LR-308 Aero M5 6.5 CM Builds????WTF

[chickon1]

I started going down this path again after having one 6.5 build that I just could never get to cycle properly.(sold it) Not having the same issue as the last one, I think I figure out that issue with the new one, but I have similar issue as others have posted on here with feeding. I put the same 308 buffer in I used on the old one and could not get the bolt to lock back, swapped it will an Ar-15 one, worked prefect. Leads to another problem.

I'm just wondering has anyone got lucky and have had no issues building a 6.5 CM off the M5 U/L? It' really ridiculous the amount of issues this builds have.

There has to be a bolt/gas/buffer setup/barrel/magazine combo out there that doesn't require any mods someone stumbled upon.

The problem I'm having is the round randomly hitting the camber face when feeding (with Magpul Mags)(seen many posts about it on here). It scratches the round so bad that It's hard to get out of the camber when it happens. This is with no mods like polishing or widening feed ramps.

I just bought a Lanzer mag to see if it increase the loading angle before I go dremel crazy. I have a match grade BA barrel, it has M4 ramps and a beveled chamber face.

(I worked pass this issue finally)
Most "get the bolt to lock back" issues are not enough gas, (even though everything people tell you is they are over gassed) to small of gas hole on the barrel, 308 buffer length is too long, spring is to stiff. It should take little to no gas to push the bolt back with a 6.5. Basically, start will the lightest factory setup AR-15 buffer tube, buffer and spring, work from there. Adjustable gas block is a must. Right now, I have mine opened like 1 screw thread.

 

[padom]

Lol. Yep every one I've built. I've built 20-30 6.5cm large frame gassers now. 5 or 6 on Aero M5 sets. Never a single issue. These arent AR15's. Need to know what parts play nice together for a reliable and accurate large frame gasser..

Proper feed comes on the chamber entrance, polished and deburred barrel extensions so your brass doesnt get gouged to high heaven and bullets scratched... proper buffer setups and right gas length...

 

[Gatorshark]

I run a JP AGB on an 18" criterion in a Mega build. AR15 carbine tube and spring. Runs like a champ.

 

[Docsherm]

I have built 3, all on A5 receivers. I had to tune them all because of the barrel differences in lengh and gas systems. Besides that I have had no issues.

 

[2aBaC̶a̶]

M5E set, 6.5 CM. The scratching of the bullet as it feeds bothers me and I'll be addressing that but it functions 100%.

 

[KnightOfNee]

Take this info with a grain of salt considering I don't know all the parts that you have on your build.


I did an Aero m5 308 build myself and ran into a few issues. I love the rifle now and it's great and runs fine with both pmag and lancer mags, it is very accurate, but it was a pain in the butt and was driving me crazy, there was multiple issues that I came across. Long story short.

1. ditch any shitty Aero bolt release and replace it with an armalite ar-10 bolt release, Aero will tell you that their parts kit fits it fine but it doens't

2. get rid of their shitty bolt with the overly sloppy firing pin and replace it with a Jp high pressure bolt with smaller dia firing pin.

3. make sure your gas key is tight.

4.get an adjustible gas block and make sure it is aligned perfectly. feather up the gas slightly, watch for any cratoring primers or hard extractor marks.


5. use only the "EXACT" parts recomended by "That" buffer tube manufacture, there are some buffer tubes designed to use ar15 buffers in them which are longer,there are also a difference in compressed length of 308 and ar15 springs" do not mix and match these" make sure you have the correct length buffer and spring or else you can have your bolt bottoming off and can damage the rifle , it can also act like it is over or under gassed due to these improper parts. the bolt may not be going all the way back or it could be going to far back and slamming the receiver on the gas key.

6. most important thing of all, check with no go and go guages before firing!!!!!!!! the large frame ar rifles are' NOT" mil spec and you can have a KABOOM, in a very bad way.

I hope this info helps, here are my specs

Aero m5 upper and lower receiver blocks
Krieger Custom barrel that I had them make to my spec
m110 contour cut down to 18" flutted with full rifle length gas
Chambered in 308 Obermeyer 1/11 twist 5R
SLR adjustible gas block
Aero boron Carrior
Vltor RE-10/A5SR: A5 Receiver Extension Tube
JP enterprise High pressure bolt and High presure firing pin
Armalight ar10 Bolt release
Geissele National Match 2 stage trigger
Fortis switch rail
American defence quick detach mount
Surefire socom muzzle brake
Vltor A5 stock "because I like the good cheekweld on this for scoped rifles".
Athlon Ares scope

 

[chickon1]

Well, I can tell you I started with a .308 shilen barrel and it ran with no issues other than the .308 buffer being to long. I opened the gas all the way up and I couldn't get the bolt to lock back, I put the shorter Ar15 rifle buffer in there, no issues.

Once I put the 6.5 barrel on it, that's where the feeding issue started and you can clearly see the bullet is to small for the feed ramps to function properly. When you let the bolt go forward slowly, it hits the bottom of the camber face. I think most manufacturers use the same feed ramps for .308 and 6.5. I just finished polishing the ramps, it was like razor blades in there. Once I get the new mag, I will test it out again.

I also have the JP LMOS/HP bolt and JP adjustable gasblock.

 

[2aBaC̶a̶]

I have some dummy rounds with 120 and 130 bullets and they will hit the face of the chamber as you describe.

The Hornady American gunner 140 BTHP load and cycle fine.

 

[DRAM40A1]

You don’t have to “stumble” into the right combo. A little research and help from the right people goes a long way. I have one Aero lower and uppers in 6 Creedmoor, 243, 6.5 Creedmoor, and 308. They all run like sewing machines. The barrels are from JP, Craddock, and Seekins. Every one of them have adjustable gas blocks from Superlative Arms except for the 308, and it has a JP.

 

[D1gger]

My 6.5 has been good so far. Nothing really special. Aero set, Wilson combat barrel, SLR AGB, Toolcraft bolt and a JP silent captured spring.
I think I have the AGB 6 clicks out to get it to lock back on an empty mag. Fingers crossed that it keeps running.

 

[chickon1]

You don’t have to “stumble” into the right combo. A little research and help from the right people goes a long way. I have one Aero lower and uppers in 6 Creedmoor, 243, 6.5 Creedmoor, and 308. They all run like sewing machines. The barrels are from JP, Craddock, and Seekins. Every one of them have adjustable gas blocks from Superlative Arms except for the 308, and it has a JP.

Totally agree, but it would be nice if they just worked, but that's part of the "build" process I guess. I will say the first one I built had about every issue that anyone has ever had..This one seems to be going better because I have been watch these forums knowing I will build another one. I really want it as a PRS gas gun, but I need it 100%.. I'll keep you guys updated..The Sgt of Arms ARCA rail is awesome BTW


thanks for the input!

 

[rpoL98]

my 6.5CM upper build:

Aero M5 upper
Faxon 24" barrel, rifle-gas
Brownells HP nitride BCG
SLR 16" rail
SLR adj GB
Armalite AR-10 rifle gas tube
VG6 65 Gamma brake
Vortex PST Gen I 6-24x FFP
AD Recon-S scope mount

Lower is just my workhorse/mule that I swap around to various uppers:
Aero M5 lower, Geissele HS-NM, carbine buffer tube, KAK 5.3oz 2.5" buffer, Slash/Heavy-Buffer 308 carbine spring, CPD 20rd mag.

first outing, all I had to do was dial in the adj GB, open 7 clicks. Only shot factory ammo, no feeding issues. Other than the romancing of the sharp edges of the barrel extension, which I do for all my barrels before assembly, it was cookbook. I chambered a round, yanked CH to extract unfired round to examine: no gouges, nothing boogered up, projectile looked fine. ho-hum.
I've built a few 308 uppers, this is my first 6.5CM.

 

[chickon1]

Update.. Sanded out and polished the feed ramps, replaced the non JP HP bolt (I had the LMOS BC already).. runs like a champ now. The buffer spring I have in it is a bit weak for bolt stop feeding but works fine other wise. Replaced that with a polished JP spring which is much stiffer. See how that goes.

I really had to go at the feed ramp before they stop scoring the shit out of the rounds.. also polished the rest of the feed area.. I barely get a mark ejecting a non spent round.|

Build out:
Aero M5 upper/lower
JP LMOS BC with JP HP bolt and firing pin
JP Polished buffer spring
Ar-15 Rifle Buffer - standard
Geissele 2 stage trigger
Sgt of Arms Arca Rail Handgaurd
BA Premium 1/8 24" 6.5 CM barrel
JPGS-8 Gas block
MBA-1 Stock
Lanzer Mag
APA LB Gen 2

 

[Billiam1211]

I've been working on an Aero M5 builder kit and have had some issues with fitment. Turns out that my Aero M5E1 upper was slightly out of spec, currently waiting for a replacement upper from Aero. Luckily their customer service is good, however I didn't realize so many people had issues w/ QC on their large frame parts. I had a barrel spun up from Craddock and it was loose in the upper due to the indexing pin slot being too wide. A couple guys recommended I shim the upper to fit better, but I opted to see if Aero would replace it with a better fitting upper.