I have a National Ordnance carbine but decided since someone out there may have another...they made many...I wouldn't add to Universal carbine topic. For a good study on this and others go to:m1carbinesinc.com. I at first thought the barrel was made by Small Arms Manufacturers Inc. as several were in the 60's but mine has 6 sets grooves. As far as the cast slide it is spec and has hundreds of rounds. I replaced the bolt assembly last year with one from Fulton Armory. It likes all ammo so far. I recently replaced original blocky front sight with MilSpec I've had for years. This carbine has been largely forgotten but had a background and was issued both in U.S. and many other countries to police and others. In reference to the slide-read about the mistake made with one they used for short time. Refer to above website to see it.