[Trunkmonkey]

I've had my RDB for 2 weeks now, and have attempted to put 600 rounds through it in two seperate trips. Serial is ZOZxx, and appears to have all the recent updates. Upon receiving it, I cleaned/lubed everything but the gas piston, and did not remove/strip the bolt for cleaning. I got an awesome 200 rounds through the gun, and then began getting some failure to feed. In the next 100 rounds of that 300 round session I had 9 FTF. The cases were bent in the middle with a gouge mark. They all came out easily by running the charging handle until they dropped out. Today I tried another 300 rounds. I cleaned all parts of the gun this time, as well as the magazines which are 30 round gen 2 Pmags for all rounds before, and this time. I also brought some GI mags. The Pmags all had 1000 rounds of suppressed shots through them and were filthy, but still functioning fine in both of my AR's, but after the FTF's I figured I should start clean this time. All the Pmags ran fine this time except for one which produced less, but the same FTF's. I disassembled the Pmag, and stretched the spring. It functioned fine after that. The GI mags would fire one shot, and then release from the mag catch, but not fall free closing the bolt on an empty chamber. Overall I got the gun very hot, and shot 296 rounds trouble free. I really love the concept, and the way it handles live fire. I'm hoping as it breaks in, it will become more forgiving with Pmags at least, as that's usually all I use and have tons. I will suppress this gun when I get another muzzle device for it soon. This is my first bull pup, and my first Keltec. Happy shooting!

 

[Grifter]

Welcome to the forum.

Check your gas system; it sounds like it is a click, maybe 2, to closed. Opening it a click or two should remedy the situation.

Give it a try and report back if you can?

 

[Trunkmonkey]

I've read plenty on the gas, and am comfortable fiddling with mechanical things. It's the first thing I did. Factory setting was on position 3. I fired one round and the bolt locked back. I continued with only one round and opened the gas further until failure to lock back. This ended up being setting 8 at first oddly. I clicked back in 2 clicks to setting 6 and fired a couple magazines until it started failing to lock back on that setting. I decided at that point just to go back to setting 3 from fully closed (factory setting), and it remained there until the problems started. Once the problems started, I experimented with more open all the way to fully closed. Nothing helped, and still ran best on setting 3. Today with clean mags, it ran tons better except for that one Pmag and GI mags mentioned earlier. I forgot to mention I was firing 556 independence brass xm193. Also forgot to mention, I did not count the failure to lock back on setting 6 as one of the failures mentioned earlier, as it did fire all rounds at that point.

 

[Grifter]

Interesting, running it fully opened still results in failure to feeds, along with deformed mouths? I wouldn't think there would be a problem with locking back with the gas nearly fully opened.

Wish I could be of more help, man, this is a strange one.

How does other ammunition fire through it?

 

[Trunkmonkey]

Oh, misunderstood you. When I started opening/closing the gas after the failures, I had mostly loaded mags, and not just one round as I had already proved that with the proper gas setting the rifle would lock back. I only did one round mags for lock back in the beginning. The issue that cropped up after 200 rounds was failure to feed. At the moment I'm thinking that dirty, weak, old magazines combined with a sharp maybe every so slightly oversized bridge on the feed ramps is causing the failure to feed that I was seeing. The rounds were most of the way into the chamber, and bent in the middle of the case where the round was dented/scratched as the tip started in the chamber, but the middle case had run up the bridge of the feed ramp, and got stuck on the way since the case was no longer straight. Pulling the trigger just getting a click, and the case was not sitting inside the extractor out of battery from the bolt or chamber. I was able to pull the trigger while holding the charging handle back, and out of battery just to check if it was possible to do it, with no live ammo of course. All ammo for all rounds was independence 5.56 xm193 except for 100 rounds of Lake City xm193

 

[squiros]

i sent my rdb in to kel tec on an unrelated matter.

i got a repair work order in and it said 'polished feed ramp' even though i had no problems with feeding at all. however, it is my understanding that feed ramps are critical in . . . feeding. you may want to contact kel tec about this, or i can send you pictures of mine.

the ammo thing may be important. on my current ammo, i'm getting failures to extract, causing failures to feed. the fired round is never extracted, and obviously, the next round can't feed. however, every round that failed to extract has a strange tear around the rim. looks like the extractor pulled the round but the round crumpled instead of being extracted. the round come out easily with a cleaning rod (just the weight will push it out). this only happens with the PMP ammo i purchased - it seems like the other ammos run fine. however, i only buy 20 round boxes of other ammo, i've not run 200 rounds because i was testing accuracy. the 20 round boxes ran without a hitch. the PMP ammo fails once per mag at least.

my pmags are brand new. i bought them for this gun and this gun only. i have no other guns that shoot 5.56.

 

[Trunkmonkey]

You definitely have an interesting issue there. I'm out of independence 5.56 now, and will be trying wolf gold next. I'll give the gun 1000 rounds to smooth out on it's own before taking any action as I've only had 13 fail to feed in 600 rounds, and believe it's really mostly magazine/break in related. Mine extracts every time except for when it fails to feed. Then I get no bang or extraction because the case never chambered or made it into the extractor in the bolt face. Perhaps your chamber is to tight. When the brass swells after firing, it's getting stuck and the extraction issue happens. Or as you said it could be ammo.

 

[IamScotticus]

rant on

however, every round that failed to extract has a strange tear around the rim. looks like the extractor pulled the round but the round crumpled instead of being extracted.

This was happening to me when I was under-gassing. There was not enough pressure to cycle the bolt to eject. The round was coming out of the chamber and riding the bolt back in, getting the case neck sheared or bent on something. Then It would wedge back in to the chamber half way. I put up pictures on one of my threads. I didn't get functioning until 14 clicks from open (clockwise) with Fed .223 55gr. I didn't shoot enough to see what it would do over 200 rounds.

With this rifle, I would say performance can be anywhere from 14-20 clicks with any ammo (except steel). You may not have a problem until you don't function at full open.

But you will have a problem with metal mags.
I looked at the differences in locking slots of metal GI and Pmags. HUGE (Donald Trump Huuuuuuuge difference. OK maybe not that huge.
But huge enough to understand why GI mags don't work. The correct phrase is GI mags DO work, The RDB mag catch doesn't work. The catch area of the RDB part is too wide and does not fully seat into the catch hole.
You can see this by removing the mag catch and inserting a GI mag/Pmag to observe how the locking tabs line up.You can see this externally by the height of the mag release closed on a GI mag compared to a Pmag.
You can see this internally by removing the GI mag spring and follower and looking in the mag while inserted with the catch in place. Pmags have more width in the locking tabs allowing good engagement. Additionally, the Pmags work well because they have extra width on top of the catch slot for engagement which is necessary because the catch slot does not allow the catch to pass through the mag wall.

I will be taking a file to surfaces on my mag catch areas in an attempt to get more engagment on GI mags without compromising the steel. And making a thread with plenty of pics, of course.

I will end my lecture by stating that KT should address this problem ASAP.
The RDB must be able to hold metal GI pattern magazines or it is not a viable fighting weapon and if relied upon as such may cost lives. (I hope they're reading this).
Rant over.

 

[Trunkmonkey]

Thanks for your input. Some small tweaks by Keltec or the end user, and I think it can be a totally viable fighting weapon

 

[Lefty2Guns]

I will end my lecture by stating that KT should address this problem ASAP.
The RDB must be able to hold metal GI pattern magazines or it is not a viable fighting weapon and if relied upon as such may cost lives. (I hope they're reading this).
Rant over.

Someone in a thread somewhere mentioned contacting KT about mag catch issues and they offered to send out a new one. It was never clear, since I don't think the individual followed up, if it was newly designed to address the issues or just a replacement (i.e. the original was faulty).

Mine has worked fine with all the GI pattern (surplus and new production) mags I own.

I'm half inclined to ask KT for a new mag release just to see if anything looks different, but they've already sent me a bunch of free parts so I don't want to push my luck (that includes updated replacement parts like the new bolt, when I was never having walking extractor axis pin issues in the first place).

If someone requests a replacement, please post details about it here so we can learn a little (detailed side by side photos, caliper measurements, anything!).

 

[Trunkmonkey]

Perhaps I'll request a new mag catch and I'll post here and in the new thread just started about this, with my results. I can't find my calipers at the moment though, so I may or may not have measurements.

 

[IamScotticus]

I have one coming. I will be making comparisons on my mag release issues post. If my results are positive, I may make an article out of it.

 

[FredleyBanyon]

Oh, misunderstood you. When I started opening/closing the gas after the failures, I had mostly loaded mags, and not just one round as I had already proved that with the proper gas setting the rifle would lock back. I only did one round mags for lock back in the beginning. The issue that cropped up after 200 rounds was failure to feed. At the moment I'm thinking that dirty, weak, old magazines combined with a sharp maybe every so slightly oversized bridge on the feed ramps is causing the failure to feed that I was seeing. The rounds were most of the way into the chamber, and bent in the middle of the case where the round was dented/scratched as the tip started in the chamber, but the middle case had run up the bridge of the feed ramp, and got stuck on the way since the case was no longer straight. Pulling the trigger just getting a click, and the case was not sitting inside the extractor out of battery from the bolt or chamber. I was able to pull the trigger while holding the charging handle back, and out of battery just to check if it was possible to do it, with no live ammo of course. All ammo for all rounds was independence 5.56 xm193 except for 100 rounds of Lake City xm193

Did this problem ever clear itself up for you or did you find a solution? I am currently having the same issue with a few mags, where the bullet is being bent in the middle due to some sort of jamming at the barrel opening and pulling the trigger gets a click. I'm hoping its mag related or something easy like filing down a sharp edge on the feed ramp. This issue doesn't happen for the majority of the PMags I own.