Can anyone recommend a good quality lower parts set, trigger ( comp or not ) pin set and buffer ? It will be on a Sendra rr and 10.5-11.5 gas impeng. Flat top upper . Please keep in mind it will be a shooter and in a dusty environment . It doesn't have to be the supper high speed low drag mall ninja edition . Just practical and reliable.
Has anyone run the comp. style triggers on select/fa ? What buffer /spring combos are available to safely play with cycle rates? I'm sorry in advance for asking so many questions that y'all have probably discussed in detail. Although this isn't my first nfa purchase its my first m16 and I just want to be diligent in my research. Any and all advise is appreciated.
Thanks

PS, I will be running a m4-2000 can on occasions

Yeah Colt makes nice parts for sure. I've also used regular cheaper M-16 parts kits from SOG Armory and DPMS and other places with no issues though. I run regular buffer springs, but prefer heavier buffers like a H3 or 9mm buffer. If you want to reduce the cycle rate I'd get an MGI buffer. My favorite trigger is the JP Adjustable single stage trigger for my M-16, but the stock trigger also works just fine. Honestly if you are familiar with AR-15's the M-16 is just like it but has a happy switch, so all your AR-15 knowledge still applies. Then more you shoot your M-16 the more you'll learn about it. And of course KNS pins are nice to protect your expensive lower and also make the trigger pull smoother.

Interesting. I got to test drive my Colt for the first time today and discovered that the OEM trigger is pretty bad. It probably will improve since it's not even remotely broken in. Another guy's well used factory had a much better pull in semi & auto. I'm already spoiled by the Geissele SSA, so was planning to go with an SSF for the RR. Aside from the 1 vs 2 stage differences, can you compare & contrast your setup with an SSF? How hard is it to modify the JP stuff to work with auto FCG parts?

When my Form 4 clears, hopefully before 2013, I may try your setup.


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Thanks for the wisdom and knowledge. I'm new to this board and it seems to be the jackpot of real world information already. I would like to say after I test fired the gun ( my sot was nice enough to let me have a test fire) it seemed to have the same cycle rate with several different uppers. Which I thought was kinda slow. They ranged from 10.5 to 16. Is this common? I kinda like the higher cycle rate guns like the Nam era XMs
Just for your information this is a completely unsolicited thank you to Guns Plus in Georgetown Texas. My much preferred sot. Great guys that aren't self important or have the personality of a wet rag. I can't say enough for good customer service and willingness to help. Thank you Kyle and Stephen.
Still open to advise and comments, Thanks again

Gene Stoner originally designed the full-auto AR15 with an ROF of about 450 rounds per minute. After the initial military trials, he was asked to speed it up, and the resulting ARs/M16s had a ROF of 650 to 700 rpm depending on configuration.

The variables that determine ROF are the gas pulse (adjusted primarily by changing the size of the gas port), buffer weight, and ammo. However, when the carbines came along, the shorter gas tube and shorter recoil pulse made gas port size critical, and you can't do much there if you want it to run reliably. To get very far out of the milspec ROF range and maintain reliabity, you'll have the best luck with a rifle buttstock and 20" barrel.

You can still do a lot in a carbine configuration with buffer weights –– between solid, mechanical and hydraulic buffers in varying weights, you've got a dozen to choose from. But not all will run with all uppers, so you do need to experiment. I've got more than a dozen different buffers in my toolbox for debugging. With an in-spec upper, I can usually get the ROF up around 825 or so with just the right buffer, and maintain reliability.

Of course, you can also shoot the hottest ammo you can find –– that'll speed it up.

A final note: I generally run mine at 685 rpm. That seems to be the sweet spot for my applications, and in addition, it can still be fired accurately (it will hold Minute of Target Car at shoots). The faster you push it, the more the target area opens up and thus accuracy goes out the window. In addition, the higher the ROF, the faster the upper heats up. Even when you bring multiple uppers (which I do recommend), a high ROF can hold you to a couple of mags before you start melting gas tubes. A slower ROF allows more shooting between either cooling-off periods, or melted gas tubes.

Hope this is of some help.

Normally shorter barrels run faster than longer ones (all else being equal) but that is not always the case. The primary drivers of ROF (in my opinion) is the gas port size, followed by recoil spring weight.

You can always tame down any given ROF by adding mass to the system (i.e. a heavier buffer) or by putting in a weaker spring like an AAC rate reducing spring.

To increase the ROF without monkeying with the gas port size you have two options.

A. Remove Mass from the system by going with a lighter buffer. Since you are already running a pretty light buffer your only remaining safe option is a standard H.

The upside to this option is it is cheap (like $30 bucks for an H buffer).
The downside is that you could end up with "bolt bounce" now that you have a lighter amount of reciprocal mass inside the buffer as an H buffer has two steel & 1 tungsten weight vs 1 steel and 2 tunsten in a H2.
Unfortunately there is no way to predict whether you will have a bolt bounce issue now or when you upper and BGC gets more broken in.

B. You could put in a stronger recoil spring to speed up the bolt return speed.
Once again the upside to try this is cheap ($30ish)
The downside is that you will need enough gas to compress the recoil spring and the only way to find out is to put a stronger spring and see if it works. If you dont have enough gas to compress the new extra power spring completely you will end up with a short stroke condition.

So for roughly $60 you could invest in an H buffer and a Sprinco enhanced (aka blue spring) or extra power (aka red spring) and experiment and see what happens to the ROF using one the other or both in conjunction.

If either of those options fail to produce the desired results or induce reliability issues, than you only option is to drill the gas port out until the desired ROF is acheived along with proper reliability. Obviously, there is going to be a point of diminishing returns where you are only going to be able to boost the ROF on a M16 to a certain level and maintain any sort of reliability. i.e. if you want MAC speed than you probably are going to need to by a MAC. However, anything between 650 and 900 is pretty safely acheivable if you go slow and don't do anything drastic.

If you need help I am in Central Texas as well and could help you out at one of the local ranges once your transfer is complete.

I have just about every "normal" buffer there is (Carbine, H, H2, H3, B, X), as well as Colt OEM M4 springs, both Sprinco springs (blue & red) and well as AAC reduced power springs, and have every gas port drill bit from wire size 55 to 35 if you want to drill it one wire size at a time.

Just shoot me an IM once your transfer comes through if you need or want help and we can figure out a time to meet.

James

Would using a 16 inch barrel with a carbine length gas system on a a2 lower with rifle stock and buffer make the gun run faster?

Shorter buffer, but also a shorter tube, so not a shorter stroke, Tony. Stroke length is exactly the same, and bounded by the carrier key and the inside of the upper receiver.

Shorties are faster because of less spring and less moving mass.

Shorter tube needs shorter spring, too, of course. I went and measured the stroke length of four full-stock and three telestock rifles, and they're all the same - about 3 3/4"