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4/1/2009 10:41:28 AM EDT
hello all... I have a question, or rather... I would like everyone's opinion.



I am currently building a rifle with a 20" barrel, and while posting on that thread, I got to thinking, and needed some input.



This barrel is a new-old stock, 20" with a 1:12 twist, etc... It is .625" at the gas block, and I am contemplating two choices here.



I currently have a LaRue LT15-12 forend on order, and I was going to use the standard front sight with a folding rear sight until I could find a railed .625 gas block, and put a folding sight on it. But, in some of the builds I have seen, people doing this had to install their front sight backwards, because it could not fold down over the forend, etc.



So, my thought was to get a .625" lo-pro gas block, and change my order to the LaRue LT15-13.2 forend, float the forend over the gas block, and install the folding front sight to the end of the forend. But, then I got to thinking about how that would effect the accuracy of the front sight, if say I had a front grip installed, and I was torquing the forend.



How say ye, all knowing and wise arfcommers... what is everyones opinion here? Should I get the railed gas block and the 12" forend, and install the sight on the gas block, or get the lo-pro gas block, and float the longer forend over it with the sight installed on the forend... esp. people that have done both. Very interested in everyones input.



Thanks in advance guys.



Trip.
4/1/2009 11:28:49 AM EDT
[#1]
i'd go with the 13.2 and put the sight on the rail. longer sight radius, looks better too.

i also wouldnt use that barrel either. you're limited to light rounds, 55gr and smaller. anything heavier won't stabilize. i'd go with a 1:9 or 1:8 if you can find it.
4/1/2009 11:51:18 AM EDT
[#2]
You can shoot 62gr bullets like Wolf etc!   talking 1/12 twist right

JUST NOT LONG SS109  62gr bullet

its not the wieght of the SS109 its because it longer  than regular 62grBALL ammo

Even 64gr ranger would Fair well
4/1/2009 12:16:08 PM EDT
[#3]
thank you, and I am aware of the limitations of the twist rate of the barrel. I like the weight of this barrel, one of the lightest I have ever seen for a 20"... I will be using virtually all XM193 or Q3131 ammo, so the 55gr. is mostly what will be coming out of the end.



My question was more in reference to how much difference would I see in deviations caused by the mounting of the front sight on the forend versus the barrel... meaning, if im stressing the free floating forend, heavy duty types like LaRue or otherwise, how much deflection am I going to get on that front sight? Is this something to be concerned about? If not, I think I will change to the 13.2" and the low-pro gas block.



Has anyone expierenced a change in the POI when using a free floating forend with iron sights affixed along with a vertical grip versus a sight mounted on the gas block, and thus not affected by the stresses on the forend.



Thank you again in advance for your thoughts.
4/1/2009 1:07:32 PM EDT
[#4]
The LaRue rails are pretty solid, I don't think you'd notice any deflection at all.

Where are you planning on getting the low pro gas block from?  The only one I've seen for .625 barrels is from CMMG, just wondering if there are other options out there.
4/1/2009 2:37:52 PM EDT
[#5]
LaRue offers this unit here: http://stores.homestead.com/Laruetactical/Detail.bok?no=45



comes in several sizes, .625" being one of them.



after talking to one of the guys at LaRue, I decided that there infact may be enough of a change in the POI to go with the front sight on the block.



I decided to go with the yankee hill unit, http://yankeehillmachine.com/store/product178.html in a .625"
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