That turned out sick. Stupid question, but that would be a URX 4 for the SR-25? I am under the impression that Aero M5 receivers aren't compatible with standard rails.

Aero M5E1 Enhanced receivers aren't compatible whereas normal Aero M5 ones are

Yep, this.

I have a URX4 on mine

Parts list? @RJeff21

Upper:
Aero Upper/Port Door/FA
Seekins BCG
PRI Gasbuster CH
Criterion 16” Hybrid CL Barrel
13.5” URX 4
Superlative Bleed-Off AGB
Griffin Minimalist FH

Lower:
Aero Lower/LPK/Carbine RE
Geissele G2S
Magpul MIAD
BRO Bolt Catch (DPMS is gone, so if this one breaks, I’ll be picking up a KAC)

NF ATACR 4-16x42 in G Mount
Reptilia Ring Cap w/ RM06 RMR
Atlas Bipod

@MNSwede

Awesome, thanks!

I have the KAC bolt catch on mine...Painful purchase at $108 but holy hell its solid.

I’m hoping with a properly tuned AGB, I won’t break one, especially with the Hybrid on there which shouldn’t have excessive back pressure with such a large bore, but I guess we’ll see.

ATACR will probably get swapped over to my Creedmoor build once I get around to doing it and this one will get a smaller/lighter LPVO.  Thinking NX8 or potentially ATACR, as it sits now it’s nearly 12lbs.  

@RJeff21 What gas system did you decide to go with?

It’s a MLGS.

Got it out to the range today.  Ran into an issue with the bottom of the BCG impacting the lower receiver extension threaded portion of the lower.  A few quarters as a spacer fixed that issue and still allows the bolt to lock to the rear.

Tried a few different match loads out.  Best load was FGMM 175s.  Three 5 round groups hovered between 1-1.2 MOA, not bad for a Chrome Lined CMV barrel and more than good enough for my purposes.  Hopefully it’ll settle down a bit more after it breaks in (like my Criterion Grendel barrel did) and allows me to dip below MOA, but either way I’m happy.

Attached File

How was your gas adjustment process? @RJeff21

You asking for the procedure or how it went?

Either way, was pretty straight forward.  Closed the gas off completely then opened it up one full revolution before starting.  Put a single round in the mag, fired, then looked to see if it locked back.  Think I ended up somewhere around 2 full revolutions out from closed (max of 4.5 with the Superlative AGB) with perfection function unsuppressed.

Then I threw the can on and checked to make sure it wasn’t horribly overgassed in that position (it wasn’t, Hybrid has a big bore and not much backpressure).  Functioned 100% for the remaining 150ish rounds, both suppressed and unsuppressed.

Beautiful, thanks for the info

The LMT MWS bolt catch looks to be pretty much exactly like the KAC catch and it's around $20. Everything KAC seems to have a special "KAC Tax".

@RJeff21 take a look at the Forward Controls Designs bolt catch. They are well-designed and made, Roger is a member here and at TOS. I have one on my in-progress .308 and have used one in an SBR for a while.

(In fact, the little one from Mega that came on my lower is up for grabs free if anyone needs a spare.)

Nice looking rifles. I have family in the Rhame & Valley City areas. Lots of good shooting in ND.

I’ll have to take a look.  Thanks.

Just took my m5 16" to the range. Bad recoil, double feeds, and bolt not locking back. I tried adjusting the gas block which brought the failure rate to about once every 30 rounds. I ordered a heavier spring and a KynShot buffer to help with the recoil.

LMT is MIM

KAC is machined

Haven't heard any reports of MWS bolt catches breaking.  You?

Sucker for FDE. Both in 6.5 Creedmoor

That second rifle looks almost exactly like my 6.5 CM AR aft of the suppressor.

Nope. I'm just pointing it out is all.

That is why one is $20 and the other is $108

Finally completed my first AP M5 (for that matter, any AR-10 style) build and details & questions here.  

But I'll dupe it and paste in the specs and a pic too and probably get more responses:


Nearly completed my first AR-10 (finally!) and looking forward to getting out and shooting it. Need to time & install the Warcomp, get the scope setup in the mount & align it then take it to the range. Maybe add the thicker recoil pad to the stock. (fail!  UBR doesn't take regular magpul carbine stock pads...need to figure that out)

So given that this is my first AR-10 build, what guidance or recommendations do you have for initial shooting/breakin/sightin process to follow?

Couple of questions then build details & pic

I'm using the AP .308 carbine buffer, spring and tube..but at the last min I decided to not use the Magpul STR stock and go with the UBR Gen 2 stock and its own tube w/spacer block. Same buffer and spring. Regardless, its a hard pull on the charging handle to retract the bolt. Is that normal?

I'm assuming I should start out with the adj gas block wide open and then adjust it accordingly until the system just cycles? First adj gas block too. I plan to get a SF 7.62 RC2 suppressor, but thats down the road.

Barrel break in: I was planning to follow Faxxon published process for their barrel. Anything to add?

Initial ammo: I have a mix of IMI, Federal and Atomic M118 and LR style ammo (both 168 & 175 SMK style). Plus M80 ball and I'm sure if I dig I can find some other variations, any suggestions what to start with? I'm planning on either ultimately chrono both of the 168 and 175 loads, see what works well accuracy and cycling and then try to standardize on one.



Build sheet:
AP M5 upper and lower receivers
AP M5 .308 LPK: I went with the basic trigger and plan to upgrade at some point, but funds and pandemic/riot buying took precidence.
Houge grip (like most of my other AR's)
Magpul 10 and 20 round mags
Magpul UBR Gen 2 stock as mentioned above. I purchased the thicker pad just in case. I was aware of this stock in the past and was looking for something more than a STR (my carbine/SBR standard), but not a A2 fixed. Rock solid, very impressed.
Faxon barrel: 16", Medium Tapered, .308 WIN, Mid-Length, 416-R Stainless QPQ
Superlative Arms .750" Adjustable Gas Block, Bleed Off - Clamp On, Melonite Finish
Mid length gas tube
Daniel Defense 7.62 Lite Rail 12.0: Ok, I'm a sucker for quad rail...and someday will buy/build a MK11 Mod 0 or M110. But once this beast was on and tight, iI love it and its not that big feeling.
Surefire 7.62 Warcomp: I can't imagine the blast/concussion if I went with the normal A2 FH, really looking forward to see how this works out.
weaver tactical grand slam rifle scope 3-10x 40mm, mildot. inexpensive, good reviews and its a start to keep the costs down. I'm sure I'll upgrade this if this rifle works out.
Midwest Industries QD scope mount, 1.5" offset, no MOA: Got to tell you, I wanted a Larue and I can't get intouch with them for an already ordered mount for another rifle and its been back ordered for 6 weeks. Like the scope, I'll likely upgrade this at some point, but should be ok to get started with. Seems well built.
Magpul QD mount for front rail
Magpul 1913 bipod
Magpul MS4 sling to start, might go with a TAB like my MK12 or more of a shooting sling.

Planning to add/update:
BUIS
Updated scope & mount
Trigger
SF 7.62 RC2 suppressor
What else?

@NukeThemTillTheyGlow

nice rail. archeological find?

for starters, I think for the Faxon mid-gas AR-308 barrels, you probably want to look into the Armalite AR-10 carbine gas tube.  I'll bet your gas tube looks a little short inside the upper receiver.

if the Aero 308 carbine buffer is the 3oz version, you might want to look into one of the 5.3oz version.
https://www.primaryarms.com/expo-arms-308-heavy-carbine-buffer-5.3-oz

just my 2 cents.  YMMV.

You must have excellent taste!

@rpoL98

Yes, it was a great find.  Not sure why they stopped making it.  Once you get it all bolted together, its rock solid...basically a big version of the rail on my MK18's.  Compliments my AR-15 quad rail (mainly KAC, some DD) collection.  For diversity & inclusion scoring, let the record show that I have one R700 in a Magpul M-Lok based stock and so far it had been welcomed into the tribe.  But I digress.

Thanks for the advice, just what I am looking for.  Can you explain the why behind differnt gas tube and buffer?  How do I measure the gas tube to see if its short inside the upper?

@NukeThemTillTheyGlow
in the large-frame AR-308 world, there's 2 gas tube standards: AR-15, and Armalite AR-10.  Barrel mfrs decide which standard they wish to build their barrels to.  AFAIK, Faxon chose the Armalite AR-10 standard for their DPMS AR-308 barrels.  and their 6.5CM barrels.  It's arbitrary.  but something you need to pay attention to.  or not.

as far as the buffer goes, the AR-308 sure packs a lot more recoil energy, so IMHO, the AR-15 5.56 buffer weight isn't sufficient. but that's just my 2 cents.  I'm sure the Aero AR-308 buffer kit, "millions sold".

hhmm, first I heard of two diff gas tube standards.  I looked at the original order docs and no mention of one vs. the other.  I assume in your pics the top one is ar-15, bottom ar10?

Finally got to "break-in" the build with about 50 rounds of my 168gr reloads. After getting a zero I tried 10 rounds shooting from a bipod. I need to work on technique; lots of hopping and jumping to the right. I seemed a little tighter off the sandbag when getting a zero. Pretty happy with the Criterion 20" mid-weight match barrel.

My 6.5 Creedmoor contribution.

@JSmitt6

How long is the barrel and rail on the bottom rifle?

@skirch56

That is a 20” Faxon big gunner barrel and Aero’s 12” rail

                                         

Seeking some clarification in regards to receiver extensions and buffers.

Right now I have the carbine system on my M5 and I was going to switch it up to a rifle buffer until someone suggested I get the Armalite AR10 intermediate receiver extension so I continue to use my stock. I was told I could use that and a standard carbine buffer. Is that true and if so would I use a carbine spring or a rifle spring?

The Armalite AR10 spring is used in both their rifle and carbine tubes. You would use a standard length H3 buffer that you would us in an AR15.

Some questions for the M5 gang:

1) What JP Silent Captured Spring should I run in my M5 if I don't have an adjustable gas block?
  a) Regular SCS or H2?

2) Is it really worth it to get an adjustable gas block on these to run with the JP SCS? My M5 has been great with the standard buffer setup and I really want an SCS because I love them in my AR15s but I don't want it to create reliability issues.

3) 6.5 CM Upper: Is it worth it to grab one? I was going to go with a LMT MWS 308/6.5 but they are completely unavailable right now. Looked at the LWRC REPRs too but I'm partial to the LMT because I've always enjoyed their platforms in the past.

I can only really answer 3.  I assembled mine from an Aero upper, Criterion 6.5 barrel, SLR agb, and muzzle device for my suppressor.  Shoots great

A Fulton Armory bolt doesn't fit in an Aero bolt carrier, if anyone else was wondering.

The .308 Fulton bolt I got from Criterion with my barrel fit just fine in mine.  I actually asked Criterion about this when I got my barrel and they told they have used Fulton .308 bolts in Aero carriers without any issues.

Attached File

I guess I'm unlucky, mine didn't fit.  I ordered a Fulton carrier, if it doesn't fit in there I'm going to throw a tantrum.

ETA: Might be because I used the Nickel Boron coated bolt. It fit in the Fulton carrier but it is tight as fuck. We’ll see if it squeezes any more accuracy out of my Criterion barrel.

The Fulton bolts come with a one piece gas ring.  Criterion actually mentioned that they recommend replacing it with three piece rings.  I wonder if it would fit with three piece rings?

Are you able to tell what exactly is causing your bolt to not fit?

The center contact point was too tight, it wouldn’t slide into the bolt channel.

It was even tight on the Fulton carrier, I could barely turn it by hand. I think it might’ve gotten coated with the nickel boron a tad heavy and will likely loosen up as it breaks in.

Hmm, interesting.  The headspaced Fulton bolt I got with my .308 Criterion barrel has the standard phosphate finish.  Maybe you are on to something in regards to the coating and possible tolerance stacking.

I don't think "tolerance stacking" can be blamed as both the Fulton bolt and Aero carrier are supposed to be DPMS spec.

I’ll shoot it in the Fulton carrier and break it in, then see if it fits into the Aero carrier afterwards and I’ll post the results.

Science!

Neither Fulton or Aeros parts are "cheap"/low quality.
If I purchased either a bolt carrier from Aero or a bolt from Fulton and these parts wouldn't work together one or the other would be returned/exchanged for parts that do work.
Science, or common sense!

I'm actually pretty stupid, so that is always a factor.

I shot the Fulton carrier and bolt, I actually saw an accuracy improvement, which makes sense as Criterion recommends using a Fulton bolt because they are headspaced with them at their shop.

Fired 20 rounds and wiped it down, the Fulton bolt now fits easily into the Aero bolt carrier.

In retrospect, I probably could've put some lube on the Fulton bolt and forced it into the Aero carrier and then cycled it and it probably would've worked.

The important thing is science was made.