First post on here, and didn't see any topics covering my question, so here it is:

I purchased an Aero Precision M5E builders kit a few months back (gray and white tiger stripe). Was going to make your bland .308, then stumbled upon the 6.5 Creedmoor and decided to make that.

So far I have:
Upper
Lower
Gisselle 2 Stage Trigger and Lpk
Mil Spec Buffer Tube
JP enhanced 308 buffer spring
JP 308 buffer

What I need:
Barrel
BCG
Gas Block

I have read some posts about conflicting barrels/bcg so I would like some advise on comparable parts.

Mostly looking to do some target shooting and perhaps some big game hunting with it.

Thanks for the help in advance.

If you want to stay on a budget look at Ballistic Advantage. If you can spend the money look at JP or Lilja.

For this cartridge, I would have a reputable smith cut my barrel for me to my specs, with a matched bolt to go with it, or buy one from a company as a set that has been doing this already for a while.

First one that comes to mind is JP Enterprises with a 6.5 CM barrel/High Pressure bolt combo and the Extended Length Gas System.

RLGS is on the short side unless you shoot 107gr SMK and 120gr AMAX, or 123gr.

As you increase projectile weight and reduce burn rate, you hit the port harder than the AR10 gas system was meant to be pressured up with, causing timing issues with the extraction and unlocking cycles, with a pretty violent cyclic rate.

You can put a band-aid or 2 on the gun in advance for the boo-boos you are about to inflict, like adjustable gas and heavier buffers, but that isn't treating the disease, just the symptoms, while adding more symptoms that shouldn't be there on a healthy patient.

Examples include:

1.  Choking the gas port restricts flow, causing exaggerated wear of the gas port, leading to faster port erosion.

2. Increasing the buffer weight to act as a rate reducer now adds that much more mass to an already massive BCG/buffer set, slamming into your breech and barrel extension.  The bolt impacts the chamber first, then rotates, followed by the impact of the bolt carrier against the barrel extension, sending significant resonant shock waves through the gun and into your optics.  It also smashes bolt catches like an abusive father smashes dishes on last round hold-open, leading to early failure of the catch.

You see that a lot on AR10s, SR25s, and some of the really high end AR10-type rifles on the market just with the normal buffer weight and a tamed RLGS.  If you try to address it by making the bolt catch out of unobtanius dens est draco, now the bottom lugs of the bolt face get peened.  We've seen that on the DPMS GII already when used with PMAGs without the modification of the follower to allow full erection for proper engagement of the catch.

Looking at the AR10 dynamically, there are several narrow windows that have to have moving parts placed within optimal movement inside them in order to:

* allow positive extraction, without excessive carrier inertia and sheer forces on the bolt
* allow enough carrier travel to activate the bolt catch across a wide range of ambient temperatures
* reduce the forward stroke velocity so parts don't get damaged/gun doesn't beat itself and accessories to pieces

These windows seem to demand a pound of flesh from what makes optimum conditions in the other window possible.

Settling on one load with one bullet weight/shape/construction will really help you open up a little with each of the constraints.

I bought a complete 6.5CM upper from Aero (22" barrel made by Ballistic Advantage). Wanted to let you know that I did have FTE issues at first. Turns out the gas port was undersized. AP got it fixed for me no problem, but apparently its a current QC issue for them that they are still resolving. Just FYI. I would still recommend BA overall for a budget barrel though.

Once they got it all fixed up though its been shooting like a dream. .8" groups at 100 yds so far.

I used a prime weaponry nitrided BCG. No issues at all so far once the gas port got sorted out.