A fellow member PM'd me last night about this,and I wrote a lengthy response so I'm just gonna copy-paste:
Yea, I've done many blade swaps between Militaries and I've never had a problem going from linerlock to framelock and vice-versa. Even between supersteels and the standard S30V. I don't understand how some guys have these lockup problems when doing their swaps.
The very first Military bladeswap I did is also my hardest-used one, and involved 3 different knives. No issues.I received a military made up of spares. It was a regular S30V blade with a brown linerlock and Ti scale. The guy I got it from (and you'll be happy to know this) transplanted his XHP blade into a Ti Military, using the framelock side and kept the brown G-10. I got the leftovers. That same week, I got another frankenmilitary but this time it was an M4 blade in a black linerlock. The second guy didn't want the M4 blade and used his regular S30V in the framelock + black G-10. I got a used Ti Military that had a badly scuffed non-lock scale for cheap after that.
So, to summarize, I have a pristine Ti scale from guy #1, M4 blade ftom guy #2, and a used-but-in-great-shape Ti framelock from guy #3. Everything fits, and so did the 2 resulting extra Militaries which I traded and sold.*That said though, there still are no guarantees, but chances are good that it'll work out. I've also done it to a couple of M390's.Let me know how it works out.
JV