Got some new help in the shop that has allowed me to get caught up and start devoting time to new projects. So my Christmas break project was tweeking the MP-5 trigger. I tweeked a lot.
I had a good prototype 18 months ago, but it went on the shelf, plus I realized that in a .308 with a longer bolt stroke, it needed some additional twists. So I have a new trigger put together. Took about 3 or 4 iterations to work out all the details, but it feels fantastic in the lower. Today I'll get it in both a 9mm and a 308 to make sure it cycles and pops a primer, so I know I have the geometry right.
Goal is to have a good pre-production trigger running at SHOT show in 2 weeks. It's looking good.
Trigger will be a two-stage. Pull will be about 4 lb. Reset will be short. Takeup will be smooth, due to NiB coating. All parts will be CNC machined from billet tool steel - nothing is cast. This will be an entire drop-in trigger group - no parts interchangeability with OEM parts. It will be ambi, so it will convert every lower to an ambi lower, though I'm still designing the selector. I can make an ugly selector that will be compatible with both metal and polymer lowers, or I can make nicer looking ones, but the two lowers will need different levers, or a different safety cam. Gotta figure out which way I want to go on that one.
Trigger pack was tested in both a 9mm and a 308, and it popped the primer, and cycled smoothly, so I got the geometry right. Next step is scaling up the one I made to make a half dozen, possibly using heat treated steel, likely a housing in aluminum.
As far as the selector goes, HK people like things to look original/factory. Regardless of whether its ambi or SEF, I would say the more you can make the selector look factory German, the better. Some folks straight wont buy it if it looks weird.
Couple of weeks of down time in March and April. My two machinists stayed home, and I found myself spending my days on facebook and reading up on covid stats. Kind of depressing, actually.
But we have rounded the bend, and I've gotten back to the grindstone. Plus, a couple of my suppliers were working while I was not. So I have trigger hubs and hammer hubs, I have springs, I have steel ready to go for all the parts, my aluminum extrusion die was completed and a first run was made for the trigger housings, and I spent time on the CNC, programming the final machining of the housing. This weekend I'll build in the prototype parts to confirm all my dimensions, and I think Monday I turn the EDM machine loose. I also need to get a small batch of housings anodized, just to confirm all my hole sizes. Hard coat anodizing adds about 0.001 to 0.0015 to a surface, so hole diameters shrink by 0.002 to 0.003. I'm using a 4mm drill for the pivot holes (0.1575) for pins that are 0.154, so after anodize, it *ought* to be perfect, though I'd like to check first before I make a bunch of them :-).