.260 Remington questions

[belizejet]

Ive decided to build a .260 Remington AR-10 for a few reasons (one being that I reload and brass can be made easily from readily available brass so it won't cost me more than .308 does already to reload for). I have a dilemma though about the barrel. I want a top notch barrel but Im torn between 20' and 22". I have decided to go with a 1:8 twist though so it can handle the bigger bullets and take advantage of the weight and BC to combat wind. I want it for long distance gong killing and maybe some hunting. It will weight a bit so I'm not lugging it around in the Elk woods. Ive been told that the extra 2"s doesn't do much for accuracy and velocity. Does anyone have experience either way. Im going DPMS style build. I already have most of the parts but the barrel is one of the last ones I need. I will be using a suppressor on it also, so gas system length could come into play.

Fire away!

[XC700116]

Longest barrel and gas system you can find in all honesty. You're giving up a good bit of velocity in 260 vs a bolt gun by putting it in a gasser anyway. It's also pretty high pressure so the longer gas system helps to tame that a touch especially when suppressed, you're going to want the dwell time as long as possible or you'll be stamping ejector marks in your brass pretty quickly. I'd be looking more along the lines of 24 or 26" to get the most from the cartridge. Either way a small gas port and a high quality adjustable gas block is going to be a must. Might be looking to add some significant weight to the BCG/buffer as well.

As for a barrel I'd be looking hard at Kreiger, JP, etc. I've also seen some really good results from Black hole lately too.

[Delfuego]

I built mine with a Lilja 24" prefit. After Dan Lilja re-profiled the breach face a little it fed like a champ. A 24" barrel is a bit long and heavy, but as XC700116 said, more velocity is better for 260. JP makes great stuff, but it is pricey. The 140-142gr bullets need to be seated out further and as the throat erodes, you may have more trouble with overall magazine length. The 123-130gr bullets are more optimal for a semi and will get more velocity. You're already gonna be cheating wind with 260 (especially vs 308); don't worry too much about real high BC bullets (like SMK142 or 140 Hybrids).

Regarding the brass, it may be somewhat complicated to form 308 into 260. If your name is Hoser, then maybe it's easy. For me, I just bought mine or reloaded fired bolt-gun 260 cases.

Be prepared for some over gassing too. I opted for the Tubb CWS instead of an adjustable gas system for simplicity, it worked great and cost $50.

6.5 Creedmore is a good option also. It has identical ballistics, but has cheaper off-the-shelf ammo and allows for better magazine seating length.

SApengiun has his JP 260 for sale. I have personally seen/shot it and it is awesome.
https://www.ar-15.co/threads/150470-JP-LRP-07-260-Rem-Full-House-for-sale

[C Ward]

Better off with a creedmore because of mag length constraints .

[MarkCO]

I tried the .260 in an AR-10 pattern rifle and I would concur with the posts above. I wish someone had talked me out of it before I went down the path. The 6.5 CM is a better choice for the gas guns IMHO.

I would consider a custom barrel with an extended length gas system and a pilot hole for the gas port so you can tune it properly once you have a good load developed.

Adjustable gas blocks in .223 open up over times and the erosion, with metal going into the gas rings can cause issues. With the AR-10, it is more prone to gas cutting and erosion well before the barrel is shot out.

[belizejet]

Thanks for the replies. I'm pretty set on .260. Looking at the numbers 6.5 creedmore and .260 rem are very close and the brass issue is solved. Also, I already have a BCG for the .260. I think I'm going with a 22" just because I may want to hunt with it and less drop with a can on it. An adjustable gas block is a good idea though. I'll pick one up.

[C Ward]

The 260 velocities that are published are bolt gun numbers . An AR10 pattern rifle is going to push the 140 class bullets at 2650 ish . The creedmoore is an all around better choice in a gas gun . Forming brass from 308 your going to have to neck turn because of donut issues .

[XC700116]

The bolt is going to be the same, and having been around a lot of 260/6.5 gas guns, I'd opt for the creed personally, the brass is a non issue when you start trying to chase the lands as the throat erodes and you end up compromising accuracy for mag length after about 500 rounds.

Also stick with the 120 class bullets and it will make your life much easier.

[belizejet]

Throat eroding after 500 rounds? Never heard that. Worst I've seen is 300wm after about 800 rounds. I think that It will last longer than 500 rounds. If that's it then I'm just going to build it in .308. Not worth eroding a barrel after 500 rounds. I may not even have a good load till 200 rounds. Who knows. I reload 12 different rounds already and wildcat two of them. Making .260 brass should be child's play. Making 6.5 creedmore brass is much harder from what I understand. I'm still saving for a barrel so I'm still
Open to options.

[Delfuego]

By throat/seating issues we are speaking of "chasing the lands". You will need to seat the bullets further and further out of the case to get the preferred jump and accuracy you want.

Even if you buy Lapua brass (@$100 per/100) it's still not that much. Changing calibers is never cheap. Also $100-$200 on brass is not much money when playing this game. Good brass equals consistency and accuracy, that's why you're buying a 260.

You skimp and it will be problem after problem. You want cheap? Stay with 308 and pick up range brass.

[XC700116]

Throat eroding after 500 rounds? Never heard that. Worst I've seen is 300wm after about 800 rounds. I think that It will last longer than 500 rounds. If that's it then I'm just going to build it in .308. Not worth eroding a barrel after 500 rounds. I may not even have a good load till 200 rounds. Who knows. I reload 12 different rounds already and wildcat two of them. Making .260 brass should be child's play. Making 6.5 creedmore brass is much harder from what I understand. I'm still saving for a barrel so I'm still
Open to options.
The throat will begin erroding at round number 1, fired down the barrel, that's the way it is. My last 260 barrel lasted 3000 rounds and was shot, the throat had erroded over .125" that's a lot of jump as you get to the end of the barrel life. It's a consideration you'd be a fool not to factor into the equation on a mag fed firearm, especially one in which mag length is extremely limited.

[MarkCO]

Yep. You are getting great advice from some very wise folks and while said differently, bottom line is consistent.

[belizejet]

3000 is what I expected. I already have long range bolt guns in .308, .243, and 300WM. I don't want a bolt gun, even if it is better. I want a semi auto that is more of a precision machine and further reach than .223, and more precise than .308. This is not a 3-gun rifle I'm trying to build. :) It will take me a loooonnnngggg time to shoot 3000 rounds through it. I'll look into the 6.5 creedmore some more but I reload and enjoy that part of it. If brass is a premium I want to make it. I don't want to just buy factory because it is already accurate. Anyone make 6.5 cd brass? It will be a few months till I can get the rest of the rifle together anyway. I'm in no hurry.

[C Ward]

Creedmoore can be formed with 308 . AR10's are hell on brass usually 4 or 5 loadings , doesn't make sense to spend hours forming cases and wasting one firing fire forming it when brass is readily available .

[XC700116]

3000 is what I expected. I already have long range bolt guns in .308, .243, and 300WM. I don't want a bolt gun, even if it is better. I want a semi auto that is more of a precision machine and further reach than .223, and more precise than .308. This is not a 3-gun rifle I'm trying to build. :) It will take me a loooonnnngggg time to shoot 3000 rounds through it. I'll look into the 6.5 creedmore some more but I reload and enjoy that part of it. If brass is a premium I want to make it. I don't want to just buy factory because it is already accurate. Anyone make 6.5 cd brass? It will be a few months till I can get the rest of the rifle together anyway. I'm in no hurry.

I get what you're getting at, but the main thing I'm trying to convey is the oal on the creedmoore allows you to chase the lands a bit while the throat erodes over the life of the barrel moreso than 260 does while still fitting the mag, so you should be able to maintain better accuracy because of that. While not giving up any performance characteristics to 260.

Then when you consider that you say it will take you such a long time to run 3000 rounds through it and thereby shoot out the barrel, the brass issue becomes even less of a consideration in reality because you aren't going to be trashing the brass at a very high rate. Just seems like a backwards way of making a caliber choice based on cheap brass for a caliber class that's only going to last for 3k rounds on average.