"Ship of Theseus" beginning build

[FOGeologist]

Update: All components save the headspace gauges are in.

Receiver set from three weeks back when I got it.

Shims (choice of three: 0.001, 0.0015, and 0.002) and proper, 15.5" length rifle gas tube from Armalite, compared to my (take off) AR-15 rifle gas tube at 15.125".

I started the shim with the 0.001" stainless sheet; these came pre-cut at 1" and work for covering an extension; you have to cut an inch off the sheet or so to give you a long-enough piece to wrap around the extension without touching the other side (leave a gap of a few millimeters). I cleaned the extension and the notched sheet with brake cleaner and placed an extremely thin schmear of contact cement on the extension and the back of the sheet with a Q-tip to hold that springy little sucker in place until the extension is seated in the upper.

The gap is located on the side of the extension to avoid any weird up/down motion.

Once applied, the shim created an interference fit with the extension that prevented me from sliding the receiver into the extension. Because I knew I had that kind of resistance, I knew that a thermo-fit would work well to get a tight fit between the two.

Per the JP Rifles video, I heated the threaded part of the receiver, turning it in my hands with it in the flame for six turns. My first attempt was unsuccessful because I was clumsy and rushing it, and had trouble holding the threads accurately in the flame front. When I tried to insert the receiver onto the extension, it went on halfway and got stuck. I applied a little heat and it came off.

I did it again, taking my time and heating the threads, doing a full six turns, and it slid right over the extension. It is impossible to rock the barrel in the receiver in any way, or to pull it loose.

So it looks like "mission accomplished."

I probably should have waited until the headspace gauge was delivered as these guns are a little easier to headspace when the barrel is out of the receiver.

[jtallen83]

I use liquid shim, lazy but it worked so far. 

[FOGeologist]

9 minutes ago, jtallen83 said:

I use liquid shim, lazy but it worked so far. 

You should consider it on your next build if you have some slop (like I did). It is wicked easy to do.

[jtallen83]

Not as easy as the Loctite.... 509...609....? I forget the number. I've never seen any slop after the barrel nut is tight, most likely don't really need the loctite but it calms my ocd.

[FOGeologist]

Update: I am still waiting on my headspace gauge from 4D Reamer Rentals, which was ordered and paid for on 09/05. So the guy is renting gauges that he doesn't have, nice.

I should buy a set and rent them to guys on here.

[DustBuster]

Cancel your order, buy a No-go and make yourself a go sized brass.  Make a comparator with a .4 inch shoulder hole to achieve this and other brass measurements.  I rented the gauges before but I never had to wait as long as u did.

[Whiskeyfish]

All in all, good read.

[FOGeologist]

Story's not done yet. Been waiting for my gauges... the guy told me they still aren't available and I canceled the order. I've put a couple hundred rounds through that barrel before I disassembled it and hadn't blown up yet, and my fired cases don't seem to need much, if any, resize, so the chamber can't be all that big.

So tonight I'm going to re-assemble, and maybe head out to the range tomorrow to see if I can get the rifle operational with some factory 180-grain Federal, you know, tune the gas block, check ejection patterns, that sort of affair.

[FOGeologist]

Milestone!

Ready to assemble

Done.

Not attaching muzzle device for initial firings. Removed (probably Chinese fakes) Magpul BUIS; the DPMS High profile of the M5 upper doesn't match the Guntech KeyMod poopy-pants handguard. I'll have to buy some kind of handguard that has a matching profile.

Draw of the action is clearly tougher with the longer rifle based spring; It's an Aero spring, and I may replace it with a Sprinco Red if I have any functioning weirdness.

Been watching the Johnny's Reloading Bench YouTube videos as he made a .308 AR in April 2019; BOY did he go on an adventure! He did eventually end up with a super-accurate AR 308, but had to go Krieger to get it to happen.

I might go and shoot this thing tomorrow to see if I can get it to do anything right.

[98Z5V]

6 minutes ago, FOGeologist said:

the DPMS High profile of the M5 upper doesn't match the Guntech KeyMod poopy-pants handguard. I'll have to buy some kind of handguard that has a matching profile.

GunTech has never made a high-profile handguard.  Ever.  Only Low-profile. GunTech clearly states what their .308AR profiles are. They are all listed as Low.

[DustBuster]

Good careful acquisition of parts, mix and match and eventually you’ll get to the finish product that you like.  Sounds like muzzle device and handgaurd are the last two to either keep or upgrade.  I have two Guntec handgaurds now, a 12” and a 15”, and I think they are fairly good quality and light, but the screws suck pretty much.  After several disassembles they are pretty much shot.  May even twist off after tightening hard once.  I may have to someday try a rifle length stock instead of my carbine collapsible magpul.  I think several guys here prefer them, it seems.

I take it Theseus built himself a ship of a hodge podge of parts and floated into the seas to slay the sea monsters? 

[308USK]

7 hours ago, FOGeologist said:

Milestone!

Ready to assemble

Done.

Not attaching muzzle device for initial firings. Removed (probably Chinese fakes) Magpul BUIS; the DPMS High profile of the M5 upper doesn't match the Guntech KeyMod poopy-pants handguard. I'll have to buy some kind of handguard that has a matching profile.

Draw of the action is clearly tougher with the longer rifle based spring; It's an Aero spring, and I may replace it with a Sprinco Red if I have any functioning weirdness.

Been watching the Johnny's Reloading Bench YouTube videos as he made a .308 AR in April 2019; BOY did he go on an adventure! He did eventually end up with a super-accurate AR 308, but had to go Krieger to get it to happen.

I might go and shoot this thing tomorrow to see if I can get it to do anything right.

If you are running an adjustable gas block, remember to open it up WIDE OPEN for the first round of shooting.  Also remember to run the gun wet...so as to allow proper seating/wearing in. :)

Aero Atlas R-One or S-One are high-profile, if that helps.

[FOGeologist]

6 hours ago, DustBuster said:

Snip

I take it Theseus built himself a ship of a hodge podge of parts and floated into the seas to slay the sea monsters? 

“Ship of Theseus” is a lesson in philosophy - “When does something lose its original nature?”

It was said that Theseus’ ship, after many long years lying in display after his famous journey, had to have a great many parts replaced due to aging. At some point the docents replaced so many parts that no one for certain could state what part of Theseus' ship was original.

So what remained, his real ship or a replica?

I suspect it was an allegorical thought exercise by the ancient Greeks - some sort of kernel for an argument.

Because, as we know, Greeks are fond of arguing. 😏

[FOGeologist]

20 hours ago, 98Z5V said:

GunTech has never made a high-profile handguard.  Ever.  Only Low-profile. GunTech clearly states what their .308AR profiles are. They are all listed as Low.

You know that this was the handguard on the original DPMS low-PSA receiver I had, right? That was appropriate for the old setup. 
 

I’ll pick up a corresponding high handguard here in a bit.

[DustBuster]

It’s a perfect name for this thread then; these rifles can be just like Ships of Theseus no doubt.  It is fun to change em up with different parts, with a smidgen of the original somewhere beneath the surface.

Edited October 7, 2022 by DustBuster

[mcconnell]

You can also check with justrails.com.  They also carry the high profile rail.

[FOGeologist]

Range Report: “Ship of Theseus” Aero Precision M5 Build

On 6 October, I took my rifle to Baker’s Draw Shooting Area in the Pawnee Grasslands. The rifle range there is only 100 yards, which, for my purposes, was just fine.

My goal was to take my newly-reconstituted now-rifle (was a carbine previously) and make sure my changes (new upper and lower, revised buffer, tube, spring, stock, gas tube, and bolt stop) were working appropriately, and to tune my PSA adjustable gas block to the new system.

My plan was to bring a box of Federal Fusion 150 grain hunting ammo and a box of Federal 180 grain hunting ammo to the field to check for function. My old setup had been smearing brass on the ejectors and tearing up rims, due to improper timing. I had used a short gas tube, an inappropriate spring, and far too light a buffer. The rifle was trying to extract the cases early from the chamber before the pressures diminished and the brass had an opportunity to shrink.

I drove an hour north to this wilderness range, and set up my target at the 50 yard line for initial shots - changing receivers and remounting my Leupold Freedom 3 - 9 x 40 scope concerned me enough to check initial shooting at a close distance.

My zeroing regime is to aim at center point of the largest clean target, fire one round, then re-aim the rifle at the same exact aiming point. Without moving the rifle, I then adjust the windage and elevation until the crosshairs are directly centered over the bullet hole. This means the scope is now aligned at point of impact. At that point I can move the target to 100 yards and I should be centered up, and perhaps an inch low. Adjustments are minor from there.

I started with the 150 grain Fusion and an open gas block, dialing inward on the 7/64th set screw one turn per shot, looking for “failure to lock back” on an empty mag (one shot in the mag). Goal here is to tune the rifle to use the amount of gas required to operate the action, without a lot of recoil slamming the rifle and operator.

“Completely Open” on that adjustable gas block is 5 turns +1 click (the system’s click adjustment is 5 clicks per full turn). To find the correct operating gas amount, I dialed in one full turn for each of the first five shots, until the rifle couldn’t lock back the bolt, then I’d turn backwards 3 clicks, then I’d try again. The “function point” is 1 turns + 1 clicks out from “Fully Closed.”

From there, I had not one, any, NO failures to feed, function, or eject. No brass damage, no blown primers, no cratering, no hammered case heads, no cartridges being ejected into the next county (like shooting an HK91). This was all due to YOU GUYS and your excellent recommendations.

Accuracy on the 150 grain Federal Fusion wasn’t anything to write home about. Best group was about 2.5". Most were near to four inches. I was careful about my shooting, taking some time to cool the barrel between shots and groups, and winds weren’t too severe - about 6 mph, and 100% from the rear.

After knocking out 4 x 5-round groups, I switched to the 180 grain ammo… and was rewarded with markedly better performance. I fired four groups of five and averaged around 2” per group. I think it’s possible to get this rifle down to about 1.3 MOA, with an occasional lucky group below an inch, if I am careful about my handloads.

Future Plans: I’ll probably buy a Krieger barrel with their version of an M110 profile in 20”; this could probably shoot a bit under 1 MOA with 168 to 175 grain bullets. I have already bought some bullets in those sizes and some AA2520 to build some loads in this range, which always seems to have an accuracy node between 165 grains and 200 grains for this caliber. I also have Varget, and will do some work ups based on both. I just want to see if the Faxon can make use of the extra effort of handloads. I'll drag out my chrono, too, to determine if I'm doing anything well in my reloading den.

I will probably lose the Leupold VX Freedom as it’s magnification is a touch low at 9x. I will probably replace it with an Athlon or an Arken, which has better magnification and a more functional build. Yes, this will bring the weight up substantially, but 300 yard sightings should be less difficult.

Weight has gone up in this rifle to 9.6 lbs, an increase of 0.8 lbs. My goal is to keep the rifle below 12 lbs with the new sighting gear and a better front handguard.

[shooterrex]

Soft points tend to deform on the feed ramps. That will open your group up a bit.

Glad your rifle is functioning well

[FOGeologist]

Update: In another thread I described how I found out my PSA adjustable gas block was hitting the inside of my too-narrow Guntec free-float handguard. I sawed off the top 3" of the handguard around the gas block and now the barrel flexes without striking anything.

Took the rifle out to Liberty Firearms Institute's indoor 100 yard rifle range and shot a box of Federal Power- Shock 180 grain, and a box of Federal Gold Medal 168 grain Sierra Matchking out of it. Here's the result. I did have to open the gas block up another 6 clicks to get the gun to run consistently. Curious.

Results from the Power Shock 180 grain; I shot 4 x 5-round groups, achieving a 2.188 MOA average.

Then, I shot a 5 x 4 round group, averaging 1.526 MOA:

So, not so great, especially for a rifle shot indoors.

Possible issues: set up took a while, and I was on the clock... the Range Officer was bearing down on me and forced me to wear safety glasses, and I could not see the crosshairs very well on this low-power (9x) scope indoors. I felt rushed and was banging out the last two groups in short time. The barrel was too hot to touch all the way through the shooting session. For a skinny barrel like a Faxon Big Gunner, with no wind (inside shooting) there was little chance to cool the barrel.

It might be impossible to get better groups than this with this rifle in this configuration. I probably need a 14x or better scope. I probably should dump the barrel and get something more rigid, and get a better handguard that I can torque effectively without worrying about timing issues; this barrel is probably right at 30 foot-lbs and may not be lashed down tightly enough to prevent whip.

[98Z5V]

33 minutes ago, FOGeologist said:

Took the rifle out to Liberty Firearms Institute's indoor 100 yard rifle range

 

33 minutes ago, FOGeologist said:

It might be impossible to get better groups than this with this rifle in this configuration. I probably need a 14x or better scope. I probably should dump the barrel and get something more rigid, and get a better handguard that I can torque effectively without worrying about timing issues; this barrel is probably right at 30 foot-lbs and may not be lashed down tightly enough to prevent whip.

I don't know what it is that's going on, but you were shooting at 100 yards, so a 9x scope's performance isn't bad.  Moving to a 14x scope isn't going to improve the performance, at 100 yards.  "Barrel whip" on a Faxon Big Gunner barrel isn't the problem, either.

If you wanna dump the barrel, I'll buy it.  I'll build a whole gun around it, and prove that barrel whip isn't the problem going on here with the groups. How many rounds do you have through the barrel now?  I'll take it off your hands, and build another gun from it.

[jtallen83]

7 hours ago, FOGeologist said:

this barrel is probably right at 30 foot-lbs and may not be lashed down tightly enough to prevent whip.

That's not gonna prevent whip, maybe change the harmonics. I've read articles that did testing with different torque values on muzzle devices and they saw issues with higher values not being as consistent.  I would bump that up past 35 for sure, I've never ran one that low.

[FOGeologist]

11 hours ago, 98Z5V said:

 

I don't know what it is that's going on, but you were shooting at 100 yards, so a 9x scope's performance isn't bad.  Moving to a 14x scope isn't going to improve the performance, at 100 yards.  "Barrel whip" on a Faxon Big Gunner barrel isn't the problem, either.

If you wanna dump the barrel, I'll buy it.  I'll build a whole gun around it, and prove that barrel whip isn't the problem going on here with the groups. How many rounds do you have through the barrel now?  I'll take it off your hands, and build another gun from it.

I think the relatively dark range and kooky optics of a pair of $7 shooting glasses they forced me to wear conspired to make the target hella-blurry. Plus the rushed feeling I was getting was not helpful to get me an opportunity to settle down, shoot effectively and take breaks to allow the barrel to cool was not helpful, either.

Barrel has about 160 rounds through it.

Clearly the brass shows much less damage from the feed ramp than the last shooting session, where the rifle was shooting better. No extraction or other issues after I brought the adjustable plug out 6 clicks from its previous location, seemingly a large adjustment, IMO.

I'll develop some loads for the rifle to see if I can wear it in a bit better, but I'm thinking a 1.6 MOA barrel with FGMM may be about as good as it is going to get in the first place.

[FOGeologist]

4 hours ago, jtallen83 said:

That's not gonna prevent whip, maybe change the harmonics. I've read articles that did testing with different torque values on muzzle devices and they saw issues with higher values not being as consistent.  I would bump that up past 35 for sure, I've never ran one that low.

I've heard of that research that someone did - I'll probably pull the handguard and use shims to tighten the barrel enough to bring the value up over 40 or so.

[shooterrex]

How would a shim change the value of how tight you tighten a barrel nut?

 

[FOGeologist]

49 minutes ago, shooterrex said:

How would a shim change the value of how tight you tighten a barrel nut?

 

Have you had to use shims to time a handguard? You have to add them such that it holds off the nut rotating into torque value until one of the threaded holes is lined up (within maybe 2 degrees either way, they build a little slop in the handguard so you can have some room to rotate it enough to make a finely-adjusted alignment with the upper rail). It requires some patience to get it to where you have an opportunity to get the nut aligned. If you add too many shims, you may have to tighten the nut a LOT to get to the next hole. Too few and it will crank past the aligned position before you reach tension.

My next handguard will be the clamp-on style. You can torque the nut to a nice 40 lbs and then clamp the guard on, using the groove in the nut to put the guard on at the desired angle - no "timing" needed.

Not a fan of "reefing" on aluminum as it seems to put some stress on the whole assembly. I couldn't imaging cranking one to (what is the upper spec?) 80 foot-lbs? Holy CRAP!