nothing needs to be done, unless you want to re-chamber it for a regular .22 rimfire-you're chamber is "spot-on"-it's supposed to be made that way.My Stevens 44 was the same, but you can use the breechblock to "roll-up" againest the case and seat it that way.

John,

You said you used a match reamer to cut the chamber so having to push the shell the last .200" into the chamber is normal. If this aspect of the chamber dosn't bother you then it will give better accuracy than other chambers. If you would rather not push the shell so hard then recut the chamber with a Benz reamer as .38 cal. mentioned. 

You also said you had trouble extracting a fired round. This should not be happening even with a match chamber. A loaded round, yes, but not a fired one. I would suggest you check the chamber for roughness and either lightly polish it or recut the chamber. Did you use plenty of good quality cutting oil when you cut the chamber? 

The Stevens action only pulls the shell out the .200" but you should be able to flip the shell the rest of the way out with your fingertip. 

Steve Durren

Hi John,
I recently returned a Green Mountain Barrel blank to Brownells.  It was to go on my Lo Wall, but when I slugged it, I found a constriction in the chamber end of the barrel.  After the slug went in about 2 inches, it fell out the other end.  If I slugged it from the muzzle end, it was tight all the way through, but it only had rifling engraved on about a third of it's diameter and the remainder was smeared. 

A Brownell tech contacted Green Mountain for me and was told by them, "their barrels are meant to be chambered from the raw end, not the machined end even though you can clearly see feathers on the raw end of the barrel where the button was pulled through.  After chambering the raw end, you are then supposed to cut two inches off the muzzle end."

If you chambered a barrel in the traditional manner, which would be from the machined end, it is possible there are some internalized stresses in the metal which when they normalized constricted your chamber.

Hope this helps, just my two cents worth. 

Hi John,
My blank was purchased as a 1.1 round which arrived as a .920 round which I had intended to machine octagon with an intrigal rib.  Perhaps the round blanks are supplied differently than the octagon.  Anyhow  I am glad yours is good.

Generic 'match' chamber reamers are usually ground with a 5° leade angle. Current thinking is that this is too steep, with most using between 1.5 and 2°. Many are eliminating the taper from the body as well.

Easiest way to accomplish this is by purchasing a 'throater' with the leade angle of your choice. Diameter varies according to the groove dimensions of the barrel, with .225 being fairly common.

For more info on this, look up Bill Calfee's articles in Precision Shooting.

It's also best to adjust the chamber depth to suit the particular ammo used, or in your case, to achieve the most engraving of the bullet while keeping the chambering force reasonable. That may require cutting the rim recess separately.

For a single shot, I'd agree the Bentz reamer is probably the best choice for an off the shelf reamer.

And FWIW, I also have a GM blank from Brownells with a huge constriction at one end. That doesn't bother me, but it also has a lot of tool marks inside, which I could probably lap out except it's already too large on groove diameter. Might be good for a Hornet, but it's completely unusable for a decent rimfire. I wouldn't even waste my time installing it on a 10-22.

Like an old timer once told me, "junk you buy, junk you get".

Rick Sanborn is the name of 'The Man' at Green Mountain, he's the headmost honcho and I've found him to be most courteous and responsive, IF you can gittaholtuvim.
Good luck, let us know how you fare, Joe