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Posted: 2/5/2024 10:20:09 AM EDT
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Just got my stamp back on a Colt AR-15 9mm SP1 conversion. Has the drilled mag well for roll pins but will be shot as a normal M16, no plans to ever use the 9mm mag block again. I've seen where it is possible to get the large hole converted to a small hole with bushings or even get them welded up and redrilled to spec. Any recommendations as to which way to go and experiences with such? The last guy I knew who was doing this sort of thing was M60Joe and he's retired. I've seen Gary's Bunker and US Anodizing mentioned in the past. Also, has anyone done work to allow the use of standard retained front pins?(build up and drill the right side for the retaining pin and spring) Thanks |
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Originally Posted By okent: Just got my stamp back on a Colt AR-15 9mm SP1 conversion. Has the drilled mag well for roll pins but will be shot as a normal M16, no plans to ever use the 9mm mag block again. I've seen where it is possible to get the large hole converted to a small hole with bushings or even get them welded up and redrilled to spec. Any recommendations as to which way to go and experiences with such? The last guy I knew who was doing this sort of thing was M60Joe and he's retired. I've seen Gary's Bunker and US Anodizing mentioned in the past. Also, has anyone done work to allow the use of standard retained front pins?(build up and drill the right side for the retaining pin and spring) Thanks I had John Norrell do it...I later heard Norrell do the aluminum welding for him and that guy passed away. Before I had it done, I inquired about building the weld up to use a standard front pin and he told me that it wasn't a good idea to subject the receiver to that much heat to do that and told me not to do that. I heeded his advise and settled just for the small front pin conversion. I had to use one of these front take down pins. Which is really annoying as I would always misplace them.  |
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Originally Posted By okent: Thanks for the reply Amphibian. I will appreciate the advice. I thought about just getting some bushings and gluing them in with loctite. Wouldn't have to send it off. Sometimes the simplest option is the best. |
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Yes, I have the .250 push pin and bushings for an SP1 upper receiver and I thought I would just cut them to the correct length and then loctite them in to the upper receiver holes in the correct clocked position. I have a machine shop and could go through all the gymnastics of turning down some bushings, press fitting them and then drilling to the correct orientation but the other way would be easier and quicker. |
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Buy new large hole uppers and build your own. https://www.robertrtg.com/store/pc/AR15-FLAT-TOP-BIG-HOLE-UPPER-RECEIVER-FOR-COLT-SP1-6p6743.htm 
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"I miss the days of being able to shoot all commies" G.B.
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Originally Posted By okent: Definitely an option but I've got a bunch of uppers I go back and forth from, including some unique uppers I couldn't build like a belt fed 9mm and .22lr. |
| M60 Joe did the small pin conversion on my SP-1 RR years ago. It’s works with every upper I have - .223, 300 BLK, .22LR, etc. Don’t spend thousands on large pin uppers. Send your RR to Gary’s Bunker for the conversion. You can use KNS pins. Swapping uppers is a non issue and in my opinion will increase the value of your RR. |
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