I've got an interesting question that I need some opinions on.

I purchased a replacement 40X rimfire bolt from Pacific Tool and Gage and it came in today. No instructions, but beautiful looking bolt.

I have a 40X barrelled action without a bolt. It is in near new condition, just missing the bolt.

Tried the new bolt in it, and it doesn't close. Guessing from other 700's I've done, I'd say .006 more to close. Bolt face is hitting barrel, so obviously left long, at least for my action. Okay, since PTG doesn't include any instructions, the queston comes up of where are the takeup tolerances in this setup. To make sure it headspaces, if I was making replacement bolts, I'd make them longer than I expected the worst action would need. But, I'd build in someplace that would be faced off to take up the adjustment. With no instructions, I don't have a clue where that tolerance has been left, and where it was intended to be taken off. I'd call Dave, but it's night and I'm impatient.

First thing I checked, is what is the extractor to bolt face measurement, and bolt skirt to bolt face measurement? Bolt skirt to bolt face is .043, minimum rf headspace. So, if I faced off the bolt to minimum closing, I'd have to face off the bolt face the same. Good enough, but what about the extractors? I check them, and they fit nearly perfectly on the headspace gage. If I set back the bolt, they'll be a touch loose. Hmmmm, will it be enough to matter? I hate to try it and have to order another bolt face. Another answer is to face off the back of the bolt extension, where it fits into the bolt body. That would set it back and not affect the headspace/extractor relationship. Might mess up the retaining pin setup for the extension though.

Easy answer is to face off the barrel and rechamber. Hate to do that on a nearly new 40x barrel. But, would work, may have to work on the extractor slots.

What would you all do? Anybody have some experience working on these and give me some tips?

dave

P.S. Had an afterthought so adding an edit. I was going to be lazy and not pull the barrel, but occurs to me I ought to at least pull the barell, and spot the lugs to see if they need lapped in. Will be a bit interesting to lap the rear lugs of the rimfire 40X, but I can figure that out. But, that shouldn't add more than .001 or .002 to the length at the most,not enough to make it work.

I've not had to fit a bolt to a rimfire 40x but generally speaking, fitting a bolt should be fairly simple, but first you will need to pull the barrel and start taking actual measurements. Pull the barrel and see if the bolt will close without the barrel. If so, then you only need to worry about fitting the bolt nose. Taking and transposing measurements for the bolt nose dimensions are straight forward, with any adjustment being made to the barrel. If however, the bolt still won't close with the barrel removed, then you will need to address that issue first.

On a standard bolt/receiver, (A) measure the distance from the face of the receiver to the bolt lug seats. (B) Install the bolt and while holding it as far forward as possible, measure the distance from the face of the receiver to the front of the bolt lugs. Subtract A from B. Next, measure the thickness of the lugs and remove the required amount of material plus about .005 from the bolt's lugs to where the bolt will lock in, then, move on to fitting the bolt nose.

Whether the lugs are at the front of the bolt or the rear, the method of fitting should be the same either way. I would think.

Thanks, Westpac,

I normally fit a barrel the way you're describing, I just set back and rechambered a .338 mag 700 Rem Thursday night, so I'm familiar with the procedure.

The gist of my question is this:

Since I had a finished receiver/barrel assembly, and a replacement bolt, should I modify the bolt or the barrel.

On thinking about it overnight, since the bolt/extractor relationship is just about right, but the skirt of the bolt is set up for zero clearance and the overall assembly is too long and hits the barrel, I think I'll remove the barrel, face it off and set it up for the minimum headspace to the bolt face, and then face off the skirt on the bolt to give .003 clearance to the barrel.

I'll make a barrel thread mandrel to put pressure on the bolt to lap the lugs while I'm at it, and get them all set up first.

The lugs on a 40x are at the middle of the bolt, it's kind of a different arrangement than usual.

Edit: Westpac, I re-read your post with more understanding this time. I'll check and see if it might be more advantageous to remove material from the bolt lugs than the barrel.

I have a choice of removing material from bolt lugs and then bolt nose, or barrel and then bolt nose. I'll see what all the measurements look like first. I think we're only talking about .006 or so overall, Since I'm going to lap in the lugs, it may be best to have the material come off the lugs and not mess with the barrel. This is a long, heavy barrel, will be challenging to handle it on my lathe, as the headstock is too small to put it through.

I'm always in the mode of not taking material off the bolt lugs, as I usually work on mausers and don't want to work through the surface hardening.

dave

quote:

The lugs on a 40x are at the middle of the bolt, it's kind of a different arrangement than usual.

But it's measured and handled the same.

If it were me, I would make the adjustments to the barrel. If you make a mistake there, it will be less costly to correct.

Read your edit. The only time I would take anything off the bolt lugs is if the bolt would not close with the barrel removed or if I were squaring up the lugs as when blue printing. If the bolt closes with the barrel removed, I would immediately go to the barrel to make the necessary adjustments.

I try to avoid removing material from the bolt unless it is absolutely necessary. Like I was saying, if there is a problem, it's much cheaper to make the correction at the barrel than having to order a new bolt.

Westpac,

Thanks again. I couldn't get the barrel loose, will have to wait till Monday and go borrow a friends hydraulic barrel vise. Might have to heat it a bit to see if there's locktite holding it in.

Then, I'll be able to see what things measure.

dave

If the 40XR is factory barreled action-
Take a breech face measurement to fwd face of aft receiver ring-
Measure breech face to aft end of bolt lugs-

Face the aft end of the bolt lugs-

Modify the least expensive part!!!


PT&G 700 bolt lugs are .020+" longer than OEM so they can be fit to molested actions.

Thanks for the advice,guys.

Well, got the barrel off today, and it was one of the hardest model 700's I have ever broken down. Threads are tight enough all the way off had to use the wrench over half way, wouldn;'t unscrew by hand. Took a cheater bar and a 4 pound hammer on the handle to shock it loose from lockup. And, threads were well oiled and not galled.

But, everything looks good. Take .018" off the back of the lugs, and .003" off the bolt nose and it'll be at factory spec, with .043 headspace.

I'll try about .016" and lap it in first.

In this case, the bolt is the cheapest and most expendable part,so I'll work on it. The secondary shoulder at the breech face makes it awkward to adjust by working on the barrel, anyway.
dave