Ruger M-77 "youth model" .243 shot tight group but off of January impact by 5 MOA

[BigFatKen]

My wife's Ruger M-77 shot right on in January, 2008. She got a nice one shot harvest of her bigger buck at 90 yards. 16+ inch light barrel.

So now I loaded 37 grains of H335 with a Hornady 70 gr bullet and three hit in a nice circle at 55 yards but at least 3 inches high and an inch left. Before I changed the scope, I shot one of the 100 gr deer bullets. Wow. It shot to the same high point of impact.

We had the house open to the humidity for the last three weeks, our small little season here in East Alabama that requires no heat and no a/c. The a/c is on now and it will likely stay that way until Fall.

Since the rifle shoots a tight group, it should not have a loose stock screw or other problem. It shot well all last year from the Sept sight-in to the January end.

Does any other member have an impact shift like this?

 

[rcmodel]

You can't change loads and bullet weights without expecting to see a large change in POI.

Hardly any rifle ever made will shoot two different loads in the same place.

You will have to settle on the 70 grain varmint load, or the 100 grain deer load.

Or sight in the rifle each time you change back & forth.

As for stock warpage from high humidity, it is very possible.

I'm not real sure whether your Ruger has pressure bedded, or free-floated barrel.

Use a dollar bill or something and slide it down the crack between the barrel and the stock.

See if there are tight place on one side and not the other. If there are, removing the offending wood will likely cure a warping problem.

rcmodel

 

[BigFatKen]

thank you

I am going to change and re-sight it twice a year. This load is much louder than in the Savage 22" barrel that is my summer critter getter.

I guess that is to be expected with 6" less barrel. This load is rather mild. Next batch of ammo will be 1.5 gr more.