Looking for .308 or .260 Build Input

[NHPiper]

So my friend offered to sell me his Aero M5 set to do a build and I don't know what direction to take it in, so I need your guy's help!

It would be really fun to setup a gasser to run in .260 Remington to match my bolt gun, but I already have several custom precision rifles that are heavy and somewhat bulky, so I don't know if I want to add another to that my inventory with those attributes. I am thinking of building a short 16" .308 with a Ballistic Advantage barrel and then trying to find a blend of making it easy to handle while retaining sub-MOA accuracy. Optic would probably be something similar to a Vortex Viper PST 2.5-10x, but maybe include an offset RMR or backup sights. Think "urban sniper" with the ability to be portable.

So is this worth pursuing? Do I set it up with a Magpul PRS or some other type of collapsible stock to save weight (could be a lost cause anyways with an AR10 frame)? I have an 18" 308 Win built off a Surgeon action and it pushed 175 Noslers at 2600 FPS. If I go with a 16" BA barrel, I would probably move to 147-168 bullets.

I will also be running it mostly suppressed, which is the appeal of a shorter barrel.

Thoughts anyone?

 

[Racer9j]

Build a .260 if you like it better. I built a Mega Maten 18" 308 and I kind of regret going that route instead of 6.5. The few ounces you save are not worth the loss of performance compared to your .260.

I don't remember my exact weight, but with the PRS stock and extended rifle length handguard the rifle is pretty damn heavy. I took the PRS stock off in favor of a MOE rifle stock (super light) and it didn't help much.

Now I'm considering rebarreling to a 22" 6.5CM barrel, but I have barely any rounds through my 18" RA ultramatch barrel so I feel like I would just be throwing money away. So my point is chose your build off the round you want to shoot, because weight savings are minimal.

But there is a lot more experience shooters in here that will probably give you better advice!

 

[KimberGuy]

18" .260 would be pretty cool in a gasser. Magpul UBR stock if you want to save a little weight vs the PRS but not have to deal with the wobble of a carbine stock.

 

[stwcattle]

I would build the 260 but I'm someone that has a JP 6 creed, 6 creed tactical rifle and a 6 creed light weight hunter.

 

[Triple D]

I'd go with a 18 or 20" 6.5 creed ballistic advantage barrel. Maybe a 22" 6.5 creed Rainier ultramatch that was fluted to keep the weight down while still maintaining velocity. I haven't tested the RA 6.5 barrels, but their 223 Wylde barrels are GTG. The BA 6.5 barrels are great, but on the heavy side.

The reason that I would go with the 6.5 over the 260 is due to the magazine restrictions of an AR-10. When loading the heavies to mag length, the bullet has to sit deeper into the case, which takes up powder volume and "may" impact accuracy. For Hornady 140's, the base of the bullet will be close to or below the case body and shoulder junction to hit mag length COAL. The 130 class bullets seem to work better with the 260 in a gasser. They can hold their own in regards to drop, but are likely to be affected by the wind more as distance is increased.

Also, the brass may get some abuse since it's a semi auto. I run Lapua exclusively in my 260 bolt guns, but when building a LR-308/AR-10ish build, I wanted to use cheaper brass, as well as having cheaper factory ammo choices in the event that the longevity of the brass would be reduced due to cycling/ejecting.

If going 6.5, it'll be recommended to get a +2 gas system. I'm not sure if the BA barrels have a reduced gas port or not, but the pressures haven't been an issue, even when running 147's as long as the barrel didn't have copper fouling. Initial rounds fouled the barrel and I got some pierced primers and ejector marks on the brass. After removing the copper, I haven't had another issue. That said, if you go with a barrel that offers a +2 gas system, you should get it.

When factoring in the above, I decided that a 6.5 creedmoor fit the bill for me. The BA barrel works very well, despite just being a rifle length gas system, with Hornady 140/147's and my initial load workup with 142 SMK's showed promise.

 

[Greg Langelius *]

I'd start building on this. It appears to follow the DPMS pattern. Then, this barrel.

Finish it up with selections from here.

Or...

Just buy this.

I've been shooting this (.223/5.56, recently competed at 600yd) for more than a half decade, and I just recently gave it to my granddaughter. I will simply replace it with another of the same.

When the time comes for a larger frame version, I'll be building as I suggested above, but will be using a .260 barrel from Lothar-Walther.

The magazine length issue with the .260 can be resolved, at least in part, by using the Sierra 140gr SMK, which is noticeably shorter, and was the only 140gr-class SMK available back when I started out with the .260. It shot great then, and it still does now.

I've been handloading .260 with Hornady brass, and the SRA 142SMK and HDY 140gr A-Max at magazine length with moderately compressed charges in my bolt guns. I'm getting ready to shoot my first test loads with the same charge and the HDY 143gr ELD-X loaded to fit the Savage D/M with the 4.4" bolt pattern, which allows a longer COAL. I have never seen an issue with the former two, but I would reduce and work back up with any semi. The 140SMK may come to the rescue once again.

Greg

 

[DavidAR10]

In 1969, we put men on the moon using slide rulers... slip sticks as we called them.

It's 2017, and some of you wish to use cordite for long distance.

There is no reasonable reason to build a 260 gasser when the 6.5 CM is available.

And it doesn't take the integral f(x) by separation by parts to figure this stuff out.

Best to all.

Even the bird house builders.

 

[Greg Langelius *]

David, I get you. Honestly, I do. I might feel as you do if I hadn't already been shooting the .260 for over 15 years.

It's been my goto 1000yd chambering since 2002. it has always worked for me, and never given me any nasty surprises.

I can use .260 brass, and in a pinch, make my own by necking up .243 (and I'm not getting donuts, either), necking down 7-08 (this is my usual method), or even necking down .308 (if I was willing to do some neck turning). I'm using Hornady 7-08 right now as the basic brass for my 260 handloads. I guess one could make 6.5CM from another case, but I don't think it would be quite so easy.

So I think I do have a good reason or three to use the .260.

Mostly, though, after the cumulative investment of time and funds into the .260, just how easily could I justify starting the whole operation up all over again in order to utilize a pretty nearly identical chambering?

I do see some advantages to using the 6.5CM. I like the longer neck. I like the shorter case for magazine feeding purposes.

But these advantages are really pretty minor and come at the price of diminished case capacity and a corresponding 50-100fps velocity deficit with comparable bullets.

I'm getting around 2850fps from my 28" barrel with H-4350 and the older 142SMK and 140A-Max. and I'm not even getting near the max charge weight. That translates into a milder load for a decent velocity, and should help prolong bore life. I've been shooting my current L-W barrel on a Savage off and on since about 2002 (or 2003?). When the Monsoons die back in another couple of weeks, I'll be load testing the 143 ELD-X. That could be a whole new animal at our local 4800ft altitude. But the 140SMK woudl still be my choice for a semi, just to allow for less charge compression.

Personally, I think you might cut us 260 shooters bit of slack. Yeah, you like the 6.5CM. I feel the same way about the .260. When we get right down to it, the cartridges are so similar, and the differences are somewhat minor. I think we'd all do pretty well with either, and I also think that for those of us who have already made the investment, swapping or adding the other makes less sense.

Actually, I don't usually respond this well to dismissive ridicule. You might want to work on that.

And finally; FYI, I was one of those NASA contractor guys with the slide rules putting those man on the Moon back in 1968 and 1969. I was responsible for subcontracting out the work constructing and shipping out the Apollo Command Module Windows to the Cape, FWIW.

PAX, Brother Marine.

Greg

 

[Triple D]

As someone with 2 260 bolt guns (which I love btw), the creedmoor is a solid choice for a gas gun, imho.

I'm guessing your 28" barrel and 2850fps reference is for a bolt gun? That's a pretty stout load, and close to where I run 142's at in my 260 bolt guns, but the COAL won't fit into a 2.820 magazine. Tossing out bolt gun info, if that's the case, doesn't really help when someone is discussing a gasser, as they are going to operate at a lower charge/pressure with seating depth constraints.

Yes, the 260 has more case capacity, but that advantage is mitigated to a degree by having to seat the bullet deeper into the powder column to get it to fit in a magazine. On the other side, the 6.5 creedmoor is a more efficient design, which helps with the lack of case volume, but also allows for a greater range of bullet and seating depth options. It's actually a big win for a gas gun: equivalent velocity and more flexibility with projectiles and seating depths.

As far as cost to get into a new caliber...it's dies and brass, and really just dies for most of us. I don't mix my brass between my 260's, or any other rifles that share the same cartridge, so I'd be buying new anyways.

Just my thoughts.

Thanks for you're contributions towards the space program. From a kid till now, I've always been intrigued by space and what lies beyond. The technology that was used 30+ years ago worked, but there have been improvements in technology and design that can do the same things more efficiently. The same could be true for cartridges too.

 

[KimberGuy]

I'm running a 22" 260 gasser. Getting 2880fps with Berger 130 AR Hybrids and Re16. No pressure signs, brass is on its 5th cycle. Try beating that with your 6.5 Creedmoor gassers.

Also, running KAC or LaRue mags will allow you to load a tad longer than 2.820.

 

[Greg Langelius *]

Yes, that barrel is on a bolt gun, an older 2001 Savage 10FP action. I just mic'd the 143 ELD-X load, it's seated at 2.855" OAL. I arrived at that length by making five dummies, chambering them all with marker on the ogive, then running them through the magazine checking them all for feeding, then stroking the seater and lowering the stem until it was snug, then readjusting the seater stem 1/2 turn, and reseating all 5, plus using that locked adjustment for everything made after.

The 140SMK is noticeably shorter, shoots about as great, and allows for less charge compression. I recommend it for semi's.

I apologize, you're right; bolt gun data probably is out of place on this forum, I had missed the forum title when I responded to the topic.

________________​

I had come out of the Corps in Feb 1968 and went back to work at IBM. It didn't work out, I wasn't the same guy they had hired two and a half years earlier, and they weren't the same company I had joined back then anymore, either. I ended up taking a job offer with one of my customers, and suddenly, I was working for a small NASA contractor.

It was Razdow laboratories, a boutique supplier of custom optics and instruments, interferometry dothingies, and early laser research components.

One of our NASA contracts was to manufacture and deliver the Apollo Command Module windows, basically an inch thick, perfectly transparent hunk of fused Iceland Spar.

Funny aside, my ancestors were Vikings...

If you saw the clip where the three Astronauts read the 'Good Earth' passage from Genesis and the camera is depicting Earthrise from Lunar orbit; that image was coming through one of those windows.

When Apollo 13 lifted off, I had just delivered a window to replace one that had had a wrench go through it ('labor troubles'), had been up for nearly 36 hours, and had fallen asleep in the VIP viewing stand. When that bottle rocket lit off, I must have levitated a full foot while coming awake. You can feel the exhaust plume rumbling inside your chest. Main Ignition begins with a humongous BAM!!!!, followed by a huge ripping sound until it goes about a hundred miles or so downrange. Worth losing a little hearing, just to be there.

Those windows priced out at around $20,000 per; in 1968...

On Dec. 24 1968, Razdow became Yardney-Razdow and staff reductions were instituted the same day, resulting in my being laid off on Christmas Eve..

I watched a couple of the very last shuttle launches from Patrick AFB more recently. Those babies had some rumble, too. That night launch was astounding from a couple of miles down the coast. The local radio station broadcasted the CapCom chatter, too.

I drove all the way back to Orlando that night utterly pissed off that they had Proxmired the Shuttle Program. Nowadays, if we want to send Astronauts up to OUR International Space Station, we have to Pretty Please the Redskys. Oh, yeah, I'm a real fan of that O'Banban fella

Everything, starting with a raw Calcite Spar substrate, that was involved with producing those windows and getting them to the Ceape was my responsibility. I managed the four subcontractors' participations and provided the transportation, including down to the Cape, personally.

I was just turning 22 then. Good God, those were phenomenal days for me back then. Still some, too...

As of this day, we are married 47 years.

Greg