i have a little kimber17 hunter in 17 hm2. most of my ammo is ely - the thing works well but every so often it keyholes. i've checked the barrel and the crown is fine. anyone have an idea or is it the ammo? the report of the rifle is the same whether it keyholes or not.got me stumped

You would have to check the rate of twist. Some makers compromised stability with slow twist rates to improve velocity and accuracy. To stabilize those little flies you need a 1-9 twist rate. Put a tight patch on a cleaning rod and mark the top dead center of the rod and where the rod enters the muzzle. Then push it down until the top dead center mark comes to top dead center again and mark at the muzzle again. Pull it out and measure between the two marks and that will tell you your rate of twist. Roughly.
Try some different ammo. Which is going to be very hard to find.

I am going to take a guess here.

It is the ammo, and the ones that keyhole are at lower velocity than the others.

I get this quite often when developing subsonic ammo.

There is a cut off velocity, below which the bullet will hit the target at an angle.

If you go further down in velocity, it becomes a keyhole.