Recently bought a Remington Mohawk 600 action with a Brown Precision 7mm-08 barrel. The stock and bolt aren't original either. I installed a Leupold VARI-X III.

I can't get this gun to shoot worth a hoot. I'm shooting 140gr core-lokt but will make some 139gr handloads soon to see if it changes anything. My group at 100 yards is about 7 inches and ranges from the top of the target to the bottom, and a couple on the side.

I wish I knew more about the history of the gun but the previous owner has passed away, but he was a master gunsmith. I just don't know if he did the work or knew anything about it.

Not sure what to do with the gun, any ideas?

I would first tighten all the scope mount screws to spec and then the rings to spec and try again if that doesn't help I'd try a different scope just to be sure it's not the scope. If that doesn't fix the problem I'd take it to a gunsmith

Tighten ALL the screws first, with an inch pound torque wrench.

Second, ditch the Core-Lokts.

I will try that, maybe even ditch the dove tail style mount and get a rail and rings. I know it's not the scope because it did the same thing with the scope it came with. Will also be ditching the core lokts for handloads.

a lot of people love core-lokts but I tried them in my Browing A Bolt when I first got it and I couldn't get them to group worth a dang, it was horrible. I switched to federal fusions and they were lights out. Now I shoot Chad's 270 loads.

I recently tried to free float my factory stock (I knew I would eventually buy aftermarket) to see if it helped tighten groups. My targets too looked like I was using buck shot at 70 yards. That was a miserable failure. I since put a better stock on it and torqued the action screws to specs. It shoots much better now. Check your action screw/s. If you have a different scope maybe on another rifle, try that too.

Zero rifles I've shot, with Core-Lokts have shot well. And ice watched many others, on my range, do the exact same thing.

Does the bullet do well on hide, flesh, and bone? Lots, and lots of people say it does. But if a guy can't put it where it needs to go, then they aren't worth anything.

Core-lokts used to be fine bullets. They changed. Now I won't touch them. They don't even kill like they used to.

I agree with checking all of the mounting screws and action screws first. As far as the Core-Lokts, I've have mixed results with them over the years. My Rem. 788 22-250 shoots them great.

You should also check how you are benching the gun. I had a Remington Model 7 that would only shoot good from the bench if the front bag was directly under the front mounting screw. Any further forward and it would start slinging shots all over the place. Not sure why those short Remingtons are like that, but they are.

While everybody here bickers over the merits of the Core Lock bullets maybe try a lighter bullet, try the Nosler 120gr Ballistic tip . 45.0 gr IMR 4895

Do you know the history of the gun? If tightening everything, really good bore cleaning and good ammo don't work. I would take it to a good gunsmith. Not having the original bolt scares me. The gunsmith can figure it out.

where are you located?

I have to ask, but are you resting the gun on the forearm or the barrel?

Do all the above and try Hornady ammo.

I'm resting the gun as close to the action as possible. Shot much better with handloads but still about a 4" group. At least it shoots in one area of the target now. Next I'll play with different loads and see if I can tighten the group.

Buzz already said it but is it clean? Try some foaming bore cleaner with a copper solvent in it and see if the patches are bright blue. The guy that taught me to reload also showed me many times that guys rifles that wouldn't shoot were usually a result of them being filthy and copper fouled. Yours may not be the case but I'd make sure it was clean before I spent money on a gunsmith.

Agreed.

Then, with any new rifle load development, I reproduce the lowest powder charge for at least 5 rounds, to foul before actual load testing. Usually I put 10 through the barrel before I actually start testing loads, but 5 may get you where you need to be.

First, when you changed out the stock, it can change up the stock to action matting and cause a bedding issue. You can't just swap a stock out an expect it to be 100% solid. Most likely, you have a bedding issue. Even as crappy as Core-Lokt ammo is, it should do better than that.

Second, if the bolt if not original, you could have some head space issue. Plus, if the new bolt is not making solid contact with the bolt lugs on the action, it can cause issues. You have multiple things going on here, and one of them could cause accuracy issues. Add all of them up, and who knows what's going on.

When you say you have big groups, what do the groups look like? As in the pattern on the paper. Is it stinging up and down or diagonal?

Once you get it shooting good take it to Jasons class, you will be very surprised what that little rifle will do.

UPDATE:
I cleaned the barrel and lessened the charge slightly on my handloads and got the group way tighter.
Here's 3 pictures showing the progress. Not sure how to rotate them.
1.) Original Core-Lokt group

2.) Handload Group

3.) Cleaned barrel and handload group

It's looking better.

Cleaning the barrel wins again ??? HAPPY you got it going your way...

Every deer i have ever killed has been with my Mohawk 600 since i was 11 years old. Would love to see a pic of yours!

Seen fouling the barrel win many times as well.

we never had any luck with the 7-08 in the accuracy department, 120 gr bullets helped a bunch.

Absolutely, and in this case apparently it was fouled to the point of 4"-6" groups. Appears it did not need bedding or free floated or action tightened or mounts tightened or several different scopes or custom loads.

Maybe it just needed a good cleaning.