I just purchased a Harrington & Richardson model 700 .22 mag on Gunbroker.com for $400.00. At the time there were 4 or 5 others for sale.
http://thefiringline.com/forums/showthread.php?p=4818229#post4818229
I currently own an H&K model 300 .22 mag and previously owned a Ruger 10/22 mag. As far as I'm concerned, the H&K 300 sets the bar for .22 mags, it will be a long, long time before another .22 mag is made to equal the H&K 300. Simple blow back design, nice light trigger pull, easily shoots under 1" groups at 100 yds. No tools required to disassemble.
Wasn't impressed with the Ruger 10/22 mag and sold it.
I'm very impressed with the design, engineering and quality of the H&R 700 .22 mag. This gun is way over engineered, way better than the Ruger 10/22 mag. I had it shipped to my gunsmith. He had never seen or knew of H&R making a .22 mag semi-auto. So when it arrived we took it a part and gave it a good cleaning. We were both amazed. The barrel is threaded to the receiver. The gun has recoil rails and a single heavy recoil spring attached to the bolt, similar to those of the Winchester 100 and M-14 design. They ride on two 1/2" square studs brazed to the receiver. The lower portion of the studs are threaded 7/16" studs. The magazine housing is attached to these studs with two full size 5/8" nuts. The hammer is a round cylinder Approx. 1x2" weighing 2 to 3 onces. The trigger housing is a milled block 5/8 x 5/8 x 1.5" steel attached to the receiver on milled dovetailed groves. Sides of the trigger housing are 3/16" thick solid steel. Trigger pins are 1/8 x 5/8". Bolt buffer cylinder shape, nylon 3/4x3/4".
Upon studying this rifle we both smiled and said 5.7X28 conversion.
Oh, mine came with a 10 round magazine. I ordered a 5 round mag. Ten round mags are available for the H&R 700. H&K 15 round mags can be mofidied to work in the H&R 700 and vice a verse for the H&K.