The Firearm Blog

Zak has written a very interesting article on “Fighting Optics for the AR-15″. He focuses on M4 type rifles and SBRs (Short barreled rifles).

Now that optics have come of age on fighting rifles, one of the most compelling reasons to have a longer barrel has been removed. With iron sights such as those on the M16A2, practical accuracy depends on sight radius; it is easier to shoot accurately with more distance between the front and rear sight. Optical sights have no sight radius; barrel or weapon length is now separated from the ability to obtain a precise sight picture. This change allows a 14.5-inch M4 to have the same sighting precision as a 20-inch M16A2 or even sniper rifle.

M4 with Trijicon ACOG 4x

Read it here.

Scope ring lapping is when you grind off any uneven surfaces on the inside of scope rings. This means there is much less chance of your scope getting scraped or dented as well as allowing more of the ring surface to come into contact with the scope, allowing less movement.

A scope lapping device

From Michael Carlin (via TheFiringLine forum)

Lapping scope rings trues the rings to each other. The new rings may have been well machined, but when mounted on various (note the intent to imply differences) recievers of the same make they may not be perfectly aligned with each other.

This was one of the reasons that when I was young the one piece base was supposedly superior. It tended to limit the amount of misalignment that the gunsmith could induce in installing two piece base systems.

So what you ask?

This is very important, for if the tube is tweaked, kinked, or otherwise stressed, the internal adjustments will be “bound up” by the stresses. Imagine what would happen to any precision instrument that was twisted about its long axis. The amount of bind will adversely affect the repeatability of adjustment.

The best scopes in the world will not perform to their potential if their mount torques the tube, and binds up their internals.

Additionally, stresses applied to the tube tend to degrade the optical performance. Optimum optical performance requires that the optical centers of the elements (lens) be aligned. This is definitely not going to be true if we twist the scope out of shape squeezing it into misaligned rings.

Those of you who mount a scope on your 2+ minute of angle rifle to shoot deer at 100 yards, never “sight in” at any other range, and have not touched the adjustments of your scope for years may find all of this very boringly esoteric.

Those of you shooting any rifle any sight matches at 800, 900 and 1000 yards, as well as the silhouette shooters, and long range varminters/benchresters may consider this much more important.

Is lapping necessary? It depends. If your are installing a $40 scope on a $275 factory rifle to shoot factory loads at a large game animal at under 200 yards… probably not.

If you installing a $500 instrument on a rifle capable of using that level of precision due to its accuracy, it definitely is IMHO worth the limited expense and effort to do so.

Guns Magazine wrote a review of the Brownells scope ring lapper.

UPDATE:

I found a very good scope lapping tutorial here.

DefenseReview has info on new FERFRANS FAS combat optic/sight

“This concept started when my instructor for the FERFRANS Full-Auto Course complained that the aimpoint and the EOTech [550-series] was too big for a sighting system. He opted to use the iron sights. So we did a lot of testing and he finally agreed that the red dot or the EOTech’s circle dot is faster, but it’s too big that it will block his view. So I thought of a smaller sight that is compact and small like the DocterSight. The only problem [with] the DocterSight is it is not robust enough for combat duty. So we created the FAS. I had some Navy SEALs test it in our full-auto course and they all love it. There were civilians that tested the fast and they have nothing negative to say about it. The dot is 3MOA. It uses a lithium battery 3V, CR2032. It similar to the DocterSight. It has a brightness sensor with the Seals using it at noon time with no problems of brightness. All other specifications are the same as the DocterSight.”

The FERFRANS FAS combat optic/sight is ideally-suited to CQB/CQC applications, but it can also be used to engage targets out to medium distances (as far as 200-300 yards) with its 3-MOA dot.

Click to expand the photos

More here.