Will a regular H&K 91 SEF semi auto trigger box drop into a plastic MSG-90 grip frame without any special selector switches?

*I have not seen one in person* However, based on the pictures I'm finding, yes that should fit and function perfectly fine. Obviously you will have an unfilled hole in the right side of your MSG90 trigger housing.


References:


http://www.hkparts.net/shop/pc/HK-German-MSG90-Clipped-Pinned-Trigger-Housing-37p539.htm


http://www.hkparts.net/shop/pc/MSG90-Ambidextrous-Selector-Lever-Set-37p225.htm


http://www.ar15.com/archive/topic.html?b=6&f=9&t=278878


 

Thanks.

I'm in search of a plastic lower that would mount up to my POF MP-5. I have an SEF lower on it now but I don't like being able to swing the selector switch down to the last position.

I would need a plastic lower that is only marked 0 or 1 and will accept the third push pin. Other than the MSG-90 grip frame does such a beast exist?

I'd like to avoid putting a stop screw on the lower I've already got. I'd like it if my favorite gun didn't look like bubba got his hands on it at one point in it's life.

The FBI lowers are marked SF  not 0-1 but they are two position ambi lowers.  For uour purposes, what you want
it just the grip frame.  I am not sure you can use the SEF selector in an ambi grip frame.   It is not long enough and not
sure it will lock into place.  If you try it I would like to hear how it works.  Everything I have even seen has said it doesn't work.
Also, its an MP5 grip frame but I think I have seen them  used on a 91.

Yeah I was going to modify the MSG-90 grip frame to fit my MP-5.

I think I have an SEF trigger box in my MP-5 though. I don't think going with a Navy Ambi lower is an option?

edit: I think a more elegant solution to my problem is a new semi  trigger box. third position on these IIRC doesn't cause hammer follow. It's just another position for semi.

Yeah, you just need some more elegant internal mods. If you have a semi-auto pack, it should already have had a pin added, which stops the trigger before it reaches the full-auto position (extent-of-travel) regardless of what position the selector is in (or even if there is no selector installed). This limits you to semi-auto-only in any position except Safe.

What you need is another pin added internally to the box, which will block the selector itself. Then it will not be able to rotate to the full-auto selection position (if that's what bothers you). It can simply be a roll pin, but the hole must be drilled in the correct location so the pin will intercept the little protrusion on the selector. I'm sure there are measurements floating somewhere around the net.

Interesting, didn't think of that. I haven't torn apart an HK trigger box in my life. I'm assuming that there will be room for all of the working parts to clear such a pin?

Neither of my POF guns have a stop in the trigger boxes. Using an unmodified SEF lower they act like a semi FAL will in the third position. Hammer follow. My fix on the one I SBR'd was welding up the longer SEF lever for the plastic housing to match the lever that came with the gun (Plastic SEF vs Steel grip frame SEF)

I went ahead and ordered the MSG-90 ambi switch. I feel fairly confident in my abilities so I'm going to get the parts in hand and see if I can modify the steel trigger box to work with it.

What could go wrong? Worst comes to worse I'll return the parts and just buy a complete semi box from HKparts. If it all works out as planned I'll have a very unique MP-5.