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5/25/2010 5:14:37 PM EDT
I am about to start my first complete build.  I got my start by modifying a complete Bushmaster I owned, and now want to build one from the ground up.  Looking to purchase a stripped lower, and found a Spikes Generation 1 to purchase.  In the description it says it has a "Low shelf for use with RDIAS."  I have tried to do some searching of the forums and I didn't find much on Low vs High shelf or RDIAS.  I am not even sure what RDIAS means and what the pros/cons are between the Low vs High shelf.  Can anyone help shed some light on this?  If I get a low vs high, will this impact the lower parts kit I get, or what uppers I can use, etc?  Essentially I am looking for what this means to the overall project.  Sorry if this has been covered elsewhere, but I didn't see it.  

Thanks in advance,
Jordan
5/25/2010 5:23:41 PM EDT
[#1]
Low shelf will accommodate a Registered Drop In Auto Sear(RDIAS), high shelf will not. You only NEED a low shelf if you plan on making that lower full auto... but it doesn't hurt.
5/25/2010 5:24:08 PM EDT
[#2]
It makes no real difference to your parts kits. Maybe for some aftermarket triggers, the high shelf may be an issue, but mostly, no.

<edit>

It is really the third pin hole that is ticket to PMITA prison. You don't want to be doing that!

Sorry, I re-read your post more carefully. Try searching the internet for RDIAS, it will enlighten you. Mostly this is a way to make a lower receiver accept an auto sear without the third pin hole. A non-issue for most people, but manufacturers tout this as a sales tool. If you are playing in the rarefied air that is FA ownership, you would be obligated to know what you are getting into.

It will not affect any upper you chose to mount, nor any regular lower parts kit. It *might* have an impact as i said with some after market drop-in triggers, they may not fit a high-shelf, but it would be spelled out pretty plainly in the product literature for the trigger.

5/25/2010 5:26:21 PM EDT
[#3]
RDIAS is a registered drop in auto sear. Little class 3 gizmo. A low shelf has the room to put one in. A lot of lowers have extra material there to keep one from being put in. Makes it harder to convert to full auto.
5/25/2010 5:27:44 PM EDT
[#4]
Gentlemen, thanks so much for the insight.  This helps me decide I can move forward as the low shelf will afford me future options without costing my anything extra.
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