Hi Folks,
I picked up my newly muzzlebraked and trigger jobbed .300 Remington Ultra Magnum Model 70 Winchester ( Its a factory gun. One of the few they chambered before the Short Mags hit town) at the gunsmith today.

After finally finding the right scope mount for it ( This particular model uses the one with the .330 hole spacing on the rear base just like the Express rifles) I went to the range for a load testing session.

This rifle will put the first two rounds within .50-1.00 inch then the strange stuff starts.

After letting the barrel cool, the next two rounds will print between 1 and 2 inches above the first two but these shots are also very close together. In fact, they look like two distinct, separate groups. The fifth shot tends be random. Sometimes falling in with the first two shots other times its a complete flier.

At first I thought it was just the load, but after testing 7 different ones this pattern still persisted. Finally, the recoil? or the backwash? from the Brake or the weight of the big 30mm scope put the mounts asunder( These were good mounts too. Redfield steel rings set in Leupold bases) and I couldn't finish my test session.

Any thoughts on what might be the culprit? I suspect a bedding or barrel floating issue with the walnut stock.

Thanks for the input,

HBB

[ 09-11-2003, 06:39: Message edited by: hillbillybear ]

Did you 8X40 the scope base screws and/or solder or epoxy the bases to the receiver?

I got one of those (but stainless/synthetic) without a brake. The barrel is slim and the milkjug stock on mine makes for a light rifle.

You have a heavy 30 mm tubed scope, eh?

Sounds like you need a lighter scope in sturdier mounts.

I have sheered off base screws and the old JRS style Leupold or Redfield ring attachments, both fore and aft, with some sharp recoiling rifles.

My 2 cents worth: Weld a picatinny base to it and use three rings, and a lighter weight scope with plenty of eye relief (Leupold).

Though the muzzle brake should tame it pretty well, so ... is it glass and pillar bedded, barrel free floated?

[ 09-11-2003, 07:56: Message edited by: DaggaRon ]

Dagga,
The rifle is a standard issue factory gun (lots of wood touching the barrel)except for the Brake and a 2.5lb trigger job.

Right now I leaning toward a lighter scope and 8x40 holes in a weaver type mount [i.e. Burris zees].

I may also have it pillar bedded and free-floated.

Thanks for the input,
HBB

HBB, you might try removing the brake and firing a group. That would help you eliminate the brake as a cause.

Mark

What happens with the next two shots after one of these weird groups? Do the shots walk right off the top of the paper? Are you right back where you started with the first two shots of the previous group?

I'm asking because I'm curious what you're doing between groups. Adjusting the elevation knob on the scope? The windage knob? Maybe you've got something loose in your scope and whatever holds the crosshairs where you set them is good for one shot, moves on the second one, holds its position for the third shot, moves on the fourth, holds on the fifth, and a sixth would be right on top of that one, but maybe you're adjusting something and starting a new 5-shot group. My hypothesis is that some little detent in the scope is not doing its job, and it takes two big nudges (recoil from two shots) to make it fail.

What kind of scope are you using?

H. C.

The first time I read this post I didn't have an answer. Something came to me much later. It may or may not be an answer. It's worth checking out.

A few years ago I replaced the stock screws on a a model 70 270 Winchester with some fancy socket head screws. Accuracy in this rifle was good, but then it went to hell much the same way you describe. I could not get it to group. It was all over the paper shifting up to 4 inches at a time. Good groups, but radical shifting. I tried varying every component but the problem remained. Cleaning the rifle one day I noticed a shinny line on the right bolt lug. I checked the action and found that the front action screw protruded into the action just a little. Just enough to push the bolt, but not enough to bind even a little when closing the bolt. I filed the action screw down and the rifle shot fine.

Not sure if this is a problem with your rifle, but it bears checking.

[ 09-13-2003, 19:21: Message edited by: RogerK ]

Sounds like the scope is shifting to me. I would change the mounts and go with a duel dove-tail mount and then start all over. Of course it could be any of the above, but I would start with the scope mounts because you know they've already gone bad.

Terry