If you use other than a carbon fiber PRI SPR forend for a Mod 0 build, or a KAC Long FF RAS for a Mod 1 build, you're just doing it wrong.
Precision Reflex, Inc., aka PRI, built all of the forends for the original SPR plus the Mk 12 Mod 0 rifle. Here's what they offer today:
AR15 / M16 Gen III Forearms Here is a reprint of an interesting article on the SPR Mk 12 Mod 0 written from a certain perspective also found on the PRI website:
Mark12 Mod 0 SPR The one strength of the Mod 0 the author did not touch on is the fact the one-piece ARMS SPR rail stiffens the entire upper receiver/forend junction at its weakest point, creating a more rigid "chassis", for lack of a better term. The best shooting SPR I've ever seen had this feature, but used a better barrel than a Douglas. The shooter in question had 38 confirmed, so he wasn't too shabby with the gun, either.
The drawbacks of the Mod 0 version the author did not mention are:
1. The fact ARMS rings have proven time and time to slip after sometimes just a handful of cycles with the throw lever. This is why MSTN quit carrying any throw lever rings from ARMS back when we were an ARMS dealer. Also, the levers allegedly break, although I've never personally witnessed this. You'll notice the author did not use the correct ARMS #22 medium rings on his beautiful S&B.
2. The added weight of the ARMS SPR rail. While it does make the chassis stiffer, it does so at the cost of an additional 12 ounces of weight. This was supposed to be a "lightweight" rifle, remember? The Mod 1 is much lighter in weight.
3. The early version ARMS flip up rear sight used with the SPR was not the low profile version shown in the article, but the original chunky version that sat so high when folded that the scope ocular lens had to be placed forward of the rear sight. This combined with the length of pull of the issue A1 stock, cold weather gear, body armor, etc., made getting proper scope eye relief difficult for the vertically challenged.
The staff at PRI personally rebuilt a large number of SPR's at Ft. Campbell for 5th Group SF. Substituting a PRI carbon fiber forend for the KAC forend of a Mod 1 was not uncommon, I was told.
