended using the faster twist rates listed for your 308

My numbers are for the minimum to maximum twist rates depending on your intended use and choice of cartridges.

120 grain bullets need to have a 12 to 15 twist rate.
130 grain bullets need a 12 to 14'' twist.
140 grain bullets need a 11 to 13' twist.
150 grain bullets need a 10 to 12" twist.
160 grain bullets need a 9 to 11'' twist.
180 grain bullets need a 8 to 11 twist.
190 and up works best with a 8 to 10 twist.

These are general twist rates for best performance but some liberties can be taken depending on the circumstances.

Hope this helps.



Well-Known Member
Jun 15, 2018
Bullet stability is a function of twist relative to bullet weight and length (length more important). It’s also affected by atmospheric conditions.

There is no one twist for all bullets of a given weight because in spite of a common weight they will have different lengths. This is particularly true with monolithics, which are longer due to having less density than lead.

It’s best to look at the specifics of a particular bullet to see how well it will stabilize at your twist rate. Plug the details into a calculator, like the JBM version (linked).



Well-Known Member
Sep 13, 2010
Although I’ve never pushed them as hard as you would out of a .308, I have shot several thousand Speer 125 tnt’s out of a .300 blk and I am always impressed with the accuracy. I would be curious to see what a Barnes 110gr black tip would do out of that barrel.

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