A buddy is considering a 308 class AR and I'm recommending that he consider 260 Remington rather than 308.  Does anyone have experience with that caliber in the AR platform?  If so, what can you share?
Keith

I would do 6.5 Creedmoor honestly.  I had a .260 chambering and switched over.  Some of the heavier bullets go over the OAL of the mags for a .260.  Also, unless he is handloading there is much cheaper match ammo for the 6.5.

I run an LRP-07 in .260 Rem, shooting 139gr Lapua Scenars at 2780.

It is an amazingly accurate rifle.  

To be honest, all of the 6.5's do the same thing...long story short, most folks want to push a 140gr bullet about 2800 (2750ish in a gasser).  However you do this, whether it is via Creedmoor, .260, or 6.5x47 Lapua doesn't really matter, IMHO.  It is just how do you want to get there?  Here are some of the differences as I have observed and pondered them all:

The Creedmoor offers quality match ammo at decent prices.  .260 offers a litany of brass choices over CM and x47 Lapua.  x47 Lapua offers small rifle primer pockets (but only one source of brass).  

They are all a means to an end, the CM and .260 are much cheaper, components-wise, when compared to the Lapua.  My concern with the Lapua in a gasser would be the treatment of your brass.  Also, I lose true, .260 RP-branded brass all the time and I don't care one bit, particularly during matches.  If I lost just one of my x47 Lapua cases, it would bug the piss out of me for a long while.

All really good points.  Thanks.
Keith

I'm a big 260 fan, s lot of which has to do with the brass selection and once you get into the 6.5 and 6mm rounds there is a lot of arguing about what is better when they are much more alike than different.

For a gas gun I'd look more at the creedmor. My 308 AR is harder on gas than my bolt guns and the creedmor gives you the ability to get the bullets a little closer to the lands.

I've had 2 different LR-260's, the current one being built by GA Precision with a 22" Bartlein pipe.  Shoots like a laser.

The problem with these calibers is getting them to run optimally in a gas operated action.  The port pressure is much higher than with 147gr 7.62 NATO at the RLGS location, so the BCG gets hit hard with gas, causing early and violent unlocking.

There are some band aid approaches to dealing with this, but the gun was never meant to run at port pressures over 17-18ksi really.

That's a great point, I've never thought of that.  Obviously, I know the pressures in AR's can cause issues, but I didn't think about the rifle not being intended to run over your stated pressures...makes sense.

Although I do believe that many companies have done fairly well in regards to development of tools (probably what you referred to as band aids) - HP bolts, low mass BCG's, heavier buffers, stiffer springs, adjustable GB's...anyhow, the bottom line is that I have seen a bunch of .260 AR's, several CM's and one 6mm CM (awesome round/rifle, by the way), and I have not yet seen any issues with any of them.  I'd love to go out and see someone running a x47 Lapua in a gasser, but I think those folks are going to be few and far between.  There's not many people who want to spend all that time prepping their brass just to have the gasser chew it up, gnaw it, and chew on it some more!!

I think when it is time for the LRP to be re-barreled, it will be in a 6.5 CM only because of the factory ammo option.

I have a 260 barrel for my OBR.  Shoots excellent.

Velocity with 142s was not up to par as you have to seat the bullet so deep there is no room for powder.

I switched to 123s and am very happy.

123gr and 130gr is where it is at with the .260 Rem and 6.5 CM, even in bolt guns.  You will beat the 140gr VLD for trajectory and match it for wind.

I've never had a problem with case capacity.

You can do a work over on the bolt and barrel extension to baby the brass, but you really need the correct gas port size, buffer weight, recoil spring, and BCG set up to handle the higher port pressures.

I've bent 3 firing pin retaining pins in just one of my .260's, pushing the 130gr VLD over 2800fps.  You really have to back off away from maximum loads, and JP has a technical note saying the same thing.

Nobody ever believes me when I tell them that. Used 120 Scenar L's out to 600 at the NRA nationals last year won the anysigt tactical rifle class, with that load. everyone was shocked that I used 120's. try to explain it, but they are convinced you need 140 class bullets past 300. I would feel ok shooting the 120's at 1000 for score.

LRRPF52, mind doing a breakdown on your velocities for the 123's and 130's. and what is your barrel length?  I've contemplated trying some 123's but the 139's have been exceedingly accurate in both of my .260's.


I appreciate it.

http://www.ar15.com/forums/t_2_219/265969_18_New_260_Remington_PredatOBR___accuracy_repeatability_exercise_.html

LaRue has been working on a 260 barrel for the tOBR platform. Link above. Maybe he will throw some knowledge this way

I'm using a GA Precision built 260 with a Bartlein pipe.  With 130 VLD's at max using H4350, I'm getting 2800fps, which is a sick 1000yd load.  It's so freaking flat, you wouldn't believe it when you see the holes on a double cardboard target at 1000yds.  When I first shot the 130gr VLD at 1000yds, I took a cardboard crib mattress box and placed it on two target stands with 1x2's.  When I drove down to the target and put a rod through the holes, it was like 15 degrees trajectory.  You will never see that with .308 Win. unless you hot rod a 30" F Class gun with some of the new higher BC pills, and even then, there will be more drop due to the weight.

The 130gr VLD in the .260 Rem or 6.5 CM is simply laser-like.

So are the 123gr SMK's, Scenars, and AMAX's, although I have a personal theory on the AMAX's working better in hot weather with less nose deformation, than in the cold.

The 139gr Scenar is super accurate for me as well, but I think it is better suited for the 6.5x284, like any other 140gr class bullet.

Panzer,
Would you share a few things with us?  First, tell us why you chose the 120gr. Scenar L over the 123gr Scenar?  I am shooting the 123gr. Scenar's and they are really accurate for me.  I am always looking for improvement.  Second, will  you tell  us a bit about your rifle? And, finally, what was your load for the 120's?

I had read somewhere (probably a Berger ad :>)) that the Berger 130 AR Hybrid is supposed to be the "ideal" bullet (weight and shape) for a gas .260.  Will you comment?

Thanks
Gr8horses

Easy. the 120L's were on clearance from midway and were right at $300/1000. So I got those. if they weren't on clerarance the choice was going to be the 123 lapua.  I loaded them with 39.0 Varget in Hornady cases with Wolf LR standard primers.  with 120 class bullets, it doesent matter either way. the 120 class shoots very flat and is within a click on windage to the 140's for a long ways, and easier on a gas gun to shoot. plus they shot extremely well. testing with 136' L's and i couldnt get them fast enough to shoot any better, with the best accuraccy actually giving the 120's a fair edge in windage. I have a box of the 130 Hybrids to play with, but I also have another 1k of the 120's to shoot too. I can see where a 130 would be just right for the 260, and the Creedmoor. the .260 has a lot of taper and case length, by the time you stuff a 140 in it and get it mag length, the creedmoor case is supposed to have a hair more room for powder. The 130 shouldnt give you any problems or cut into your capacity if you made them mag length.

The rifle is an Armalite AR10 with a KAC m110 Stock, and sws Rail, GA trigger, and had a NF 3.5-15x50 F1 Mil/Mil for most of its life. ( now has a 5-25 ATACR mil/mil F1) The barrel is a 23 in 1/8 twist Bartlien 5r that was a remington Varmint contour blank that was just turned down for the diameter of the barrel extension, then the standard taper to the gas block, which I had made .750, with a syrac gen 2 adjustable gas block, then the rest is set up with a collar for an AE30 supressor that was made in 6.5, with 5/8-24 threads. I keep a M110 FH copy on the threads usually as a protector, comes off easily to direct mount the suppressor. I also painted the rifle the tradional ugly as hell, yet beutiful, Rhodie cammo like the FAL's, and on a whim decided to shoot it in the NRA national Championships at Camp perry last year in the Any sight match/tactical rifle category. I won that, despite some struggles shooting that rifle set up in tradional positions. The 120's did awesome at 600 with a 198,199,199 with 10-12 x's even in some tricky winds. On a GOV computer right now, cant link to photobucket. here is a thread with it pictured however, second page.

http://www.ar15.com/forums/t_2_381/269329__ARCHIVED_THREAD____Who_can_build_a_6_5_Creedmoor_SR25_.html&page=2

Wow...that is impressive.  Im gonna have to step out on my Scenar's to try these lighter pills.  Is your Bartlein 22" as well?  No seating depth issues with the 130 VLD (I assume you're running pmags)?

Thanks again.

Here's your pic.  Very nice.

Yes, 22" Bartlein.  I also have a 20" BHW I'm either going to sell or build up into an upper and sell.

Panzer,
Nice rifle! A coupla' three more questions.  First, my assumption is that you are using the KAC stock because you are doing 3-position type shooting, and my question is would you change it for another if you could?  Second, will you provide us your COAL for the 120's and how you got there?  Third, you said that you're using Varget as your powder.  Will  you please give us your rationale for that?  Lots of people are using H4350 for the .260, but I have read that Varget or IMR 4320 or 4064 should be a better choice.  How did you decide?

Thanks,
Gr8horses

Thank you!

I used the M110 stock because I had it ( I was going to do a "mini" M110 ish copy on an AR15 years ago, those KAC parts went to a SAM-R Build) It did help with the positions though. If I were to change it, I would go with a straight up A2 stock. I shoot with that stock on 94% of the rifles i do shoot alot. ( I am High Power shooter mostly, Shoot on the All Guard team, so our main rifles are AR15A2's for 100-600 yards,  and the 308 AR10 set up like an A2 for Long range 800-1000 yds. So to me that stock feels like home when I get behind it. I do have another m110 stock that I might finally do my Mini m110 on this year)

the 120's I load to 2.755 coal For no other reason than that number was out there for 6.5 Creedmoor for alot of loads, just happened to work out for me as well. The 39.0 Varget, thats the factory recipe for the Hornady 120 A-Max thats on the box I saw. I started at 37.5 and went to 40.0, 39.0 was the best with a big node from 38.8-39.2. Velocity in the 23 in barrel without the suppressor is  2860 fps avg.  pressure signs didnt start until I got close to 40.0, but the groups opened up as well. ( I also know that it used to be 44.5 H4350. That shot well too, but the Varget load was more accurate and the rifle seemed to function smoother with it.)  Also its easier to load. Normaly I just dump the charges with a redding 3br, in two steps, so the charge is cut in half each throw, it seems to be much more consistent when cut in half. I have a pretty big Node to work with, but the ammo I used for the nationals was actually charged with a Prometheus I borrowed from a friend of mine. That thing is AWESOME if you can ever get ahold of one. fast and every charge is to the individual kernal of powder.

I still use H4350 for the occaisonal 136-142 load, but so far it just hasnt been worth it, except to burn off some odd lots of bullets. the 120's took me to 1200 before without an issue. I would most likely run the 130's with h4350 however and adjust the gas accordingly.

Thank you very much.  This has been very helpful.  I appreciate your time.

Gr8horses

For some reference,
Left to right,
120 Scenar L
130 Berger hybrid
136 Scenar L
140 Hornady HPBT
140 Berger Hybrid.

when can you guys sell me a barrel?

I've basically scrapped my .308 AR10 build and will sell everything off in order to now build a 260 Rem.

(it was an Armalite and finding a barrel was a PITA)


I'm reading that the 260 over the 6.5CM has an advantage when it comes to brass in that when reforming 308 to 6.5CM there is a 'donut' that forms in the case neck because of the shoulder and all the brass has to go through the extra step of trimming the entire case neck.


OAL is also supposed to be identical for the 308 and 260.


I'm not sure there is a reason to go with the 6.5 over 260  if I reload. Maybe if I only buy commercial ammo then 6.5CM may be better.

Lack of factory ammo options and the fact it may be awhile before I get into reloading, is why I scratched 260 off my list and got 6.5C.
Ballistics on 260 are great, if you wanna reload, give it a shot.
I have done some reading that led me to believe certian bullets may give some mag loading/feeding issues due to oal.
But that is just reading, I have no real world hands on with it.

Agreed. These are the same reasons I went with a 6.5 Creedmoor even though I reload and could work with the other calibers I was considering (260 being one of them). The 6.5's are something I am already messing with and they offer some really good specs. Besides, I wanted another 6.5 and in true arfcom style if I want one of the other calibers it'll just become another future project.

Between this and the 6.5G comments today, youre a big tease

You will more than likely get the donut from sizing down the .308 to the .260 as well.  I've got the donut from doing this.  

If you introduce a gas gun specific set of loads for the .260 Rem, that would be great, especially if they were competitive with 6.5 CM pricing from Winchester and Hornady.

I actually like the 123-130gr class of bullets from the .260 Rem gasser better than 139/140/142/143gr.

Any insight on why you chose 260 over Creedmoor? Glad to hear that some good 260 ammo options are coming to the table.

I asked in the Industry forum.....


His answer was basically "because that is what the .mil wanted"


So I imagine that "they" did their homework and for whatever reason found the 260 edged out the 6.5 CM


If big Army goes 260 expect the ammo industry to follow.

So what is ideal length in the 260 platform?


LRRP, your opinion please.  I realize that many say barrel length doesn't affect accuracy.....but that is simply not true......because you lose velocity.  which in turn effects accuracy.


Is 20" too short?  IS 22" THE IDEAL?

Maybe so. Would be cool to see some new 6.5 bullets.

Wish we had access to whatever process and testing was done. On the commercial side of things pretty hard not to go Creedmoor just on available ammo choices.

And was it still hitting with boring regularity out to 1,000 and beyond?

2 uppers...get both !

Even an 18" is going to have more performance than you need at 1000yds.

My 16" 6.5 Grendel is still hitting with boringly-predictable impacts at 1200yds with factory 123gr AMAX.

When I first shot my Bartlein barreled 22" .260 Rem at 1000yds through a crib mattress box so I could gauge danger space, it was so flat, it was scary.  The path was maybe 15 degrees at the most, nothing like the downward arc of a .308 Win.  That was with the 130gr Berger VLD.

I would look more at whether or not you want a compact gun, and then look at how much dwell time you want.  The less dwell time with these slow-burners, the better.  

An 18" .260 Remington is boring at 1000yds, and you won't see but .4 mils drop difference with 130gr, and .1 mils wind drift difference compared to a 22".

It might even run better since it can relieve the gas system pressure sooner.

My 130gr VLD load would be supersonic still at 1375yds from an 18" at sea level, and since the twist rate is so tight, it doesn't care about going through transonic.

If I take 2 barrels of the same diameter, the 18" will have more stiffness than the 22", leading to more accuracy potential in the whip axis.

Excellent information. Thanks.  So with these slow burning powders in the 260/6.5 having a rifle length gas tube and shorter barrel will keep that pressure spike to a minimum with shorter dwell......which I guess is better for barrel and BCG life.

That said, pressures obviously go right back up with a suppressor.


Hmmn, 18" with rifle gas system sounds about right.  Going shorter would need a Middy gas system which is going to make a much longer dwell I'd imagine.


EDIT: Ok Mark, Gonna start piecing together my build 'sans barrel'........gonna wait on one of those LaRue 260's that are sure to come

since y'all asked:  I have an ArmaLite AR10 upper and lower with the A2 buttstock.  Installed a Rainier Ultramatch barrel in DPMS pattern, 22" with a +2" gas system, JP Enhanced "high pressure" bolt on a Radical Firearms bolt carrier.  Slash's Heavy Anti-tilt buffer.  SLR adjustable gas block, ATC SR25 Gold trigger, ArmaLite forend.  "Little Bastard" brake.  JP recoil spring (not the captured one).  Had to use a GG&G rail with low mounts to get proper head position (more forward and lower).  Weaver Tactical 3-15 scope.  This results in a very low recoil rifle... easily spot bullet hits out to 1000 yds.

Ammo is handloads:  123 AMax, 38.3g Varget, Necked down and outside neck turned LC LR118 brass, Winchester primers.  OR: same bullet, WW 243 brass necked up and 39.3g Varget.   Either of these loads with either CCI or WW primers gives right at 2800fps with extreme spreads of less than 20fps, and will shoot nearly 1/2 MOA out to any distance you can see the target.

Rifle weighs right at 15# empty, but balances very well and is no problem for my 68-year-old carcass to pack around the field for the typical long-range match.

forgot to add:  Bullets seated to 2.82 OAL...the ArmaLite GenII magazines will do this....Magpul likely will not.

That is a post to make ya smile.

I have a DPMS lite hunter in .260 that I take out in to the woods looking for antlered things for some reason (don't recommend, just get a bolt gun, they're lighter, I'm about 10 lbs with a Trijicon AccuPoint 3-9x). and I have a .260 with a JP Rifles precision barrel that I built and haven't got around to shooting yet...

Somebody a while back I forget his username had some pretty high marks on the MOA all day thread with one with I think a Kreiger barrel.

Interesting, I may have to try and get a hold of some of those mags, my OAL was set pretty much precisely by the max length I could fit in the Magpul mags. ETA probably won't work with DPMS platform, so nvm.

Just a note.... the ArmaLite AR10 magazines will ONLY work in an ArmaLite "B" lower.

Am I to understand that you are running DPMS style BCG's in your Armalite AR10's?


This is the $64,000 question that I can't seem to get a definative answer on.


I'm in the process of divesting myself of all things Armalite because future barrels/mods to my rifles will be near impossible because everything seems to be DPMS/SR25 style....barrels and barrel extensions, mags, Bolt Carriers, etc


Maybe I need to find someone with a DPMS BCG and throw it in my Armalite and see if it works.

ArmaLite Inc. has been making the newer AR10As for years now, which take the SR25 mags.

No reason to ditch the company.

I see a lot of people say this but I don't understand. Do you see Armalite barrel extensions becoming hard to get? No question the DPMS pattern guns have more options but I don't think the Armalites a bad starting point.

Ok, not ditching the company.  I should have been more clear.

Ditching everything I have that is B-series.

Not sure if the new A-series changed not only the lower but also the BCG and barrel extension.


It's becoming very difficult to find Armalite BCG/extension barrels.


The new Gemtech suppressed bolt carrier is SR25 patterened.  


Too many "new things" that are SR25 patterned.  I think it may be easier to just switch now before it's too late.



Getting all the "old project" builds up and running and sending them off to the EE.

You can buy a extension from Armalite and have a barrel built in any chambering and profile you want.

If options are what you are after there is no question that the DPMS pattern is the far and away winner. I noticed you say SR25 patterned but I was under the assumption that the SR25 had its own BCG that was not interchangable. Is that not the case?