u/Alone_Ebb_326

Hey everyone,

I am trying to get an ARC-Fire V2 forced reset trigger running in a native Foxtrot Mike FM-9 "Foldy Boi" integrated folding lower with a standard FM-9 upper.

I have ran into a major travel restriction and need to see if anyone has successfully used an extended buffer tube to solve it.

2" Travel Bottleneck & Failed Function Check

• The Setup: Native FM-9 Foldy Boi lower, proprietary 5.0" folding RMB buffer, FM-9 bolt (internal weight removed/hollowed out), and a timing shim on the ARC V2.
• The Problem: When performing the manual dry-demo function check (holding the trigger down and racking the charging handle), I get absolutely zero forced reset or forward trigger slap.
• The Diagnostic: I separated the upper and did a rod test on the buffer. The system hits a rock-solid, hard metal wall at exactly 2.0 inches of travel.

What I’ve Tried So Far

1. Verified the A5-length tube that comes stock on the Foldy Boi (7.75" internal depth).
2. Removed the internal bolt weight so the folding RMB's front bridge nose plunges completely inside the bolt cavity.
3. Swapped the ultra-stiff factory FM-9 AR-10 spring for a standard-weight Sprinco White carbine spring to rule out premature coil bind.
4. Result: Still hitting a hard wall at exactly 2 inches. Because standard semi-auto only needs about 1.75" to cock the hammer, the gun cycles fine on semi, but mathematically cannot reach the ARC trip lever which requires a 3.0" to 3.25" runway.

The Proposed Fix: 8.5" JRC Long Tube?

Since the proprietary 5.0" folding buffer cannot be shortened or replaced without breaking the folding capability, my math says I need more internal tube depth.

I am looking at buying the Just Right Carbines (JRC) Long Buffer Tube, which has an 8.5" internal depth (adds 0.75" over the stock A5 tube). Combined with a standard Tubb AR-15 flatwire spring, this should theoretically unlock a 2.75" to 3.0" manual travel window.

My Questions for the Sub:

1. Has anyone successfully installed an 8.5" extended tube (like the JRC) on an FM folding lower to solve forced-reset or LRBHO travel constraints?
2. Did it give you the necessary 3-inch stroke to trigger the forced reset smoothly?
3. If you did this, did you have to tune out live-fire over-travel using spacers (like Armaspec or quarters) to protect the bolt catch, especially when running suppressed (I plan to use an AB F4 can)?

Any insight or alternative suggestions before I buy the new tube would be heavily appreciated!