So the new upper(first one ever) is at the shop getting the Brake/Comp welded on.  I've been reading a bit about optics mounting, along with BUIS.  The free floating rail/handguard(MidWest Gen 2 SS) will deflect slightly when a lot of pressure is applied to it, and from those I've held and read up on that pretty much goes for all of them(rails/guards).  So I'm curious about peoples thoughts on mounting back ups.  Obviously you want the main optic on the upper itself, but in using back ups, if the front is mounted on the top rail, near or forward of the gas block and the rear on the upper, will the rail receive enough pressure to deflect and mess up zero or POI/POA if shooting off bags or utilizing a VFG/AFG?

 

Seems like there is no other place to mount the front site, so I may be over thinking this too much.  Joe

It depends how much you care. If it is really mean to be backups, then having them on (and with a long sight radius) is more important then how much they deflect. By moving them close in you are introducing error anyway. If you want a short radius iron sight, then go with the JP tactical sight mounted at 45 on the handguard.

 

However, there is a better way.

 

Mount them on the barrel. Even if you have a low profile gas block hidding under the hand guard, you can still mount iron sights on the barrel itself.

 

Take something like this.

 

Your barrel in front of the gas block, unless a funny profile, is a very bit thinner then the portion where the gas block lives. The sight clamp on mode actually makes up for that so you can attach it very solidly.

 

Here is what mine looks like, you can see the gas block under the handguard

 

 

 

Because you don't push on the sight, it is just fine by itself over there.

That's why I prefer standard FSB on my social guns. You can get rails that are cut out for a standard FSB and still give you a longer rail/reach. If you are avoiding a fixed front sight because you are worries about seeing a FSB in your optic, if you run with a lower 1/3 co-witness and get enough practice on it you never even notice it.

Well if your really want to you can mount a standard front sight there too, taper pins and everything.

 

I don't like what they do to scopes though. With a red dot, sure they work great.

Joe i think I know exactly what your asking and it hasn't really been answered yet. You are wondering if the concept of the free float barrel will flex more on a rest. And I think that's a great question. I guess it boils down to do you think the one fastening position for the free float will be less rigid then the attachment point of a barrel itself (with a FSP). Because most will agree that the actual barrel will bend a little when leaned on.

 

Can a difference be discerned? Someone with a free float would have to do a test with the bags under the guards, and then the bag under just the barrel to compare the groups.

 

I like the question though.

Sorry, I guess I should have said that. Yes it makes a difference, not so much on sandbags though. The difference is noticeable when you zero with no pressure on the handguard and the you shoot bracing the handguard hard against a support like a wall, edge of a window, etc.

 

One of the techniques for stabilizing for longer shots in improvised position is to really push into whatever you are using as a rest, and that is when you see it most. You also see this with standard handguard except now you are pushing against the barrel which includes the sights. I'm actually not convinced the the same exact dynamics are at play in the two cases, it is possible that in the non free float model the issue is less barrel flex and more changing how the barrel whips around when it fires, but the result is the same.

Well if your really want to you can mount a standard front sight there too, taper pins and everything.

 

I don't like what they do to scopes though. With a red dot, sure they work great.

 

 

what do they do to scopes?

 

I have a 3-9x scope on my 308 AR with a big standard FS right in front of the scope and it disappears when I look through the scope..

what do they do to scopes?

 

I have a 3-9x scope on my 308 AR with a big standard FS right in front of the scope and it disappears when I look through the scope..

 

I use a lower power scope, like 1-4x and it is a lot more noticeable, you end up with a shadowing of the lower quarter which I find really annoying.