Call it what you may, GAP may not be in your available price range.
That being said if you want a downright near 100% copy, GAP is one of the very few that can duplicate a M40 series SWS; Eric Reid, Mark Hall or Yoda himself.
I know of only 3 other riflesmiths that can build a near clone M40-series combat ready weapon to exacting USMC SWS specs besides GAP.
1. TBA
2. DD Ross
3. AJ Brown
GAP makes great rifles, but their clones aren't 100%. For example, they don't black oxide their barreled actions, they cerakote them. The A3 pictured on their site has M5 bottom metal, but the rifle doesn't have the PGW EFR. They are more expensive ($4,800 for their A3) than other gunsmiths and you're still not getting a 100% clone. If you like GAP, just buy one of their other great rifles. As for the other gunsmiths you listed:
1. I've never dealt with TBA or have seen any of their rifles, so I can't comment on how correct they are.
2. Dan Ross makes great rifles, I have a few from him. The downsides to going with him is the price and the wait. You could be paying a lot more than other gunsmiths and will probably be waiting over a year due to his lead times. However, he knows the A3 like the back of his hand and I guarantee he'll build you one to 100% spec.
3. STAY AWAY FROM ALAN BROWN!!! That's one of the absolute worst recommendations you could ever make for a gunsmith! He put out quality Mk13 Mod 0 builds years ago, but in the past few years his builds have been absolute garbage! A few of my friends got their rifles back and had to send them to competent gunsmiths to get them fixed. A lot of people, myself included, had to request our parts back after 3 fucking years of being lied too about our builds. All of this is heavily documented in the Mk13 thread over in the Vintage Section on this forum, read it before sending anything to Alan!
Reach out to RW Snyder. I had him build out an M40-66 rifle for me.
Robert Snyder builds great guns, he's built some for some friends and myself, we're extremely happy with our builds! Also, there's also no such thing as an "M40-66," that's a made up designation from some guy who is building M40 "clones."
I called Raven and Rivers bend. They are both very knowledgeable and seem to build it how you want. Raven is 1,500 and Rivers Bend is about 1200. If you want it milspec then they will make it happen. Parts not included of course, which the parts are about 2k.
I haven't seen any of River Bend's clones, so this is another gunsmith I can't comment on.
On the other hand, I've seen dozens upon dozens of Raven's clone builds and they are perfect! Mark Williams is the only gunsmith I've seen on these forums discussing the minute details of various military rifles. A 2112 friend also taught him everything there is to know about gunsmithing for the entire M40 series. I also send him original military takeoff parts for him to examine, in addition to detailed photos and measurements from original rifles in my collection (M40, XM3, etc).
All of this detailed information in his knowledge base allows Raven Rifles to produce some of the best, most accurate clones I've seen. His lead times are also pretty short, he knows what he's doing with this rifles and gets it back in your hands as quickly as he can. There's a reason why people are lined up just to have him build their M40xx and Mk13 Mod x rifles!
