.257 or .260

G

gdcpony

New member
Ok, I know this is an odd question for the reloading section, but I think you all will understand the question more. I am about to start on a long awaited build of an LR-308 into another rifle. While I dream of a 1000yd AR type rifle, I know that my level of practice, budget, and typical use would not make that practical. It would be for varminting out further than my AR can reasonably reach (450+).

So with the parts all picked out, I am just picking a caliber. It doesn't affect the cost of the build regardless of which I choose. There is only which suits my tastes and performance requirements more. After all, the round must be accurate, suitable for both varmints and deer, and reasonable to reload.

I am a nostalgic guy so the first plan was a .257Roberts. In my 26" barreled Mauser, it sends my favorite 100gr GameKings out at 3200fps loaded with H414, and still over 3100fps with Varget. With the 90gr it is faster, and deadlier on groundhogs. However, the pencil barrel and loose tolerances of the old sporter leave a good bit of accuracy to be desired. I have the gear to load it, but I am on the last firing of my brass and have only 20 (out of a former 500) left to load up. Hunting bullets are easy to find and reasonably priced by today's standards.

Then I started looking at the .260 Remington. The BC on 120gr bullets is great for the weight. I can make new brass out of .308 (something I have never had to do before) which I have plenty of once fired for. At extreme ranges it out performs the .308 in drift and speed, which is a great plus for me being that I despise that round. It is a proven performer in the LR platform already as well. However, I find myself left wanting in bullets that are for more than matches, it doesn't have that "one off" effect I like, and I would have to start from scratch loading a new round as well.

So which one? The oldie, but goodie, one off round, or the newer more efficient round.
 
I love the .260 Remington and I have two in bolt guns, however, it is not a friend in the .308 pattern ARs.

If you want to build a .308 pattern AR in a mid-bore, the 6.5 CM is the ticket. We have built several and that cartridges just does better in the .308 pattern auto-loaders. I'd drop down to a .243Winchester as a second choice, which gets you back to the .308 based brass.

That said, the 130 grain bullets in the .260 are fine for hunting and I have shot a lot of them with smiles on my face.
 
260 or 243. Both proven performers at distance, both will easily put down deer, and there is massive bullet selection from every bullet manufacturer.
 
I have owned my .257R in a small ring Mauser w/ 1.5-5 Leupold for 40+ years. It has accounted for about 20 deer, countless fox and coyote.

But, as much as I love my .257 I would not build a new one. I can get a .260 to do everything as well in a short action with better bullets.
 
Since you can't cram a 257 Roberts into an AR, isn't your question kinda silly?

Or is this "do I build a mauser or do I build an AR" question instead?

Jimro
 
IMO ,gdc,you may have one foot in one world,and the other foot in a different world.
The .257 is a fine cartridge.Key is to understand its niche.It came from the 1920's.The parent case is the 7x57. There was no short action,and there was no .308.There was a 300 Savage and a 250 Savage,each admirable in there own right.
It was so simple to rebarrel a Mauser in 7x57 to 257 R with no other changes.

Woodchucks to white tails,eyeball range estimation,iron sights to at most 6x on a hunting rifle,300 yds was a long,long shot.
With the light recoil of the .257,no real need to flinch.Its easy to shoot well.

You can get a clean kill on a deer,and eat pretty near the bullet hole,not 1/3 the carcass bloodshot and shredded.
There is where the elegance of the .257 lies.Perfectly.

But an AR(10 or LAR) is not a Mauser.It was designed for the 308 parent case.Why even think about fighting it?Hint,to make it more clear,6mm Rem vs .243,pretty much the same.But in a Mauser,go 6mm,and in a modern .308 length short action,go .243.Why fight unnecessary problems?

As has been mentioned,the 257 is from poor to impossible in an AR.Max cartridge length 2.800,and the .257 has more case taper so mag stack issues are likely.

Look carefully at the long range bullets available in 25.Fewer in Match.I think Berger has a 110 gr.Compare to what is offered in 6mm and 6.5.Ballistic co-efficient matters at 1000 yds.

I suggest,love the 257 R for a 300yd + elegant,balanced,delightful sporting round.

And look to what is tried and proven for a long range AR.
 
If it were me, I would go with .243 Winchester. You can buy all the parts for that conversion. The last think I want to do is be the guinea pig that has to figure out all the gas handling problems for a new AR round. Where to put the gas block. What diamer hole in gas block and barrel. What size gas tube. What buffer to use. What spring to use. You could fight with it forever before you ever got it to run reliably. You might have it running reliably and beating the hades out of itsself and not even know it.
 
Well, I did go with the .260, but I feel that I should put one thing right. You can indeed put a .257 into an AR. It has the same COL even though the brass is longer.

I figure though that with a .257 already in the house, why not play with a new caliber?
 
I will not argue that the .257 R can be stuffed in a 2.8 mag box.It can.

But the .257is not at its best loaded to that length.Its pretty deep seated.I load mine long ,in a Mex Mauser standard box.

SAAMI put the max length at 2.780 because some rifle mfgrs offered the .257 in a short action.

The .257 was initially wildcatted out of 7x57 brass to work in a7x57 mauser rifle.Max LOA for 7x57 is 3.065.

I have not conducted tests,but I suspect that if you tried to use a 20 rd magazine with the .257 R you would have problems.The .257r is a more tapered case.I suggest it would require more "banana" curve in the mag.
IMO,your .260 was a good choice.
Note that when the serious and successful went after a 6.5 1000 yd ctg,the went with a shorter catridge,the 6.5 Creedmore.You might read up on that one.
I really like my .257,it has served me well.For long range shooting,well,I'm realistic!Mine is an Ackley,I hot rod it a bit,and I like the 115 Nosler Ballistic Tip.With a BC of about .435,its just not going to run with the bullets available in 6.5 at long range.
But for hunting at sensible ranges,its great.
 
I build a few rifles for myself every year.
I have built only two 260 rifles.
I have built only two 257 Roberts rifles.

I consider them to both be a handicap, compared to a 140 gr boat tail at 3400 fps coming from a 7mmRM.

There are guys with much more ability than me that could outshoot me and my 7mmRemMag rifle(s) with their 260.

An my son can do more chin ups than me with a 30 pound pack on his back.

The point is the 7mmRemMag makes it easier. If the limit for the rifle, scope, bipod, sling, rear bag, and ammo is 10 pounds, make it a 7mmRM. That is a man sized gun. But if you only weigh 105 pounds and can only carry a 7 pound rig, then get a cartridge that is much lesser, like a 260 or a 257.
If you can only carry 5 pounds, get a 223. If you can carry 30 pounds, get a 50 BMG.

But if you are a full sized man, don't buy a little girl's bicycle.
 
Well, at the risk of not sounding very manly, per Clark's thinking, I have a 260 and am very fond of it. If I had to choose between a 257 and a 260 on a new rifle, I'd go with the 260. Only small reasons to do so, but they would push me to the 260. The 6.5 Creedmore would also be a consideration.
 
Clark,the 7 RM is a good cartridge.No argument.I've had 3 of them.I still have one.
I built my .257 because I wanted more edible meat out of a deer/antelope size critter.
It sure works good..I don't see where that has anything to do with bicycles or gender issues.

But what I wanted to ask you,if you go back and read the original post,
What does a 7mm Rem Mag have to do with an LR-308 based build?(A .308 sized AR?)

You have to start with a 2.8 in mag box.
 
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GDC,

The reason the 260 isn't used much in the AR platform is the heavy for caliber match bullets end up seated way deep to fit the magazine. Hence the Creedmore, and Grendel cartridges. Shorter than standard 308 casings, so that the bullet can be seated longer.

As for the 257Roberts, it is indeed made from 7x57 Mauser casings. I got 100 PPU 7mm Mauser casings for cheap, and necked them down to the 257. Work fine...

PS, For the Roberts try some Reloder 17, and Hogdon Hybrid 100V. Giving great accuracy and velocity out to 450yds for me...
 
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