[GranddaddyB]

I have a pre pictanny rail model that I have hi point pic rails to install. I am wanting to flat top it with a red dot and flip up ar 15 sights front and rear. If I use a low profile set up should I get reasonably close to factory sight picture? Or should I use a rear flip up sight and leave the factory metal sight on?

Thanks in advance.

 

[RACHGIER]

I think we have a terminology disconnect? A sight picture is, by definition, the view of the shooter when the sights and target are aligned. The sight picture is how you, the shooter, want it to be.

Also, by "flat topping it" do you mean a full length 20" rail that runs from the cover to the FSP or just new short rails on the cover?

If it's just the short rail on the cover and you go with front and rear flip ups, you'll be changing the sight RADIUS, not the sight PICTURE. By shortening your sight radius like that you will be giving up quite a bit of accuracy.

If you go with the rear flip up only and keep the factory FSP to maintain the sight radius, you'll need to get a measurement on your new flip up rear to determine the height of the new aperture as compared to the old factory rear. The FSP does have some elevation adjustment to it, but everyone who has tried to go with rear flip ups has either maxed out the elevation on the FSP, or ordered a new longer shank post from Longshot Manufacturing.

 

[moona11]

Longshot has a full length rail.

 

[undeRGRound]

I think we have a terminology disconnect? A sight picture is, by definition, the view of the shooter when the sights and target are aligned. The sight picture is how you, the shooter, want it to be.

Also, by "flat topping it" do you mean a full length 20" rail that runs from the cover to the FSP or just new short rails on the cover?

If it's just the short rail on the cover and you go with front and rear flip ups, you'll be changing the sight RADIUS, not the sight PICTURE. By shortening your sight radius like that you will be giving up quite a bit of accuracy.

If you go with the rear flip up only and keep the factory FSP to maintain the sight radius, you'll need to get a measurement on your new flip up rear to determine the height of the new aperture as compared to the old factory rear. The FSP does have some elevation adjustment to it, but everyone who has tried to go with rear flip ups has either maxed out the elevation on the FSP, or ordered a new longer shank post from Longshot Manufacturing.

I did mine the reverse, I got a pass-thru base optic (Monstrum) and used a UTG low profile peep sight, and had to lower my front post about .375" and that necessitates cutting the post shorter and drill and tap the bolt hole. It was darn close, near perfect at 25 yards but I really should get a real target in front of it and zero it properly. I'm also "guessing" at 3/8 because I recall coming up with 5/16 to 3/8 and figured the extra would give me more adjustment if I made a mistake somewhere.
I also removed less from the bottom of the post, because it already had a gap, so there's that to consider.
I used the old carpenter's rule "measure twice, cut once" but it was more like "measure ten times" instead :rotfl:

WARNING: "ALL THE ABOVE IS FOR INFORMATION ONLY" DO NOT USE my measurements as a guide, due to possible manufacturing changes in any of 3 manufacturers, this was 100% CUSTOM and a complete mix and match process.

 

[RACHGIER]

I did mine the reverse, I got a pass-thru base optic (Monstrum) and used a UTG low profile peep sight, and had to lower my front post about .375" and that necessitates cutting the post shorter and drill and tap the bolt hole. It was darn close, near perfect at 25 yards but I really should get a real target in front of it and zero it properly. I'm also "guessing" at 3/8 because I recall coming up with 5/16 to 3/8 and figured the extra would give me more adjustment if I made a mistake somewhere.
I also removed less from the bottom of the post, because it already had a gap, so there's that to consider.
I used the old carpenter's rule "measure twice, cut once" but it was more like "measure ten times" instead :rotfl:

WARNING: "ALL THE ABOVE IS FOR INFORMATION ONLY" DO NOT USE my measurements as a guide, due to possible manufacturing changes in any of 3 manufacturers, this was 100% CUSTOM and a complete mix and match process.

The problem here is the fact that the OP needs to provide full details of his intentions. Full length rail or short rails?
True co-witness, lower third, or dot only?
Does he understand a see through RDS mount with low profile BUIS will require a huge cheek weld shift and possible cause issues if he wants to line up the dot with the FSP instead of going dot only?
What MOA is the RDS?

 

[undeRGRound]

I hear ya, (regarding OP) I just wanted to offer my own additional outta the box solution. In retrospect, my situation would have been much simpler if I had just added an 8" section of 3/8" riser under the Monstrum and the peep sight.

But I think I could not find anything less than 1/2" so I did it the hard way.

 

[undeRGRound]

I have a pre pictanny rail model that I have hi point pic rails to install. I am wanting to flat top it with a red dot and flip up ar 15 sights front and rear. If I use a low profile set up should I get reasonably close to factory sight picture? Or should I use a rear flip up sight and leave the factory metal sight on?

Thanks in advance.

PS: WELCOME TO THE JUNGLE, WATCH OUT FOR THE LIONS AND TIGERS AND BEARS, OH MY!!!