6mm Creedmoor project--the gathering

[stagpanther]

Lots of goodies arrived today--the only things missing are the lower, barrel, gas system parts and compensator. They should (hopefully) all arrive by the end of next week.

I expressly spent big bucks on getting mostly top-quality parts. The really interesting thing is that in the end it was not a whole lot more than my xx308 builds using budget parts--I figure the total cost of the base gun will come in right around $1,200 total.

My first big order of Guntec parts which are made in Arizona. These guys build for the military and LE communities and even before I put the stuff together I can see a qualitative difference in their manufacturing. The NIB BCG is about the beefiest one I've ever seen--both carrier and bolt look like they will withstand pressures in multiples of what the cartridge is rated to--but that's just a "first glance guess." The LPK includes extended pivot pins--a nice touch. They also go out of their way to include stuff in the parts that otherwise you would have to pay for as extras--the rail comes with a barrel nut shim in case you need it, the minimalist stock comes with a quick-detach sling point.



I decided to stay with a Jard two-stage adjustable trigger with bottom adjust. This is "old-school" since it requires tapping the grip screw hole in the lower--but my opinion is that this is less likely to drift in tolerance than a top-adjust arrangement since I've seen those types start to dig divots in the floor of the lower over prolonged use. I talked to an an engineer at Jard about my assessment and he agreed it was a sound one.

[stagpanther]

Aero Precision lower came in today so I was able to build the lower and some of the upper. Like the other xx308 build I did with an Aero lower--this one had some oddities that make it "not play well" with non-Aero parts. The lower mates OK with the Guntec billet upper--but if you look closely you can see a gap in the rear. Install of the Jard trigger went fine--except that the Guntec safety would not seem to work--only Aero Precision's would. The Aero lower features a set-screw of some sort aft of the grip screw hole which I've never seen before in a lower--wondering what that is? Aero has carried on the fine tradition of making their pivot pin arrangement just a tad different from everyone else's--not as bad as my other Aero lower but this one still takes a bit of fore/aft pressure too get the pibot pins to engage/disengage--and the front pivot pin hole in the lower is still a few .00ths of an inch wider than most everyone else's--meaning the pin itself, if not one of Aero's, will not protrude enough to be easily pushed out (I highly recommend Guntec's extended pins for exactly this reason).

[ed308]

I think you're referring to the set screw to take up slope b/w the upper and lower. I've seen gaps like that in some of my builds with Quentin Defense uppers receivers and another brand lower. I like the FDE and black. Went with the same colors on my 6.5 Creedmoor Aero build.

[ed308]

I just checked my Aero upper and lower. I can see a little light through mine as well.

[ed308]

Looks like I can't upload a photo of the gap in mine. But similar to the gap in yours.

[stagpanther]

I think you're referring to the set screw to take up slope b/w the upper and lower.

I thought about that--like a wedge to take up wobble between the upper and lower? Not very reassuring in terms of precision of fit--I don't like the fact it pushes up on the pivot pin (if used)--not to mention possibly introduces an asymmetry in the slide of the carrier into buffer tube. But what do I know--I guess they put it there for a reason.

[stagpanther]

While awaiting barrel arrival...hot off the press, creedmoor brass necked down to 243--super easy to do and no need for turning as far as I can tell.



After measuring--it appears all the displaced brass flowed right up the neck--simple trim takes care of that.

[stagpanther]

Barrel came in today--looks like a true work of art! Here are a few detail shots--keep in mind this is fresh out of the box prior to cleaning. Notice the recessed target crown (despite coming threaded for a muzzle device), nicely ramped and radiused chamber face and the wide channel main cartridge ramps.

[stagpanther]

Solid Odin fluted SS adjustable gas block with XL rifle gas tube.

[stagpanther]

Took a break from my work and finished--almost--the assembly, you might notice that the muzzle is missing a device--courtesy of the guy in shipping who didn't read the complete order and forgot the compensator.



Anyways, very easy and straightforward assembly--for an AR 10 platform, anyway. The only small snafu involved the parts kit--and I was prepared for that by ordering Aero's LPK as "back-up." This is the biggest AR10 style rifle I'be built--yet one of the lightest, interestingly enough. The shims included in the rail turned out to be all necessary to clock the rails attachment bolts.

[ed308]

Nice. What optics do you plan to use?

[stagpanther]

Thanks--For now I'm "stealing" a SWFA SS scope off of one of my other builds--I'm thinking of taking the plunge and buying my first nightforce after saving up some sheckles.

One thing about high-quality parts that you don't seem to hear about--they simply go together easier making the job easier. I hope this means better tolerances--and better reliability/accuracy. Very impressed so far with the Odin barrel and components.

About 8.5 lbs without optics and mount.

[stagpanther]

A tour through my spare parts bins revealed I had a spare 308 5/8 24 brake stashed--so on it goes while awaiting the comp--along with a magpul FDE grip which makes it a bit more "feng shweizy" 20x SWFA SS scope from my 6.5 creedmoor build--hopefully won't take too much to get on paper. Deer season opens in a week, so things are going to slow down a bit, but I'll try to complete headspace/chamber checks and get some test loads through soon.

[surveyor]

That's a nice looking well thought out build.
I'm looking forward to seeing your loads for it.

[stagpanther]

That's a nice looking well thought out build.
I'm looking forward to seeing your loads for it.

Thanks--I'm starting out conservatively and simply using Hornady's published loads (mostly cause their ELD x's were the best performers in my 6mm predator build).

[stagpanther]

whipped up some test rounds with superformance--strange powder with strange after-burn smell, but had some "Houston--we have a problem" issues right off the bat.

First and foremost--the extractor on the bolt is so overpowered that it simply won't let go of extracted cases--ruined quite a few cases in the process of trying to get around that.

The gun has a big "bang" when you pull the trigger--but almost zero recoil. Don't know if this is due to the extra long gas system, the heavy duty BCG or the buffer spring being too hard..or simply the lightweight 6mm bullets--but I had to open the gas port on the block almost all the way to get the bolt to lock back. I'm not kidding--it doesn't feel anything more than a 17 hmr. Anyway looks like I have some work to do to get things tuned, but that happens with "exotic" calibers sometimes.

[stagpanther]

The bolt carrier group is a "high pressure" system of the kind espoused by JP rifles. I took the bolt apart, stoned the edges of the extractor and sure enough found two plastic donuts stacked atop the spring. Took one of them out, reassembled everything and the first dry-cycle of a dummy round processed and manually ejected no problem. Hopefully it was nothing more than that causing the issues.

[stagpanther]

The 1.5 lb pull two stage trigger is fine--except for one thing--all the other two stage triggers I have are 3.5 lbs pull and up--but a two stage with just 1.5 lbs pull, for all intents and purposes--is the same as a single stage with some overtravel since it's very hard to discern where the "wall" is before breaking. Like duh--shoulda figured on that I guess.

[stagpanther]

The "acid test" for any AR in my book is how well they can cycle berger VLD's with their secant ogives (not the AR hybrids). Most AR's don't pass in my experience without some damage to the bullet. So I whipped up a ladder to test today driven by 4350--which seems to be a consensus good 6mm creed powder.



However my tuning work is yet to be done and I still have a few things to figure out. Even after I pulled a donut from the extractor spring I had intermittent case hang-ups on the bolt so not ever cartridge was successfully fired unblemished. I swapped the bolt with a PA10 one and the case hang-on issue went away immediately--but I still have a tuning issue to resolve since I failed to get bolt lock-back at the end of the mag. My brass is leaving the port at 3 to 4 o'clock--so things are looking good there. My next area of attention will be the buffer spring--I usually have a stock of spare springs over a wide range of power.

Comparing the extractors--I notice the heavy duty one is actually a bit bigger--wider with a wider circumference. I didn't notice this at first but I'm now convinced that is what is trapping the creedmoor rims and causing the failure to ejects. I'll either trim the extractor down or replace it altogether on the original bolt.

Despite the issues, I did get one OK group which I think shows the promise of the gun once I get the kinks worked out.

[ed308]

In the picture above, are a couple of the couple rounds suffering bullet runout? Or is something in the holder causing the case to tilt to one side? Or maybe that's what your referring to in your post.

Fact Check: I know very little about secant ogives. I loaded up my first 140 gr Nosler Custom Comps and shoot them over the weekend. Best group I could do out of my AR10 in 6.5 CM was 1" with H4350 at 37 grs and 2.775 OAL. That's the starting point listed in Nosler's load data. Back to the drawing board I guess. I've got other powders to and bullets to try.

[stagpanther]

In the picture above, are a couple of the couple rounds suffering bullet runout? Or is something in the holder causing the case to tilt to one side? Or maybe that's what your referring to in your post.

Fact Check: I know very little about secant ogives. I loaded up my first 140 gr Nosler Custom Comps and shoot them over the weekend. Best group I could do out of my AR10 in 6.5 CM was 1" with H4350 at 37 grs and 2.775 OAL. That's the starting point listed in Nosler's load data. Back to the drawing board I guess. I've got other powders to and bullets to try.

The cartridges were just tilted in the tray--plus my cell phone tends to distort things a bit. Having said that--i don't really do concentricity checks.

Interesting your results--I've noticed nosler is usually pretty close to spot on with their recommended loads (meaning the ones they say they have the best accuracy with)--and the custom comp is an excellent performer.

Finding good loads for my 6.5 creedmoor build for 140 gr bullets is pretty challenging--so what you're experiencing isn't all that unusual I think. 130 gr bullets seems to be the sweet spot for my 20" BHW barrel. I stumbled upon a stellar load unexpectedly for my 6.5 creedmoor: 130 gr sciroccos driven by 38.7 to 39 grs of RL 15makes teensie weensie groups.

This 6mm creedmoor is a new beast entirely from any other xx308 build I've ever done--this XL rifle gas system on a 22" barrel changes the feel of the gun and felt recoil significantly. It's definitely a challenge to tune--but that's how I learn. I have a strong feeling it will be a great performer once I find the sweet spot(s).

Secant ogive is berger-talk for very high angle/long taper ogive bullet--but also generally means very high BC. In most conventional AR extensions based on or close to the M4 ramps I've found that the grendel and creedmoor general fail to get the necessary lift to the case on the feedramps prior to the bullet making it's way to the chamber--the result often being the bullet meplat smashing into the chamber face or glancing off it damaging the bullet on the way in. That's why berger developed the AR Hybrid VLD. This Odin barrel is the only extension I've ever tried which successfully got a gredel or creedmore based cartridge with a regular VLD to chamber without issues--at least that I know of. I think almost all AR cartridges take a bit of damage in cycling.

[stagpanther]

Often times it takes a while to "sleuth" what is going on with a build and why--and this one has thrown some good loopers at me. : ) Anyhow, I took a closer look at the tolerances between the Aero lower and the upper--and the Aero is pretty far out of whack--just as bad as the one I bought two years ago. It won't even mate with any of the uppers of the 5 other xx308 builds I have. The problem appears to be that their selection of pivot pin holes position will not allow proper alignment of the rear of the upper to the rear of the lower--the charging handle prevents the upper from seating properly--which of course affects the operation of all the other components. I don't know if it's on the Aero website--but the bottom line, IMO, is that Aero's 308 lowers are going to operate reliably with minimal issues ONLY with their own uppers. The first one I thought was just bad luck--but two, nope--you're outa there.

[ed308]

Yep. No standards for the AR1O. I bought all Aero for my 6.5 CM except the barrel. Mine functions fine. About the only thing I didn't like is the designed for the enhanced upper. You can't lap it. Not sure if it's needed it, but always lap just to be safe.

[stagpanther]

It really doesn't make mush sense to advertise "compatible" when it really isn't. Even PSA's lower works with every upper I have--though their pins may have some issues. Anyways, I'm not upset--that much--I expect 308 parts not to be cross compatible even when people say they are.

[stagpanther]

Odin's Atlas comp came in today--pretty novel approach to a compensator. It has an inner main body of steel and pretty much is omnidirectional in it's port holes. Over the "core" there is a titanium sleeve which can rotate on the fly and has an index mark on the rear for alignment adjustments. This way you can clock your timing on the fly





I ran to the pit to take a quick few test shots of the hunting VLD's driven by 41.9 grs of 4350. I can't say for sure the comp is responsible, but things seem to shoot better today. I had a nice 0ne-holer going with the first three shots before I choked and pulled the flier in the upper left.



I still have to get to the bottom of the bolt extractor issue--but I'm getting closer to a fine-shooting build.