"D" reamer for 22 magnum

[radkins]

I need to cut a new chamber in a 22 magnum barrel blank and just got to thinking that might be a good place to try a home made "D" reamer. I was going to buy a reamer but even at about $50 (it seems 22 rf reamers are about half the cost of most) it seems like a waste of money for a tool to remove such a small amount of metal, especially since it would most likely be a one time use. I even considered just using the lathe to bore this straight wall case chamber but I'm a bit puzzled at the correct way to do the throat if I attempt that method, I have a 1/8" diameter carbide boring bar to use for this if I go that route.

Any suggestions would be appreciated, I am not necessarily stuck on the idea of the "D" reamer and would be open to other suggestions. I also would like info on the 22 magnum chamber, mostly the throat shape. I realize that for this chamber the throat is probably nothing more than shaving the rifling a bit but how far from the bullet nose to the beginning of the lands?

[JCHannum]

A D reamer is not difficult to fabricate, especially for a straight wall cartridge with minor metal removal. As for chamber dimensions, the SAAMI specs have the information. Do note that the 22 Magnum and 22 Long rifle use different bore and rifling specifications.

http://www.saami.org/PubResources/CC...e/22%20WMR.pdf

[radkins]

Do note that the 22 Magnum and 22 Long rifle use different bore and rifling specifications.

Yes I am aware of the differences but this does bring me to another question, I bought this blank from a guy who decided not to use it and it was intended for the 22 Magnum with the proper bore size and 1-in-14 twist rate. Far a while I considered chambering this barrel in 22 Hornet instead, would that have been ok? I am not changing my mind about the 22 Magnum but I can get another one of these blanks for less than $50 so if that twist rate would be ok for the Hornet I might just buy that blank for a future project, it's 4140 and 1" O.D.



Unfortunately I can't open PDF files right now due to a software problem, going to try to fix that today.

[JCHannum]

The 22 Magnum uses the same .224 & .219 bore and groove diameter as the centerfire 22 calibers. As long as you are sure the barrel is 4140 steel, I see no problem in chambering it in 22 Hornet. You might also consider 218 Bee, which has recently come back into use. It has a bit more power than the Hornet.

Take a look at the Green Mountain gunsmith specials for a 21" 22 Magnum barrel for $33.00. Some other good buys there in other calibers as well.

http://www.gmriflebarrel.com/barrelb...-barrel-blanks

[radkins]

Take a look at the Green Mountain gunsmith specials for a 21" 22 Magnum barrel for $33.00. Some other good buys there in other calibers as well.

http://www.gmriflebarrel.com/barrelb...-barrel-blanks

Whoaa!! Well that explains why he was so willing to sell that cheap! That's undoubtedly the barrel blank I have since it is a Green Mountain and that description is it to a "T". I only gave the guy $30 for it so basically I saved shipping costs, however that 17 caliber blank looks extremely interesting.


I guess my question about the Hornet was mostly concerning the twist rate of 1-in-14 since this blank was sold as a 22 Magnum barrel.

[Bob Ford]

Radkins,

I have .22 Hornets with 1 in 14, 1 in 12, and 1 in 9. The 1 in 14 is marginal with 50 gr Hornady SX. Lighter bullets are fine. The 1 in 12 is marginal with a 63 gr Sierra. Good for less than 100 yds. The 1 in 9 I am still testing as I have time, but looks promising.

Bob

[JCHannum]

The .17 HRM is a lot of fun. I don't know what you are making in 22 Magnum, but a switch barrel 22 Mag/17HRM would be an interesting project.

I see no problem with a 1 in 14" twist for the Hornet, that is what I chose for my 218 Bee, and it performs quite well. The Hornet was originally developed from 22LR rifles, notably the M1922 Springfield and the 1 in 16" twist often recommended is a carry over from those early days.

[radkins]

I tossed around the idea of the 17 HMR but in the end decided the 22 Magnum would be an excellent companion to my Colt New Frontier also in 22 Magnum.

[radkins]

Ok, I've been reading what I can find on how to make a "D" bit, probably over-complicating things but I have an idea I would like an opinion on. I think I will shape the bit on my lathe then harden before grinding the flat because it would seem to be less likely to warp if done that way. Now the question, I have access to a slow water cooled grinder that would allow me to hollow grind the flat surface instead of just milling it flat BUT would there be any advantage to doing this? To do it properly would involve building a jig which I don't mind doing but if there is no benefit from hollow grinding then there's no point in going to all that trouble. I know this is making a big deal out of making such a simple reamer that can be bought for around $40 new (rim fire reamers are $39.00 at Midway) but this is hopefully going to be the first of several I would like to make in more complex calibers, any thoughts on the hollow ground surface?

[JCHannum]

I can't see any advantage to hollow grinding, or grinding after hardening. The way I have been shown to make D reamers is to turn to shape, mill to half thickness and then harden. To harden, chuck the reamer in the drill press and turn at lowest RPM while heating and quenching. This will prevent warping.

Lightly stone the flat surface to sharpen. There are differing opinions on drawing the reamer back or leaving it as hardened. I have used as hardened with success.