Asking for a friend: .308 Aero Precision M5 Build, Axem 18" barrel...

[StarWolf]

As the title says, I'm asking for a friend and as such I'm afraid I don't have pictures and I'm still trying to get some exact info from him...

1) NOT an Armalite AR10 Recoil System
He has a .308 JP Precision (JPSCS2-10 I think) captured spring assembly that claims to be designed to work in standard 7" M16/M4 length buffer extension tubes used on DPMS LR-308.
https://www.jprifles.com/buy.php?item=JPSCS2-10

2) 5 oz for the JP Precision captured system according to the link above.
    2a) He has also tried a Expo '.308 Heavy' carbine buffer' that claims to be 5.3 oz that weighed in at 5.1 oz on my baker's scale.
    2b) He has also tried a Aero Precision .308 buffer that weighs 3.8 oz. (verified on my baker's scale.

3) The JP Precision captured system claims to be compatible with the 7" buffer tube.
     2a) Sample measured 2.502" for the Expo 5.1 oz .308 carbine buffer. (I've seen these +/- ~.015" maybe)
     2b) UNKNOWN but the Aero .308 carbine buffer came in close to 2.5".

4) AR-15 mil spec buffer tube internal length just shy of 7". (~6.95")

5) Whatever JP Precision uses in their 'standard' .308 system?
     5a) He has also tried a Sprinco Orange .308 Heavy Carbine spring.
     5b) He has also tried an Aero Precision .308 gold colored spring. (It's a bit longer than the Sprinco but a lighter spring rate. (I don't have the number of coils or wire diameter etc..)

6 & 7 & 8.) Gas system length AR-15/DPMS .308 rifle length.
I don't have an exact measurement of the gas tube length that he is using or a photo down the mag well.
He has assured me that the gas tube is in the exact center of the M5 cam pin cutout looking down the magwell.

9) No photo of the bolt face but it is an Aero Precision .308 bolt carrier group. I think it is NiB finish.

10) No photo available.

11) Gas Journal Dia = .75"
      UNKNOWN Gas Port DIA.
     Another barrel identical to the one he is using allowed a .089" drill shaft that measured .088" to pass through the port into the barrel. It would NOT allow a drill marked .093" to pass through the port.
(I have read in other threads that the gas port for this 18" length barrel with a .75" gas journal and a rifle length gas should be .095" minimum.)

ADDITIONAL DETAILS:
18" Axem barrel (LOOKS like a Ballistic Advantage except for the manufacturer listed.) Nitride finish
      Barrel is marked '.308 WIN 1/10 4150 CroMoV' about mid length. There appears to be a proof mark over the chamber that looks like a half circle with a dot next to and centered on a short line.
Aero Precision M5 receivers, Aero handguard, Aero BCG, Using one of the MagPul lightweight PRS stock.

The rifle appears to be failing to extract and failing to load a second round after being touched off.

[shooterrex]

The short heavy buffer w/the springco orange spring. Open the gas port up a few thousandths.

The "silent recoil system" doesn't seem to work well for most folks in the large frame guns.

[StarWolf]

Well, as it turns out he's not been able to make it run with parts swapping.
He mentions that the barrel nut was slightly misaligned and he 'buffed' the gas tube to get it together. So the gas tube is probably slightly misaligned as well as the tip being malformed.
I wish he'd mentioned the misalignment. I'd have tweaked it for him. I offered to realign it but he plans to swap the handguard to one with a different style barrel nut that has more alignment options and reassemble with a new gas tube. He didn't want to deal with the current one any more. I gave him the orange spring and heavy buffer just in case as I won't be local to help him on it. He'll need a few more tools to do the barrel installation.

Edited May 2, 2023 by StarWolf

[98Z5V]

What malfunctions is he having - the friend?  I'm leaning toward the barrel, and the gas port diameter.  But I don't know what the malfunctions are.  All other parts look okay, to make a functional gun.

On 4/28/2023 at 10:58 PM, StarWolf said:

11) Gas Journal Dia = .75"
      UNKNOWN Gas Port DIA.
     Another barrel identical to the one he is using allowed a .089" drill shaft that measured .088" to pass through the port into the barrel. It would NOT allow a drill marked .093" to pass through the port.
(I have read in other threads that the gas port for this 18" length barrel with a .75" gas journal and a rifle length gas should be .095" minimum.)

THIS is the only issue this gun has, right now, on paper and written word.  Punch that gas port up.  Report results back. 

Fancy complicated guns with fancy complicated parts - like his fancy complicated recoil system - sometimes require a little "extra love" - so he might be punching that gas port up to about 0.098"

Bottom line - You Don't Complicate Shiit with Complicated Shiit. You make a running gun, first - simple operational parts that work - and then add your Complicated Shiit, based on gun performance, and evaluate it it one piece at a time, and see how your gun reacts.  Make adjustments off that information. 

Edited May 2, 2023 by 98Z5V

[98Z5V]

Race Gun Parts  - like that recoil system - belong in Race Guns, that you make money from, in Professional Competitions, and those Race Gun Parts are all tailored to your load, that you're shooting for whatever "Power Factor" that you're trying to meet for that competition, to win Prize Money.

Race Gun Parts don't belong in operational guns - that you want, or need, those guns to eat a variety of ammo, on any given day, in any given circumstance or weather condition... 

My $0.02 on Race Gun Parts. 

Don't Complicate Shiit with Complicated Shiit.  You'll be better off, in the long run.

Edited May 2, 2023 by 98Z5V

[StarWolf]

Two potential issues on paper... gas tube/barrel nut/gas key alignment and gas port size.

The OTHER problem is that he just mentioned to me yesterday is that the gas tube port in the barrel nut was just slightly misaligned. In his excitement to get it finished, instead of fixing the alignment he buffed the end of the gas tube to fit through the misaligned hole. So the end of the gas tube is buffed smaller AND the tube is probably flexed a little bearing on the nut and/or the upper receiver. That means it probably doesn't align too well with the gas key. For the first time yesterday he mentioned that the action was catching as he attempted to draw the bolt back with the charging handle and that the bolt would close when he pulled it back and let it go but that if he eased it down it might stand off on the gas key.

With respect to the race gun parts...
I can only suggest the parts to him before he goes out and buys the 'mall ninja tacticool' stuff or gets AR-15 parts instead of the .308 specific bits he needs. I gave him a spreadsheet of the suggested parts.

IF I were him:
I'd fix the barrel nut alignment.
I'd replace the gas tube with one that was unmolested and verify he hasn't screwed up the gas key by dropping it on a misaligned gas tube.

THEN if necessary I'd step up the gas port with the orange spring and heavy buffer in place until it balanced out and worked. Part of the reason I gave him the spring and buffer is I feel a little guilty since he started this path and I'm going to be out of area before he finishes it.

I've offered to do the first two items but he wants to trade the handguard and figures he's not in a hurry to get it working now and might as well do the gas tube and alignment when he does the new barrel nut/handguard. I might even buy the old handguard from him but I don't need more crap to move halfway across the country.

Edited May 3, 2023 by StarWolf

[98Z5V]

9 minutes ago, StarWolf said:

That means it probably doesn't align too well with the gas key.

If that's the case, then it's an AR15 gas tube in a .308AR gun.  AR15s have a lower height over bore, and not the proper height over bore that these Large Frames need.  IF the gas tube is the proper length, but it's AR15 bend, then the only solution is get ahold of White Oak Armament and get a custom gas tube with the proper bend.  IF the gas tube is too short, then the answer is easy  - get an Armalite AR-10 gas tube.

[98Z5V]

21 hours ago, 98Z5V said:

Another barrel identical to the one he is using allowed a .089" drill shaft that measured .088" to pass through the port into the barrel. It would NOT allow a drill marked .093" to pass through the port.

^^^  From what you stated, and I quoted.  Looks like it's coming from me, but it's not.

21 hours ago, 98Z5V said:

THIS is the only issue this gun has, right now, on paper and written word.  Punch that gas port up.  Report results back. 

^^^  My estimation.  Fix that first.  Very first.  If it's never fixed - then the gun isn't gonna work, no matter what you do to it. 

[StarWolf]

I'll reiterate to him.
Hopefully he'll let me know how it goes.
I'll be about 4.5 states away by then.