Interresting. The Numrich kit uses a standard M2 bolt too ( but some have built up soldering on the lower , center rail so as to stick further down into the mag.) . The barrel does lock into the upper bolt lug cut out and does protrude out to the M2 bolt face for proper headspace. However , it does use a H&R Reising M65 type mag in it's own modified A3 triggerguard. That may make a feed ramp necessary where as a M2 doesn't need one. I do have a Springfield .22 , but never paid any attention to the feed ramp area. I'll have to look at it closer next time.
Chris