Reflex Red Dot Problem With BR99 Shotgun

[Odd Job]

I have a BR99 shotgun which has an integrated Picatinny rail on it. Because the comb of the buttstock is relatively straight with the rail, I have had to put a Yankee Hill Machine riser on the gun so that when I mount the red dot I can sight appropriately.
On the Yankee Hill Machine riser I mounted a Burris Fast Fire III in a Burris Flat Top adapter to protect the glass. Here's the setup:







When firing this shotgun with the Burris on it, it is very comfortable and easy to aim and it retains a good zero. The sight can take the recoil and that's the reason why I chose it.

The problem is that it is shooting about 6" too low, and I have run out of UP adjustment on the Burris.

The way I see it I have two options:

1) Get a different sight with more adjustment range. The trouble with this option is I want a reflex sight, not a tube, and there aren't that many options in my price range to replace the Burris.

2) Get a canted rail to replace the Yankee Hill Machine. One such example of these is the canted rails for crossbows, such as what Truglo makes. I have bought one of those in the past for my crossbow and the Truglo riser is really low quality and won't do. The one I had didn't even have parallel holes in the rings and it fell apart after only 5 shots with my crossbow.

What do you guys recommend I do?

 

[Walkalong]

Flip the riser around and make sure there isn't an issue there? I have that same riser on an AR and like it, but one never knows. Can't hurt to check. Double check the mounting of the dot on the rail. Might be my imagination, but the whole setup looks canted up. Might just be the pic though.

 

[Odd Job]

I have another YHM riser and also another FF3 (without the flat top adapter). That's on my SIG522.
A guy on Rimfirecentral suggested I do a little swap and see what happens.
It'll be a while before I can do it but I will post back when I know more. I doubt the YHM riser is out of spec, those things are well machined.

 

[Odd Job]

I just checked both rails, they are both straight with a metal ruler I have, and both of them are parallel to one another and the host rail of the firearm.



When I checked the two Burris Fast Fires, the one on the shotgun doesn't adjust as much in the UP direction as the one on the SIG522.
However I am not convinced that the difference in elevation on the two dots is enough to get me on target, and I am also reluctant to swap the sights because I will be operating at the upper limit of adjustment even if it works.

In the interim I have taken off the Burris and put on a well-used Mueller Quickshot. This sight has much more adjustment range but is lower quality and won't stand up to the recoil over time. It should get me through the next range session and in the meantime I think I will have to get a 30 MOA riser for the Burris.

I am not sure what the reason is why I can't get on target, but I don't think it is a fault of the YHM rail or the Burris.
It may be that the barrel is angled down with respect to the receiver rail. I've looked at the X-rays and can't see anything obvious, but X-rays may not tell the whole story...