View Full Version : Shimming a bolt, and headspace

02-12-2008, 11:07 AM
I have read about shimming a bolt on a Rem 513 to change headspace. Can a bolt on a 40X be shimmed? All in the name of controlling ignition.

Kent Owens
02-12-2008, 11:35 AM
Yes, a bolt from a 40X rimfire can be shimmed to tighten up headspace. I have shimmed some bolts just experimenting with headspace. However, this does nothing in the way of changing ignition? Didn't help or hurt accuracy either. When you put a shim in the bolt front end it just moves the bolt nose closer to the case rim. Firing pin fall is the same.
I would recommend that you set the barrel back to correct headspace instead of shimming the bolt. That's the correct way to do it, and most folks would say the same.
If none of this makes sense, let me know and I'll try and dig my way out of what I tryed to say here. Just trying to help.

02-12-2008, 12:34 PM
I understand what you are saying. I am not a gunsmith, nor pretend to be one, but I always try to make things better, and I like to know what makes things work. On rimefirecentral, some posts suggest shimming up a bolt on old model 513's to improve headspace, help ignition, thus helping accuracy. This is of there is a problem to start with.

Kent Owens
02-12-2008, 02:39 PM
I don't have a 513 to look at but if I recall the bolt handle revolves around the bolt like a 52 Winchester does. If thats' the case, if you installed a shim in front of the bolt handle body then it would move the whole bolt body forward by the amount of the shim thickness. This would allow a tighter headspace and shouldn't shorten the firing pin projection from the face of the bolt.
When you shim a 40X, only the front half of the bolt moves forward by the amount of whatever your shim thickness is. If that makes sense. I am not a gunsmith either, don't even want to be, I just like to tinker with my own stuff.

02-12-2008, 08:40 PM
The change in ignition is supposed to come about because, when excess headspace exists, the case can move back away from it's firm seat against the barrel. The firing pin blow is absorbed differently when the case moves forward and thus ignition could be affected.

There should be little difference in how correct headspace is established, that is with a shim or by setting barrel back. Both ways would probably give the same result.

02-12-2008, 09:00 PM
Here's an interesting Bill Calfee article on headspace and ignition:


02-13-2008, 06:58 AM
If you do a search on this board (I don't know how to put a link) "shim 52d bolt", you'll see a thread started by me. On page two, Calfee says don't shim breech bolts, pretty good thread. Thanks, Douglas

02-13-2008, 09:38 AM

I don't know how old your 40X is, or if Remington ever changed the way they made them.
The factory originally made the 40x for the bolt face to contact the rear of the barrel. The barrel had a .010" ring turned on the barrel face. The bolt face recess depth was made deep enough to contain the entire rim thickness. When closing the bolt "metal to metal" was to require a 3 to 5 lb. force. This according to Remington was a safety feature to reduce the possibility of a slam fire.
If your 40X is shimmed it may not close, or if it does headspace may not be altered if there is contact unless you trim the bolt face to something less than a case rim thickness.

Someone here was at one time making shims for this purpose.