oversize chamber

Perhaps what he is asking, is that some people like to chamber the barrel first, then do all the rest after, such as turning down the tenon, thread and cone/recess.
 
I chamber first, but the key is almost to full depth. Check for runout and then cut the rest then finish running the reamer into headspace.
 
Suputin said:
I get the idea of measuring the distance a headspace gauge protrudes from an existing barrel for that rifle but how would I get measurements for an action for which I don't have an existing barrel or which has been modified by lapping the mugs and facing the action or going from an OEM recoil lug to a thick match grade recoil lug?

I can work out how to make a gauge to measure the action and another to measure the barrel itself but how to relate those two measurements to each other? That seems to be the trick.
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If you want to get the headspace on the dot and the action is glued into the stock and you don't have an old barrel to get the headspace from the old, just leave the chamber a few thousandths short and finish by hand. Even if you do have an old barrel, doesn't mean the headspace is correct on the old barrel. To finish by hand, remove the barrel from the lathe, screw it onto the action with the go gage in place with the stipped bolt in place. Use a feeler gage between the barrel shoulder and the receiver face to determine how much deeper the chamber needs to be cut. With the barrel in your barrel vise, turn the reamer in by hand to deepen the chamber pushing on the rear of the reamer with thumb pressure. When doing this, I've only seen the reamer cut on the shoulder and never on the body, so unless you get carried away you aren't going to push the reamer sideways enlarging the diameter of the chamber. If the action isn't glued in, then just take the action out of the stock and use it to test all fits while the barrel is in the lathe. Remember to torque the barrel down and check that the bolt will just close on the go gage. It's not uncommon to have the headspace tighten slightly when the barrel is torqued down from when everything is fit in the lathe and going in a thousandth or two from the bolt just closing on a go gage before the barrel is torqued won't hurt a thing as it will usually tighten up. Now making each barrel have the same headspace when going from one barrel to the next barrel for the same action is best done by using a measuring tool such as the dial indicator tool in my post above somewhere.
 
Perhaps what he is asking, is that some people like to chamber the barrel first, then do all the rest after, such as turning down the tenon, thread and cone/recess.
Click to expand...

Exactly.

I am reading about people cutting the chamber before the tenon is threaded. I have John Hinant's book and he talks about this as well. One reason given is that the sideways pressure of turning and threading the tenon can push the barrel out of perfect alignment so it is best to do it after the chamber is reamed.

So regardless of weather the action is free in my hands or glued into a stock, how does one measure the correct headspace without the tenon being threaded and without having an old barrel to measure?

I have an idea for a measuring gauge but it is something I am going to have to make and try to see if it works.

Right now I am threading the tenon before reaming the chamber because it seems like the most direct method of measuring the headspace.
 
Any measurements that you do are based off the shoulder and the relationship to the go gage no matter how it's done. You can cut the tenon and the shoulder without threading the barrel or rough out the tenon if you don't want to go full diameter, but if you don't have at least the barrel shoulder cut however much you run the reamer into the chamber is just a guess. As to sideways pressure of turning and threading the tenon pushing the barrel out of alignment, that's easily checked by measuring runout of the chamber before cutting the thread and after cutting the threads. If your runout has changed, then something moved. I doubt very seriously if anyone cuts the complete chamber fully to depth before cutting the tenon, shoulder and threads. Which is done first doesn't seem to make any difference with the final results. I like reaming the chamber first as I indicate on the projected throat and when you are running an indicator over the top of lands it's not exact depending upon how good your indicator is. I have a lot more faith on what the indicator is reading when I check the neck runout after reaming the chamber. If there is much differenece, then I'll reindicate the neck back in and then cut the tenon and thread. The indicator reads better on a round smooth surface than bumping from land to groove. Does it make any difference, who knows. You do the best you can and live with what you get or you do it over. As they say it's not rocket science, but as long as you have done the best that you can with the chambering and setup, then it's up to the barrel and ultimately the shooter to get the best out of the barrel.
 
Suputin said:
Exactly.

I am reading about people cutting the chamber before the tenon is threaded. I have John Hinant's book and he talks about this as well. One reason given is that the sideways pressure of turning and threading the tenon can push the barrel out of perfect alignment so it is best to do it after the chamber is reamed.

So regardless of weather the action is free in my hands or glued into a stock, how does one measure the correct headspace without the tenon being threaded and without having an old barrel to measure?

.
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As to cut pressure pushing the chamber out of center, it ain't going to happen. The workpiece is rotating remember? Given worse case conditions of a dull cutting tool and a hardened workpiece you may move the rotational center off axis but the chamber, if it is already cut will still be on axis when the cut is stopped. Granted in this worse case condition the tenon may have a slight taper but it still will maintain cyindricity with the chamber.

Again as to measuring headspace on a non threaded tenon, see below;
Note that this measuring collar is not threaded and so it will fit either a threaded or non threaded tenon.

image upload

You could measure directly from the base of the headspace gage, and some do, but if the depth micrometer is not held perfectly the micrometer, if it tilts, will give you a measurement error;


free image hosting
 
That what Jerry's doing in the last pic??? I SUCK at.... I can't get three readings out of five doing it this way and I'm perty octopus-handed.
 
It's a heck of a lot easier to repeat depth mike readings with Jerry's first photo than with the second photo.
 
If I have to measure as the second photo shows, I cut a thin ribbon of masking tape and wrap it around the back of the gauge so the gauge fits snugly in the chamber but not so snugly it affects the gauge from 'shouldering'... that takes the 'rocking' out of the measurement. I've done it that way for many years... and it will be one finger right opposite the end of the gauge pushing hard against the gauge...
 
Mike Bryant said:
It's a heck of a lot easier to repeat depth mike readings with Jerry's first photo than with the second photo.
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I use a gauge like the one Jerry is using along with a plug gauge that is shaped like the bolt to measure the depth of the breach cut measured from the tennon shoulder. I also measure my threads with 3 wires and a mic to duplicate barrels or to machine barrels for actions that are glued into stocks. There was an article on some of this in P.S. a couple years ago by an upstanding man named John ??? (I cant remember his last name). It was this article and a few conversations with John that has helped me duplicate barrels as accuratly as I do.
 
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As far as the cutting oversize, if you cut too much with out cleaning the reamer it will cause it to cut over size especially if the reamer cuts more on one side than the other becuase the flutes on that side pack and push the reamer off center. I only cut .025" at a time then I clean the reamer. It takes longer but helps with the problem you asked about.

Gary
 
glbreil said:
As far as the cutting oversize, if you cut too much with out cleaning the reamer it will cause it to cut over size especially if the reamer cuts more on one side than the other becuase the flutes on that side pack and push the reamer off center. I only cut .025" at a time then I clean the reamer. It takes longer but helps with the problem you asked about.

Gary
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I drill and ream to .020" under the case shoulder OD so there isn't a lot of metal being taken out with each cut. Typically I will go .050" deep before cleaning the reamer.
 
I uunderstand when predrilling and boring that the situation is different but Skeet did say he was cutting the whole chamber with the reamer.

Gary
 
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