Geissele SMR mkIV Barrel Nut: Is this normal?

[elephantrider]

After installing a Geissele SMR mkIV barrel nut for the first time, I noticed a small ding that has me wondering if I did something wrong. The the hole that I used to torque the nut was deformed a little bit and the finish cracked and flaked off around it as well. It looks like the stud in the supplied wrench did not bear evenly on the hole in the nut and pushed the edges of the hole into an oval shape.

I followed the directions and torqued this to 40 ft-lbs. I used the supplied wrench. The only odd thing I noticed was that the the wrench was somewhat difficult to get onto the nut to tighten the nut and slid on quite easily the opposite direction (as it would sit to loosen the nut). It took a little bit of pressure and wiggling of the wrench to get into position to tighten it. It makes me wonder if the either the stud on the wrench or the holes in the nut are a little off.

Since this is my first Geissele rail, I'm not sure if this is typical of their barrel nut/wrench interface or not. I definitly don't mean this as a slam on Geissele Automatics as I am a huge fan of their products. Ordinarily I'd contact the mfg., but I thought I'd ask here first since there are so many knowledgable GA rail owners here.

ETA: The affected hole does now have a small raised lip/burr around it. If the holes in teh nut didn't line up with the side rails, I don't think I'd be able to slide the rail over the nut because of the added thickness to the nut and the close rail to nut fit.

Pics are of the hole in question and the other untouched hole as well for comparison.

[markm]

No issue that I'd worry about. Put the rail on and go. :confused:

[Kenneth]

Yes you did not turn the wrench around to turn it the opposite way.

Ask me how I know... I pushed mine a little further than that and my damage is exactly like that but a little worse and my Rail was a PITA to get on and off die to the barrel nut being out of shape.

It was a rookie mistake on my part and it made me sick when I did it.



After reason your post further if you cannot get your rail on your in for a bit of sanding on the barrel nut. Not that I recommend doing that but I made mine for that way.

[elephantrider]

Yes you did not turn the wrench around to turn it the opposite way.

Ask me how I know... I pushed mine a little further than that and my damage is exactly like that but a little worse and my Rail was a PITA to get on and off die to the barrel nut being out of shape.

It was a rookie mistake on my part and it made me sick when I did it.



Not sure what you mean about turning the wrench to turn it in the opposite direction? As far as I can tell there is only one way to orient the wrench to tighten the nut. Am I missing something here?

I basically did what Trident did in this MkI install video (except 40 ft-lbs). 1:20 minute mark
http://www.youtube.com/watch?v=6mfBZ8BVfhw

[Kenneth]

Well here is the mistake I made. For some dang reason I had the wrench backwards like I was going to loosen the nut and then went to tighten it. It made the hole oblong shaped like yours.

That's is what I did anyway to get that damage.

[C4IGrant]

Nothing to worry about. Question though, did you use a calibrated torque wrench?



C4

[elephantrider]

Question though, did you use a calibrated torque wrench?

C4

No I didn't. I see how that could've contributed to it. I should probably invest in a better torque wrench.

[C4IGrant]

No I didn't. I see how that could've contributed to it. I should probably invest in a better torque wrench.

This would be my guess (too much foot pounds of torque).


C4

[elephantrider]

This would be my guess (too much foot pounds of torque).


C4

Grant, any recommendations on quality torque wrenches?

[AKDoug]

Over the years I have owned torque wrenches from Craftsman, Snap-On, and even a Master Mechanic one from True Value. At one time or another I have had them checked and I've checked them using my own method (using weights to check) to keep an eye on them. At this moment, not one of my torque wrenches have ever failed a check, even the cheaper Taiwanese ones. Talking to my Snap-On dealer, torque wrenches rarely test off spec.

I'd be totally confident using a torque wrench from Craftsman, and that's the one that is in my gun room. If I'm working on an aircraft or a diesel engine, my good Snap-Ons are going to be used.

[netchemica]

Do you guys set the torque wrench to the torque spec provided? You guys know that you need to recalculate the torque setting when you use a spanner tool, right?

M1=M2 x L1/L2

M1 is the torque setting of the wrench
M2 is the actual torque applied to the nut
L1 is the normal length of the wrench
L2 is the extended length of the wrench (wrench + extension)

So if your torque wrench is 10 inches long and you have a 5 in extension, you'll set your torque wrench to 20 ft-lbs to achieve a 30 ft-lb torque.

[elephantrider]

I thought I would circle back on this issue I was having. I was able to get a new wrench and barrel nut from Geissele Automatics thanks to their awesome customer care.

I removed the barrel nut above using the previously untouched hole. There was a tiny amount if deformation on one side of the hole, but nothing nearly as bad as pictured above. The new wrench slides on and off the nut a bit easier than the one that was supplied with the rail. I am pretty sure the index pin on the first wrench was misaligned at least a little bit. Over torqueing may have done most of the damage, but the wrench didn't help the matter.

I haven't had a chance to install a new barrel nut yet, as I want to calibrate my torque wrench first so I can see to what degree, if any, I was over-torqueing the nut in the first place.