I have a RR lower transferring to me and kinda want to do some upgrades/maintenance to make sure it last. This is going to be a blaster/shooter MG for me.

Its a converted colt SP1 lower.  I think at one point it had a 4 position selector in it but has a 3 now ( the stops had been milled off)  The previous owner said before he got it it had been sent out to M60 Joe and had the front pin converted from large hole to small hole. You can see the brass bushing  and has a front pivot pin that ls longer than the receiver with a ball detent.  The rear take down is the captured style but noticed when out it has a lot of movement.  

I was going to replace these with some KNS pivot and take down pins.  It has a KNS non rotating sear and trigger pin kits installed all ready.  

Also want to order a Geissele SSF trigger for it, but they are supposedly not compatible with KNS trigger pins ( but hear they are working on making some that do work together)

It has a H2 buffer and magpul ACS stock don't think I will / need to change anything there the end plate does have to hook attachments on either side and I might swap it out for the magpul ASAP plate.  Also dont care for the stock A2 grip so I will be changing that and adding the BAD leaver ( I am used to using them on my other rifles).

Any other upgrades or maintenance stuff you guys would recommend for one of these?   I was a little bit bummed my seekins 300 blk upper ( the camo one) didn't fit the pin holes don't  line up correctly I didn't try forcing it and just gave up figure I will deal with that another day.

And some pics for the range today got one of my cans out of jail so figured best way to break it in was with some FA mag dumps right?







The RPM on that diablo upper is insanely fast.

KNS pins work fine with Geissele SSF so definitely keep those.  Another thing you should seriously consider is a POF buffer tube specifically made for countering carrier tilt found in piston systems, it will protect your lower from the carrier hitting it before entering the buffer tube. As far as your upper not fitting you can usually do a little sanding of the upper to make it fit and use an accuwedge for a wobble-less fit.

Check out this thread about Geissele triggers and KNS pins.

http://www.ar15.com/archive/topic.html?b=3&f=118&t=386767

I have an SSF in my 614 and do not use KNS pins.  See also:

https://www.google.com/search?q=geissele+kns+site%3Aar15.com

for numerous old threads on this subject.

From the man him self ;) posted this in the Geissele industry forum.

I think one of the problems was people would over tighten the kns pins and it was binding the trigger as we'll

It's my understanding that KNS pins are only a problem for high speed Geissele triggers. While KNS pins are not as precisely machined as Geissele pins they will protect the lower better since Geissele pins still rotate in the lower. Someone correct me if I'm wrong.

I have never converted a receiver to small pin with brass...  I use 7075 Aluminum.

I should clarify it's the color of brass so I assumed that's what was used.

If the OP doesn't plan to use Piston Uppers, I suggest replacing the buffer tube system with the VLTOR A5 buffer system.  It will give you higher reliability than the CAR buffer System and still allow you to use a telescoping stock.

Edit to add:
Replace all the parts in the lower with Colt OEM M16 parts, order extra trigger/hammer springs too.

Wasn't installed by me.

Well that's an interesting wrinkle.  

Hmm ya owner I am buying it from said previous owner had the work done by you guess not. Oh we'll not that it really matters a ton I guess

It could. There are very few(count two) smiths I'd trust to work on one of my transferable M16's. When you are paying the price of a new car for a lower, I'd want to be sure someone who knew what they were doing worked on my lower. There is a reason m60joe is always suggested. Just my .02.

I also know the owner before as well I will just ask him next time I see him.  He is a smith of sorts well kinda one of the designers of the sparrow and other Silencerco products, Mike Pappas.

Oh yeah, It's Mike Pappas?  That's cool!