I am trying to sight in a .243 pre-64 Model 70 rifle, and am getting 5/8" groups at 50 yards, but only 3"-4" groups at 100 yards with all my various loads. I know the scope & mounts are OK, so what is the problem that I'm overlooking ? Thanks (I also posted this question on the SMALL BORE forum - just wanting more opinions).

The bullet diameter or the weight of bullet/twist of the rifle!

Unless you are shooting in heavy wind.

H

Since the rifle is a half century old can you tell us how it shot in the past?

No, I just bought it, but it looks almost new - couldn't have been shot much.

Is it fouling up quickly? Accumulation of bore fouling can cause such things, if you shoot a few groups @ 50 then move to 100, where accuracy goes to pot.



The original M70 .243's have 1/10" twists, so they should stabilize any reasonable .243 bullet up to 105-grain spitzers with no problems!

Scope parallax? easy to check. I have seen some scopes that had 2-3" at 100y. Just a guess.
C.G.B.

Frank

Have you ever actually measured the twist? I realize that it ought to be a 1-10, but just remember that back in the day Winchester would do all sorts of custom options. I don't know if that included twist rates or not. Either way, it's worth checking. Secondly, I would for certain try it with a different scope of known performance.

Gabe

Hope you are not insulted buy the thought of letting someone else shoot it ! Also are you changing the power setting on your scope ? Thats a prety cool rifle and I would certainly expect it to shoot better than what it is doing for you, although the 50 yard group is about what I would expect. ...tj3006

Give it a good cleaning first, no telling what the previous owner's cleaning habits were. Buy a box of Winchester Power Points as I have always found that they shoot well in all pre-64s I've owned. Then I'd look at the shot pattern on the target and look for horizontal ( usually your front sling stud is catching on your rest) then verical stringing which is indicative of a bedding problem as is two shots together followed by a third flier.

If your rifle appears to "scatter" them all over, then I would check the scope, mounts, etc. But aside from that rudimentary diagnosis protocol, I strongly recommend a competent gunsmith to look at bedding, crown integrity, etc. If you try to fix it yourself, you might compound the problem.
jorge

There are a number of areas on the Pre 64 M70 Winchesters that can contribute to accuracy. It is a featherweight? It is usually indicated on the barrel, left (off) side near the rear sight where the calibre is stamped. My experience with pre 64 fwts is that they heat up quickly and shoot their best when allowed to cool between shots.

Areas of attention:
These tips come from an excellent article called "Tuning the M70 Winchester" by Bob waller in Gun Digest Treasure 4th Edition published late 60s or early 70s.

1. Forend pressure.
The rifle stock ought to apply firm pressure to the barrel right at the tip of the forend for about 2". The rest of the barrel ought to be free-floated. A free-floated barrel should not touch the stock during firing. As you know the barrel vibrates (even more so for a fwt) when fired. If the barrel (except for the pressure at the forend) touches the stock during firing it will put accuracy off considerably. A simple paper thickness test is not conclusive as it might pass this test but still vibrate against the stock during firing.

Also check the action bedding. this tends to be fairly ordinary on the M70s

2. Trigger Pull
Whilst the M70 trigger is excellent for a factory rifle it is usually too heavy and that can throw accurate shooting off. It is best to have it adjucted by a competent gunsmith to a crisp release at about 2.5 lbs.

Regards,
Magnum