I have a Colt 6520, and I see that Grant at GandR has Colt M4 upper receivers for sale. I’m interested in getting one of these and converting my 6520 to 6720 configuration. Only prob is that the 6520 doesn’t have the f-marked FSB. Has anyone else done something similar to this, and will I be able to zero the carbine if I convert it?
The differance between an “F” marked and non-“F” marked is 1.94 vs 1.98 in hieght, with the "F"marked being the taller. So you’ll probably just screw your front post up higher - it may even stick at or even a turn above the ears. at OWRST case senario you’d ahev to buy the bushmaster style taller post [like a $2 part I think]. If that doesn’t bother you, then it will work. If it does bother you, or alternately, if you really wan tit to eb correct, you need an “F” makred unit.
Thanks man, I appreciate the info. I knew the F was higher, I was just wondering how high that post was gonna have to come up. If it’s gonna protrude up out of the sight ears, I’m probable gonna leave her alone and use her for a KISS rifle. It’s just so light and handy that I wanted to be able to put an optic/BUIS on a Flat-top, but I really like things to be “right” so I guess it’ll get left alone.
A bunch of us made this swap a few years ago, before the 6720 was offered. The consensus seems to be that they work fine with the existing front sight. I know mine did.
yeah honestly, if someone didn;t point it out you’d probably never notice.
Or, look at it another way - the cost of an “f” mark sight base isn’t really much - you’ll be spending more on the correct m4 upper, so at that point what is a few bucks more?
Finally, you could always sell it and get the colt 6720 - it’s your 6520 with a flat - top. you might lose a little in teh deal, but probably not anywhere near as much as a new sight base, new upper, plus installs would run you.
For the record, I put magpul furniture on my 6520 and I love it as is for a back up and/or KISS carbine.
Ok thanks guys, I’m gonna go for it. I’ve got some sentimental reasons that I can’t/won’t sell it, so my choices are as is or convert. I really like the way Eric’s looks with the T-1 on it, which is what I had in mind to begin with. I do appreciate the info.
Eric what T-1 mount are you using?
I hate to speak for Eric, but that looks just like my American Defense high mount on my T-1. I swapped all my Larue’s for ADM and I’m very pleased.
Harold
ADM AD-T1M. I like it.
i like it too!