I'll start by saying that I am a complete noobie.
I finally got all my pieces and parts and want to try helmet mounting my new PVS-14.
TNVC J-Arm
Norotos USGI Rhino Mount
I think I understand how these are supposed to go together but the arm attachment point doesn't seem to want to go deep enough into the Rhino mount to latch. I've tried squeezing them together and wiggling them around. The spring loaded arm moves as it rides up onto the block? inside the mount. It's close but not making it over. I'm thinking something needs to be shaved just a little bit but I'm not sure what part and I don't want to mess up brand new parts.

Anyone else seen or heard of this happening? Easy solution? Thoughts?

I concede it's also possible that OP is an idiot and just not going about it correctly.

Thanks all

I had that happen. So I lightly sanded down the faces of the J Arm attachment point until it would latch in the mount. Took ever so little sanding to accomplish and has been rock solid since.

Thanks!
Are you talking about the 2 bumps on the front that are meant to seat in the bottom of the mount attachment (well?) That makes sense.

Each J-Arm could fit different, so maybe try adding chalk, ink marker or the like on the J-Arm, insert it into the mount, see where you find rubs marks and start sanding there. If no rub marks on the sides then the front 2 points could be the culprit.
In my case I could see the rub marks on the sides of the J-Arm that gave a hint where to start.

Both of mine were this way. Angle grinder is the fastest way if you have a steady hand.

Friend of mine had this issue with a TNVC J-Arm and Rhino mount. I walked him through sanding it to fit. I believe TNVc set got a bad batch of J-Arms recently.

Mine where both xls from tnvc so that would make sense. Easy to fix with a little elbow grease.

This is why you get a Rhino-2 instead

I have a TNVC multicam painted j-arm from 2018 and one that came from NGI recently.  Neither of those will lock into the rhino 2s I have but they work with an early rhino.  Both of them from tnvc have the 'bumps' that stop them from rotating, I have 6 USGI surplus j-arms with the locking pins that work fine in either.

The tnvc ones will fit with a little trimming so its not a big deal.  They may work fine with wilcox bayonets or newer norotos mounts, or different rhino 2s than I have.

Interesting. I didn't expect such a simple (milspec?) device to be so problematic.

Thanks to everyone for the help. I started with some light sandpaper, then moved up to a course file and finally ended up in the garage on the belt sander. The latch will engage now but it's not the positive "click" I was expecting. It doesn't take much force at all to release it and doesn't inspire confidence. Guess I'll start saving for a higher tier mount system.

Keep going till it clicks.....your almost there

Like I said 2 minutes with an angle grinder. God gave us 10 fingers for a reason.

https://www.snipershide.com/shooting/threads/yet-another-mount-question.6978269/

Second post.

Yea forgot to mention, the tnvc supplied ones even when filed to fit do not engage a lot, it only takes like .030" movement to release them - thats why I use the surplus ones I have.  You can even look at them and see the latch sits higher and does not engage much at all compared to the surplus j-arms I have.  I have been using the usgi j-arms for a while with a single -14 and have never disengaged one by accident, a tether is a must though just in case.  

Out of the 3 j-arms I've bought used over the last year, 2 didn't fit. One took a lot of hand sanding and the other took an orbital sander.

as was said previously, a tether is mandatory!

Wilcox G-11 or switch your rig over to dovetail.