Bedding questions

T

tmas

New member
I'm workin with my inherited 7mm rem mag model 700. Ive had 3 shot groups as small as close as .45" center to center, which I am extremely content with and wouldn't look for better. But i've experienced a "2 group" issue. I'll shoot a 5 shot group, and have 2 .5" groups about 2" apart. I don't think its a barrel heat issue, my group today put shot 1,3,&4 in .4", and shot 2&5 2" straight down but only .65" apart. It is consistent like this too, they arent just random fliers.
My dad was a gunsmith and has this gun bedded interestingly. It is a wood stock. The barrel and recoil.lug are bedded, but from the lug back the action is not. It was probably.bedded in the late 70s. I've been wondering if perhaps my foregrip pressure changed and moved my groups, maybe something as simple as my swivel stud sitting on the bag for a couple shots.
So, I guess i'm just looking for direction and some insight here. For now my next step is going to be taking my swivel stud out and ensuring my gun is sitting exactly the same on the forend for each shot.

I can post some pictures of the bedding and my groups when I get to a computer...my phone wont let me.
 
Sounds like your rifle is properly bedded, don't mess with it. The "2-group" issue is characteristic of loose scope bases. Sounds like one or both of your scope bases are loose. Remount them using LocTite to keep the screws tight.
 
Mrawesome22...no, a "bedded" barrel means that it is set in an epoxy or glass bed to create even pressure the entire length. I'm guessing it was done like this because some "sporter" barrels seem too flexible for floating.

Scorch...that was my first thought when I started shooting this gun, I pulled mounts and rings...which were all tight...and lock-tite them a couple weeks ago, still shot 2 groups.
 
I see a few things to check. First, the scope may have a loose lens element or reticle. That would explain the precision of each group, but displacement. You may wish to try another scope.

The other thing that comes to mind is what may be happening with the rear of the action. There must be a second or third screw in the rear of the action, unless there's a screw in the barrel itself. If there isn't a screw holding the barrel into the forend, the rear screw(s) may be causing uneven barrel pressure and/or be affecting barrel vibration. Pillar bedding the rear screw area could help.

If there isn't upward pressure on the barrel as the front screw is tightened, the barrel could be bouncing off the bedding, creating vertical stringing, or in this case dual groups. You could try placing a shim in the forend to accomplish 4-5 lbs of upward pressure on the barrel. (Upward pressure can be checked by starting to tighten the screws a little, then placing your finger or thumb against the barrel where it meets the top of the forend, part way up the barrel channel. As the front screw is tightened, you'll feel the barrel being drawn into the forend.)

Next, are you sure all your ammo has the same loads? It's common for different loads to print a few inches apart.

If you can post pictures, it would be helpful.
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BTW: If you are going to change things, do one thing at a time, so if it's corrected, you'll know what the problem was.

John
 
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My $.02...
Going from sub-moa to 4" would indicate more than barrel harmonics.
I suspect the action has loosened and is now moving in the stock.

Whatever was holding it tight, despite the lack of bedding, is no longer doing it's job. It's a wood stock, wood compresses, and changes dimensionally with temperature and humidity.

Are you shooting in different conditions (colder?) than in the past?

The receiver not being bedded in a wood stock could easily cause stress points that will vary with environmental factors.

If you can't figure anything else out, I would bed the receiver. I've never known a properly bedded receiver to negatively affect accuracy.
 
The barrel and recoil.lug are bedded, but from the lug back the action is not.
Click to expand...
This can work if there is a pressure point at the end of the forearm. There should be 9 lbs up pressure on the barrel to work well. Wood stocks are always changing unless sealed well. Newer bedding methods have the action bedded & barrel free floated, as i am sure you know. Before you make changes to the rifle. Try bench rest prep of the brass, or at least sort it by weight after FL sizing & trimming. Sort by 1/10 grain. This may get rid of the flyers.
 
So, I'm thinking I'll try shimming the front of the barrel to create upward pressure next time at the range...would something like a business card create enough upward pressure? I'm not sure how to estimate what puts 5 or 9 lbs of pressure. Say the shim works, what is a more permanent shim, or would I need to re-bed the barrell with a little build out front?

I'm thinking of upgrading to a new stock rather than changing the bedding my father did. I've been eyeballing the reasonably priced Boyd's laminates...i'd probably have to do some custom fitting and bedding on it based on reviews I've read...i'd like a bedded action and the first couple barrel inches., I'll see the next couple trips @ the range go after I try shimming and possibly mounting a different scope.
 
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