Home Forums Hunting & Shooting Gunsmithing adjusting the firing pin on the kimber 8400 (Pictures)

That screw your talking about at the back of the bolt shroud adjusts the spring tension on the safety lever. It has nothing to do with firing pin protrusion. The firing pin protrusion is determined by where the shoulder stop on the firing pin meets the firing pin stop inside the bolt. This can only be adjusted by machining material off of either the firing pin stop on the firing pin itself or machining the internal stop within the bolt. It is easier to turn the reguired amount of material off of the firing pin as it is more complicated operation to remove it from inside the bolt. If your firing pin is protruding .035" from the bolt face and you want it to be .055 then you would need to remove .020" off of the firing pin shoulder stop. Before you have that done just make sure there is not a piece of dirt or brass shaving stuck in there preventing the pin shoulder stop from actually bottoming all the way on the shoulder stop inside the bolt.

That is the only Kimber bolt I have seen with a screw in that hole, that screw being there is new to me! Normally that hole is an open gas release port, at least on all the kimbers I have.

On further examination I have to say the photograph is very deceiving, Bit of an optical illusion, what you are seeing that looks like a screw in the pic is actually the shoulder stop on the firing pin which is visible through the gas port hole in the bolt body because you used a flash when you took the picture. Go look closely at your bolt again and you will see that there really isn't a screw in that hole. Geeze, Had me going there for a minute, that was a whole lot of typing over something that isn't even there.

Now I think this mystery is coming together. I will make sure there's no brass shavings or anything keeping the firing pin from bottoming out. If nothing there then I will take it to a smith. Thanks.

Also, which way do you turn the rear end screw to loosen the safety tension??

RBH and Bushrat,
I just disassembled my 308 Montana, loosened the set screw and unscrewed the slotted screw. I almost made the firing pin disappear into the bolt. I screwed it clockwise and made the firing pin protrude further. So....that tells me the screw effects the amount of protrusion.

Bushrat IS right on that one pic. What appears to be a screw is just a portion of the firing pin assembly.

Bushrat or whoever is was does bring up a good point. RBH, from a re-assembled rifle, go to Position #2, remove the bolt and unscrew the cocking piece and firing pin/spring from the bolt sleeve. This you would do to clean gunk, hardened grease or de-grease for cold weather use. Thoroughly clean out the interior of the bolt body, especially way down where the shoulder of the firing pin comes close to the end of the bolt.
You are just going to make sure there is NO extraneous metal or buildup preventing the full fall of the firing pin.

As far as the headspace problem, I meant with the rifle itself - a bad chamber ream job. But you've had it too long and it would have showed up at the first range session.
As long as we are on this, I like to bump the should back .003" and check for easy chambering on my 300WSM. I assume you know those tricks, etc..

Please keep us posted.

thanks for the feed back, I'm thinking I just have a shortly protruding pin at its farthest out point. I'm thinking I've never had the problem before because I've always had very tight primer pockets and now after several reloads, some primer pockets are starting to get a little loose. Perhaps with the shallow primer strikes, primer pocket tightness is the threshold for the malfunction to show up. I will prime some empty cases and just fire some primers and see, as I make several different adjustments. Is there any danger to the gun or rifling for firing primers only?

No danger in firing primers only. I've done it out the back door on occasion to test something - I live in the country. I always swab out the barrel before putting it away.

A test might be to size 10 brand new shells, prime 'em and see if you can get any to fail. Then try it with some of your used cases.

Keep us posted.

RBH,
I just miked the diameter of the 300WSM firing pin near the end. It is .057". That gives you some visual idea as Brownells recommends .050"-055" protrusion.

Don't forget to swab out that firing pin shoulder area inside the bolt. Bushrat suggested to check that earlier.

Big Whoop you are correct, I was going from memory, must have been remembering something else I took apart, the kimber is unajustable concerning safety lever tension. Got to my safe this morning and took some kimber bolts apart, I should have done that in the first place. Sorry for the confusion.

The screw at the rear of the bolt does adjust the pin depth until it hits the stop inside the bolt body.

Put the bolt in the rifle and close it, turn the safety lever to half cock, remove the bolt from the rifle, flip the safety to the fire position, turn the shroud that holds the safety lever counterclockwise the firing pin will snap/drop into the fired position, the pin will protrude out the face of the bolt. Loosen the lock screw in the cocking piece circled in black in the second picture, turn the slotted adjusting screw at the back of the bolt clockwise and see if the pin protrudes from the bolt face farther, if it dosen't it is already bottomed out on the shoulder stop inside the bolt. If you turn the screw counterclockwise it will withdraw the pin into the bolt. One thing you have to watch for, once the pin has reached its maximum protrusion and bottomed out on the shoulder stop inside the bolt body you must stop turning, if you keep turning you will notice the rounded front portion on the cocking piece that holds the lock screw will start pushing away from it's position in the cam slot at the foot of the bolt handle. These must stay in contact. retighten the lock set screw. Once you have done this you can turn the shroud back clockwise, it will take a little force to turn it back and cock it, then you can reinstall the bolt in the rifle. If this dosen't give any improvement then some machining may be necessary.

Bushrat, good explanation. RBH has been shooting the rifle for awhile and only NOW is acting up. IMHO I am looking at a buildup of "gunk" inside the bolt impeding a full and strong pin strike.
Or, some problem (primer pocket) associated with multi-loaded brass. Although I must say the strength of WSM brass is quite surprising. I have discarded brass that were reloaded 8-10 times. I didn't want to tempt fate.
Hopefully he can come to a good resolution.

I'll keep you guys posted. Thanks for all the input.

Just an update on my findings. I measured the firing pin protrusion using my manual callipers (Bottom Part) and compared it to my kimber montana 308 which has never misfired. The 308 has .060 protrusion. Comparing that to my 8400 WSM, I found my WSM only protrudes .040-.045". The firing pin protrudes no further than that max and does decrease as screw is dialed counterclocwise (as bigwhoop described). Things are clean and debris free inside the bolt. I'm thinking at this point I need to machine off about .010-.015 off the shoulder-stop of the firing pin. Can this be done by a competent gunsmith or will it ruin my firning pin?? The smith I'm thinking about is very familiar with remingtons, winchester and savages but has never worked on a Kimber rifle? What say you?

It's a simple task for a competent smith, if he can't do that properly he shouldn't be working on guns.

Well, just got it fixed. Went by to see Jody Perry Gunsmith (JP Precision) in Anniston, Alabama and he machined down the firning pin shoulder 15 thousanths. Now it protrudes and even .060. Looks like my problem should be fixed. From what I could tell, he really knows what he is doing. May have him build me a custom rifle as he does that quite freqently. He was more than reasonable on his costs and a very nice guy to deal with. Any body looking for a gunsmith in east Alabama or western Georgia (along I-20) feel free to give him a shout.

Glad to read you got the problem resolved. Sounds like a competent gunsmith. I'm curious if you asked or he said what would have caused this to start now after quite a few rounds? Galling? Wear? Mid-life crisis?

I think that the firing pin was just short enough to misfire on brass that the primer pocket is just not quite as tight as it used to be. I'll know more when I pull the bullets of misfired brass. I just have the lee hand primer that doesn't seat very deeply at all (just flush or a hair below). I noticed last batch of loads had several brass that required very little pressure to seat the primers.

Were you using different primers prior to this?

I use my Lee Hand Primer for everything - 100's of primers a year.

Well, rifle is on way back to Kimber. I'll let you know what they find.

What happened that you are sending the rifle to Kimber now?

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