I have a full auto SP1 conversion and I have heard that sometimes the holes in the lower egg out.

I'm curious if those KNS pin protector kits are any good or do anything.

I started a thread on getting a 9mm upper, and nobody even mentioned the KNS kit, which is kind of telling, because supposedly 9mm uppers chew up lowers.  

Considering how valuable the FA SP1 is, I'm wondering what can be done to harden it against damage.

So I guess the questions are:

1. What kind of damage is done to ARs by shooting them,

and

2. What is done to prevent it?


I never really did any mods on my ARs before, so I'm kind of a newbie.  I'm actually kind of surprised by how little knowledge I managed to pick up on the subject over the years.

You might try posting in this forum: https://www.ar15.com/forums/Armory/M-16/23/

Ive read KNS pins are even worse to use with a 9mm upper. If a pin breaks, you likely will not know leading to even worse egging.

I dont shoot 9mm in my m16, but if i was going id use either Mean arms or CMMG delayed blowback systems.

I think you’re overthinking it. They’ve been around since early 60’s. You’re GTG.

I thought about that, but I was curious to see what kind of damage and wear the semi-auto versions show.

I'm starting out at square one here, I've owned 6 ARs, but they were all safe queens and I never did any mods or upgrades

Edit:

Non issue.

If you want to shoot 9mm, buy a subgun.  I considered the pins for mine, but then I thought about the 80%ers I’ve finished and how hard that aluminum is to drill through.  No pins on mine and I doubt that I will put enough 5.56 and .22lr through it to wear it out.  Mine is a Fleming SP1 and I have three subguns and zero plans on getting or assembling a 9mm upper.
Check the M16 forum here and look for some of Amphibian’s links to info on his site.  He has some good info on 9mm conversions that I would use if going down that road.

I added KNS anti-rotation pins to my RR SP1 early on but still broke one of the pins. I can't say whether it was due to shooting a Oly 9mm upper or some suppressed Beta mag dumps but it was almost impossible to tell it was broken.

Changed back to standard pins and it has been setup that way for 20 years, no elongated or worn out holes yet. I really don't shoot the 9mm upper much these days but do shoot a ton of 22LR and haven't had a problem.

One KNS pin I do believe is worth installing is their non-rotating sear pin for the SP1. I could see the standard pin rotating and tend to think since this hole wasn't anodized after being drilled the KNS pin eliminates whatever possible wear may occur there.

I used KNS non-rotating pins on my two m16s for almost 20 years, until I swapped to a Geissele SSF. The KNS “arms” burnished the anodizing on my factory Colt lower. I removed them and haven’t used them since.

If you don’t already have your 9mm upper:

A CMMG radial delayed blowback upper theoretically would be softer on lower frame pins but I don’t know if anyone has any long term experience or hard data. They are quieter with a can (less port pop) but the ejector springs inside the bolt don’t last long, maybe 1000 rounds. The delayed blowback setup with bolt weights also gets you away from swapping in heavy buffers. Endo mags preclude mag well adapters. Gets expensive but manual arms and mag pouches for AR mags serve double duty.

I won't use a 9mm setup on a valuable transferable lower.

That said, 30 years and a lot of FA fire later my transferable SP1 hasn't damaged the pin holes.