Just bought a nice clipped and pinned HK semi burst ambi group complete, for an HK sp89 and it doesn’t fit. The space between the pins is not wide enough to slip it over the sides of the shelf. The metal section at the rear mount hole is also too narrow but might go on if pushed hard. The original slides on nicely in that area. The clipped and pinned work is very nice but the space is never wide enough. I have been working on this problem with other German SEF grip frames to fit PTRs and was hoping this one for an HK would be different and actually fit (at that price). (how does the ambi lever come apart?)
The 3 German SEF grip frames fit to PTRs I have is the same problem at the shelf (nice work but not wide enough space). I got that part to fit with a dremel, making the tabs very thin – it fits after the metal insides are removed. The second problem with these is, the grip frames are more narrow than the PTR grip frame and have some visible variation in width between frames, where the whole top of the frame slips over the bottom edge of the receiver – one fits tight but good, another will barely fit with some dremel, and the third is visibly more narrow at the metal cross piece and might fit a 91 or maybe with even more dremel. The ambi pack above was ok in this respect except at the end where it turns metal.
The other problems with the German SEF grip frames fit to PTRs are easy to fix. The mount pin holes are slightly off, and it helps to take a little metal off the rear edge so it doesn’t get stuck in the buttstock.
I got one SEF to fit and I’m working on the others. I guess I can widen the burst grip frame between the pins, though at that price I shouldn’t have to. The rear part is probably best widened a little with some tool to bend it slightly. I was going to buy a semi burst for a PTR but that might be even more difficult to make the rear fit plus another dremel job. Maybe this week I will find time to measure the PTR and the 91/SR9 receivers and grip frames width with a caliper.