Thanks to M4carbine.net DDM4 and BCM

[Devildawg2531]

Thanks to a lot of reading posts and a few questions I have completed my 2 M4's. Lightweight DDM4 V3 with Aimpoint Pro and now Precision 18" BCM Stainless Barrel with Geissele SSA-E trigger (thanks to Grant at G&R Tactical). Both have the Vickers VCAS slings and have been 100% funtion through about 1500 rounds (I know low round count).

I do want to add BUIS to the BCM rifle but as you see in the picture below the scope is right above the rail. I have the scope mounted with Badger Ordnance rings and it is rock solid. But do I have this mounted too low to add BUIS? What do I need to change to add BUIS?

Thanks

[a0cake]

The way you have the scope mounted on that BCM is anything but rock solid. It may feel that way but trust me that it's not. Look into an extended mount that will let you stay on the receiver without going half on the rail half on the receiver with a two piece.

This one is one of the best options out there, along with offerings from Larue, ADM, etc.

http://www.bobroengineering.com/view/product/8/

I have the "slightly forward" version of the above mount on my BCM MK12. I use an A2 stock and don't shoot NTCH so I don't need the extended throw mounts. As you can see, there is plenty of room for a back up sight.

http://www.hunt101.com/data/500/2011-10-23_17-19-06_772.jpg

[Devildawg2531]

The way you have the scope mounted on that BCM is anything but rock solid. It may feel that way but trust me that it's not. Look into an extended mount that will let you stay on the receiver without going half on the rail half on the receiver with a two piece.

This one is one of the best options out there, along with offerings from Larue, ADM, etc.

http://www.bobroengineering.com/view/product/8/

I have the "slightly forward" version of the above mount on my BCM MK12. I use an A2 stock and don't shoot NTCH so I don't need the extended throw mounts. As you can see, there is plenty of room for a back up sight.

http://www.hunt101.com/data/500/2011-10-23_17-19-06_772.jpg

a0cake - please educate me what isn't solid about the way the way I have the scope mounted? I have read nothing but positive feedback about the Badger Ordnance rings. What do you mean by shooting NTCH? I thought my issue was the Badger rings were just too low to use BUIS and I want to have BUIS as this is potentially a hard use rifle.

Thanks for the feedback.

[a0cake]

While that DD rail is sturdy, it is not a true monolithic rail. Optics should not be mounted on it, either in whole or in part. Putting one ring on the actual receiver and one on the rail compromises the rigidity of the mounting solution. The receiver is for optics, the rail is for accessories. While it may "feel" like it's not moving there IS flex in that rail. How much of an effect that bears on your shooting is dependent on many factors, mainly your ability and consistency. Either way, it's not the right answer. This is why you don't see two piece rings being used all that often on AR's. Forward extended one piece rails are the solution for getting proper eye relief and keeping the mount on the receiver.

PS. By NTCH, I mean "nose to charging handle."

[Devildawg2531]

While that DD rail is sturdy, it is not a true monolithic rail. Optics should not be mounted on it, either in whole or in part. Putting one ring on the actual receiver and one on the rail compromises the rigidity of the mounting solution. The receiver is for optics, the rail is for accessories. While it may "feel" like it's not moving there IS flex in that rail. How much of an effect that bears on your shooting is dependent on many factors, mainly your ability and consistency. Either way, it's not the right answer. This is why you don't see two piece rings being used all that often on AR's. Forward extended one piece rails are the solution for getting proper eye relief and keeping the mount on the receiver.

PS. By NTCH, I mean "nose to charging handle."

a0cake - thanks for response. I am getting sub MOA 5 shot at 100 yards groups from my stainless BCM from a bench with TAP, Black Hill's Match and FGMM and I don't feel any flex - but appreciate the lesson.

Now that I know I will defintely be moving to a forward eye relief 1 piece mount. Are these all basically set up to allow for BUIS? Is there any advantage to the quick release mounts other than they come off faster? I plan on keeping the scope mounted permanently and it looks like the non quick release versions are less expensive and I'm guessing a little more stable.

[a0cake]

a0cake - thanks for response. I am getting sub MOA 5 shot at 100 yards groups from my stainless BCM from a bench with TAP, Black Hill's Match and FGMM and I don't feel any flex - but appreciate the lesson.

Now that I know I will defintely be moving to a forward eye relief 1 piece mount. Are these all basically set up to allow for BUIS? Is there any advantage to the quick release mounts other than they come off faster? I plan on keeping the scope mounted permanently and it looks like the non quick release versions are less expensive and I'm guessing a little more stable.

While it may not be noticeable off a bench, I'm sure you can imagine that improvised shooting positions would put more stress on the rail / forearm. That's when it becomes noticeable.

As far as BUIS under a 1 piece mount, you're generally going to be good to go with most folding BUIS. Where you can have problems is with the Butler Creek flip caps on the Ocular Lens side. My SS 3-9 with caps is a close fit with the MBUS but it's fine.

Modern QD mounts (not old ARMS crap) from ADM, Larue, and Bobro are rock solid. They are more expensive, but think about it this way. What is the point of the BUIS if you have to bust out tools to get your busted optic off? For that reason, on AR's, I use QD mounts. Return to zero is excellent with the Bobro as well.

[Cesiumsponge]

The integrated mounts are usually available in several heights so BUIS shouldn't be an issue with some measurement. If going Larue, the ones with integrated rings are bombproof. The 5/8" picatinny riser (LT-101) that allows you to tune height and distance with your own rings...I've bent mine before. They'll replace stuff no questions asked but there is a strength limitation to everything.

[Smash]

a0cake - thanks for response. I am getting sub MOA 5 shot at 100 yards groups from my stainless BCM from a bench

a0cake has a very valid point.

Think about why you free float a rail? Because when you run up and jam the rail into a barricade or other supported position it doesnt affect the barrel. This helps the rifle maintain its normal accuracy profile. The rail will flex. While your setup may shoot your 5 shot group at 100 nicely while benching, pressure in any direction on the rail will change your impacts with your optic mounted in this manner.