I'm setting up a new Rock River Varmint rifle with a 1.5-5X Leupold scope, and I'm not sure which ARMS Swan Sleeve, or GG&G Rail to get.

The upper has the regular low-profile flat-top, *NOT* the EOP.

The scope is approx 9.1" long, and has eye relief between 3.7" - 5.3" (depending on power).  The distance from the rear bell to the front of the turret is 6.1".  This dimension allows us to calculate the least amount forward the forward ring can be and still maintain a given eye relief.

I am assuming that a proper cheek weld on this rifle puts my eye between 1.5" and 2" behind the flat-top, which means that the rear lens must be  about 1.7" - 3.8" in front of the rear of the flat top for proper eye relief.

So I obviously need some sort of Swan Sleeve which extends beyond the front end of the upper's flat-top.  The question is:  which one?

The candidates are:
ARMS 36EX: about 8.5" long overall.  Not sure if this is long enough.

ARMS 36SEX: 14" long overall.  If the scope's rear bell is adjusted 2.5" forward of the rear of the flat-top, there will be approx 2.5" "extra" mount in front of the scope's front lens.

GG&G GS-1: I'm not sure how long overall this is, but it is advertised as adding 3" to the rail length.   My estimates put that at around a 9.5-10" overall length.

It is pretty imporant to not have the scope mounted too far back, which would mean with proper eye relief, my head would be way back on the stock.  I want to be able to get an aggressive hold on it, just about at the "nose on the charging handle" point.

How have other people solved this problem?   I would appreciate any pictures of different configurations, if possible.

thanks much!
Zak

Oh, I should mention that I'm planning on using Leupold rings.  If I assume either rail adds 0.5" of height, here's the focal-plane height (over flat-top) for some rings:

Leupold QRW Low: 1.73"
Leupold QRW Med: 1.85
Leupold QRW High: 1.98"
Leupold MK4 Med: 1.84
Leupold MK4 Super-high: 2.4

So it looks like either "Med" or the QRW "High" will get things lined up right.

-z