My weird build journey... becoming the "Theseus' Ship" of AR-10s

[FOGeologist]

Intro: I am Nick, "FOGeologist," a long-time complainer on gun forums about everything under the sun. Don't take anything I say too seriously.

I wanted a .308 AR for a long time, since I saw what accurate hammers they are. Never had an AR-15 that wasn't the "cat's meow," so I thought, "Wouldn't that be great in a larger caliber?"

Yes, you are shaking your head right now. But that was a long time (and a lot of ignorant suppositions) ago.

WHAT I DID: I am truly a SUCKER for a good bargain. When our friends at Palmetto State Armory came out in the early teens with their PA-10, I bought a Gen 1.

I was teaching then, and making 35% of a normal salary, so I scrimped and saved and bought parts to go on the stripped lower. I got a PA upper, acquired a take-off 16" bull-barrel from a DPMS that had been rebarreled, and bought parts to fit the gun - KAK 18.2 ounce double-ejector BCG, an ar-15 carbine-length 7" depth buffer tube, PA-10 3.8 ounce 2.53" buffer. And an 11", 27-coil spring (I believe it's a PA spring).

Full assembly was completed in 2016.

The gun was... hard to load - DPMS mags had to be slammed into the well. Fully-loaded mags weren't functional; you have to download one round from max to get them to function. Furthermore, the gun was hypersensitive to hot loads, showing primer cratering, ejector smearing. It could shoot anywhere between 2.5 MOA and under 1 MOA, but that DPMS barrel was NATO spec. I bought a new Faxon 18" Big Gunner in .308 in 2020 to try to tame the weight and pick up some FPS, along with an 8-pos adjustable gas block and the 15" gas tube for rifle-length gas performance. I just checked the port on the Faxon - I stuck a .093" drill bit into the hole and it barely clearances.

I have been showing high pressure signs on the case heads again - ejector smears, flattening, then popping primers. Ejection is extremely positive to 5 o'clock. I think I am under-buffered and undersprung, and am ordering a 5.4 ounce buffer and a Sprinco Orange spring in accordance with the gunsmith suggestions on this site. Accuracy was incredibly, horrifically bad, like 13" at 200 yards - with my handloads. I think it's possible a primer got stuck on the chamber face and the rounds were going into the chamber crooked - the first round would be 9" right of the group. I found it (and shards of other brass on the chamber face) at the end of my shooting session. Yes, I know how MF'n dimwitted that was.

Now I am thinking that I am going to dump that PSA lower and upper; there's an Aero M5 on AR15 Discounts at a bargain price. I will rebuild this gun until I get it right.

[shooterrex]

Welcome from KY.

I don't think the receivers are the problem. I have a rifle from PSA and a pistol I built off of  a PSA receiver set.

How tight did the barrel fit into the upper receiver?

You are on the right path on the recoil system.

[Armed Eye Doc]

Another question, are you sure your scope (I'm assuming here) is mounted tight?

[Windwalker]

Just built a second AR308 using a PSA receiver set and it shoots lights out just like my other PSA 308.

[shooterrex]

If the barrel isn't a snug fit in the upper receiver you can bed it with this.

[FOGeologist]

Both of my barrels were very tightly fit into the receiver. Torques met the spec; I’ve been using Guntec free-floated fore-ends on my rifles (yeah, I know you’re shaking your head right now, thinking of going a different way here shortly) and attaining the required torque with their godawful wrench is like being killed.

another note: velocities are off the chart high… like 2890 at starting loads with X-Terminator. 2990 at midpoint with strong signs of pressure: an 18” barrel should produce a couple hundred less FPS THAN A 24” test barrel.

I will rent a headspace gauge and remove my extractor and ejectors and HS this muther to ensure I don’t have a freak show of a bolt head or something.

[FOGeologist]

Scope is tight. It’s a nice VX Freedom 3 - 9 x 40 chosen as a balance between magnification and weight.

Mount is tight.

I was having weird problems with two scratches on the neck of the extracted cases; with the barrel off, the chamber is 1000% easier to inspect and clean. I think the barrel extension is a touch new and still not broken in. I will polish the feed ramps a touch to ensure the sharp edges are OK.

Yes, the PSA Gen 1 has M4 feed ramps as does the Faxon Big Gunner.

I did buy the Aero M5 upper and lower set yesterday. Should be coming in to my dealer early next week. I should be able to assemble and test end of next week.

 

[BrianK]

Welcome to the forum!

[Cunuckgaucho]

Welcome from BC

[98Z5V]

14 hours ago, FOGeologist said:

another note: velocities are off the chart high… like 2890 at starting loads with X-Terminator. 2990 at midpoint with strong signs of pressure: an 18” barrel should produce a couple hundred less FPS THAN A 24” test barrel.

What references are you using for your loads?

[MikedaddyH]

On 8/29/2022 at 7:31 PM, shooterrex said:

If the barrel isn't a snug fit in the upper receiver you can bed it with this.

Never seen this stuff before ! LOL 😂 

[FOGeologist]

Thanks for your responses.

Sprinco Orange came in… 28 coil. H3 buffer arrived as well; it’s 3.25” or thereabouts, far too long for the 7” tube. Maybe I could get a longer tube, but I think I’ll send it back in exchange for a 5.4 ounce 2.5” buffer instead.

I am using Western Powders guide for my 8lb jar of X-Terminator. I wish I had just bought Varget. Varget is what every smart person SHOULD be using for every centerfire big-bore rifle cartridge they reload. Hell, I used it to build a pin-accurate .223 load nearly 20 years back for a 52-grain Sierra Match King flat-base bullet that shoots a dream from the AR platform.

[jtallen83]

19 minutes ago, FOGeologist said:

Maybe I could get a longer tube, but I think I’ll send it back in exchange for a 5.4 ounce 2.5” buffer instead.

Something to think about, might not matter to you but a longer tube seems to provide a wider option of weight on buffers, you can just flat get more arse behind the carrier with it.

[FOGeologist]

Hmmmm.

I'm shopping right now... I can return the buffer to Primary Arms and buy a shorty 5.3 ounce... or I can buy a new tube.

I find it deeply weird that no manufacturer bothers to, I dunnow, MEASURE AND REPORT the length of their tubes.

You know, provide factizoids for us builder-types to ensure we buy components that match our needs. Why in 2022 does an internet  customer need to coach a partsmaker to break out a ruler and type in a couple lines of text in an online site?

Edited September 3, 2022 by FOGeologist

[jtallen83]

2 hours ago, FOGeologist said:

Primary Arms

I'm ordering an A5 style tube they have on sale right now, never heard of the brand but figured I would try them for the price. Light on detail, like you said about nobody using a ruler;

https://www.primaryarms.com/triarc-systems-a5-extended-receiver-extension

Edited September 4, 2022 by jtallen83
clarity

[Albroswift]

Rifle length... When you get it post back with the ruler!

[FOGeologist]

12 hours ago, Albroswift said:

Rifle length... When you get it post back with the ruler!

Hmmm, if I go rifle length, I’ll need to change stocks away from my feather-light MFT stock. Mission with this gun was to build something no heavier than an AR 15 rifle.

Plus, I’d need a rifle length buffer. I think I do have both components laying around, however.

[Magwa]

On 8/30/2022 at 10:21 PM, 98Z5V said:

What references are you using for your loads?

That is the info i seek as well what powder? what primer and how much powder are you crimping enough  to much? how old and what brass are you using how many times have they been fired? and what bullets and how much do they weigh.

[FOGeologist]

1 hour ago, Magwa said:

That is the info i seek as well what powder? what primer and how much powder are you crimping enough  to much? how old and what brass are you using how many times have they been fired? and what bullets and how much do they weigh.

Loading manual: Western Powders.

Powder: Ramshot X-Terminator. Cases: Lake City, various. Previously reloaded commercially. Once fired by me. Suspect primer crimps were over-reamed or pressed.

Bullets: Hornady FMJ-BT cannelure, 150 grain

Starting load: 40.8 grains and velocities are supposed to be 2723 fps on 24" test barrel (Actual average of 5 shots 2830 fps on 18" Faxon Big Gunner) NOTE: Awful accuracy and would not cycle action (Did not try to adjust gas)

Max was loaded to 45.3, and oddly got the best group of the day. 3 of five primers popped out. Group was still awful, like 8" at 200 yards. Worst pressure signs, tons of ejector smearing (meaning dwell time was a mess)! Should have stopped firing at 43.8 grains. Highest velocity I saw was 2933 fps.

With accuracy so poor I moved to Barnes 168 grain TTX SP bullets; starting loads (same powder) 38.3 grains, moving in .5 grain increments up the ladder to 42.6 grains. Accuracy a mess. Primer going crazy at 41.1 grains. Hell, I didn't even record velocities since the gun was barely shooting, and primers were popping, I couldn't load a magazine into the rifle because Palmetto State Armory's Gen 1 dimensions were just about useless.

When I cleaned the rifle, I found a primer that had hammered itself into the chamber face and was just pounded thin enough to allow the bolt to seat. I think that bastard had been in there from my previous range session where I couldn't see it, and had messed everything up with this range session. There was a host of other crap in there too.

[Armed Eye Doc]

16 hours ago, Albroswift said:

Rifle length

A5 should be the same as an Armalite AR10 carbine receiver extension.

4 hours ago, FOGeologist said:

MFT stock

This should work with an A5 tube.

[FOGeologist]

1 hour ago, Armed Eye Doc said:

A5 should be the same as an Armalite AR10 carbine receiver extension.

This should work with an A5 tube.

Hmm, making sense. I will hang with the 3.25 H3 Armalite buffer and replace the tube with Armalite 7-7/8” ( I think). Can I still use my Sprinco Orange or do I need the Armalite spring?

[98Z5V]

3 hours ago, FOGeologist said:

Powder: Ramshot X-Terminator. Cases: Lake City, various. Previously reloaded commercially. Once fired by me. Suspect primer crimps were over-reamed or pressed.

Bullets: Hornady FMJ-BT cannelure, 150 grain

Starting load: 40.8 grains and velocities are supposed to be 2723 fps on 24" test barrel (Actual average of 5 shots 2830 fps on 18" Faxon Big Gunner) NOTE: Awful accuracy and would not cycle action (Did not try to adjust gas)

Max was loaded to 45.3, and oddly got the best group of the day. 3 of five primers popped out. Group was still awful, like 8" at 200 yards. Worst pressure signs, tons of ejector smearing (meaning dwell time was a mess)! Should have stopped firing at 43.8 grains. Highest velocity I saw was 2933 fps.

With accuracy so poor I moved to Barnes 168 grain TTX SP bullets; starting loads (same powder) 38.3 grains, moving in .5 grain increments up the ladder to 42.6 grains. Accuracy a mess. Primer going crazy at 41.1 grains. Hell, I didn't even record velocities since the gun was barely shooting, and primers were popping, I couldn't load a magazine into the rifle because Palmetto State Armory's Gen 1 dimensions were just about useless.

When I cleaned the rifle, I found a primer that had hammered itself into the chamber face and was just pounded thin enough to allow the bolt to seat. I think that bastard had been in there from my previous range session where I couldn't see it, and had messed everything up with this range session. There was a host of other crap in there too.

X-Terminator is a fastass powder, generally used for varmint projectiles (light projectiles).  For .308 Win, 150gr projos, you're at the upper limit of projo weight for that powder.  It's no wonder it's not doing well.  You should probably move to a slower powder for better results. Or use a projo in the 120gr area if you keep using that powder. 

A 168 Barnes solid copper projo is WAY too much bullet for that powder. Look for powders in the RL-15 or Varget or Accurate 2495 (and 2520) range, for powder speeds.

Here's what X-Terminator is good at:

X-TERMINATOR is a double-base spherical powder designed for the high volume 223 varmint hunters who demands a clean burning, accurate powder. Excellent flow characteristics and small grain size allow trouble-free loading in small diameter case necks. It performs extremely well with light to medium weight bullets in the 223 Remington. It is also an excellent choice for 17 Remington, 20 caliber cartridges, 222 Remington and the 45-70 Government. Made in Belgium.

Edited September 4, 2022 by 98Z5V

[98Z5V]

14 minutes ago, FOGeologist said:

Hmm, making sense. I will hang with the 3.25 H3 Armalite buffer and replace the tube with Armalite 7-7/8” ( I think). Can I still use my Sprinco Orange or do I need the Armalite spring?

The Sprinco Orange spring is specifically developed for short 7.000" internal AR15 carbine extension, on a .308AR, using 2.500" buffers.  That's it's sole purpose.

Armalite AR_10 Carbine extension, VLTOR A5 extensions, and the MAgPul SR-25/M110 extension are all 7 5/8" internal depth, and will work with 3.250" buffers. 

Use the Armalite EA-1095 recoil spring, or the Sprinco Red spring, if you change to one of those extensions.

20 hours ago, FOGeologist said:

I find it deeply weird that no manufacturer bothers to, I dunnow, MEASURE AND REPORT the length of their tubes.

You know, provide factizoids for us builder-types to ensure we buy components that match our needs.

The good companies list those dimensions. 

[Magwa]

19 hours ago, FOGeologist said:

Loading manual: Western Powders.

Powder: Ramshot X-Terminator. Cases: Lake City, various. Previously reloaded commercially. Once fired by me. Suspect primer crimps were over-reamed or pressed.

Bullets: Hornady FMJ-BT cannelure, 150 grain

Starting load: 40.8 grains and velocities are supposed to be 2723 fps on 24" test barrel (Actual average of 5 shots 2830 fps on 18" Faxon Big Gunner) NOTE: Awful accuracy and would not cycle action (Did not try to adjust gas)

Max was loaded to 45.3, and oddly got the best group of the day. 3 of five primers popped out. Group was still awful, like 8" at 200 yards. Worst pressure signs, tons of ejector smearing (meaning dwell time was a mess)! Should have stopped firing at 43.8 grains. Highest velocity I saw was 2933 fps.

P>S> the Ramshot X-Terminator IMO is to fast a powder for 308 and 168 size bullets it might work with the smaller bullets 150 etc, but being a fast powder it builds pressure to fast with the big bullets IMO

With accuracy so poor I moved to Barnes 168 grain TTX SP bullets; starting loads (same powder) 38.3 grains, moving in .5 grain increments up the ladder to 42.6 grains. Accuracy a mess. Primer going crazy at 41.1 grains. Hell, I didn't even record velocities since the gun was barely shooting, and primers were popping, I couldn't load a magazine into the rifle because Palmetto State Armory's Gen 1 dimensions were just about useless.

When I cleaned the rifle, I found a primer that had hammered itself into the chamber face and was just pounded thin enough to allow the bolt to seat. I think that bastard had been in there from my previous range session where I couldn't see it, and had messed everything up with this range session. There was a host of other crap in there too.

Well popping primers is a big stop sign BUT if the brass was primer crimped when new and you or someone else reamed it to big then it is hard to tell but the accuracy is whacked, I would recommend new brass and only use 20 of them for testing  save they other 80 till you have a load that works, as for the function of the gun others here know way more about that than I ever will and will help you get that figured out . I would stick with the 168 range of bullet but I would not shoot the barnes till you have a good load they are to costly  get some Hornady  165 ELD match bullets they are awesome and much cheaper... try some IMR 4064 and check your crown on that barrel. 10% below max and just get it cycling don't try max charges till you get the gun working properly then you can take good brass and do a ladder test with your choice of powders to find a good node to work from for accuracy... consistent crimping will produce consistent pressure. I think loading for semi auto's is harder than bolt guns... And take heed of what 98 said that Ramshot X-Terminator is to fast a powder for that 168 size bullet  big pressure with that fast stuff ....

Edited September 5, 2022 by Magwa

[FOGeologist]

I am getting loads of great advice in this thread. Thanks for your help!