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Posted: 3/19/2015 10:37:48 PM EDT
| So I just got a cheap protacgear helmet to use with my pvs14, and today was the first time actually clicking the J arm into my rino 2 mount. the J arm clicks in, but it is EXTREMELY touchy. If I barely push down in the release it instantly pops right out. Is this normal? I tied a piece if cord around part of the helmet and attached it to the 14, to be safe, but just messing around with it, I've accidently released the J arm from the mount twice already. |
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opps differnt problem tried to find some pics but didn't. okay, looking at the j arm, note the angle of the latch. when the arm is inserted, the angle should still be close to the same. if it isn't, the latch isn't engaging completely. look at the nose that inserts into the mount, you can see the catch part in there, check for sharp edges and it isn't rounded off. lastly, look at the spring under the latch. it should take some force to push it down, if it doesn't, the spring may be bad or someone replace the one that is there. if any of these problems exist, it seems to be easier to just get another j-arm |
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Tolerance stacking.
J-Arms are not the most precisely or well built pieces of USGI equipment. Related anecdote - I sat with some military supply personnel who had just gotten boxes of brand new RHNO IIs and J-Arms to fill BII shortages for an inspection (Rhinos and J-Arms tend to walk off and/or get lost frequently), and we had to individually fit and match J-Arms to RHNO IIs to find ones that fit. About one in three J-Arms wouldn't fit, but would fit perfectly fine in another mount. Mind you, these were not eBay, knock-off, Chi-com, clone parts, but new in box, bagged, bubble wrapped USGI-contract parts that were drop shipped to unit supply. FWIW - sometimes removing the magnet on the bayonet receptacle helps the fit of the J-Arm. It is what it is... if you have access to multiple J-Arms (might be worth checking a surplus store), I would try to try a couple out before buying, otherwise, it might not be a bad investment to pick up a couple cheap, used J-Arms to ensure that you get one that fits. Another option that might be worth trying if you're up might be to simply shorten the latch so that it's a little bit more difficult to accidentally release. The best option of course, is to just switch to a dovetail interface and rid yourself of the bayonet once and for all. 
~Augee |
I think I have like a dozen J arms . How that happened I don't know... But what Augee said is my experience. Some are tighter fitting than others. Magnets will fuck you every time and I always remove them.  I never rely on a magnet in a box to turn my scope off. The on/off switch works just fine for me. 
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