I have Winchester model 70 that I just had some work done to. I had heart barrels put a new barrel on the gun and free float it and they also glass bedded the action. The barrel has a 1:7 twist. My problem I'm having is when I got the gun back in January 2017 I worked up a couple loads and shot them the best group I had was a 1/4" @ 100 yards with a load of 38grs of imr 4350 and a 115gr Berger bullet COAL is 2.255" which is seated .015" off of the lands. Now I went to go do some nuisance deer hunting and now it won't even print a 1" group @ 100 yards. So I went back to the reloading bench and started to try and figure out what went wrong. I couldn't find anything reloading wise wrong so I started over they best group that I could print is a 3/4" group. My question is can I load more powder in the case to take up some of the extra air space to achieve a little higher pressure and higher velocity? Loads that I have worked up starting was 34grs of powder too 38grs of powder. Can I go over that?

One you have not listed a caliber. Second I would think 3/4" groups should be plenty accurate to kill deer. I would just go hunting, or build a bench rifle.

The gun is chambered in 243. can you answer my question?

Before changing the load I would look for other variables. If I am reading your post correctly you had a rifle/load that shot 1/4 groups, changed nothing and now it shoots 3/4 groups. If that is the case I would look at a few variables

Is the crown good, did it get damaged?

When was the last time you cleaned the barrel?

If in a wood stock how is the bedding? I know that you said it is glass bedded but you can still have warp-age in the wood.

Optics tight?

Can you consistently shoot 1/4 in groups? Don't mean to offend but few people can. The rifle may be fine it may be you.

I know it is not answering the question you asked but I would look at other things if you think the load has not changed.

The question is: can you increase the load from 34 to 38 grains to 1.increase pressure & 2. increase velocity. The answer is an increase in powder will increase both, but is it safe? that is a different question. It's possible that your rifle will handle an increase in powder, but I wouldn't make it a quantum jump. In a sense, you have answered your own question. Among the possible reasons stated above, you might continue with load development and find that a load with slightly more (or less) powder or different powder gives the results that you are seeking.

From your questions about does increases in powder increase velocity, etc, before I did anything, I'd get a couple of good reloading books and read them. Your questions do not indicate a firm knowledge of reloading.

ok I just loaded 3 different loads went out and shot them first one was 38.5grs next was 39grs and last was 39.5grs. All seated .030 off of the lands and the best one that grouped was 39grs and i grouped a .289" group at 100 yard. Thanks for all your help.

Not so fast.

How many shots in the group? How many groups for each powder load?

If only one group per load and only 3 shots per group you have likely learned nothing. Normal variation for several other factors determining group size masks true differences among the different powder loads.

Try comparing several 10 shot groups for each load. I guarantee you'll be surprised. And I doubt you will consistently see 0.289 inch groups from any load you try.

3 shots per group and 3 groups per powder load.

quote:

Originally posted by vicvanb:
Not so fast.

How many shots in the group? How many groups for each powder load?

If only one group per load and only 3 shots per group you have likely learned nothing. Normal variation for several other factors determining group size masks true differences among the different powder loads.

Try comparing several 10 shot groups for each load. I guarantee you'll be surprised. And I doubt you will consistently see 0.289 inch groups from any load you try.

Re-read this^^^^^
What you do with this VALUABLE information is totally up to you.
Zeke

there is a million reason a gun will go from 1/4 to 3/4s and I doubt if you will ever know why, as it can be shooter error such as trigger pull, bad day or whatever, just try and duplicate what you had as best you can, keep playing with it. Unless your shooting bench rest competition, its a moot difference.

I did get a chance to play a little more with it and I found a load that I can consistently shoot a .289" group at 100 yards until the barrel fouls out or gets hot.

That's par for most barrels, and I suggest the fouling etc. will come to pass after a few hundred rounds polishes the barrel out. Don't let it get too hot...Most barrels shoot less well when new then better at some point then return to shooting less well again as they wear out. Its that interim where they shine. but sounds like you have a handle on it now.

I believe its shooter error when groups vary that little. Attitude, health, bad days and good days apply to shooting just like any other sport..I asked a great benchrester how he aways shot so well and never had a bad day..He said I drink a lot! and Ive always been to lazy to flinch

And don't fall into the old "you must shoot 10 round groups to be sure" thing. I have never seen any animal wait around for three shots, let alone 10. It is the first three that count in a hunting rifle.

I agree, Im a 3 shot group person, and Im primarily a hunter..If I miss three shots then most of the time I suspect the animal is further than I should be shooting..Its been a long time since I wasted 3 shots..but Ive flubbed the first shot on more than a few occasions.