Impact not the same with two different slides.

[drw]

I have a CM9 and I bought a second slide off of Gunbroker. They are identical. One shoots dead on.....same sight picture and the other
shots high. The difference is about 6 inches at 30 feet. My pistol has 600 rounds with the original slide that shoots higher than the other complete slide that I bought. I can see no difference in the slides or the barrel. They both look the same............minimal barrel wear on the second slide. Go figure????????

[finpro]

Do you find any differences in the heights of the sights? If it is the sights, the differences in rear sight heights minus front sight heights, for each slide, should be about 2mm, with the old slide's difference being more.

[drw]

I did measure the height of the sights and they are the same. I will have to test it again, but the slides measure the same and both his slides have the dual recoil spring. Both slides seem to have the same pull tension.

[finpro]

First, the bad news: This is a mystery. The sights would have been the easy answer to the question and a relatively easy fix. For a 6 inch difference at 30 feet, using my Old PM9 sight radius as a guide, as I wrote, this suggests about a 2mm difference between the slides. If, as you wrote, this is not the case, you might use calipers to measure anything else that could impact barrel-slide-frame alignments in the two slides. Pay special attention to the front rail tracks in the slides. Also measure and compare everything with the slides installed, as differences here might explain what you see. I don't know if the sight adjustment formula directly applies to the alignment of non-sight parts, but I suspect it would be, at least, roughly close. If so, 2mm is a lot to be off in a product like a Kahr slide and normal wear of several hundred rounds would not likely explain what you are seeing re the point of impact.

You mention that they both use the same type of recoil spring, which sounds like there are different recoil springs used in each slide, though I may be misunderstanding you. If so, you might swap recoil springs just to see if this changes anything.

Now, the good news: Slides don't commonly wear out and your new slide seems to work perfectly in terms of accuracy. Solution: Just use the new slide. I have never heard of having to replace a slide due to normal wear, so this likely would be a permanent fix, at no cost beyond what you have already paid. If you ever needed to switch to the old slide, you could adjust either your sight picture or the sights. If you wanted to change the sights, check dawsonprecision.com, which sells different height sights for C Series Kahrs and I understand will make custom height sights on special order. I have bought sights from them and can recommend them highly.