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Posted: 8/24/2008 11:10:23 AM EDT
| Ok here we go again im still lookin for an RDIAS but i keep seein colt sp1 conversions. Whats the bag with these guns? Is everythig on them interchangable with all AR parts. I used to think I knew plenty about ARs but now that im lookin to spend full auto type money all I seem to have is questions. |
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Note that the Colt AR-15 Model SP1 has model-specific upper and lower receivers that are NOT INTERCHANGEABLE with standard M-16 (or ANY other AR-15) upper/lower receivers!!! The SP1 uses a front pivot 2-piece screw that is .312" in diameter and is offset in position from the military-spec. front "captive", spring-loaded push pin, which has a diameter of .250". Colt AR-15 SP1 receivers are generally well-made pieces, being only subject to the quality (or lack thereof) of the actual full auto conversion. All "aftermarket" AR-15 RR conversions are subject to BOTH the quality of the receiver manufacturer AND the quality of the conversion. Many of the aftermarket companies making AR-15 rifles/parts at that time were not up to the task of making quality parts which were within "mil-spec". For those familiar with the "plug-and-play" lowers made by RRA, Stag, Bushmaster, etc. these days, the pre-'86 aftermarket lowers would be your worst nightmare! For example, it was not uncommon for uppers/lowers to need to be "fitted" to each other, since they just wouldn't fit each other as-manufactured. Some manufacturers substituted cast aluminum for the standard forged 7075-T6 aluminum. The best (and most expensive) way to get an M-16 RR is to get a factory Colt piece. This is the only way to guarantee the quality of materials, specifications, and workmanship of the extremely valuable lower receiver. In addition, the Colt rifles usually have all their other parts made by Colt, meaning the subcomponents are also of the best quality available. |
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The aftermarket RR conversions run the gamut from excellent to poor. It is difficult to know what you're getting unless you can inspect the individual rifle and are very familiar with the conversion process (and how it can run afoul). The QC with most of the aftermarket receivers themselves was spotty back then too, but there are some out there that are within spec and can accept unmodified uppers. Some of these lowers have also been "corrected" in the 20+ years since manufacture, and are more or less in-spec now. I would recommend either a high quality steel RDIAS or a factory select-fire Colt (AR-15 Model 613 or 614, or any of the "M-16" marked receivers). |
Steel JCB RDIAS, Bushmaster host |
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