W748 powder temp sensitive?

[GhostRider32]

OK guys, need some help here. My 12BVSS .308 shot great 2 days ago but today, shot really terrible. I was using Varget mostly the other day with regular Winchester large rifle primers and even shot a few rounds with some W748. The 748 grouped well also 2 days ago. Why would it shoot better 2 days ago than today. The temp was about 15 degrees cooler today and I've heard that W748 is temp sensitive. Is this true? I also took the stock off to adjust the trigger. I tightened the stock up but don't think I overtightened it. Is it possible to overtighten the stock and cause other problems? I ran a dollar bill the length of the barrel and didn't feel any snags like if the barrel was touching the stock. Lastly, I checked the lands by using the Nosler book way and they are at 2.840 so I set my reloads at 2.830 COL. When it shot so well, I had my reloads at 2.800 COL.

Now granted, there are several variables here as to why it shot so poorly but my main concern is could I have tightened the stock to much? If it's just the W748, I can deal with that.

[Rodger Peterson]

I submit that the 748 is fine. Temp sensitive refers to velocity and ignition. I would believe that by breaking down the rifle you must be sure all is tight and sight it in from scratch. .030 difference in OAL isn't going to cause enough difference to cause what you describe. Good luck.

[somerled]

A lack of consistency in anything will impact groups. Taking the stock off and using less or more pressure on the screws will definitely impact results. I suspect that is probably the main culprit, but all of the factors you mentioned probably played a role.

[rn22723]

Too many variables.

Yes 748 is notorious for being temperature sensitive, but usually in when temps are a bit higer. If you want to experience the best accuracy potential with your gun I would stick to one powder each shooting session, ie do not swap between Varget and 748. Or else clean your barrel between different loads. If it were me, Varget and the CCI BR2 primer seem to a match made in heaven in either WW or Lapua brass!

A fellow would be well advised to check and see if Savage has torque specs for the action screws of the action? Then for the sake of repeatability get a torque wrench and use it! Helps eliminate variables.

[GhostRider32]

Well, I think I found the problem or at least a major contributing problem. I checked my loads again and the COL was 2.835 to 2.840 so some of the bullets were touching the lands. I should have realized this when the bolt was a small amount harder to close on some of the loads. DOH..... I will check on the torque specs though. I am going to reseat the bullets to 2.800 where I had excellent accuracy.

[plateshooter]

On Savage Shooters . com, it is noted that Savage torques their synthetic stocks to 25"lbs. I have my 12FV in a Duramax stock and I torque it to 45" bls with great results on the target.