To successfully build a cosmetically Retro AR-15, you need to plan the build and build to the plan, or you risk committing a Bubba The Gunsmith level atrocity on your firearm.
There are good sources of retro information out there, but the good sources of parts are drying up. This is due in part to a crackdown by the government and ATF on availability of surplus parts, especially barrels. One of the better sources of retro barrels is police guns which are being updated, but the smiths and armorers doing this now realize that these barrels are not scrap, if still serviceable, and price pressures have driven barrel prices up.
You can go insane with fealty to detail on a retro build, which is another reason for a plan — and a budget. Our goal is to build a cosmetic copy of the Son Tay Raid CAR-15. It should build to a lightweight and accurate gun, because it’s a 13-year-old kid’s first (supervised, naturally) build. We’ve got most AR armorer tools so that’s not an issue.
Thanks to the endless modularity of ARs, we can always modify our Colt Model 630 / early USAF GAU-5/5A clone for greater accuracy. To get it built and out of the planning stage, we need to execute the planning stage first.
So our first tasks are to: decide how accurate the build will be. Thanks to Congressman Hughes and Tax Chiseler Chuck Rangel, we can’t build an MG. Building an SBR is fine and good but no help with a gun that we’ll expect a kid to use. So we’re going to make a compromise there, and use a 16″ carbine barrel. (Other options are to go SBR or go to a shorter barrel with a pinned flash suppressor).
We’re going to make three other concessions to practicality: we’re going to use a non-Colt, non-vinyl-acetated-aluminum stock, we’re going to use a modern barrel with faster rifling, and we’re going to use — at least at the beginning — a generic lower parts kit. We also may substitute an Armson OEG for the correct AimPoint on this build.
Why the substitutions? The Colt stocks are rare and expensive. The original 1:12 barrels are rare, expensive, and won’t stabilize heavier projectiles, including 62 gr. NATO and 77 gr. match. (Current barrels also have improved feed ramps). And original LPKs are harder to come by right now.
These substitutions, except for the 16″ vs. 11.5″ barrel, should be nearly invisible without close examination. They should produce a six-plus pound, naturally handling AR that will exude a Vietnam vibe but digest a wider variety of ammunition.
We’ll keep you posted as we wrench this thing together and take it out to the range.
For background on the raid, start here with an official DOD Doc Dump. Included are a planning/briefing document, an interview with one of only two SF participants without prior Vietnam combat, and a JCS AAR.