Home Forums Hunting & Shooting Hunting Rifles Kimber Montana rifle barrels - stress relieved?

Anyone happen to know if Kimber barrels are stress relieved?

I'm starting to think barrel heat plays a big part of my group size in the summer. I do load development mostly in the winter. Temps in TN are 20-30 degrees in the winter with the occasional dip into the teens. I try to mimic my hunting temps (NW PA, CO/WY) and shoot when its colder and usually at daylight. I can find a really good sub-MOA load for all my guns. I shoot the same load when the temps climb above 70 and they open up about 50%. Especially with 5 shot groups and even letting the barrel cool 2-3 mins between shots. The reason I'm suspicious is that the first 1-2-3 shots go exactly where they are supposed to then start to wander a bit.

I really dont think its bedding (rifle is bedded) or scope/mounts (Talley, SHV) because all my Kimbers are bedded and set up the same - and judging from my notes, do the same thing. It could be something in my technique but my notes clearly indicate a trend of larger groups in the summer using the identical rifle/load/bench set up. I'm blaming it on the barrel......

I believe they use Wilson Barrels. I see in Wilson arms literature that they are air gauged and lapped.

How temperature sensitive is your powder?

Those little pencil barrels heat up FAST. With Mrs Blacktailer's 308 I can shoot 2 shots and the barrel is warm, 3rd shot and you can't hold your hand on the barrel. Here where the temps are high 2 digit in the mornings I have a towel soaked in water that I put over the barrel after 2 shots.

Barrel heat plays a major factor. Those barrels are too thin for bench shooting groups. 2-3 shots and let it cool back down again.

As far as barrel manufacturer, if memory serves me correctly
Bergara and criterion have made the majority of (possibly all production?) kimbers barrels post 2014. To check which barrel you have. Look at the breech face, with the bolt open/removed, at the extractor cut and you’ll see a stamped B (Bergara), C (Criterion) or nothing (Kimber).

If you haven't made a kill in three shots, it's probably time to quit anyway.

Yes, that is what MCMXI has posted in some previous threads.

Cooper and now defunct LAW.

Yep, those are the facts.

There are many things that can go wrong with a barrel during manufacturing and some you'll never know unless you section the barrel and take measurements. Heat treat can be off, the bore might not be concentric to the O.D., the chamber might not be concentric to the bore, the material might not be uniform, unbalanced residual stresses may exist, the bore might vary significantly in I.D. the length of the barrel and on and on. All of these issues exist in every barrel to some extent, we just have to hope that the errors are small enough that we don't see any evidence of them at the target.

The original question was whether or not Kimber barrels are (were) stress relieved. The answer is yes, as are Bergara and Criterion and just about every barrel in the industry, but if you saw how they were stress relieved at the facility in NJ you'd soon realize that the position of the barrel in the container that goes into the furnace isn't going to result in uniform stress relief when comparing barrel to barrel.

Thanks for info. I think its a heat-barrel issue. Its groups well except when it gets warmer - I never shoot till the barrel gets hot.............

It is a Criterion barrel.

As to powder: IMR 4451, H4831, Re 23, Re 26 - I use 'temp stable' powders exclusively.

No idea. IMO that’s waaaaaay over thinking it.

You have a hunting rifle.

Steady, breath, shoot.

I have 3 kimbers and they’re all bad ass.

Light contour barrels have a narrow node typically as compared to heavier barrels. The powders you mentioned are typically pretty temp stable but even a 30 fps change can bump you out of a node. Get a good chrony and use it both seasons and track speed with targets.

Putting a round in a hot barrel can "cook" it a bit. If the barrels hot and you chamber a live round and let it sit for a minute or two while getting ready to shoot you are going to have more temp variation than you will do to weather alone. You can eliminate that variable by allowing plenty of cooling time.

I also get into shooting position and get mostly ready to shoot before chambering and then don't waste time sending it when my barrels on the warm side.

Bb

Bb - you bring up a point I hadn't considered - thin barrels, small changes in velocity, accuracy nodes. Looking over my notes between late Dec/Jan and this past week, a 50+ degree change in temps did cause increases in velocity, or at least the velocities I got this past weekend are 24 to 50 ft/sec faster than my Dec/Jan loads. Interestingly 30 ft/sec is about exactly the delta for all powders listed except Re26 which showed upper 40's ft/sec difference.

Whatever the reason, I do see changes in group size between winter and summer using 'temp insensitive' powders. POI doesnt change much, or at all, but groups are definitely larger in summer vs winter. And velocities are slightly faster as well using temp insensitive powders. None of this will move bullets enough to miss/wound elk out to sane distances. When I think about the distances I've shot elk, anything less than 4 MOA would work.

I still find it irritating.........

I've been shooting 270s for over five decades......usually loaded with 4831s.

Two years ago, I was loading for my two 6CMs with RL16 and was very impressed so I tried it in my Kimber MA with 130TTSX.
I was very pleased with performance and temperature stability....... from winter wolf hunting to June black bear.....I'll be getting rid of my H4831.

Maybe drop the charge 1/2 grain or so and try it during the hot months. See if the group comes back together. I used to have the problem even with sendero weight barrels with large cartridges and powders like RL25 that were temp sensitive. I had a 300 ultra sendero II that shot 200g accubonds into 1/4 moa groups with RL 25.

A 50 degree change in temp meant 100 fps change in MV and 2" groups. I no longer use RL25 or RL22 because of the temp sensitivity. I figured out how to adjust loads for different Temps and stay in nodes but I don't get enough range time to do all that anymore.

Bb

There's no such thing as a temperature insensitive powder, just powders that are less sensitive than others. Even then, that sensitivity is going to be dependent on the cartridge/load. Of those powders listed, Reloader 26, in my experience, has been been fairly picky in varied temperatures.

I own several Kimber Montana's and a few Sub-Alpine models, as you know these are very lightweight hunting rifles so if you are getting the first three shots out of a cold barrel grouping tight before they open up IMO thats all you can expect out of a pencil barrel and more than you should ever need from a hunting rifle...I certainly would not worry about it...Good hunting...Hb

I have five Kimbers presently and they are all great shooters. During the summer I always bring a minimum of three rifles/handguns to shoot as barrels cool down.

I don't have too much of a problem holding sub-MOA with my Mountain Ascent in .308 Win. Yes, my groups will open up a bit after three rounds but I can still keep them under 1" at 100 yards.