Done! Aero M5 in 6.5 Creedmoor

[Mountain]

This project started as a NES group buy port cover. Heck, once you have the port cover your almost there!




Lower was also a group buy acquisition, upper and BCG from Brownells. Some parts like the RRA NM trigger, Hogue grip, etc. I had in the stash. More or less a budget build as far as AR-308's go. Barrel is a 20" 416R from Ballistic Advantage. I really like the stock- a Luth AR that IMO is better and cheaper than a PRS. JP forend is the only expensive part relative to what's available.

Good news / bad news from the first range trip. Bad news is that it is short stroking most of the time. I was very careful when assembling the gas system but who knows- that's always a likely culprit for short stroking. Good news is that despite the inconsistent feeding, accuracy looks good so far. ~.4" groups at 50 yards with Hornady factory ammo. Sub MOA with semi-auto is always nice. Trigger pull is a bit heavy, so I can improve on that and probably get better groups.

The AR-308 buffer spring that came with the Luth stock was big time heavy! Really took some effort to charge with that spring. I'm going to try a standard AR rifle buffer spring to see how that will cycle. If a standard spring is good enough for my .458 socom, it should be more than OK for 6.5 Creedmoor. I've built a few AR's and this is the first one that did not run like a champ on day one. Hopefully the solution won't be too elusive.

 

[Mountain]

Stopped by the range after work for further testing. Runs better with the standard rifle spring but still stove-piping every 4 or so rounds. Assuming I'll need to work on the gas system to straighten this out. I don't think it's anything hanging up upon feeding as single feed and semi provide the same accuracy. Also no difference between a Pmag and steel mag. Both mags 10 rounds...

Accuracy continues to improve despite my lack of skill and the gorilla trigger. I think I am mistaken about this being the RRA trigger. My highpower AR breaks at 4.6 lbs and feels like a feather compared to this monster. Wind was ~10 mph variable and gusting to 15 mph, but I don't think it's much of a factor at only 100 yards for 6.5 Creedmoor.



Starting to group very nicely. All are 3 shot groups because I know I have a gas problem and I'm being cheap. Group at center was my warm up at 50 yards. Bug hole upper left was my next group at 50 yards. All others including group just right of center are at 100 yards. Looks like there's some good potential once I iron out the kinks and install a decent trigger.

Edit:

Grabbed the calipers and measured group sizes. Splatter targets make nice pics but are kinda crappy for measuring groups- you have to look a little closer to measure where the projectile cuts the paper.

50 yard bug hole .340" edge to edge minus projectile .256" = .084" group size

100 yard group sizes .514", .504", .447", and .406". MOA ranging from .388 to .491 right off the workbench. Nice testimonial for the Ballistic Advantage barrel. Yeah, only 3 shot groups but with a top shelf trigger I should do better with even 5 shot groups.

 

[mac1911]

I only have diagnosed 1 AR 10 and it was stove piping.
It was a factory 308. It would stove pipe and try to feed the next round and they would jam up.
If you single loaded this rifle the empty would stay inside and just sit on top of the mag.
I called RRA and they sent out a new bolt with a "updated" extractor. Worked flawlessly.

Only input o have

 

[Mountain]

It was really random. Some rounds would eject consistently then one would stovepipe. With the heavier spring, some would barely drop out and many would stove pipe.

Anyway, accuracy meets my expectations. Guess I'd rather be fighting extraction issues than crappy accuracy.

 

[1903Collector]

Hope you get your function issues squared away. That thing is sweet!!! the wheels in my head are spinning now...LOL. My first 6.5 Grendel build had feed/extract issues at first and I could not figure it out but after about 50 rounds or so it cleared up and it runs like a champ now. I chalked it up to things smoothing out and wearing in after a bunch of rounds.

 

[Mountain]

Well, cost a little extra $ to fix but at least I didn't have to pull apart the upper assembly. I had a hunch that it was a bolt problem and installed a JP High Pressure bolt last night. I immediately noticed how smoothly the rifle would cycle by hand. The 'bad' bolt was obviously binding now that I had something to compare. Hit the range after work today and the AR-6.5 CM ran like a champ, even with the fairly hot Superformance Hornady hunting loads. Hornady warns not to run Superformance in large caliber AR's with barrels shorter than 20", so mine is at the bare minimum. Went back to the heavier 308 buffer spring as well. Borrowed my Geiselle NM trigger (set at 4.6 lbs) from another AR to make the below shots:



Shots at center were Hornady match. The Superformance group was a little bigger than that, with shots more randomly spread rather than stringing like this. Bit of a surprise for me was how well the Winchester Match shot in this rifle, with a one hole group to the upper left. I've tried several lots of Win Match in target barrel .223 AR's and never had as good of a result as with Federal Match or hand loads. Honestly, this 6.5 CM group is my best 5-shot 100 yard group ever at ~.112". Not sure I'm going to beat that with hand loads. I'll have to send a nice email to the folks at Ballistic Advantage- accuracy like this requires a barrel 'done right'.

- - - Updated - - -

Hope you get your function issues squared away. That thing is sweet!!! the wheels in my head are spinning now...LOL. My first 6.5 Grendel build had feed/extract issues at first and I could not figure it out but after about 50 rounds or so it cleared up and it runs like a champ now. I chalked it up to things smoothing out and wearing in after a bunch of rounds.

Perhaps bolt to barrel extension fit? Maybe mine would have broken in eventually.