Deep/long Chambered Barrels

[CurtInAtl]

I understand the process of finish reaming and head spacing a short chambered barrel but how do you do the same with a long chambered barrel.

I understand the basic concept of turning down the face and shoulder of the barrel to get the proper chamber length but how do you check the head space as you are turning it?

Do you put the barrel in the receiver and check it with a gauge periodically or do you use measurements from the bolt face to the ridge that the barrel tightens against or something else?

[donmarkey]

From everything I was taught, proper headspacing should always be done with the barrel off the receiver no matter if it is short, long chambered, or just a blank. Chambers and tenons should be cut in a lathe with the bore lined up concentric and axially (probably spelled wrong). After the receiver is trued measure from the bolt face to the outside, then measure from the outside to the inner torque ring in 3 places (98 mausers). After doing your math and you know your tenon length and your headspace requirements. Insert the go guage into the pre chambered barrel, measure, and correct the overall chamber and tenon size. Either up or down depending if it is a long or short chamber. I always use the inner torque ring as my bearing point and cut the tenon .003 longer, so it just looks like there is no gap but doesn't actually bear on the outer ring. I am a firm beleiver in not hand cutting a chamber, too easy to bell out the mouth. If I use any prechambered barrels I prefer long chambered, if you are spending the money to have it prechambered why would you want to pay for a reamer too? Plus with the tolerances on reamers, you can't guarantee you will get a good chamber, your remer could be smaller than the barrel maker's reamer. The same reamer should be used from start to finish (other than a rougher). Short chambered barrels serve one purpose, they allow a guy without a lathe to get a reasonable accurate job done by hand, if you own or have access to the tools, why use one? I chamber all barrels in the lathe and make sure anyone else doing my barrels does the same.

Don

[lemski4]

First the tenon or threaded shank of the barrel needs to fit fully into the action and bottom out on the inner breaching ring, ( Mauser)the shoulder can touch or not that's up to you. So if the measurement from the outer ring to the inner ring is say .750" your threaded shank or tenon needs to be .750, now if you do not want the shank to bare on the outer shoulder give it say + .002-.003" if you want the crush fit subtract - .002" from the .750 measurement. Now once the barrel is fit to the action, remove it and using a completely striped action and striped bolt in the fully closed position measure from the bolt face to the outer ring, lets say that measurement is .790", that is the measurement you want to duplicate with the headspace GO gauge in the barrel, and measuring from the back of the headspace GO gauge to the shoulder, BUT remember to add or subtract for any deviation you added or subtracted from the original inner ring to outer ring measurement. This is the measurement you want to duplicate with the headspace GO gauge in the breach end of the barrel measuring from the GO gauge to the shoulder. To do this you need to face off the breach end of the barrel and the shoulder the same amount. Once you have this done replace with the NO_GO gauge and try it in the action and see where the bolt handle is, you'll want the bolt handle with out putting any pressure on it to be about half way closed on the NO-GO gauge. It sounds complicated, but once you do one or two it'll get easier, just remember to measure often, and go slow,you will have the barrel tightened on the action many times, but is worth it not having to rent or buy a reamer.

[dirtyjim]

another tip is to make a spacer that fits over the threads to place your depth mic on then measure down to your gauge.

the first couple of barrels i did i placed the base of my depth mic on the gauge then measured down to the shoulder. using the spacer makes it much easier.

for the spacers i use tractor pintle bushings that i face off then part off around 1" long.

[Spiris]

Better late than never here, and I must say that I have nothing but respect for those with the equipment and knowledge, to spin up a barrel on a lathe large enough to cut and ream a chamber, and then fit it to the receiver and have the go and no-go gauges be thumbs up.

 

I use a 7x12 mini-lathe that limits my options, and for me, I prefer to have short chambered barrels that have the exact tenon length that I make, so I can snug up the barrel and hand finish ream. I have a background in math, especially trig that comes in handy once in a while, and the discipline to measure twice and cut once. A sharp reamer and a guide has always given me clean, smooth chambers. I make do with what I have, and attention to detail has not failed me. In my case, a short chambered barrel is better.

 

 

Spiris

[CurtInAtl]

Spiris, have you seen Les Brooks'.pdf on threading and chambering a barrel blank using a mini lathe?

 

It isn't the ideal tool for the job but it shows that it can be done if that's what you have to work with.

[lemski4]

Yes Les Brooks is a very nice guy, and very talented, he taught stock making when I was at Trinidad State Jr. College going through their Gunsmithing program.