I'm gutting my m16a1 lower so I can keep the original parts fresh.

I am getting ready to buy a Geissele SSF. I also want a LPK for the other small bits and pieces. Any difference between getting something like THIS Versus THIS?

Whats left after that? Just the stock, spring, buffer and tube right? Anyone know which ones they are or where to source? I wouldn't mind changing to an adjustable stock, but I want to keep the buffer/spring the same type as so far everything has been working good on almost all my uppers.

All depends on what you want.
My RR is Colt, so I prefer to keep it all Colt.
Colt parts are getting hard to come by.
Specialized Armament still has them, but pricey.

Colt M16 Fire Control Parts

Dont overthink it.

I have over 100K rounds with no issues using Bushmaster parts I bought in 05.

Thanks for the advice.

The only thing I don't know is the correct buffer specs to get. Is the buffer tube exactly the same size as current ar15 ones? Do I need a particular buffer spring? What about the weight of the buffer?

Here are two options I see:

1.

Will something like THIS kit work to replace all the lower parts, as long as I swap out the included trigger for the SSF? What about the buffer? Is it too light (I believe 3oz according to description). Do I need h2 or h3?

2.
THIS and replace trigger with SSF


The second option seems to be the correct buffer tube length and buffer if I am trying to reproduce reliability of stock m16?

Sorry, I know that I could just "test everything for myself" , but with limited free time I'm leaning heavily on your guys infinite wisdom to cut down on trial and error!

Rifle tube is same. Stock is slightly different. A1 is slightly shorter A2 is bigger and includes a spacer usually. Rifle buffers and springs are same.

That is a semi auto parts kit.

I edited my post to clarify my options, but looks like your lightning fast reply was quicker than my edit. Here is the options I put:

1.

Will something like THIS kit work to replace all the lower parts, as long as I swap out the included trigger for the SSF? What about the buffer? Is it too light (I believe 3oz, according to the description). Do I need h2 or h3?

2.
THIS and replace trigger with SSF

Does it matter that they are semi-auto parts kits if I am replacing fire control group with SSF?

Is option #2 an effective copy of what I got now (minus trigger)? If so, I'm guessing that's better than messing with shorter tubes and different buffers? Adjustable stock would be nice, but not at the expense of reliability.

OK guys, just bought it all. Stuck with KISS and just ordered what I know should work.

CMMG ar-15 A1 receiver extension and stock kit..... Seems like this is a reproduction of the m16a1 stock and buffer parts. (right?)

m16 Parts kit

Geissele SSF

Thanks for the advice

Just wanted to give an update for those that land on here in search of similar. I replaced everything on the lower with the parts I linked to and everything turned out great.

The "cheaper" lower parts kit was almost perfect. The auto sear spring was bent out of shape. I contacted the company and the owner replied same day, apologizing and sending out a replacement with priority mail. Everything else fit great

The CMMG kit was a direct replacement. The buffer was the exact same weight.

As far the SSF goes....Theres an AMAZING part and a negative part. The negative part is that for the cost, I don't really see the benefit (except one which I will discuss). I have upgraded triggers on all my rifles, but that's because I generally use them for accuracy work. With the machine gun, I'm focusing more on staying on target than anything else. So the fact that it's a cleaner lighter break, is mostly moot. In that regard, it's just not worth it.

However, there was one HUGE surprise benefit to the SSF. I have a shorty 22 upper that I have tuned to work with my m16. I could never get it to reliably work full auto with subsonic rounds, only hypersonic or standard rounds that were at the edge. I think there wasn't enough umph to reliably reset everything. No big deal as for full auto purposes, using regular rounds is fine. I was worried that using the SSF would lead me to having to retune and figure things out all over again as I have read someone having a negative experience with the SSF and 22 uppers. To my surprise, it worked even better! Both my standard velocity and subsonic velocity rounds worked full auto! I'm guessing it's because of the lighter/smoother trigger requiring less to reset.