Strange grouping problem

I

imq707s

New member
I've been doing some load development for my Ruger 7mm RM and I found a load that seemed to be working really good. I went home, loaded some more identical loads and went back to the range a few days later. Now instead of the nice 5/8" groups I got before, I'm getting some strange patterns. Each shot goes a little right and above the last shot. If you connect the dots you get a 3" 45 degree line. I've heard that this could have something to do with the action bolts that hold the barrel and action to the stock. Could they be getting loose? What is the correct procedure to tighten the three action bolts on my Ruger Mark 2 all-weather rifle? Thanks.
 
Generalizin': A rising, vertical string is a bedding problem, usually excessive pressure toward the end of the forearm. A horizontal string is commonly caused by canting the rifle during aiming.

Did you shoot several groups, that day? Was the first shot always at the low-left, with progressive movement always upward and to the right?

Have you checked tightness of all screws? Did any seem "a little bit" loose? Did you check the owner's manual about any sequence in tightening the stock screws, or the inch-pounds specification? If you don't have an owner's manual, check at your gun store, or call Ruger.

What brand of scope?

Dangfino,

Art
 
Moving groups like that usually indicate a scope mount that has worked loose.
 
If you let the rifle cool down after shooting a "string" and don't tocuh it, where does the first shot of the next string fall? If it starts back at the orginal location, it's the bedding. If it starts approx. where the others left off, it's either the scope or the action screws. My bet would be on the scope.
 
Like Mal H, I suspect that if there's successive wandering of the zero, that the scope mount is the problem. If the screws are too lose, it will wander. Another problem is poor alloy materials for the scope mount. As the receiver heats up from firing, the scope mount will expand/contract at a different rate from the receiver; and this too will cause the zero to wander.
 
4V50Gary: "As the receiver heats up from firing, the scope mount will expand/contract at a different rate from the receiver; and this too will cause the zero to wander."

Stipulating the first clauses to be correct, I think that the result would more likely be a rising string rather than some sort of "wandering". Even at that, I'm dubious about two or three inches of wandering...

I've been using aluminum bases for a long, long time, and have never noticed this sort of problem.

FWIW, Art
 
I owned a rifle that did that same type of thing. It turned out the stock was warped. Try shooting one round, wait five minutes with the action open to let everything cool and then fire the next shot. If they stay in the same group now shoot five quick rounds with about 20 second wait between shoots. If it strings out it is the stock, when the barrel gets warm it presses against the bad spot with increasing tension and moves the aiming point of the barrel.
 
You must log in or register to reply here.
Back
Top