Sticky bolt after second shot

I'm hoping you guys can enlighten me on a issue I had at the range yesterday.

I was sighting in my 300WSM with 200gr ELDX Hornady Precision Hunter and noticed that with a cold bore the rifle or a rifle that had rested 5mins(ish) between shots it functioned as expected and the spent cartridge was easy to extract. If however there was a round followed in close succession or there was a string of shots fired, then the bolt got sticky and there were pressure signs on the brass (bolt face extractor slot was visible on those cases).

This is the first time I've come across this before (I don't reload, and every other rifle I've used .223, .308 and 7mm-08 have all eaten up factory ammo no problem at all). If the ammo does not cause a sticky/stiff bolt of when the rifle is cold, but does when the chamber or rifle is warming up, what does that mean/indicate?

FYI The rifle (Kimber Montana 8400 WSM) is not new, but new to me. I understand that the rifle had fired approximately 200 rounds from new from the previous owner. As I only had one brand of ammo to try out I could not compare another brand to see if the same problem exists.

I'm guessing the factory rounds may be too hot for the rifle, but keen to hear if I've missed something. I did run a bore-snake down before shooting and periodically through the range session. Could a fouled bore/carbon deposits cause the increase in pressure?

That's a different one. Kimbers seem to have very tight chambers...even new brass can be tight in mine. I think it sounds like a very minimal change in chamber dimensions after the heat of the first shot remains...and the tight chamber is enough to make the next shot a hot one?

Could there be a build up of carbon in the chamber?

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Originally Posted by 199p

Could there be a build up of carbon in the chamber?

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is something like that visible to the naked eye, or only with a bore scope?

It was certainly odd. I hope there is something I've missed, rather than a too hot round as the precision hunter ammo really shot well. It was nice change to question my shooting ability (now where the bloody hell did that go!) only to find the groupings nicely hidden inside the black inch square at 200 yds.

My guess would be carbon build up I had it happen with a 7saum I had I changed to a foaming bore cleaner by gunslick probably solved

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I've heard a few reports in various different calibres that the Hornady Precision Hunter ammo is "hot" and this itself maybe the heart of your problem.
Is the bolt close on cold bore round tight ? is the bolt close on follow up (warm bbl) shot noticeably tight or tighter than cold ? If you wait 5 - 10mins for bbl/action to cool down how's the bolt close ?
I assume from your description that after cooling down then you're not seeing the over pressure signs - right ? This to my mind suggests carbon fouling is not a major factor. But by all means give the barrel a thorough clean and de-carb - that cant hurt.
Are you running a suppressor or brake ? Suppressors can lead to bad carbon fouling more quickly.

I'm running a Hardy suppressor.

I don't recall the tight chamberings either when chambering rounds from cold or warm. Extractor recess marks not present on the rounds fired from cold/cool rifle.

Not the first rifle to find Hornady factory ammo a bit too hot for the chamber.
I had it with my 6.5 Grendel. Big extractor marks and case headstamp becoming faint.

What do the primers look like when it is sticky verse when the extraction is fine as it sounds like a typical too hot load

Are they tight to chamber going in? I found issues with the necks on reloads bieng too long and needed trimming but that’s on hand loads not factory.
I think crushing the case neck tip into the rifling was causing crazy pressure

If I was hand loading and found these issues I’d back it off a little on powder charge. And running it over a chrony is good when funny things are happening

Also just cause it’s a Kimber check that the screws holding the action in arnt too long and causing issues as they sometimes come a mil or so too long
Same with the front scope ring screws
Could just be getting hot, expanding and binding.


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Yes I trim my front scope screws...a bit of the wife's or @MSL's lipstick on the bottom of the front mount screw will let you see if there is contact. I think if was carbon it would do it every shot. You could also run the rounds through a body die carefully... a body die makes a world of difference in my 280AI.

If you want to check the rifle using a videoscope Kimber, let me know. I have one here.

Thanks @planenutz I may take you up on that offer. Gave the rifle a good clean with boretech c4 last night. Promised the boy a hunt before the school holidays end, so only likely off to the range later in the week to see if it happens again. Will also try out another brand of ammo to compare.

Bit of an delayed update...

Rifle was thoroughly cleaned and carbon removed. Over the new year I had a few range sessions with the rifle. Tried some Remington 150gr factory ammo as well as my chosen 200gr Hornady Precision Hunter. My observations were, that from cold first and second shots with both ammo choices showed not stickiness in bolt at. If rifle was shot and allowed to cool between shots from there on, then there was no perceptible issue.

Now I did do a test where three shots were fired in close succession. The third shot of each type of ammo resulted in a sticky bolt for that respective round.

It seems that a warmed up rifle is the issue. Now this is not a goat gun, so I'm unlikely to fire more than one or two rounds in a hunting situation, so I'm thinking that what I am witnessing isn't such of a problem in reality but appreciate any thoughts on the above.

I can only think it is because Kimbers are known to have tight chambers. My 280AI won't chamber well with brand new brass unless it is FL sized (using Redding 0.020 comp shell holder).