[ThomasA]

Seems like everytime I look at different cantilever mounts for the DMS-1 that people are using, no one just sticks it forward on the free-float rail. Why is that? I have a very solid free-floating forearm by YHM and I'd rather just stick it up front and not bother with finding the farthest reaching cantilever mount I can find.
-Thomas

 

[ForTehNguyen]

eye relief

 

[hikeeba]

eye relief

I think ThomasA is referring to mounting a scope using rings (for example), with one ring mounted onto the upper reciever, and the other ring mounted on the railed free-float handguard. Another example would be spanning the upper receiver and handguard with a scope mount that has a longer solid base.


ThomasA, I think people don't do it because no matter what brand or how solid you feel the free-float handguard is, it is still a separate and independant piece from the receiver. Being a separate piece, I guess the possibility exists that it could potentially move independently from the receiver, i.e. if bumped, bashed, or jarred; thus the plane of the top rail would/could be thrown off, which would throw the optic off. Think about the FF handguard for a second... It is attached at the barrel nut area, and the rest is free-floating. You could give teh FF handguard a good whack on the end, bend it, and it will still be free-floating and not touching the barrel. In this case, the alignment of the rails would then be off, right? OK, now picture that scenario on a smaller, less visible scale - Scope mounted with one ring onthe receiver and one ring onteh FFHG, BASH! Ooops! Hmmm... Looks OK, I'll keep shooting. Hey! My POI is now off! Jeepers! What the hey?!?

Also, and I do not foresee this to be a major issue, but the top plane of a FF handguard isn't always on the same exact plane of the top of the upper receiver. However, the differences in top rail height, in most cases, is so minute that it could easily compensated for when sighting in an optic.

A scope whose mount is attached to the upper receiver only is attached to one single piece and plane. Sure, if you bash on the mount hard enough, you could possibly knock the optic out of whack. But mounting to the receiver only gives you the most solid mounting option, as well as giving you the best chance to be truly aligned with the bore.


Does that mean you can't mount an optic on a FFHG? Nah. If you want to try it, sure, go right ahead. Do you have a long eye relief scout scope you are thinking of trying?

Another alternative would be to drop some coin on something like an extended model A.R.M.S. Inc Swan Sleeve, with which you could use regular height (not crazy-tall) rings.

 

[ThomasA]

the DMS-1 has a 3.5" eye relief. With the nose at charging handle position, that would put even most cantilever mounts partially on the free float tube. Everyone I see using a DMS-1 avoids this and just extends their stock out more, moving their face farther back from the charging handle. I do not want to do this.

I know if the FF handguard is not perfectly aligned with the receiver and you put individual scope rings on the FF and the receiver that it will torque the scope's body, and distort the lenses internally. But if you use a solid one-piece mount across the seem of receiver/ff then I don't see there being a problem, I guess. That's what I'm curious about.

-Thomas

 

[M Hatter]

I think ThomasA is referring to mounting a scope using rings (for example), with one ring mounted onto the upper reciever, and the other ring mounted on the railed free-float handguard. Another example would be spanning the upper receiver and handguard with a scope mount that has a longer solid base.


ThomasA, I think people don't do it because no matter what brand or how solid you feel the free-float handguard is, it is still a separate and independant piece from the receiver. Being a separate piece, I guess the possibility exists that it could potentially move independently from the receiver, i.e. if bumped, bashed, or jarred; thus the plane of the top rail would/could be thrown off, which would throw the optic off. Think about the FF handguard for a second... It is attached at the barrel nut area, and the rest is free-floating. You could give teh FF handguard a good whack on the end, bend it, and it will still be free-floating and not touching the barrel. In this case, the alignment of the rails would then be off, right? OK, now picture that scenario on a smaller, less visible scale - Scope mounted with one ring onthe receiver and one ring onteh FFHG, BASH! Ooops! Hmmm... Looks OK, I'll keep shooting. Hey! My POI is now off! Jeepers! What the hey?!?

Also, and I do not foresee this to be a major issue, but the top plane of a FF handguard isn't always on the same exact plane of the top of the upper receiver. However, the differences in top rail height, in most cases, is so minute that it could easily compensated for when sighting in an optic.

A scope whose mount is attached to the upper receiver only is attached to one single piece and plane. Sure, if you bash on the mount hard enough, you could possibly knock the optic out of whack. But mounting to the receiver only gives you the most solid mounting option, as well as giving you the best chance to be truly aligned with the bore.


Does that mean you can't mount an optic on a FFHG? Nah. If you want to try it, sure, go right ahead. Do you have a long eye relief scout scope you are thinking of trying?

Another alternative would be to drop some coin on something like an extended model A.R.M.S. Inc Swan Sleeve, with which you could use regular height (not crazy-tall) rings.

I understand this is different... but it's kind of the same too... What about all the people who have their iron sight mounted to a free float handguard??? Everything you just said about problems with the scope being mounted to the handguard, would apply to a sight being mounted to the handguard too!! Maybe we better go back to pining them to the barrel...