I am building a long range 5.56mm AR, using the SAM-R Krieger 20" 1-7.7 barrel and other goodies.

The idea is that the main optic will be a nice glass scope.

The problem is I have both rails and only want to keep one.

Sampson Rifle length rail with Matech BUIS.  Can use rail covers and rail cover with tape switch cut out for light.  The bipod mount will be an ARMS #32 (not pictured).

Other option:

ARMS #59 slimline rifle length with #40L BUIS.  Matches all the arms products going on rifle.  Very solid rail.  Disadvantages, top rail length not full length (it's a bi-level), can't use a flip up front sight rail mount, have to use PRI flip up block.  Also much less usable rails but do you really need all that space?  Only mounting a light and it has a side rail for that.  And how far up the rail do you need to mount a long range scope?  They also sell an extra rail to make it one length.  The Matech has adjustable distances but how many times will I be shooting over 200 yards with only the BUIS?

Tough choice..........

Out of those two options I would go Samson.  That is unless you want to add a heavy, non mil-spec complient, split rail system just for shits and giggles...

From your options, I'd pick the Samson.

Samson.  Swap out the TD guards for KAC and bounce the #40L over to the from the ARMS over to the Samson.

I have had to make the same decision and choosed the Samson.

Why? Because the Samson is much more lighter, cheaper (this means, you will get more money for the ARMS when you sell it) and a Troy BUIS and TD foregrip will fit on the rails. ARMS is a little bit non-milspec!

SAMSON

Lets say cost is no issue....the weight is not that bad...it is the slim version.  Plus it's a long range rifle, heavy is not bad.  A vertical grip will not be used.

Sounds like you want to use the ARMS, I would go samson though.. the ARMS is heavy.

the samson would be lighter


the arms would have leave you with no doubt in your mind that the top rail is true and you dont have to worry about twisting it.

Quoted: From your options, I'd pick the Samson.

+1 with the options listed.

But if you really want to know what I would do? I would sell both and buy either a LaRue or DD one-piece FF rail.

I don't own any ARMS rails so I'm not sure what makes them non-milspec but I do see a lot of pics with them on rifles used by operators from mfr to army sf.

I'd go with the samson as well b/c it seems lighter and i think you'd want to use a flip front for the sam-rish look...