AR15 Rail - pros & cons of 7.0 vs. 9.0

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frenchman

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Kind of new to the AR thing. Picked up an LMT 16 & 10.5 and want to put a rail on the 10.5. It has a standard FSB so if I go 9.0 I need a new gas block.

What are the pros & cons of 7.0 vs. 9.0?

Optics are an Aimpoint M4B.

Thanks for your input.
 
Welcome to the world of AR addiction. Excellent choice on your AR, LMT are fantastic.

Now as you mentioned installing rail longer then 7" on carbine gas system requires removal of the front sight post and installation of gas block.

If you'd like to keep the fixed FSB (I prefer that) you can install Daniel Defense 9.5" FSP rail that extends past the FSB both sides and underneath, little more rail estate and fixed FSB. Otherwise you'll require gas block of any rails longer than 7"

Generally longer rail lets you install more gadgets :)
 
The only accessory I'll be mounting is a vertical grip. The 10.5 will never see a bipod so I'm thinking 7.0 is probably fine.

The only thing I'm not sure about is how good the sight picture will be out of my Aimpoint with the FSB instead of a fold down front sight. Freakin hard buying this stuff sight unseen + it's mucho bucks if you don't like the setup!

I did look through a 16 upper that had an Eotech mounted. It had the FSB and I can't say I was a fan of seeing the FSB through the sight. Perhaps you get used to it or perhaps it looks different through an Aimpoint?????
 
The FSB should be of no issue provided you use your CCO properly. The key is to shoot with both eyes open and focus on the target not the reticle. That being said, there are still those who prefer an unobstructed view. If a 7.0" rail system is most appropriate for your needs I suggest you leave the FSB on. Try shooting with the new rail system. If you hate the FSB then replace it. If it isn't an issue, you saved yourself some money and time.

TDC
 
No different. If you install the riser on your Aimpoint it puts the FSB in the lower third....not great but better than right in the way of your dot.

my 2 cents
 
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The plus side of the absolute co-witness is if you are ever in doubt of your optics zero you can simply flip up your iron sight and check....provided they are zeroed.
 
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frenchman said:
Kind of new to the AR thing. Picked up an LMT 16 & 10.5 and want to put a rail on the 10.5. It has a standard FSB so if I go 9.0 I need a new gas block.

What are the pros & cons of 7.0 vs. 9.0?

Optics are an Aimpoint M4B.

Thanks for your input.
Click to expand...

Go with the 7" - why screw with a perfectly good gas block? if you change to a new one, you can only use a screwed on. I will take a pinned gas block over a screwed on for a 10.5". The CompM4 factory mount will put the dot at the right spot -which was designed for M4 with fixed FSB.
 
frenchman said:
Kind of new to the AR thing. Picked up an LMT 16 & 10.5 and want to put a rail on the 10.5. It has a standard FSB so if I go 9.0 I need a new gas block.

What are the pros & cons of 7.0 vs. 9.0?

Optics are an Aimpoint M4B.

Thanks for your input.
Click to expand...

Lots of brands make the longer rails with the cutout that go around the FSB, Check out the Troy,Samson or MI brands as they all have these.
 
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