New 6mm creed barrel from McGowen

[stagpanther]

Going to have to take a break from my 284 win project--the fine folks at McGowen just sent me a custom-cut 6mm creed barrel which I had made in a 7 twist to see if it will handle the 108 eld and heavier bullets better.

An interesting new service they provide is that they will cut you a "stub"--which represents your chamber to bore portion of your barrel from the shoulder forward-- at the same time they ream the chamber on your barrel. You can instantly see how a bullet at a given seating distance will "jump" to engaging the lands and rifling.

[ed308]

Following. 6mm CM might be on build list. But may in a bolt action.

[stagpanther]

Following. 6mm CM might be on build list. But may in a bolt action.

I'm sure it would be great in a bolt gun as well--but the 6.5 and 6 creed are "tailor made" to perform well in a semi-auto action IMO.

[bfoosh006]

Very nice.

In for all the info.

[stagpanther]

Et Voila, as they say. Down in the single digit temps at the moment but if it warms up a bit I'll try to get a few break-in shots today.

[stagpanther]

Warmed up enough that I decided go out and shoot a few "break-in test groups." I don't expect great results because this is a stop and clean thing, as well as figuring bugs should they present themselves.

And that they did.

I've always had a love/hate relationship with Aero Precision's 308 receivers--the thing I love about them: their uppers generally clock extremely well to their rails--and I really like their barrel-nut configuration for attaching barrels to their uppers.

Unfortunately the same cannot be said for their 308 lowers in my experience--EVEN when mated to a matched upper of theirs. Based on the half dozen 308 builds I've done using their recievers--their lowers tend to have mediocre to poor fit with uppers which often create all kinds of headaches. This build--like another I did recently using receiver pairs I bought from AP--tend to have real problems getting tight enough tolerances to allow the alignment of the magazine to bolt catch in such a way that allow for consistent and reliable feeding from magazines--anyone's magazine. It's an annoying issue which often results in extensive work to fix.

Despite all that, I managed to get a couple of fairly decent groups which I hope promise good things to come.

[stagpanther]

The whole purpose of this build is to see how well I can drive a 110 gr or heavier bullet--so I decided to spend time concentrating specifically on the 110 matchking. I want the COL to be at least 2.8--but I needed to do a few things to get to the point where that will (hopefully) work.

I ditched my KAK BCG and put a standard DPMS one on, as well as put a new Aero bolt catch on. To take the wobble out between the receivers I did a bit of bedding on the rear part of the lower were it meets the upper. All that seems to solve the bolt missing picking up a cartridge from the magazine problem--but the bullet nose was still glancing off the chamber face on the way in--imparting a very small nick in the nose meplat--but nonetheless affecting the accuracy/consistency of the cartridge. This is actually quite a common problem with cartridges based on the Creedmoor and Grendel cases in my experience. This is mostly due to the bullet not quite getting enough lift by the lips of the magazine and case shoulder off the ramps prior to the nose of the bullet reaching the chamber face. I remember that I initially had a similar problem with my first 6.5 creedmoor build--and the solution proved to be the easiest and cheapest (I like those) I simply took a brown ell's 308 mag and slightly turned up the feed lips. So I think I'm ready to go with the next round of tests. : )

[jetinteriorguy]

Mm, long pointy bullets. About a month ago a friend came to the range with me and brought his shiny new AeroPrecision 6.5 Creed to try out. He brought along a few different types of factory ammo. Once we got it sighted it was shooting pretty good for him, except with one type, I forget what it was. So at the end of our session, he handed me five rounds of the troublesome ammo and asked me to give it a try. The first four shots made one slightly elongated hole, and true to form for me the last one just had to be 1/4" away. Sure put a smile on his face, mine too.

[stagpanther]

Mm, long pointy bullets. About a month ago a friend came to the range with me and brought his shiny new AeroPrecision 6.5 Creed to try out. He brought along a few different types of factory ammo. Once we got it sighted it was shooting pretty good for him, except with one type, I forget what it was. So at the end of our session, he handed me five rounds of the troublesome ammo and asked me to give it a try. The first four shots made one slightly elongated hole, and true to form for me the last one just had to be 1/4" away. Sure put a smile on his face, mine too.

Nice--it's a great accuracy cartridge--when things are running right.

Both creedmoors shoot exceedingly well. If you took some calipers to that factory ammo--I'm willing to bet the COL was under 2.8 for the higher BC/SD bullets. As good as they shoot--they could probably be better because the freebore would allow more than 2.8 COL for almost all bullets for both the 6 and 6.5 that I've tried. However, the case design already has much of the bullet forward of the case mouth. It's my nature to try to extend the COL--not only to get the bullet closer to the lands--but also to gain powder capacity in the case. The problem is in the geometry of the cycling of the components--most magazines, ramps etc do not allow for enough lift in longer COL cartridges to "gracefully" clear the chamber face. You can easily verify this by "dry-cycling" some cartridges and observing the damage to the bullet upon feeding. The radiusing of the chamber face is another area that I think with just a few thousands inches extra polishing in the area where the bullet is in-coming I think would also help make it easier getting the longer COL, higher BC/SD bullets to chamber better. My wild theory is that the "angled feed" also introduces slight asymmetry in the cartridge's ability to seat concentric to the chamber. Pretty much without exception, I've noticed that cartridge designs that have "bullets long in front of the case mouth"--like the Grendel, valk, creedmoor etc. can end up jamming or being "resistant to extraction" even when the bullet still has plenty of "jump" left to where the ogive engages the lands.

[jetinteriorguy]

I’ve always been concerned about Bullets being bumped off center in AR’s due to both the type of feed ramp and the violence of the action as it cycles. You would think barrel makers would consider this when designing their barrels, or at least a different feed ramp design just for this reason what with all the different calibers available for the AR platforms.

[stagpanther]

You would think barrel makers would consider this when designing their barrels, or at least a different feed ramp design just for this reason what with all the different calibers available for the AR platforms.

Yeah--I've often thought about why "optimized" extensions aren't more commonly used--it seems just about everything is based on standard M4 ramps.Presumably bolt lugs would need to be altered a bit also. So what, right?

[sevt_chevelle]

I've always had a love/hate relationship with Aero Precision's 308 receivers--the thing I love about them: their uppers generally clock extremely well to their rails--and I really like their barrel-nut configuration for attaching barrels to their uppers.

Who would you suggest using for Ar10 receivers? Aero's Ar15 receivers IMO are top notch.

[stagpanther]

Who would you suggest using for Ar10 receivers? Aero's Ar15 receivers IMO are top notch.

It's a tough world in 308 builds--because there really is no such thing as a standard though early on DPMS sorta took a lead as they were a major bidder in a military contract. As I said I LOVE Aero's uppers and rails--but their lowers are not engineered as well IMO--especially if you attempt to use them with non-Aero parts or mated to a non-Aero upper. To be fair--other 308 receivers from other manufacturers also tend to be "picky" about what they work well with. PSA lowers tend to play well with most other manufacturer's uppers in my experience--but then again you really have to use mostly their LPK's to ensure proper functioning of things like the pivot pins.

A 308 lower may seem like a "bargain" when priced around 150 to 200 +/-, but what I've learned over time is those annoying gaps or cants between the upper and lower can cause all kinds of headaches with getting the finished build to operate reliably well. My opinion has evolved to the point that in the 308 world--at least when building something "touchier" than actual 308/7.62 x 51--it likely will be well worth the extra money to spring for a precision billet and matched upper and lower set. A precise fit with trued "bore" of the upper probably is well worth the premium in extra money.

The builds I do with Aero's receivers I generally expect that I'll have to buy almost all the parts from them of I want to make it run well. Even when I do buy exclusively their parts, I almost always have some final truing work to do to get the upper and lower to truly mate well without wobble or flex. A few thousandths of an inch here or there can make a difference in how well the BCG "succeeds" in introducing a cartridge cleanly and reliably and without damage from the magazine to the chamber.

It's also possible that I'm not a very good builder.

Sorry, I know that rambling didn't really answer your question, I guess what I'm really saying is be careful and ensure parts compatibility, and no matter who's receivers you get, it's probably a really good idea to get matched upper and lowers as well as parts kits in the event the receiver manufacturer also makes parts kits. Mil-spec means something in the AR15 world--it doesn't in the 308/AR10 world.

[ed308]

I only have one Aero AR10. But my Enhanced upper and their lower for my 6.5 Creed fit together nice and tight. I did use all Aero parts. I use Magpul mags exclusively with my Aero BC and HP bolt. No feeding problems. Don't forget the screw in the lower for snugging them up. About the only negative I can say about mine, wish I could've lapped the upper but that's not possible with the enhanced version and the lapping bars available. Fortunately, mine didn't need to be lapped.

[stagpanther]

I only have one Aero AR10. But my Enhanced upper and their lower for my 6.5 Creed fit together nice and tight. I did use all Aero parts. I use Magpul mags exclusively with my Aero BC and HP bolt. No feeding problems. Don't forget the screw in the lower for snugging them up. About the only negative I can say about mine, wish I could've lapped the upper but that's not possible with the enhanced version and the lapping bars available. Fortunately, mine didn't need to be lapped.

The 308 lowers I bought apparently are all gen 1--including the enhanced builder sets--not a huge deal, but it would be kinda nice if there was no fitment issue to being with.

[stagpanther]

I just checked my builds--I thought I had matched sets but I don't, my mistake; though my most recent lowers do have the tension screw--which as far as I can tell simply applies upward pressure on the bottom of the upper's pivot pin collar. Works--but not as ideal as a proper fit. Lots of people think the wobble makes no difference between the upper and lower--I disagree.

[stagpanther]

Went out today and tried some handloads in the sierra 110 MKs and the 107 RDFs.

It did not go well.

Both cartridges I seated the bullets to a COL of 2.79, but for some reason I haven't quite figured out yet the matchkings would intermittently jam into the chamber face pushing the bullet back--whereas the RDFs ran flawlessly.

Conditions were pretty cold--in the low 20's with a crosswind of maybe 14 mph. That's actually pretty calm for on the coast. Both loads chrono'd velocities well under what I expected from the data and QL formulas I used; not sure how much of that is or is not attributable to the cold.

Even though the 107 RDF's cycled, fired and ejected without issues--I strongly suspect they are still being damaged somewhat in the feed process--most of the groups were around MOA or slightly larger, though 43.1 grs of 4000MR turned in an OK group.



This gun should be able to group will under .5 MOA IMO so I figure I still have more work to do on getting a better feed from magazine to chamber.

[stagpanther]

OK--so I did some trimming on the magazine feed lips and bent them up slightly to get a better pitch angle of the cartridge--and that seems to have helped some, I went out for a quick few shots of a couple of the better groups from yesterday--and I noticed a definite improvement though a couple of dry-cycled cartridges are still showing a bit of wedging going on in the process of chambering. This group of 107 rdf's was in the running for being around .3 MOA when I pulled the last shot on the upper left. My curse I'm sure was louder and heard further away than the rifle report.

[stagpanther]

Unfortunately I'm about to run out of powder for the rdf load I'm working on, so I can only test a few more charge weights. I also just got in some Lapua 6mm creed brass--and like their 6.5 it seems to be targeted to the precision shooters crowd--most notably it has a small primer pocket and small flash hole. Just out of curiosity; I decided to load duplicate loads using both the lapua and starline brass and will test them side-by-side. Although I haven't water volume measured the respective cases--it became immediately apparent the lapua case has a slightly smaller capacity in that the upper loads seem to compress more in the seating process.

[stagpanther]

I got some new lapua small primer brass in and decided to see how they would do with the 110 MK's. I decided to try some old tula small rfle magnum primers since I read someplace that the PRS crowd highly values them. I also finally decided to replace my dog-grooming table that I was using as a bench since it had become much too wobbly. I decided to get a Caldwell Stable Table since the reviews seemed OK.

As for the table--it's a definite step up from what I had been previously been using, but it has several significant negatives--though I think I'll be able to develop work-arounds. The steel legs work well on uneven ground--as long as the very end of the legs are what is contacting the surface--I'll probably come up with some stake points of some sort sooner or later. The rotating bench post and the table collar have to be torqued very tight to remove all wobble--in addition the Teflon gasket tends to creep outside the collar--got to come up with a better plan for that. The table itself has scant real estate available for much else than the gun itself, but I can adjust to that. Biggest annoyance in the design to me is the hard-plastic table surface; it supplies about as much traction as ball bearings on the surface of a frozen pond. As a consequence, it was very difficult to keep any of the rests from moving around on the surface; even when applying the slightest of pressure. At the very least I will put a rubber coat/mat of some sort on the table top.



I haven't had much luck getting really stand-out results with the 110 MK so far, my last go with superformance was less than stellar. Today I decided to switch to H4831 and things improved somewhat--over half the charges grouped at or slightly under MOA, with this group of 41.8 grs turning in the best results so far.



Considering the issues of adjusting to the new table--as well as below freezing temps and crosswinds of over 20 mph--I think I will revisit this combo when I get some adjustments done and the weather gets a little better.