T91 Free Float Idea

[Tortirioan]

Does anyone know id the T91 upper barrel nut threads are the same on a standard AR? I ask because I was looking over the system and you might be able to retrofit a free floating rail to it by modifying whatever barrel nut comes with the rail. (this is all under the assumption that the T91A1 upper is just an ar upper that they tweeked)

[apex]

The Wolf A1 is a tweaked AR-15 upper, and the barrel nut threads are the same. What is not the same is the height of the flattop, size of the oprod/gas tube hole, the added steel plate riveted on to the outside of the tube hole, no magazine claw flare extension (the little bump most AR uppers have on the left-hand side above the magwell, purely cosmetic), and the obvious lack of a forward assist and wedge-shaped brass deflector.
I've read that the actual T91s are a different spec than AR-15s and the Wolf uppers are built to be US spec, but since I don't have access to an actual T91 I can't verify this.

As for your free-float idea; because of how the barrel nut, handguards, and piston system all interact with each other, if you were to install a free-floated handguard you will have to modify either the piston assembly or the gas block in some fashion- there's no getting around it. The barrel nut is sized as is so the piston op rod and the sleeve's spring retaining buffer rest on top of it, also preventing the sleeve and springs from traveling rearward preventing malfunctions should the piston sleeve itself come loose/break. I would also not recommend modifying the barrel nut itself regardless of whatever handguard you plan on using as this could cause unseen issues and lead to a potentially catastrophic failure. The T91 barrel nut is already very thin as it is, and because of how everything interacts with each other you're going to be running the gauntlet of "is that enough material?" to a major structural component that basically has to be able to hold the barrel to the action while both a high-pressure burn is occurring and after the bolt slams on to it during the return stroke. Remember- if there is one crack in the barrel nut parallel to the barrel, the nut has ZERO strength and WILL break. Once that happens, you would be basically holding a grenade.
See this video for a brief example of what could happen, best case scenario

Luckily for Eric, the firing pin could not strike the primer of the second round as the bolt just threw the round into the chamber and did not engage the extractor so the round was not held against the bolt face. Had the round fired, Eric would likely be missing some left-hand digits from the shrapnel alone.

That all said, modification is possible, see this post from our site admin!
viewtopic.php?p=1536#p1536

[Tortirioan]

I was not thinking of modifying the existing barrel nut but instead I was going to have something custom machined, I want to have it in my hands that I can do measurements and make a real plan before moving forward. I was a full time gunsmith for 6 years so I am well aware of the dangers here. The best solution would be to engineer a custom rail and barrel nut that will work for the wolf t91 right out of the box. But that would be down the road after some prototyping and a lot of testing. Thanks for the Info.

[apex]

I'm not trying to discourage you, but this is the relationship between the barrel nut and the piston assembly:

IMG_0952.JPG

Unless you plan on using a barrel nut that requires very accurate timing, you will have to modify the gas system in some fashion.

[Tortirioan]

Thank you! That picture is super helpful, and I thin it would be relatively simple to index something like that. Do 90 degrees of smooth surface around where it will index and you'll be good to go, with a semi decent cnc machine could do that all day long.