[rob17]

I have an MRO optic mounted on the pic rail near the rear in position T5. I noticed if I tug upwards on the MRO or even the pic rail itself, that it will jiggle / raise up the rail a millimeter or so. Has anyone else noticed this?

I'm wondering if its my rifle or an inherent design flaw?

Its just one more thing that could affect the long range accuracy of this rifle if the pic rail can move around during fire.

 

[Lefty2Guns]

Might it just be an 'illusion?'

Firstly, mine arrives tomorrow, but from my understanding (i.e. looking at pictures/videos of it broken down) the pic rail is attached to the barrel directly. When you pull up, is it moving in relation to the handguard etc. or actually separating from the barrel?

I'd try it when it is broken down if you haven't and confirm that the wiggle isn't just the handguard kind of shifting a little vs actually separating from the barrel assembly (which, yes, would be bad...).

 

[rob17]

Might it just be an 'illusion?'

...

Reasonable question. I just removed the Larue QD/MRO optic. Unknown to me, it was sitting on top of two alan key set screws. The screw over T5 has a washer unlike the others. I found this screw to be a full 1.5 revolutions loose (a lot!). All the other screws were tight.

After adjustment just now, the rail no longer wiggles up and down.

Something for the rest of you to keep an eye on.

 

[MarkB1]

Thanks for the info.

 

[Lefty2Guns]

I found this screw to be a full 1.5 revolutions loose (a lot!).

That would have been my other guess! Glad you figured it out. I believe they apply loctite on all their screws, but I may need to throw some in the range bag if anything shakes itself loose.

 

[Tallen]

When I replaced my FH with a brake, I found the rear screw on my rail was loose. Fixed with loctite.

 

[ktwm]

BTW.

That rear screw is not supposed to be completely tight, it should be loosened 1/8th of a turn from tight (and held from loosening completely out with loctite). the special washer is a spring type wavy washer that keeps the rail down and the gun accurate.

If this rear screw is completely tightened down, you will have vertical stringing accuracy issues as the barrel heats up and expands during shooting.

 

[rob17]

BTW.

That rear screw is not supposed to be completely tight, it should be loosened 1/8th of a turn from tight (and held from loosening completely out with loctite). the special washer is a spring type wavy washer that keeps the rail down and the gun accurate.

If this rear screw is completely tightened down, you will have vertical stringing accuracy issues as the barrel heats up and expands during shooting.

The screw loosened up again.
I looked in the manual, and I didnt see your advice documented in there. I can see a lot of people not realizing this is necessary.

 

[Lefty2Guns]

The screw loosened up again.

I must have gotten a "Kel-Tec's greatest hits" edition of the RDB, as after all the bolt carrier issues I experienced, I am now having this issue as well.

After having read about this here, I specifically checked for rail secureness before taking it out yesterday, and there was virtually no perceivable movement. 400~ rounds later, I check it again when home/cleaning and I notice not only vertical, but also lateral shifting (maybe a millimeter or so).

I retightened (minus 1/8th turn) and think there was at least 2~ full turns of the screw out.

Did you find a solution? Ask kel-tec? Get a response?

I'm thinking it might be time for some red loctite...

 

[Lefty2Guns]

Solved this one myself.

Removed the problem screw and spring washer last night. There was some evidence of red loctite coming out of the bottom (the screw hole is tapped all the way through the rail) but I didn't see any on the screw itself at that point (and it offered zero resistance when loosening/tightening anyway).

Degreased the screw, spring washer and screw hole thoroughly with simple green (there was a lot of dirt/oil actually). Made sure q-tips/paper towel came out completely clean. Dried thoroughly using my compressor to ensure all liquid was blown off/out. Reapplied red loctite to the screw threads and tightened it down til it stopped, then backed off 1/8th turn as directed (I made a little "tape flag" on the shaft of the screw driver to better visualize how much I was turning).

Fast forward to today, I put another 400rds through the RDB, including some bumpfire mag dumps with the intention of heating things up. Seems to have done the trick, as the rail/screw is secure so far.

Will of course keep an eye on it.

 

[MarkB1]

Thanks. Something to remember. By the way, it sounds like your bolt is working fine now.

 

[Lefty2Guns]

By the way, it sounds like your bolt is working fine now.

Oh the things a little missing weld can do!

I'm at 800 rounds since the bolt fix and it's running like a top. I've thrown some garbage at it to see if I can trip it up, and so far only Tulammo gives me any trouble (a double feed here and there out of 100 rounds bump fired).

Considering I never shoot the stuff except for testing new rifles, I can live with that.

 

[MarkCO]

With the Tula, if you put one more turn of gas in, it will likely clear up.

With about 2500 rounds on my RDB now, there is not a threaded screw that has not loosened up. In fact, the butt pad assembly fell off at one point. I have tightened the pic rail screws several times.

With everything running well at this point, I am getting ready to do a full detail strip and clean and will likely go ahead and locktite most of the threaded fasteners.

 

[Lefty2Guns]

I had my buttpad come loose as well now that I think about it (I was bump firing, so it was off my shoulder and getting a good beating/shaking about).

Degreased the screws/holes and redloctited them. Don't think I've noticed any other loose screws, bit will keep an eye on all... 50 of them? (Don't actually know how many there are, but I really wish kel-tec would move away from that means of assembly).

 

[HBeretta]

Solved this one myself.

Removed the problem screw and spring washer last night. There was some evidence of red loctite coming out of the bottom (the screw hole is tapped all the way through the rail) but I didn't see any on the screw itself at that point (and it offered zero resistance when loosening/tightening anyway).

Degreased the screw, spring washer and screw hole thoroughly with simple green (there was a lot of dirt/oil actually). Made sure q-tips/paper towel came out completely clean. Dried thoroughly using my compressor to ensure all liquid was blown off/out. Reapplied red loctite to the screw threads and tightened it down til it stopped, then backed off 1/8th turn as directed (I made a little "tape flag" on the shaft of the screw driver to better visualize how much I was turning).

Fast forward to today, I put another 400rds through the RDB, including some bumpfire mag dumps with the intention of heating things up. Seems to have done the trick, as the rail/screw is secure so far.

Will of course keep an eye on it.

likewise, i noticed rail 'jiggle' recently and just tightened the screw well. thanks for clarifying ktwm - i'll back it off an 1/8th of a turn and will loctite.

also want to note that i lost a 408 shield screw(cheek rest) on the receiver, called kel-tec they're sending me a few. i was going to loctite but if i ever decide to duracoat the gun...want to be able to remove it easily.