After talking via PM's with a Kel-Tec representative where I voiced my concerns about the issue of the cracked receivers and if there was any sort of unsafe condition or possible design flaw. Our concerns are unfounded, the SU-16 is designed to allow the bolt to impact the receiver, but not with full impact obviously. I will post some quotes of our conversations.
My question:
We have had alot of reports of broken receivers, bolts impacting the back of the receivers and such. I have advised the group to check the piston rod to make sure it's not loose and is properly staked, but even those that are seem to have clearance issues where they are just starting to impact the back of the receiver area. I checked mine and with the piston rod properly staked and tight, I am starting to see impact marks in the corners on the rear receiver area and dimple marks from the firing pin. I don't imagine the F/P will do much damage, but if I can hold the bolt back and it will contact the back of the receiver then that tells me it may be too close. Can you tell me if there is a specific amount of clearance suggested? I also checked the opening for the charging handle and it isn't damaged, but does have a slight impression in the end of the slot where it is hitting during recoil.
Kel-Tec's response:
Not sure what clearance you are asking about.
The bolt carrier does contact the back of the reciever during normal shooting. It's possible it might be hitting harder than usual with some high power ammo. I'm not 100% sure why the recievers are cracking. It is designed to handle the impact. If the piston rod works it's way loose, then the piston efectivelly gets longer, and more gas pushes the bolt carrier back farther.
The op handle should not hit the cutout slot for it during normal shooting.
One thing I am curious about, is if these people that have the back break on them are shooting in cold weather when it happens. We don't get much cold weather in florida. I should be able to check the repair logs and see if there is a trend.
the back of the reciever was beefed up about 6 mounths ago to help with this. but some people still have issues.
I did not realize that it was designed that way, I thought any contact with the bolt to the receiver would definitely crack the receiver which is what the the group thought also. We were thinking that the contact was a fault that needed repairing, but we didn't understand it was designed that way! If it's OK with you I will post this info on the board and explain the contact is normal and not to worry about it.
Do you think if the op rod is hitting the rear of the travel slot it will crack the receiver, could this be a warning sign to look for?
The Op-rod will never hit the rear of the travel slot, the flat back of the carrier block (where the firing pin is) will always hit first.
The zytel that is used is impact modified....if our molder is giving us the stuff we pay for.
So there it is in black and white. The bolt is allowed and actually designed to impact the back of the receiver and it was beefed up about 6 months ago, also the op rod is not supposed to hit the rear of the travel slot due to the bolt hitting first. As a precaution I would highly suggest that every time the rifle is disassembled for cleaning, check the piston rod/bolt for tightness to keep from having any unnecessary problems. I would also suggest using normally factory loads or "standard velocity" loads if reloading yourself to keep from having the bolt impact the receiver too hard and cracking it.
I know that this had concerned me once I found out, but now knowing that it is designed that way makes me feel better knowing there isn't a problem, just something we didn't understand! And IF there is a problem Kel-Tec will stand behind it 100%! So we need to put this thread to rest! ;D
