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Posted: 11/27/2024 6:03:01 PM EDT
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Over the years, I've missed two opportunities to have the POS oversize front takedown pin on this receiver brought to proper spec. At one point, I think grafting half a modern lower to the nameplate and FCG pocket was possible... but Noveski (?) stopped that a LONG time ago. Someone else was using steel inserts red-loctited and pinned into place, then drilled to spec. The last time I considered this, I had missed the most recent NFA magician's cutoff. Is there anyone reputable still doing this kind of repair? |
Disclaimer - OP is bad at knowing things, and might catch on fire.
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
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Can someone explain the benefit of this conversion to me? Is it just for quicker upper changes while on the firing line? This conversion would be interesting if there were a pin that mimicked the look of a standard lower once installed. It would need to have a captive ball or detent in order to work obviously. I am aware of the kns pin, but it doesn't quite look right. |
Joined:
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Posts:
212
EE: 100% (16)
SD, USA
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In my opinion, unless you have the provision for the spring and detent to retain the front pin, it’s kind of a waste. You’re still going to have to use an aftermarket pin and the only advantage is that you can use standard uppers readily. I like to put stuff together and I opted to get the original large front screw and buy several SP1 stripped receivers. I’ve assembled three uppers now and am going to do a fourth once I figure out how I want to make it. Again, this is my distorted view of the SP1 world and it works great for me. |
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Originally Posted By slap_shot: Can someone explain the benefit of this conversion to me? ... if there were a pin that mimicked the look of a standard lower once installed. ... Originally Posted By Dakota_Don: In my opinion, unless you have the provision for the spring and detent to retain the front pin, it's kind of a waste. You're still going to have to use an aftermarket pin and the only advantage is that you can use standard uppers readily. I like to put stuff together and I opted to get the original large front screw and buy several SP1 stripped receivers. I've assembled three uppers now and am going to do a fourth once I figure out how I want to make it. Again, this is my distorted view of the SP1 world and it works great for me. If a "special" SP1 lower is the only Colt-Civvy-Bastardized(tm) rifle in your collection, that same plan leads you to needing duplicates of other uppers if you want the option to run them FA. Slapshot - I'm at the point that I don't care if the adapter has pink cat ears and a bedazzled pic of Lil Pony hanging from it. My priority is the function. Yes, you can use offset adapter pins. Those bring along more negatives than positives, IMHO. - You need to keep two screwdrivers on hand if you want to swap uppers. - You need to be VERY careful of orientation when tightening them down so you're not putting extra stress on the takedown holes on the lower. - You need to be VERY careful if you shotgun the rifle. It's easy for the upper to hit the front of the magwell and put extra stress on the thinner parts of a very expensive lower's front takedown holes. The bushing also tends to turn a bit when you do this, leading to misalignment. - Its easy to loose a small but important (and impossible to replace on a short timeline) part of the offset kit while changing uppers at the range or in the field. - It's god-awful annoying to have lego-like conformity and interchangeability in all but ONE rifle. Having a selection of different ARs, I'm very interested in being able to swap different uppers onto the RR at will. Want to run the 9mm in FA? Swap upper and buffer. Want to run .22 in FA? Swap upper. Want to move back and forth between a standard M16 upper and a shorty? Pop, swap, pin. And, if absolutely nothing else, it will be SOOOO nice to only worry about a single pin with a built in retention feature. Even a plain pin with a locking bail to flip over and engage the far end would be an incredible improvement over that awkward to install, impossible to keep oriented, adapter pin set. |
Disclaimer - OP is bad at knowing things, and might catch on fire.
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
Joined:
Nov 2022
Posts:
213
EE: 100% (16)
SD, USA
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Originally Posted By Amish_Bill: If one or more SP1s are the bulk of your collection, getting some large pin uppers is a simple way to gain flexbility. Don - this looks like the camp you're in. If a "special" SP1 lower is the only Colt-Civvy-Bastardized(tm) rifle in your collection, that same plan leads you to needing duplicates of other uppers if you want the option to run them FA. Correct. My bastard is transferable and I don’t mind having duplicate uppers for it. I’ve also had to get the relief cut in most of the SP1 uppers for the sear, but I have a buddy that does it cheap. I absolutely hate the adapter pins and I have no desire to send the lower out. It’s a good compromise for me. Keep us updated with what you find, as this comes up regularly and the ones doing it are getting fewer. Good luck with your project! |
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I can think of a couple different ways I would do it if I had to. I like the idea of just putting some bushings in there and drilling it out. A little bearing set on them and they should stay in place. I guess a little set screw could do the same from the front or bottom of the ears. Of course, it wouldn't take all that much to throw a bunch of weld in there and drill it back out. I guess a guy could build up a fence too. In the end, I think it all depends on how much one wants to spend on the conversion, and what exactly the end goal is for usage. |
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M60Joe was pressing in aluminum rod, drilling a small hole to tap in a blind pin, then milling the correct milspec diameter front pin. I would definitely not weld it up if not cracked and if other options are available. It seems that a slightly oversized 7075 rod that’s been placed in the freezer overnight and pressed into a warmed up receiver, then once at temp homeostasis, mill flush with the ears, mill the front pushpin hole. I’d bead blast the anodizing first, then reanodize the whole thing. |
| After the conversion is made to small hole on the registered lower sp1 receiver, what pins are folks using to attach the upper and lower in front? Are we still stuck with KNS? Nothing against them, I have their anti-rotation pins on other rifles but I am just curious about other options. |
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OP: To each his own.................. truly. I just either buy one of these: https://www.robertrtg.com/store/pc/AR15-FLAT-TOP-BIG-HOLE-UPPER-RECEIVER-FOR-COLT-SP1-413p6743.htm Or as another pointed out, my last flat top upper was a large pin one I had laying around. For 50.00 they cut the sear "ledge" out and done. Assembled it with what I wanted ............. done. |
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