I recently ordered one of LMTs 37mm M203s from Browenells. (I finally broke down and couldn’t wait on DSA any longer.) I cannot get it to light off any primers and that’s with multiple hits. I know, it’s new and I can send it back to LMT under warranty but just seeing if anyone else is having trouble with theirs.

How is LMT CS?

I've heard LMT has good customer service.  

But I would check your ammo first.  The problem with 37mm signal launchers is the lack of standardization of the chambers and cartridge dimensions.  How does this relate to light primer strikes?  Well your rim recess at the end of your barrel could be cut for thicker rimmed shells,  allowing the shell to slide too far into the barrel and away from the firing pin.  Also,  I've had some shells that don't let the primer stick out enough.  And this is with my deftec standalone that I tightened up the lockup significantly.

There are firing pin protrusion gauges available for sale.  So you could check that yourself.  But I would be willing to bet that if you put a 40mm barrel on it with "mil spec" ammo,  it would work fine.  

So you can try different ammo,  or some tape around the shells to have them stick up a little farther.

Yep, I ordered some different cases to check just that. They will be here Saturday

Standard Mil Spec 40mm ammo use different primers than pistol, rifle, or shotgun ammo. The problem is not uncommon among 203s. Years ago I bought a bunch of copper primers that are used in M781 blanks, which work every single time. Most all of my reloading is done with those. Perhaps if you contact Steve Brown he can hook you up with some primers? His contact info is in this forum somewhere. He sells the 781 blanks and cones and zincs on gunbroker. I think that is where I got my primers. Also, you can do a search on primer hardness, and try the softest commercial ones if Steve doesn't have any. I think I was using CCI small pistol before I got the copper, and sometimes it would take two or three strikes to set them off with the 203. 79 on the other hand doesn't care what primers I use. GROG