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"Ship of Theseus" beginning build


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Built .308 AR from Gen 1 PSA gun in 2016. Gun ran, but did not run well. Some changes were made... gun worse than previous. See thread "Ship of Theseus" thread previously made from late August 2022.

Rebuilding now with different receiver, this time with knowledge gleaned from this site. Will make one post per decision/action per day taken.

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My Waterboard data:

1. PSA Gen 1 upper and lower. Can't stuff full PMAGS into receiver at all. Have to download 1 round. Even partial mags have to be aggressively slapped into the mag well; been like this since Day One. Suspect bought incorrect bolt stop?

2. Dumping PSA Gen 1 receiver set for Aero Precision M5 2 Sep 22. Set should be here late this week.

3. New barrel: Faxon Big Gunner, 18", rifle length gas. Stock port is 0.093" which is normal, according to Faxon. Mine was clogged like a sonofagun with debris of every kind: carbonaceous powder residue, pieces of gook, parts of old shoes, a piece of a Tennessee license plate, and a Democrat voter registration card of a person who died in 1869. Clear now. Note: Positive ejection was never a problem - it was far too hard, timed at 5 o'clock, and flying 25' away like it was an H&K 91/G3. Will leave muzzle device off rifle until function checks are complete.

4. Gas system: Adjustable gas block with 8 clicks from almost completely blocked to "fully semi-automatic" (LOL), or as you Normies might say, "fully open." 15" gas tube, flowing freely. Tube is inserted 3/8" into gas key on KAK BCG. May have to think about a longer tube. Method of testing will be: Fire commercial ammo with adjustable gas block fully closed, then open it a click, fire rounds, and keep doing this until the weapon ejects properly every time.

5. BCG: KAK heavy duty with dual ejectors. These love to smear case-heads when handling high pressure loads. Do far less damage when load is in spec.

6. Tube and Buffer: Currently running 7" deep, no name mil-spec with 3.8 ounce PA-10 buffer. Tube is not perfectly run in to the end of the ring, but no evidence of impact of BCG to the ears on the threads or anything; changing to Spike's Tactical SLAX-500 7-7/8" buffer tube with either Sprinco Red or Armalite spring, whichever I can get a hold of, and a 5.7 ounce, 3.25" Armalite H3 buffer, which is in my possession.

7. Handguard is a Guntec Keymod special from six years back. Please don't bust my balls over it. Have torqued to 40 lbs-ft using their nearly useless wrench.

8. Powder loaded was X-Terminator. Turns out it's really suited for small caliber stuff, and works the treat in the 3 AR-15s I have. Not viable for 150-grain and up projos in a 30-cal bore. Results prove it - velocities 200 fps higher than a much longer barrel should produce, primers popping all over the place, and case-head smears. Will load up trial load with 165 grain Hornadys on Varget or some other better-suited powder.

9. Rifle has been completely disassembled down to component systems, and will be carefully rebuilt and test-fired using commercially-loaded ammo to initially set operating pressures, and for function and zeroing purposes. All components should be here for final assembly within two weeks, and initial testing should occur by 21 September. Looking for low pressure signs, function, accuracy, reliability.

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Tempting me: Aero Precision Stainless Steel Gas Tube - Rifle Length. It is 15 1/8" long, which would put the gas tube a full 1/2" into the carrier key, as opposed to 3/8".

JUST CHECKED: my gas tube is 15 1/8" already. So this is a no-go.

Does anybody make a 15 1/4" tube? Is it advisable to use something like that if it can be gotten a hold of?

Edited by FOGeologist
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17 minutes ago, FOGeologist said:

Tempting me: Aero Precision Stainless Steel Gas Tube - Rifle Length. It is 15 1/8" long, which would put the gas tube a full 1/2" into the carrier key, as opposed to 3/8".

JUST CHECKED: my gas tube is 15 1/8" already. So this is a no-go.

Does anybody make a 15 1/4" tube? Is it advisable to use something like that if it can be gotten a hold of?

There are sources for this 15 1/4" tube. Don't know if it's worth $15 to fix a problem I am unsure I'm having. Will wait until function test to see if this will be necessary.

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39 minutes ago, shooterrex said:

#4 start w/gas block all the way open and load 1 round in the magazine at a time. Shut down gas block a bit at a time till gun doesn't lock back on the empty magazine. Then open back up just a bit. Don't worry about where it throws the brass. Worry about if the gun runs or not.

This makes sense. It gives you a "lockback" indication which is a function test in itself.

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OK, update time.

Annnnd, it’s complicated. 🙄

I will probably be returning my Spikes Tactical buffer tube when it gets here. It’s too deep, and I was going to replace it with a VLTOR product…

Then I measured my existing 7” tube and discovered it was 1.17”, which is apparently Commercial. All VLTOR tubes seem to be mil-spec, and my Battlefield Minimalist Stock is a Commercial stock as well, and I’m looking around at receiver extensions trying to find a 7 5/8” to go with my new 3.25” H3 Armalite and…

It’s tough. Alternative: sell BMS stock and tube, return all purchased components and buy a kit from somebody.

I could also just go to a standard A2 setup, but the original concept was “under 9 lb 308 AR with scope.”

I guess I could also just replace my 3.8 ounce 2.53” buffer with a 5.4 ounce Expo Arms 2.5” buffer, return my Armalite 3.25” H3 5.4 ounce buffer, and stay with my 7” system and use the Sprinco Orange. That would save me some dough. 

Edited by FOGeologist
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1 hour ago, FOGeologist said:

trying to find a 7 5/8” to go with my new 3.25” H3 Armalite and…

Just got a brand I hadn't seen before from Primary Arms, a tad deep. I haven't turned it into a receiver yet so can't comment on fit but finish looks good. It's mil spec size for the stock.



pretty pictures here;


Edited by jtallen83
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New wrinkle: Two take-off parts from the small-frame PSA gun aren't able to work out on the M5 chassis: The main pins are the same diameter, but need to be longer as the front ears and rear pin area are thicker on the M5 than the PSA AR-15-width PA-10, and the bolt catch for the .308 is different than the AR-15 size.

Everything else seems to have migrated over without concern.

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So, a changing philosophy of use means changing approaches.

Forget carbine-lengths, weird buffer sizes, adjustable stocks - going rifle length. Fixed stock. Getting missing components and sticking with the Guntec rail for now.

The light-weight aspect of this build I am casting aside; any real use of a 30-caliber semi-auto rifle will be a SAPR or DMR role, not something you will haul around. Gonna get it running well, put on a bipod, and use it for precision work. Target weight: Under 12 lbs with unloaded mag.

Ordered an Aero Precision fixed A2 length buffer tube, spring, and rifle buffer, an Aero set of takedown and pivot pins, a Hogue Overmolded fixed rifle stock, and an Aero Precision 308 Bolt Catch.

Transferring lower parts as we type here.

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In today: rifle buffer tube, spring, buffer, front pivot pin.

Still awaiting Midway delivery of buffer tube retainer and spring that flew into the ether and vanished into one of the other 11 dimensions WHEN I was disassembling it.

Coming soon: rear takedown pin, Hogue overmolded fixed rifle stock in FDE. .001" stainless metal foil for bedding (Faxon Big Gunner is sloppy in new Aero receiver).

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Optics Planet has shipped my gear in two separate batches; the pivot pin and Aero Precision rifle-length buffer tube kit has arrived and has been installed into the new lower receiver I like that the pivot pin has a divot in the middle so your pushing tool doesn't scratch the pin, run off, and scratch the lower. Not that this could ever happen to a mega-expert like me. :laffs:

The other shipment with the bolt-catch and stock and takedown pin is arriving today.

After that stuff gets put in,  I'll take the bolt apart in preparation for the headspace gauges, then I'll foil the barrel extension and thermofit the barrel into the upper.

At that point, all should be good to go.

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