I was adding a new grip to one of my rifles and I noticed that the FF rail I had on it wiggled. At first I thought that the screws holding the FF rail to the barrel nut had come loose even though I used red lock tite. It was not the rail. The barrel nut was loose!
I removed the Midwest Industries 10" FF rail completely. Then the flash suppressor and then the gas block and gas tube. The barrel nut was loose enough that I was able to undo it without a tool.
The odd thing is I have never touched the barrel nut EVER. I cut the delta ring assembly off this rifle to install the FF rail.
The rifle has less than 500 rounds fired through it during three total range sessions. Not what I would call heavy use.
My first mistake was taking this rifle in on trade. It was a NIB Stag Model 1. Yes I know. I have made the required upgrades short of replacing the barrel.
My second mistake was obviously going cheap and installing the MI rail.
Since the FF rail bolts directly onto the barrel nut I assume this is the cause of the nut working loose. The MI does not have any lugs or anything else that would help reduce or eliminate rotation. The only thing that would be in the way of it rotating is the gas tube! Ok its a shitty design. I agree.
So I have decided to restore it to its orgininal configuration. I ordered a new delta ring assembly and barrel nut just in case along with some new FSB taper pins since I can’t find the OEM pins. No loss. I have a spare F marked front site so no need to buy another.
Eventually I will just add a DD Omega rail or a VLTOR CASV-EL to it.
Any idea if replacing the barrel nut with a new one will help? I will torgue it down to spec and rebuild the rifle.
Pisses me off. I know Stag isn’t exactly a tier 1 rifle but holy crap! After less than 500 rounds the barrel nut works loose!
Well another lesson learned the hard way. On the plus side I caught it before I shot it again.
the handguard might have helped, but the nut was either loosened up by someone and not tightened down properly again, or it came from the factory loose. might not have been loose enough to wobble- but was loose enough that firing it wore the threads enough for it to wobble. i would doublecheck your threads and make sure they’re not chewed/worn to the point that they’re unsafe to use- if the anodize is all worn off or you find little sliver-rings of aluminum, call stag- they probably owe you a new receiver.
this has always been Stag’s problem… they make pretty good parts, for the most part, but QC is basically non-existent. i buy CMT parts all the time, but i’d never, ever, ever trust any assembly from the factory.
You realize, that a random front site base off of another barrel, isn’t going to just pin right up to your barrel, right? If it does, you should go buy a lottery ticket tomorrow.
Thats not neccessarily true…you can, but it takes someone really knowing what they are doing, and a non-standard pin size.
Marvin Pitts pinned a KAC flip up sight base gas block to a Colt 6921 barrel for me, and all he did was drill out the grooves the next size up, and used a little big larger pins.
Of course you cant just order a new FSB, put it on the barrel, and expect to tap pins in.
i suppose so long as you could drill your own holes in the new device, you could get it close enough to ream everything out. would definitely work better with dowel pin holes than reamed… you could probably even just ream to 2/0 and use a slightly longer pin
You need a jig to properly set up and align the FSB with the index pin on the barrel extension, and a jig to reem out holes that are already there, and reem larger holes, and use larger pins, to end up with a properly aligned and set up FSB.
The point is, it IS possible, but not by most folks, working out of their garage, using a bench vice. And to be done properly, by a shop, new parts are used…that is different than trying to match up a barrel and FSB, that has already been reemed and are mismatched.
indeed… i happen to own an FSB jig. i did, however, successfully fabricate my own blocks out of softwood before comp1911’s jig came out, and successfully install a few FSBs over the years. took about 45 minutes of setup, getting everything mic’d and clamped… and was a brow-dampening ordeal.
but i’ve never tried to install a new FSB over an old one. thanks for posting that, belmont- it’s actually pretty simple. i think i’d actually start with a 3/32nd drill, to ensure no over-bore. then hand-ream. once the FSB material was cleared, the “pilot hole” of the barrel would guide the reamer through. there’d be a bit of over-bore with the reaming, but if you were careful, you could still use 2/0 pins- just run them through long and cut to fit.
ok so restoring it back to its original configuration is out given the FSB issue. It will have to go back to the way it was with the rail installed and a lo-pro gas block intsalled or a new ff rail and a the lo-pro gas block installed.
Well that sorta sucks. I got all the parts on order already from BCM. Oh well more for the spare parts drawer.
Thanks for the heads up on the FSB.
Guess I will start hunting for a DD or a Larue or a Troy ff rail.
I am almost certain that the barrel nut was not tightened properly to begin with. I have seen it even on the VAUNTED Colt M4.
I have not used this particular model before. Is there anything that prevents the handguards from rotating? Screws or anything? FWIW- I bought an open package Troy MRF from GandRtactical and it worked pretty damned good. I think it cost around 179.00.
No anti rotation provision of any kind. Since this is a range toy/plinker for my son I was not worried about any real hard use. He is 6.
The Troy has some lugs that protrude from in onto the upper reciever that keep it from rotating. The Larue and DD rails have their own anti rotation setup.
I will re-install the MI rail since returning it to a standard M4 configuration will be problematic considering the FSB/taper pin issue.
I feel pretty confident that once I properly torque it down to spec this problem won’t happen again.
I went down to my friends store, Bravo Arms in Colorado Springs. I told him about my issue and he gave me free reign of his workshop! Thanks Brian!
I reinstalled the barrel using the original barrel nut and torqued it to spec. I can see now that the factory did not tighten it down properly. The now newly installed barrel nut sits two more notches over from the original location. I can see from where the gas tube has rubbed the original notch from being removed and reinstalled when I put on the FF rail.
I doubt it will come loose again. I was tempted to put some red lock tite on it but decided against this. Proper torquing should work.
I put it all back together gave it a test run. Works great. No more wobble.
I guess I will have to use the parts I ordered to restore its factory configuration as the base for another build. I am sure builds have been started with less than a barrel nut, delta ring assembly and taper pins by others.
Thanks for the help and advice to stay clear of attempting a FSB re-install.
I saw a jig being sold recently that appears to be a block of steel to clamp the barrel extension and a t-shaped bar that goes out to align the FSB.
I have not personally tried one of these, but it does not look like it’s very solid.
My FSB installation jig is built on a 1" thick x 5" wide fixture plate.
Even with such a fixture, it’s a pain to install a new FSB on a previously drilled/reamed barrel.
It takes one setup to locate the centers of the old holes and then a 2nd setup with the new FSB in place to drill the new FSB.
Even worse is installing a used FSB on a pre-drilled barrel.
That’s when I jump to oversized taper pins.
After discovering what a total nightmare it would be to install another FSB I really had no choice to reinstall the FF rail and lopro gas block. I shot another 200 rounds through it today and it is rock solid.
I cant blame MidWest Industries at all for this issue. It was just one of those things that make owning an AR interesting. Should have been done better at the factory is all.
