EDITED:
I had some problems with a 12" Fortis Rev and sent it back. I believe there may be a design flaw resulting in the slippage of the forearm on the barrel nut. All forearms will flex up, down and sideways if you apply enough pressure, but they should return to the installed location. But the Fortis will stay up with some pressure because the clamp includes the bottom rail and the way it is machined the rail portion will spread as pressure is applied to the rail. When the rail spreads in effect it loosens the forearm. My forearm would actually stay in a shifted position resulting in a shifted point of aim with BUIS.
Here is a drawing, part of which I borrowed from BCM's website. I may be wrong, but I think this is why my forearm shifted on me.
Attachment 26932
I believe the solution is to leave more material inside the bottom and top rails to reinforce them and keep them from spreading. I really loved the Fortis, but a forearm that allows a significant
change in POA with irons is a problem.
Last edited by ScottsBad; 07-04-14 at 13:42.
Scottsbad, that's interesting and useful info. What kind of force are we talking that may have caused this? I've yet to have any issues with mine, so I'm curious if I may be able to replicate the problem you had. Looking for a good reason to buy a kmr as it is.
I really appreciate everyone's feedback here. Right now, the fortis rev caught my attention, but I'm open to any suggestions. I currently have the DD MFR, which conducts heat quick when put to extreme use. I am looking for something light, does not conduct heat as fast, something that looks industrial looking. So if you guys have any other suggestions, I'm open.
Whenever I install a new forearm system that I've not used before I test it frequently to make sure the nuts are not coming loose, that the forearm is not shifting, Etc. So periodically for the next four or so trips out shooting. I check the tightness of the forearm and one of the things I do, which may seem funny, is I hold the barrel or muzzle device in my hand and press the forearm up, down and side to side with my thumb just enough to flex it. I observe if it is returning to a the installed position. Then I shoot a few round with the BUIS to ensure zero. I don't use a whole lot of pressure, I just want to make sure that if the rifle gets bounced hard that the BUIS will stay on zero.
I do this on trips to the range, and repeat on maybe four trips, if all is well I don't check zero again for quite awhile. With the Fortis Rev it took three trips before I visibly noticed a shift of the forearm up and loss of zero.
I've done this with the KMR, the DD Light and MFR, the old Troy VTAC Extreme, Apex Machine 12" and the NSR. The only one that I had a problem with is the Fortis.
Also, when I removed the Fortis Rev I noticed wear marks on the barrel nut where, apparently, the rail had been spreading against the nut in the area of the bottom rail.
Now maybe some folks don't care if this occurs and are thinking they will not have a problem. Fine, I'm just posting my observations, my experience, and my concerns.
Like I said, I actually really like the Fortis Rev. It is an unconventional profile, but I liked it. It was very well priced and I was putting it on my, I guess I'll call it my test rifle. BTW- It was a BCM barrel nut and upper receiver.
YMMV
Last edited by ScottsBad; 07-07-14 at 12:18.
I think all of the tube and light rails will heat up quickly, the MFR heats up slower than some. The more material the slower the forearm will heat up. So a full railed forearm like the DD Lite heats up slower, it has more surface area, and more material, but it also weighs more. Putting panels on your forearm will take care of the issue for most people.
A lot of folks are not as crazy as I am about testing out rifles (in my own way obviously). I don't torture test them on purpose, I just subject them to little tests and check to ensure screws are not coming loose. I test to ensure they will shoot reliably with any kind of ammo I might use. That they shoot when dirty. That they shoot with any magazine I have. That the optics and BUIS don't shift. I check for odd BCG wear. Odd buffer wear. Lug wear. I look for marks on the ammo cases and where my brass lands. And just general functioning. Especially when the rifle is new or changed. And I check the parts before I install them too.
It is really surprising how many issues I find. The rifle may run fine for most, but I tend to put a some extra effort into the details.
YMMV
Last edited by ScottsBad; 07-07-14 at 12:48. Reason: trouble with spelling a grammar today
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