I may be in need of a rebarrel or have the chamber recut. My accuracy is going to crap on my 338RUM. I cleaned the bejeezus put if the barrel and managed an ok group at 100 a few weeks ago. Yesterday, I tried again and shot horrifically. 4 inches at 100. Unacceptable. Next range session I will try some factory ammo to rule out my handloads, but suspect throat erosion. If I buy one of those bore cameras, will it be obvious if that is my problem, or shall I bring to a Smith and have it measured. Unbelievably, our local master gunsmith does not have the capability to measure throat erosion. So I guess I'm looking for suggestions and ideas. It's kind of too late to mess with before this hunting season. But something should be done I guess. If it needs a barrel, I have no idea what to get. Never had a barrel replaced. When it's all said and done, I would like similar performance since I am all set up for one load with it. I have a lifetime supply of components for it and like using it.
Thoughts?

I am in west Michigan if that matters. I guess I would prefer dealing with a michigan gunsmith just to eliminate shipping through ffl, or I could drive the gun some place.

How many rounds do you have through it? I'd think you'd need 3000-5000 rounds through it before groups start opening up.

I'd expect a scope failure before the throat being burned out and would suggest putting on a known good scope as a first step in trouble shooting.

I have in the 400's of rounds through it I guess. I did a bunch of reading last month on it, and the fire breathers can smoke barrels a lot faster. I thought 3 to 5 thousand rounds were for 308 type rounds. If it makes any difference, my brother's 300 RUM is doing the same thing and he sent it back to the builder and said the throat was toast, so he is re-barreling currently and he had about 500 rounds down his tube, but it was a lighter weight barrel.

You need to find a smith with a good borescope. I don't suspect much throat erosion but I'll bet you have tons of copper deposits. Give the bore a thorough cleaning with good copper solvent, examine the crown, and make sure the bedding is correct. I'm sorry, but I don't think 400 rounds will ruin the throat unless it was shot in two or three days.

Had one in the shop just the other day, bore scoped it looked OK, Client decided he wanted a new barrel so I started to pull the scope mount off; guess what, loose base screws on all four of them. He went home and will get me a progress report, hope it was the problem.

By the way, you don't need to use an FFL to ship if it is your gun, ATF allows the "..owner to ship to.." for repair or modification.

Yup, been there. Guy shipped me a rifle to rebarrel and when I get it, I notice the Weaver Pivot Mounts. The base screws were nice and tight but the pivot rings just didn't lock up tight. Swapped on a set of Weaver bases and rings, mounted a scope, and proceeded to shoot several .5 MOA groups. Shipping on that Bull Barrel behemoth was ten times what the "repair" cost.

And even if the mounts are tight it's a good chance a scope on a 338 Ultra has taken a crap.

Thanks guys. I mounted the new scope last season and it has under 100 rounds on it, but accuracy was getting suspect prior to that anyway. I locktite every single screw. I will pull it all apart again. I might not get to it prior to hunting, just have to keep my shots closer I guess, and elk are large targets. I will shoot some factory ammo at the bench to rule out my reloads as well. Ill check back on it, but it might be a while. Not sure I have a day to pull it all apart, put back together and re-sight. I have to travel to get to a range, so that sucks. Thank you for all the insight.

Worked over the scope mounts good . . .

What about the action to stock screws?
Foreend contact.

I can check the screws. The gun hasnt been apart in a while. Its in a McMillan and its bedded in, free floated barrel, but I will definitely double check them. thank you.

I think 400 rounds with a 338 RUM could easily cause enough throat erosion to compromise accuracy. I good smith may be able to set the bore back enough to regain some accuracy for a while before a rebarrel.

A 338 RUM will last much more than 400 if its taken care of and not heated up. I have seen 7mmRUM go in 600-800. The 338 EDGEs are lasting 1200-1500. Some even have 2000 through them and they are .5 moa.

It is very possible that over cleaning it is your problem, been there!

I had a very accurate 7 Mag and I clean the bore like you stated and the accuracy went way south, I almost cried. Shooting maybe fifty rounds, cleaning but not scrubbing it, then shooting three fouling shots and stopping. Then next day it was first shot cold barrel dead on, with a 5/8 inch three shot group.

Maybe, maybe, maybe