I'd call Bushnell CS and ask them what their riser height is to co-witness.
1-800-423-3537
(913) 752-3400

 

.83 gets you absolute co-witness

 

THIS, in my experience at least with the same red dot.

 

Riser help

Hey Fellas, I'm new to the forum, I'm wondering what size riser i can buy that will give me a lower 1/3 co-witness on my Ruger 556 with a Bushnell TRS-25? I read above that the .83 gives absolute co witness so would a 1" riser give me the lower 1/3? I prefer not to have my sight picture crowded with the front sight. I would just buy the Trs-25 with the high rise mount, but they seem to be on back order and hard to find. The rifle is bone stock now, I'm trying to do a couple mods starting on a modest budget. ( optic, quad rail, fore grip, sling) Thanks for any help in advance.

 

I have the trs25 ar optics with high rise mount from bushnell and it does not cowitness absolute or lower one third with a ruger BUIS. What I have researched is that 1/2 gives you absolute and .83 gives you lower one third. I do not have any first hand experiance with any riser other than the one that came with the trs25.
I think you will like the trs25 I am very happy with mine.

 

I have the trs25 ar optics with high rise mount from bushnell and it does not cowitness absolute or lower one third with a ruger BUIS. What I have researched is that 1/2 gives you absolute and .83 gives you lower one third..

No, .83" will give you absolute co-witness with a true, F marked height front sight. One inch will give you lower 1/3, but sometimes the LED housing is in the way of the sight for a lower 1/3 with the TRS-25.

If the Ruger does not match to this, then the front sight base is not a true F marked height, as advertised in their specs.

 

I looked a little more and I am wrong. The .83 will give absolute and 1" will give lower 1/3. On my ar556 with factory trs25 riser I think it is 1" you can jot see thru rear sight the dot sits about a 1/4" above front sight.

 

Just also wanted to add....I have this exact setup, and .83 gives absolute co-witness.

 

I own 3 ars and none have anything but factory irons. I may be the only us shooter who has 3 ars with no mods as they came from the factory.