[Bronco96]

Same as others, exactly the same as several found online. Back of receiver area where the Charlie is pinned to the butt stock broke clean off. 3 weeks later and after being mislead and deceived by CS I finally started calling 3 times a day. 2 days into that my rifle is en route home. The charging handle had dug into the receiver at the back of its slot 3/16" as well. I really liked the configuration of this rifle, the AR mags, the piston system, the NOT another AR15 and good accuracy with super light weight but when I pushed them about what will be different about my new plastic (they call it polymer, whatever, breaks like plastic) they said manufacturing materials and techniques were unchanged. I'm posting because I want a good reason not to sell at a loss as this is my teotwawki/apocalypse rifle, not to mention my 11 year old was firing it when it broke and I don't want to risk anyone getting hurt either. If anyone knows a serial number range these failures are confined to or has proof the new gun parts are somehow better please post up.
PS, pic of my son is 2 rounds before it let go, crack is visible if you can blow it up enough.
Cheers, Jim

 

[Bronco96]

Can't get pics to load

 

[Junkie]

Polymer and plastic are synonyms.

I'm surprised at that. How old is yours?

I'm surprised you had CS issues. A friend of mine shot out the bore on his (he was at least the 3rd owner) and they charged him $40 to transfer the warranty to him and then sent him a brand new gun.


I like using imgur.com for image hosting. An account makes it easier to keep track of your images, and lets you delete them later if you want, but isn't mandatory. Once uploaded, there's a box that says "BBCode" and if you copy that and then paste it here, the image will show up. If the image is too big here, add the letter h before .jpg and it'll be a reasonable size.

 

[zaitcev]

There's no need for imgur here, KTOG supports attachments.

 

[Bronco96]

Catastrophic failure was at 5 months and 26 days after purchasing new from Buds. Approximately 300 rounds of factory Federal .223 brass cased ammo. No suppressors or hot reloads, no bump firing and I'd shot 60 to 100 rounds per range trip so this wasnt a mag dump torture test either. Fortunately I watch my son closely when he shoots even though he has better safety habits than any range officer I've ever met and I stopped him from continuing when I saw the angle of the butt stock change

 

[Bronco96]

The charging handle apparently beat the snot out of the back of the slot

 

[jonnin]

There would be a recall if a whole run of guns were doing that. Yours must have had an unusual defect that is not replicated across a range of serials. This is analogous to the air bubble that was in a 1911 I had. This caused a metal part to shatter after just a few shots fired. Its was not the manufacturing technique or the brand, but a rare defect. Odds (on the order of winning the lottery) are that it won't happen again.

I advise: send it in and they should send you back a brand new one.
If you feel you can't trust the brand or the model, do that anyway, then sell the new gun and buy an AR or something. But I have said it before and I will say it here: no brand has produced 100% of guns with no defects. It always stinks when its YOUR stuff that breaks, of course.

 

[notavampire]

So unnerving to see these malfunctions. I too have my SU16 as a bug-out teotwawki rifle, but right now it's looking more like a 'use-this-til-i-can-get-better' stopgap, like a disposable, expendable rifle you can't rely on for too long. Even more unnerving knowing that every time I shoot it to get more proficient with it is bringing it closer to its inevitable failure. I really wish they'd make a receiver with aluminum parts on high-stress areas or something. Not an engineer, just a customer who wants a rifle that won't fall apart.

 

[zaitcev]

I'm not unnerved in the slightest. As Mr. Bronco pointed out, the damage of the charging handle slot is plainly visible and should warn anyone with eyes that his rifle is unscrewing itself. There are also traces on the inside of the receiver if that starts happening. But it's still a dumb design. Interestingly enough, George seemingly rectified this problem for RDB, only to be undone by some monkey in the factory who forgot to weld things together, making it possible for the pieces of the carrier to separate. At least when the bolt group comes unsprung in RDB, a thick steel piece protects the shooter's face, which is an improvement.

 

[Bronco96]

Rifle should be back tomorrow with a new receiver in place. If you Google "SU16 failure" there are several guns broken exactly like mine and further searching finds even more. They know about this problem but it seems they're happy to roll the dice and just fix the ones that get sent back but who knows. My current plans is to keep it for back up to make use of all the AR mags with 28 rounds left in them and get a decent US made AK.

 

[Junkie]

So unnerving to see these malfunctions. I too have my SU16 as a bug-out teotwawki rifle, but right now it's looking more like a 'use-this-til-i-can-get-better' stopgap, like a disposable, expendable rifle you can't rely on for too long. Even more unnerving knowing that every time I shoot it to get more proficient with it is bringing it closer to its inevitable failure. I really wish they'd make a receiver with aluminum parts on high-stress areas or something. Not an engineer, just a customer who wants a rifle that won't fall apart.

By no means does it happen to every gun. A friend of mine shot out the barrel on his SU16, which took quite a while to do (and will happen to anything if you put enough rounds through it). No other problems.

 

[Bronco96]

Receivers shouldn't break apart on any gun, ever.

 

[TheJackal]

Improperly staked gas piston, I would say.

Bit concerning that it still seems to pop up from time to time. I thought they had rectified this issue quite a while ago.

 

[Bronco96]

Jackal, is that something they likely fixed when they replaced the frame/receiver?

 

[TheJackal]

Bronco96 - I would hope so. It was a known issue by Kel-Tec some time ago. Apparently some of the gas pistons were not properly staked into the bolt carriers and would back out over time (they're threaded in, and then staked so they can't back out) This extra length caused the bolt carrier to slam against the back wall of the receiver under recoil (in normal operation, it should not touch) and busted the back out of the receiver.

I'm not exactly sure if there is a way to visually tell whether the piston is staked in properly or not.

My Su-16 has had over 1000 rounds through it, I believe, and it's fine. I double checked the piston after I found out about this issue and mine seems to be staked properly.

 

[Bronco96]

Thanks for the info, I'll check it and keep an eye one that if I keep it. My biggest disappointment is that I've wanted a Sub 2000 for years and now that they are becoming available I just don't know how I feel about all the plastic anymore. I am somewhat relieved to know that it may have been caused by the gas piston thing, that's at least assembly error and not crappy design and materials. If that makes any sense

 

[zaitcev]

The staking area is at the thinnest part of the carrier where it can be most easily deformed into the thread, e.g. at the top side. See the attached picture.

The free travel must not exceed 162 mm.

The design, IMHO, is not excellent. The biggest problem that I see is that the travel is limited by the spring at full compression. Anything goes bad there and the carrier will slam the receiver. The tube has enough space for a coil coming on top of another. It is being mostly prevented by the large diameter of the guide rod, but I'm not 100% confident. The second problem is the critical pin that connects the rod and the piston. If the rod head breaks or the pin shears, same result transpires. And of course the infamous thread that can unscrew. I'm sure either Eugene Stoner or M.T.Kalashnikov could do better.

 

[Bronco96]

Thank you guys for the info. Certainly was more than the folks at Keltec did to inform and reassure me. You guys are great.
Cheers,
Jim

 

[TheJackal]

Does anyone think that perhaps inserting some kind of buffer spring or pad at the back of the receiver might help mitigate this effect? I considered it as a failsafe, but I'm not sure the tolerances inside the receiver permit it.

Also, Zaitcev, when you say "free travel" are you referring to the travel of the bolt carrier inside the receiver?

 

[zaitcev]

Yes, it is the total length of travel of the bolt carrier from the full-forward (battery) position to the full rear stop. Sorry if my terminology is not proper.