My Oly lower will not function with per-ban thermold magazines -- ie.  the bolt will not release forward after charging the weapon.  I believe that it has something to do with the original SAAMI specs used with the older Oly receivers, based on a comment  from a member on a previous thread.  Is there a way to modify the magazines, an/ or bolt release slightly so that they will function?  Is this a problem unique to Oly receivers? Your comments are appreciated..

The oly mag well is out of spec.

You have two choices - grind a section of the first rib off the thermolds so it will be able to seat higher or grind a bevel into mag well so the mags will fit.

Canadian-Tactical...from his posting he says the bolt won't release after inserting the mag. It sounds like a different symptom than what you are recommending.

CentralLine...are they new Thermolds? If they are, the feed lips are striking against the bolt carrier. If this is the case, just take a knife or razor blade and scrape it across the lips of the magazine a couple of times. New thermolds lips have to be very slightly trimmed so that the bolt carrier clears them. I have a bunch of new thermolds and had to do this with every one to get them to work in my RRA lower.

What I did with my Thermolds (RRA receiver), is lock the bolt open, slam the mag home, and then cycle the bolt across the mag a few (maybe 10) times.  That cured all my ills.

Does the bolt go forward at ALL?  Maybe there is something with your bolt hold-open?  Could be that those mags are pushing the bolt hold-open up for some reason.  Something to check.

-Gloftoe

OOps - my mistake...
We had a number of Oly lowers up here of that era that had the problem I related, my mind jumped to it before I had read the question.

- you might be able to solve this prolem by relieving a pice of the rear of the magasine - look at them compared to the USGI mags - depending upon the year of manufacture the Thermolds will have either U or V notches in them - if the mag sits to hight it will not allow the bolt to go forwad as the bolt catch cannot depress due to being caught on the rear of the mag.

Quoted: Brand new Thermolds usually need the bolt to be run across them several times to slightly shave/widen the feed lips. -Troy

I tried this on a new Thermold in my PreBan Eagle Arms lower and the lips cracked the fist time I fired a live round, scrapped the mag.

Central --

USGI mags work?  That's the quick solution.

If the receiver is cast and out of spec contact Oly.  The last I heard they were repairing these and the repair comes out with a new forged receiver with the same serial number.  All perfectly legal and about a hundred bucks.

-- Chuck