Keltec Su16CA Riser question

[Monorchid]

Hello, I recently bought a Keltec Su16CA 5.56 rifle. I also got a TR-25 red dot sight to use with it, however you can't just put it on the gun because the rear sight covers part of the sight. I don't really want to remove the rear/front sights from my gun either.

My question is, what is the best height of riser to use with this combo? I read that you want the sight as close to the bore axis as possible(for precision shooting) so should I get a .5mm, .83mm, or 1mm riser? With the stock being recessed down unlike AR-15's, it seems difficult to find the right one for the gun. I personally am leaning towards the .5 riser but i'm not sure if it would clear the rear/front sights.

Also just to be clear, I don't care about keeping the rear sights functional while the red dot is on, I will remove the red dot sight from the gun if I need to use the rear sights.

Thanks!

[kcheung2]

I presume you mean inches and not millimeters, because 0.5mm is about the thickness of a fingernail.

While the bit about closeness to bore axis is true, it applies mostly to precision shooting with a scope & bolt action guns. A red dot is not intended for shooting small groups in paper, and the height above bore of a Su16 is already pretty high so an extra half inch or so won't matter.

If you want a lower 1/3 cowitness then go with a riser, but it looks like if you mounted the TRS-25 directly onto the rail then you can get absolute cowitness with the front sight.

correction: looks like it's lower 1/3 cowitness even if mounted without a riser.

[Calico1404]

Remove the rear sight, you literally just push a plastic tab and it will slide out, then back the sight off. Your RDS will then just barely clear the front sight post.

[Monorchid]

I went ahead and removed the rear sight, which worked out fine but... My girlfriend has to lower her head down a lot to get a good cheek hold on the stock, since the stock is repressed down so much. IT looks really uncomfortable.. Might get a smaller riser anyway to help her out a bit. Not sure how much it would help her though honestly, she's just so small.

Thanks for the suggestions.
And yeah I miswrote when I said mm haha.

Also with no riser the red dot when zero'd (in my house, can't get anywhere with range right now) is right above the front sight posts(duh I suppose!) Would it go above the rear sight much if I got a riser? I know this is probably a dumb question but I suck at visualizing this kind of thing.