Oh great and mighty Kimber Montana experts, lend me your years (eyes) for a moment if you would!
I have a puzzling problem and I could use some input.
(warning, long post...long and short, this Montana shot great and then all of the sudden started shooting horrible and there was no changes to instigate the change between when it shot great and bad. Standard checks of known issues and obvious problems...including me as the shooter...result in no smoking gun...if you think you might have an idea, read on for the full story!)
I have a Montana 8400 in .338WM. Got it off the buy/sell board here over 1.5 years ago. Topped it with a brand new Burris E1 3-9x50 scope on high Warne mounts. Scope and mounts weren't my first choice but what I had available at the time and I was itching to get out to the range to see if I had got a good one or one of the Montana's folks complain about.
My first range session I was very pleased with the rifle. Two three-shot groups yielded 1MOA or better at 100 yds with handholds, but felt with some practice and load development could easily improve that figure. Shot it only once or twice more that year before hunting (which was a bust) and then didn't shoot again until a week ago or so. The rifle was stored indoors in a safe for the almost year that it didn't shoot.
Last week I loaded up the same "mix" from before which had shown around 1MOA at 100yds but this time I could NOT get it to shoot consistently. First two shots were low and to the right but very tight-3rd shot was about 3" away further to the right. Made an adjustment and was 5" high of the bulls eye but dead on (so about 8" higher than first group, but I had made a one inch vertical correction to the scope). Subsequent shots were all over the place. I thought maybe the scope was a little sticky for some reason and went back to original settings. Bottom line at 100yds it was all over the place. I was shooting from a very good lead sled and paying attention to trigger discipline. 200yd resulted is holes all over the paper (no further adjustments to the scope...just trying to figure out where it was shooting) and attempts and further ranges of course were futile. While I can generally get good accuracy in various rifles I shoot, I thought maybe I indeed was pulling some. Also my first inclination was that I had a defective scope as a friends rifle exhibited the exact same behavior when his scope went bad.
The following steps were taken. Checked torque of rings and bases (I use a calibrated torque wrench). Replacement of scope with a known good Leopold VX-II 4-12x40 and reloaded again making extra sure we were loading consistently. (Measured powder each time, check bullet concentricity, etc). Then I sent the rifle out with my friend who is a very good shot to try and eliminate me as part of the problem (Plus, I couldn't go to the range that day).
Results were as bad or worse then before. Again, was shot from a lead sled with a shooter that routinely shoots long range with his various rifles (hunting and bench rifles). At 100yds shots were over 5" apart and at 200yds he couldn't even paper it!?! He tried all the tricks, said he'd never experienced such a thing.
After searching for answers, I came across this thread (and others) and hoped I had found the answer. Though I haven't read anyone having a good shooter and then having it go bad all of the sudden.
Tonight, I checked all the problem spots mentioned. My findings are: The mag box is NOT binding at all. The barrel is free floated and not touching the stock. The action does not appear to be moving as shown in this thread at all. All the screws (action and scope bases mount) are of proper size and NOT touching/bottoming out on the barrel. The front action screw was torqued at around 45 in/lb and the rear screw was at about 55 in/lb. So not under or over torqued, though not identical (and of course checking torque to find where it's at is not quite as precise). The scope bases were not loose nor were the rings. Also the crown seems just fine and no obvious issues in the bore. Looking down the bore the barrel seems as strait as can be. I'm a bit at a loss. I could bed the action, but I don't feel that is the issue....Once I get it shooting good again, I will most likely bed the action to try and make it even better but I don't want to go there at this point as there seems to be another issue at play here.
The Warne bases I got from my local smith were not the part no. for the Kimber Montana but the smith said they were the exact height and contour and proper screw spacing. He milled the screw holes to accept screws appropriate to the kimber. The base is in fine shape and the screw holes have very tight tolerances, I don't think there is anything moving there, though the thickness difference between front and rear seems to be about .131" whereas I believe the measurements listed for the Talley LW rings shows a .125 difference. I doubt this is the cause but I have some Talley LW rings FOR the 8400 and will mount the scope with those for the next test to to eliminate one more issue (plus I prefer the Talley anyway). I also noticed one of the shells I had shot was was prepping for re-loading seem to have a burned area around the primer. I don't think it was overloaded as the primer wasn't bulging or anything, my thinking is that the primer pocket might not have been fully clean and when it seated it didn't get a good seal. The bolt face has a very small divot it looks like corresponding to the burn mark on the case head. However, I do not see how this could affect accuracy as it is not changing any dimensions as far as holding headspace and keeping the case square, but I mention it anyway as I'm grasping at straws here.
I put the rifle back together torquing the action screws to 45 in/lb. Chambered a shell to make sure there was no play in the bolt...everything is/was tight. When the rings arrive in the next couple days, I will probably throw a few more rounds down range on the off chance the rings/bases somehow were the issue or the mismatched action torque. I will try shooting with bags under the mag box rather than the fore end as some have suggested and see what happens.
I didn't mean to write a book, but I figure better to have all the information up front. I do have pics I took while the action was out and would be happy to email them if someone would like to take a look. I would love to hear your thoughts if this is something that rings a bell or you have experience with.
Thank you for your time.
Geej
