Ok here is my deal. I just bought a Rock River Arms 9mm upper to go on my Bushmaster upper. I put the upper on and pulled back the charging handle and the bolt hung up half way in the receiver. Once we got it apart and began trying to find out the reason why we noticed that there was a little line machined into the bottom of the 9mm bolt whose only purpose it seems is to snag on that little step on the AR hammer. Caught it everytime. Now my original plan was to have an AR that was quiclkly convertable from 9mm to 223 and I was going to use the same hammer. Rock River tells you that you must have the 9mm hammer. Seems like I could round off that little step on the hammer and it wouldn't mess with the 223 function and allow for the 9mm bolt to pass properly. My question is.... is there some legal reason why you're not supposed to use the 223 hammer with the 9mm upper? I mean it's not like it will go full auto... and by the way the full auto M16 hammer wouldn't have caught anyway as it doesn't have that little step in the front. Apparently (this is just rumor as I don't own one) the Colt 9mm Sporters are the same way... the 9mm Bolt won't work with a regular AR hammer. Did Rock River do this so you'd have to buy one more part or are there legal concerns?
Modifications and the Law
- Thread starter Ryu
- Start date
- Status
HankL
Member
Just a WAG and conjecture here boss. Perhaps the 9mm hammer is lighter due to the differences between rifle and pistol primers??? Lawyer stuff??? 
Zach S
Member
Legal reason? Not that I know of.
If you can just round off the hammer, go ahead and try, I cant imagine that modifiying a .223 hammer would work, seems like someone would have caught on to that by now. RRA just copied the Colt parts, I think American Sprit Arms(?) did as well. The 9mm buffer is different too. I dont know how its different, I just know it is.
FWIW Olympic makes (or made) a drop-on 9mm conversion that uses the .223 hammer and Sten magazines. The parts arent interchangable with Colt type 9mm parts though. I have never handled an oly arms 9mm (or an ASA), so I cant comment on quality.
If you can just round off the hammer, go ahead and try, I cant imagine that modifiying a .223 hammer would work, seems like someone would have caught on to that by now. RRA just copied the Colt parts, I think American Sprit Arms(?) did as well. The 9mm buffer is different too. I dont know how its different, I just know it is.
FWIW Olympic makes (or made) a drop-on 9mm conversion that uses the .223 hammer and Sten magazines. The parts arent interchangable with Colt type 9mm parts though. I have never handled an oly arms 9mm (or an ASA), so I cant comment on quality.
Yeah, just try it if you want. There are no legal ramifications. It's your gun. It's not going full auto, or SBR, or anything close to illegal. Sheesh...
But with that said, you do this at your own risk, don't hold me, THR, RRA, the US government, etc, etc, responsible if you blow your self up. I just said that to cover my butt. Half the fun of guns is breaking them trying to figure out how they work. My guess is worst case scenario you will be buying two new bolts after you are done playing.
But with that said, you do this at your own risk, don't hold me, THR, RRA, the US government, etc, etc, responsible if you blow your self up. I just said that to cover my butt. Half the fun of guns is breaking them trying to figure out how they work. My guess is worst case scenario you will be buying two new bolts after you are done playing.
carpettbaggerr
Member
- Joined
- Nov 13, 2003
- Messages
- 1,676
I'd guess you could modify it. But it's cheap to replace. See here -- 9mm AR FAQ
carpettbaggerr: The idea is to have a hammer that will work both 9mm and 223. So just replacing the hammer would be defeating my purpose.
Risasi: I agree. It's fun to try new things. I don't think it will blow up LOL since i'm just rounding the hard edge of the little step on the hammer.
HankL: "Lawyer stuff???" I was just referring to legal matters that might be of the gray area type. like, is the 9mm bolt considered a full auto bolt when combined with the 223 parts kit? I didn't know. Didn't think so but thought that might be a reason why it seemed that the 9mm bolt was specifically designed to not be used with the semi 223 hammer. The weight factor is a very good point. It may be too heavy or too light to clack off the 9mm. Good heads up. I'll keep an eye out for light primer strikes or primer punctures. Lighter or heavier firing pin spring would remedy that though.
I know that the 9mm conversion will work with the full auto 223 lowers. My buddy owns a Colt full auto and a Rock River 9mm upper and that thing is a riot. But the full auto 223 hammer is flat in the front and has the little hook in the back. So I just thought it stood to reason that rounding out that little step on the semi 223 hammer wouldn't hurt the 223 action and might allow for a hammer that can swing both ways between 9mm and 223 for quick caliber changes. I modified the hammer and will post a range report as soon as I can take her out. If it works both ways it will make for a great little tag team... a 10" 9mm AR (once a Get my paperwork back that is) and a 20" 223 that can be changed back and forth with just a simple push of a button and an upper change (2 minutes tops).
Risasi: I agree. It's fun to try new things. I don't think it will blow up LOL since i'm just rounding the hard edge of the little step on the hammer.
HankL: "Lawyer stuff???" I was just referring to legal matters that might be of the gray area type. like, is the 9mm bolt considered a full auto bolt when combined with the 223 parts kit? I didn't know. Didn't think so but thought that might be a reason why it seemed that the 9mm bolt was specifically designed to not be used with the semi 223 hammer. The weight factor is a very good point. It may be too heavy or too light to clack off the 9mm. Good heads up. I'll keep an eye out for light primer strikes or primer punctures. Lighter or heavier firing pin spring would remedy that though.
I know that the 9mm conversion will work with the full auto 223 lowers. My buddy owns a Colt full auto and a Rock River 9mm upper and that thing is a riot. But the full auto 223 hammer is flat in the front and has the little hook in the back. So I just thought it stood to reason that rounding out that little step on the semi 223 hammer wouldn't hurt the 223 action and might allow for a hammer that can swing both ways between 9mm and 223 for quick caliber changes. I modified the hammer and will post a range report as soon as I can take her out. If it works both ways it will make for a great little tag team... a 10" 9mm AR (once a Get my paperwork back that is) and a 20" 223 that can be changed back and forth with just a simple push of a button and an upper change (2 minutes tops).
- Status
