Brownells Gunsmith Tech Corner - April 2007
By Mike Watkins
Question: This question is in connection with a Winchester Model 70 Post '64, push-feed, G1,94x,xxx.
The piece was re-barreled in 6mmXC, previously a .243, and while it feeds nicely, it will not eject spent cases. While working the bolt, the front of the case falls into the right bolt-lug recess due to the ejector pressure, with the case barely extracting from the chamber, leaving the case resting on top of the magazine in the open receiver. This is not a happy situation during NRA rapid-fire events. While in its .243 guise, it ejected nicely.
Scuttlebutt has it that a 22-250 extractor may remedy this situation, although I cannot visualize how that would help. Surely Winchester made their Post '64 offerings in 22-250? If you have any knowledge of a fix for this situation I would be most appreciative to know of it.
Answer: As the 6mmXC a shares the same rim size as both the .243 and the 22-250, it should work just as well as the rifle did in the original chambering. Also, if there was a difference between the extractor for the 22-250 and the 243 I am unaware of it. If it were my gun I would try a new extractor spring and possibly the plunger first; then maybe a new extractor. Lightening up the ejector spring might help in some cases but I wouldn't do it on a competition gun. We need maximum reliability in rapid fire so ejection should be brisk. It still doesn't make sense that the gun worked before and now refuses to eject such a similar case.
Question: What is the difference between Weaver and Picatinny bases/mounts? I have an Aimpoint Quick Release Ring Mount for my AR-15 but don't know which base to use. The rifle has the carry handle. The one I have is for the Aimpoint CompC sight.
Answer: The Aimpoint mount should fit on any base. A Picatinny base is mil-spec while a weaver is not. However, a weaver ring will fit on either a weaver or Picatinny base, but a Picatinny ring will only fit a Picatinny base.
Question: I have a Ruger GP -100 six inch barrel and adjustable sights. I need a higher front sight than the one provided by the factory since my rear sight is adjusted all the way down. Is the Millett front sight that I referenced above higher than the one provided by the factory. If so, I am curious as to how much higher. My gun is grouping extremely well at 25 yards off the bench with two inch groups, but the +P rounds that I am shooting are about 3 inches high. My rear sight has screwed in as far as it will go, so that is why I am looking for an aftermarket front sight. Is this problem common for GP-100's with adjustable sights?
Answer: The front sight blade you inquire about is the same height as the factory original. It’s not uncommon for the point of impact to change with a change of ammo, so this is not an isolated incident with just the GP-100. I checked our inventory and could not find any sight that was higher than the factory sight.