6.5mm Creedmoor vs 6.5mmx47 vs .260 Rem

I would choose the 260. Easy to get cases. I like the case taper especially for semi auto. You can neck down 308 brass and turn your necks and get great cases. I also have a few thousand 308 cases on hand. So for me it's a no brainer to me

All 3 are great. But like the other guys said 6.5creedmoor doesn't have good brass. So to me it's between the 260 and 6.5x47. Why bother with the 6.5x47 when the 260 is easier to get cases and factory ammo for and I believe the 260 has better velocity.
 
Buy the dies at my man Whitten. I think that's spelled right. Custom micro dies. Ready to role.
The hell with that small primer buddy, I like my butts big! That 6.5 Super LR/S girl is hot! Anyway, people stop buying all the Rem and Win. brass so we can use it to size up to the lady! We do not want to turn her little pretty neck. Thanks, Management
 
Yea, you right their, the 260Rem. is a better shaped cartridge for auto loading.
I would choose the 260. Easy to get cases. I like the case taper especially for semi auto. You can neck down 308 brass and turn your necks and get great cases. I also have a few thousand 308 cases on hand. So for me it's a no brainer to me

All 3 are great. But like the other guys said 6.5creedmoor doesn't have good brass. So to me it's between the 260 and 6.5x47. Why bother with the 6.5x47 when the 260 is easier to get cases and factory ammo for and I believe the 260 has better velocity.
 
The 6.5 Creed ,"bless his heart" just needs some damn good brass period. The 6.5 Creed would be great if it wasn't for the cheap Hornady brass.

Do you own and shoot a 6.5 Creedmoor? I have been since 2008 and always hear on the internet how horrible the Hornady brass is but have never had any problems with the thousands of round I have shot. Have brass with 8 loads on it still tight primer pockets. Just wondering what your basis is for the comment.
 
Do you own and shoot a 6.5 Creedmoor? I have been since 2008 and always hear on the internet how horrible the Hornady brass is but have never had any problems with the thousands of round I have shot. Have brass with 8 loads on it still tight primer pockets. Just wondering what your basis is for the comment.

+1
I have been shooting it about that long too. Still have the original brass and most of it has 8 to 9 firings with 2800 FPS+ loads. It still services as good practice brass. Hornady brass is match brass. I would definitely put it ahead of Nosler or Norma brass that costs a lot more. The Creedmoor family is growing and the popularity is already bringing other manufacturers to the table. That cannot be said for the 6.5x47.
 
Back in 07 or 08, when Tubb shot that bluish looking tube gun, I think, I talked my friend into buying one as soon as it hit the market. I wasn't impressed with the brass, period. I'm sure I can call Creedmoor back and ask the cute little California girl that answers if people call in sometimes with complaints about their arraignment with Hornady. Its not rocket science comparing brass fellows. Lets just see how much pressure they will hold before "flopping" above whats stated safe. Then compare that to the same test with norma or Lapua brass. THAT WAS A JOKE. But it would prove a point. I base my previous comment on the fact that I've been shooting the same 270Win since I was 11yr. I have reloaded every brand of brass available that I know of for my old gun. Bottom line is brass varies from batch and American brass tends to be less quality in a few ways. That's all. Lets not have to change a tampon over it.
Do you own and shoot a 6.5 Creedmoor? I have been since 2008 and always hear on the internet how horrible the Hornady brass is but have never had any problems with the thousands of round I have shot. Have brass with 8 loads on it still tight primer pockets. Just wondering what your basis is for the comment.
 
I notice you seem to be wearing a little sponsor patch from Hornady at the bottom of your post.. Would that have anything to do with your opinion?? Remember this about me as well as you, opinions are like asses, we have many. Lol, Smile
Do you own and shoot a 6.5 Creedmoor? I have been since 2008 and always hear on the internet how horrible the Hornady brass is but have never had any problems with the thousands of round I have shot. Have brass with 8 loads on it still tight primer pockets. Just wondering what your basis is for the comment.
 
Do you own and shoot a 6.5 Creedmoor? I have been since 2008 and always hear on the internet how horrible the Hornady brass is but have never had any problems with the thousands of round I have shot. Have brass with 8 loads on it still tight primer pockets. Just wondering what your basis is for the comment.

Just to play devil's advocate, I happen to get great accuracy out of Hornady brass, but I do find it soft. I have cases with 3 firings and several have pretty loose pockets. I'm firing 123gr bullets out of a match barrel and I'm about 7/10ths below book max with no gas leaks or primer flattening. It's not a myth, it does happen.
 
+1
I have been shooting it about that long too. Still have the original brass and most of it has 8 to 9 firings with 2800 FPS+ loads. It still services as good practice brass. Hornady brass is match brass. I would definitely put it ahead of Nosler or Norma brass that costs a lot more. The Creedmoor family is growing and the popularity is already bringing other manufacturers to the table. That cannot be said for the 6.5x47.

My experience as well. I have 260, 6.5CM, 6.5-284, 6.5 SAUM.

My favorite to shoot - 6.5 CM. I like them all, the CM is just so easy in so many ways.

I have had no problems with my 6.5 CM brass. I use Lapua in my 260. It is very nice as well. Maybe I'm not loading my 6.5 CM hot enough. But I get 2830fps with a 140VLD
 
That's why I started shooting the Creedmoor but not why I kept shooting it. It's an excellent well though out cartridge that performs. And as you mentioned my sponsorships are there for the world to see so not a secret. That said I don't sell out and bullshit people for sponsors. My reputation is worth more to me than any product or internet forum. I have turned down more than one sponsor who had a substandard product. The 6.5 Creedmoor, brass and all, is not one. There is no need for high pressure in the Creedmoor as it does fine to get the heavy bullets fast enough without it but it can be pushed.

Seeing as you didn't answer my question I will assume you are basing your opinion not on personal use and sending thousands of rounds of Creedmoor down range but on internet rumor mil. That's a mistake. Any product can have problems. Even your beloved Lapua but using a small problem as a basis for an over all opinion of a product is also a mistake.

As for calling around on you, if someone is it surely isn't me as honestly I don't care who you are and I have better things to do with my time. You are brand new on this forum but with your posts already on not just this subject I can see it probably won't last.
 
Just to play devil's advocate, I happen to get great accuracy out of Hornady brass, but I do find it soft. I have cases with 3 firings and several have pretty loose pockets. I'm firing 123gr bullets out of a match barrel and I'm about 7/10ths below book max with no gas leaks or primer flattening. It's not a myth, it does happen.

Never said it was a myth but different chambers and barrels also come into the equation. It's not just brass. The book listed loads are very low so if you are getting pressure below them then there might be something else going on.
 
Well, from what I know, and it ain't much, 6.5 Creed and 140gr at 2830fps is standard. You must be using H4350? You using 43gr. powder? I don't think you want to go higher...I would like to see how close to 2,900fps you could get , though, I'm game for experimenting, Bro.
My experience as well. I have 260, 6.5CM, 6.5-284, 6.5 SAUM.

My favorite to shoot - 6.5 CM. I like them all, the CM is just so easy in so many ways.

I have had no problems with my 6.5 CM brass. I use Lapua in my 260. It is very nice as well. Maybe I'm not loading my 6.5 CM hot enough. But I get 2830fps with a 140VLD
 
Well, from what I know, and it ain't much, 6.5 Creed and 140gr at 2830fps is standard. You must be using H4350? You using 43gr. powder? I don't think you want to go higher...I would like to see how close to 2,900fps you could get , though, I'm game for experimenting, Bro.

43grns I am getting 2920-2930fps with the 140 AMAX. 26.5" barrel. Shoots great. Ran it in a match about 4 weeks ago.
 
I was not refereeing to you in anyway Rob01, lighten up Brother, we're all just surfing the "World Wide Web." Damn, and I thought I needed to get laid.?????????
That's why I started shooting the Creedmoor but not why I kept shooting it. It's an excellent well though out cartridge that performs. And as you mentioned my sponsorships are there for the world to see so not a secret. That said I don't sell out and bullshit people for sponsors. My reputation is worth more to me than any product or internet forum. I have turned down more than one sponsor who had a substandard product. The 6.5 Creedmoor, brass and all, is not one. There is no need for high pressure in the Creedmoor as it does fine to get the heavy bullets fast enough without it but it can be pushed.

Seeing as you didn't answer my question I will assume you are basing your opinion not on personal use and sending thousands of rounds of Creedmoor down range but on internet rumor mil. That's a mistake. Any product can have problems. Even your beloved Lapua but using a small problem as a basis for an over all opinion of a product is also a mistake.

As for calling around on you, if someone is it surely isn't me as honestly I don't care who you are and I have better things to do with my time. You are brand new on this forum but with your posts already on not just this subject I can see it probably won't last.
 
I was not refereeing to you in anyway Rob01, lighten up Brother, we're all just surfing the "World Wide Web." Damn, and I thought I needed to get laid.?????????

Just fine in that department so don't lose any sleep tonight but when I see BS being spread anywhere but a field then I will say something especially when it's a product I have many years with and know all about it. More than most.
 
Damn, that's crazy you said that, because if you would to ask anyone about me and my sister , they all will say we're loud. Sorry if I rub off wrong, I don't mean to. I was the ADHD kid growing up that held a lot in cause my parents raised me to stay out of trouble. Then when the wrong person come along and hit me the gates of hell would unleash. Older age has calmed me alittle. I even had issues with it in the service. Caused some resentment from higher ups, so I understand now whats going on. Thanks for the heads up.
Bully, loud and proud may not be a good way to start. I've shot with Rob, I have found him to be a great source of fact.


R
 
Guys close to me will tell you I don't mean to come across wrong. I have found out that I have to be out of mind and out of site under certain situations in life. Things tend to go easier on me that way. Its kind of like easing your toe in the hot tub.
 
My loads are currently 142SMK with enough RL17 to get 2850 FPS. Could get more out of it but no need. It is in an accuracy sweet spot there.
I have a load with the Berger 130 VLD pushed by H4350 that tops 3000 FPS without being over pressure. I have just begun to shoot the 6 Creedmoor more and I really think it should go mainstream too. It is very accurate and shoots a little flatter than the 6.5 version.
 
My loads are currently 142SMK with enough RL17 to get 2850 FPS. Could get more out of it but no need. It is in an accuracy sweet spot there.
I have a load with the Berger 130 VLD pushed by H4350 that tops 3000 FPS without being over pressure. I have just begun to shoot the 6 Creedmoor more and I really think it should go mainstream too. It is very accurate and shoots a little flatter than the 6.5 version.

Yea, I like that 6mm Creed also. But, my eyes are really on the 6.5Super Lr/S. The one with .055 free bore. I bet you can get 3,000fps easy with 140gr loads. Whitley stated over 2,900 without any pressure what so ever. I've called all over about this cartridge. Even got transferred to the man himself, Whitley. I even hunted down 2,700 Win. brand .243 brass with my name on them, off the books. But, in the end I had to go Lapua, just for piece of mind with brass availability. My next build though, shoot4fun, will be a 6.5 Super LR/S. I would like to see someone build the long action one, (has more freebore) and set them long bullets out some with extra powder. What we talking about here fellas, "I feel", is 6.5/.284 performance with barrel life on par with the Lapua and such. I predict future practical tactical long range "Big Dog" here. I was right about the 260 in the mid 2000's or the reign of the 6.5mm's. But, have to admit I didn't see the reign of the 6mm's coming. I predict they will fall away some and people will say it's because missed calls by the score dude (because less impact). Sometimes it is and sometimes its just a grown man not liking you," fudging your hits." One of them kind of matches. WHAT GOES AROUND COMES AROUND.
 
Hey shoo4fun, what kind of effects in this Alabama heat and weather, are you having shooting Reloader Powder? I mean, how much does it effect your group if you work a load up on a 90F. day in the south then drive to an area similar but say less humity or pressure. I keep hearing how tempermental Reloaders are. I know there great for getting max velocity though. I use RL19 and RL22 in my 270Win. and 7mmSTW. Well, RL19 in the 270 and RL19/22 in the STW.
 
Yea, I like that 6mm Creed also. But, my eyes are really on the 6.5Super Lr/S. The one with .055 free bore. I bet you can get 3,000fps easy with 140gr loads. Whitley stated over 2,900 without any pressure what so ever. I've called all over about this cartridge. Even got transferred to the man himself, Whitley. I even hunted down 2,700 Win. brand .243 brass with my name on them, off the books. But, in the end I had to go Lapua, just for piece of mind with brass availability. My next build though, shoot4fun, will be a 6.5 Super LR/S. I would like to see someone build the long action one, (has more freebore) and set them long bullets out some with extra powder. What we talking about here fellas, "I feel", is 6.5/.284 performance with barrel life on par with the Lapua and such. I predict future practical tactical long range "Big Dog" here. I was right about the 260 in the mid 2000's or the reign of the 6.5mm's. But, have to admit I didn't see the reign of the 6mm's coming. I predict they will fall away some and people will say it's because missed calls by the score dude (because less impact). Sometimes it is and sometimes its just a grown man not liking you," fudging your hits." One of them kind of matches. WHAT GOES AROUND COMES AROUND.

If one wants 3,000 with a 140, and long barrel life to boot, one needs look no farther than the 6.5 SAUM.

Hint....



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Yea, a buddy of mine shoots the 7mmSAUM, and he is having a hell of a time finding brass for it. Plus barrel life with that short stubby round and all that fuel would probably only be worth 1,200 rds, and that's hunting accuracy. That's why I think the 6.5Super LR/S is perfect. You get 3,000fps performance with barrel life on par with the 6.5Lapua most likely. Plus you don't have to depend on purchasing one brand of brass. All in all you win,(Short Action, Cheaper brass, 3,000fps performance, extended barrel life, 30 degree shoulder, long neck, more efficient powder consumption, and it could be loaded with any 308 type cartridge brass with various work loads on you considering neck turning and case trimming an all.)
If one wants 3,000 with a 140, and long barrel life to boot, one needs look no farther than the 6.5 SAUM.

Hint....



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If the 6.5 Super LR/S and the 6.5 SAUM used the same powder your comparison might be somewhat valid. They don't though, so it is what it is.

From what I understand I would not be surprised to see the SAUM at least match or surpass the Super L/R in barrel life with moderate loads and hit with more authority as well.

Maybe someone else can give more firsthand info?

XTREM HTR16 gave the hint. I guess no one took it?
 
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There's a giant thread in the 6.5 Saum and they are getting 4000+ rounds through the barrel with one setback of the chamber in the 2000+ round count. 4000 rounds of 140gr pills at 3150 sounds tough to beat.
 
Sorry to get a little off topic so I will say that of the 3 asked about I only have experience with the 6.5 Creedmoor and own a rifle in that caliber. It shoots well.

Anyways -
RE: the 6.5 SAUM, the following quote is from George Gardner that I got here http://www.snipershide.com/shooting...ap-extreme-hunter-6-5-saum-2.html#post2452698
Im back in town and unthawed, the Icebreaker was a great time as usual. The Xtreme Hunter is just at its debut, Im not one to just throw a product at guys without a year of testing. Yes I have over 3400 rounds on my rifle now and its still shooting sub 1/2" Bryan Yeung on Team GAP shot one to 2800 and it was still in the 1/2 " range. This is proven. Its not a real secret its about Pressure!! The 308 runs at at pressures of 53000-58000 PSI I wanted to find a case that would make 3100 with a High BC Bullet at that same low low pressure. The Saum was wat we landed at with lots of testing. With a 140 JLK I could get 3080 FPS with only 53000 PSI I shot this load for a year, guys there are many to witness, I shot this at Lonestar, Snipershide Cup, PTS, Maammoth, and Nor-Cal I shot this at last years IceBreaker, and this years as well , with alot of practice in between, all on the same original Barrel. It still shoots great. The same load is now 3020 but with 63 grains of H1000 and the 130 Berger im getting 3180 in this same warn out ;) Rifle with that group at 1157 to prove it still has some life. Guys this is Legit its about pressure!!!! This cartridge is Game Changing and the Xtreme Hunter is the only rifle a Guy needs in N America.

2 guys now have commented after shooting one. both Quotes were Identical!!! " This is the Deadliest rifle Ive ever shot"!!! Both guys are far from Amateur!
 
I guess it depends on what you mean by 1000 yard competitions. As far as I know this means (6.5mm wonder gun) F Class Open, with joystick-equipped tripod front rest etc, or perhaps Long Range Highpower Any/Any. With any of your caliber choices, in F Class you will be outgunned by 6.5/284. I have also seen people shooting Any/Any sling with 6.5/284.
 
I guess it depends on what you mean by 1000 yard competitions. As far as I know this means (6.5mm wonder gun) F Class Open, with joystick-equipped tripod front rest etc, or perhaps Long Range Highpower Any/Any. With any of your caliber choices, in F Class you will be outgunned by 6.5/284. I have also seen people shooting Any/Any sling with 6.5/284.


After wearing the barrel out on my 6.5-284 in 900 rounds/1+ moa and having it set back only to have it shooting 1+ moa 400 rounds later I won't do one again. Granted I was pushing 140's to 2950fps with H4350 which was a hot load in my rifle. Maybe if i had worked up a load with H-1000 the barrel would have lasted longer???

I have less than 300 rounds through the 6.5 Saum, most of them with a medium load of 60.9 gr Retumbo at 3125 fps, hoping for 3000 before I hit 1 moa, we'll see. All I have to say is a guy needs to shoot one of these at distance to "get" the realization of how easy it is to hit steel in severe winds. I brought a friend out to introduce him to long range a while back. I dialed for him, told him the holdoff and we didn't miss. No use in wasting ammo so we put the 6.5 Saum up and got the 223's out for some challenge. Same winds of 12-20 mph and it was very hard to hit the same steel with the 223's.

If I were to shoot F-class again I'd be using a 7 or 30 with heavy bullets both would shoot inside of 6.5-284 and get better barrel life. 230's at 2940 is even more awesome!

Personally my vote goes for 6.5x47L of the three medium sized cartridges. I like the concept of the PPC attributes - case efficiency, brass quality and extended case life. Seems like 99% of those who build one immediately posts up some 5 shot groups with all touching and small vertical at distance. The only thing I'd do differently is have it throated farther out and shoot hybrids.
 
How far would you have it throated out? Can my can smith extend the throat even after chambering. I'm just having a hard time to get him to listen about things like that, he said the short case had plenty of room to set out them 140 pills. Can you use a Micro Adjustable Reamer Stop Kit (MARS KIT) to go back and extend the depth after cut. Damn you got me worried about my little 6.5 lady! I was wondering if extending the throat for 136-142and even 150gr bullets would help me keep that case feeled with fuel more and not compressed or reduced!
After wearing the barrel out on my 6.5-284 in 900 rounds/1+ moa and having it set back only to have it shooting 1+ moa 400 rounds later I won't do one again. Granted I was pushing 140's to 2950fps with H4350 which was a hot load in my rifle. Maybe if i had worked up a load with H-1000 the barrel would have lasted longer???

I have less than 300 rounds through the 6.5 Saum, most of them with a medium load of 60.9 gr Retumbo at 3125 fps, hoping for 3000 before I hit 1 moa, we'll see. All I have to say is a guy needs to shoot one of these at distance to "get" the realization of how easy it is to hit steel in severe winds. I brought a friend out to introduce him to long range a while back. I dialed for him, told him the holdoff and we didn't miss. No use in wasting ammo so we put the 6.5 Saum up and got the 223's out for some challenge. Same winds of 12-20 mph and it was very hard to hit the same steel with the 223's.

If I were to shoot F-class again I'd be using a 7 or 30 with heavy bullets both would shoot inside of 6.5-284 and get better barrel life. 230's at 2940 is even more awesome!

Personally my vote goes for 6.5x47L of the three medium sized cartridges. I like the concept of the PPC attributes - case efficiency, brass quality and extended case life. Seems like 99% of those who build one immediately posts up some 5 shot groups with all touching and small vertical at distance. The only thing I'd do differently is have it throated farther out and shoot hybrids.
 
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I have been shooting 6x47L for about as long as the brass was available. My reamer is set for throating out as far as possible for 115's, though now I shoot 105 hybrids with quite a jump. Years ago at the end of a barrels life I experimented with R-17 and how fast I could push 105's and 115's before the bolt got sticky. 3340/105 and 3250/115 were when the bolt got sticky. I used two pieces of brass and the darn things still held a primer. I'm thinking it was mostly due to how far out the throating was that permitted such high velocity. Nobody go out and blow up their 6x47's please, it was just a experiment.

Honestly I haven't given any thought as to the freebore I'd want with 6.5x47L because it's doubtful I'd ever do one since I'm so happy with the 6 and own the reamer and custom dies already. Most of my rifles reamers are set for the bottom of the baring surface of the bullet to be 1/4 or so up into the neck so I can take advantage of maximum powder capacity and the other benefits of doing so.

Most gunsmiths have separate throating reamers. I stood there and watched my gunsmith set the throat exactly where I wanted it on my 30 cal years ago. It didn't take him very long to do it, IIRC less than a hour.

I used to be hung up on having bullets as close to the lands as possible providing the load shot well, not anymore though. Both my 6 and my 30 shoot about as accurate as a rifle can with hybrids and a good jump.
 
I have a .260 and have no legitimate complaints (really, I love this gun), but I picked up a 6.5 Creedmore case off of a public range and thought "Wow, this looks really smart". Alas, I think my next barrel will be a 6.5x47. Going to run it mild with 123gr or maybe 130gr bullets. Barrel and case life being the emphasis. I like the idea of small rifle primers, lapua brass, and I think it's just enough for the kind of hunting I'll be doing (prairie dogs to mule deer).
 
If you truly want a gun to shoot 1000yd competition, then why limit yourself to the initially mentioned cartridges? I have a 6.5x47, and I love it. It hammers deer and groundhogs frequently. Tack drives too. Very easy to load for. But for 1000yds? I guess you could, but why would you want to? The 6mm Dasher is currently king of the 1000yd game, with a current 1000yd world record aggregate match score well under 3 inches. Thats my opinion
 
Nothing sticks out because they are a wash ballistically. Pick which name sounds coolest to you and go with it. Me personally, I'd pick the 6.5x47 first and the .260 second mainly for the Lapua brass. I would not take a 6.5CM if you gave it to me, because of the brass. The brass sucks. Yes, someone will come on here and say they have some with 15 firings on it and the pockets are still tight. Yeah....ok.

+1 To the Lapua brass. Personally I ended up with a 6.5x47L and have been really pleased with it. I had posted it up for sale but just couldn't part with it so for now it's here to say. I haven't shot it out to 1k yet but the cartridge is capable. Good luck with whatever you decide to do.
 
First of all my friend, research the velocity differents achieved by improving the 260Rem cartridge case. Just by having a 30 degree taper shoulder the 6.5 Super LR/S uses that fuel more efficiently. Your right it does have less case capacity but can it use the fuel it has to get more miles per gallon like a fuel injected engine vs. carbureted, lets say??? That's the question I would like to know. How hard can this cartridge be pushed without pressure signs? That's all. Thanks for chimming in I would like to know. Theirs one guy at the top in practical matches I know of that shoots this round but I have know idea how to contact him. It would be nice to talk with him and see why he chooses this round over the others.
You're totally tripping. Case capacity is king, and the SLR has LESS than a 260. What on earth would lead you to believe it would outperform the 260 by ~150-200fps?
 
What is the difference between a SLR and the 260 Ackley Improved? Assume the 260AI would have a 40 degree shoulder which would mean more room and more efficiency than the SLR and the 260


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First of all my friend, research the velocity differents achieved by improving the 260Rem cartridge case. Just by having a 30 degree taper shoulder the 6.5 Super LR/S uses that fuel more efficiently. Your right it does have less case capacity but can it use the fuel it has to get more miles per gallon like a fuel injected engine vs. carbureted, lets say??? That's the question I would like to know. How hard can this cartridge be pushed without pressure signs? That's all. Thanks for chimming in I would like to know. Theirs one guy at the top in practical matches I know of that shoots this round but I have know idea how to contact him. It would be nice to talk with him and see why he chooses this round over the others.

Researching what velocity gains internet commandoes get from various cartridge improvements is pointless. There is no standardized pressure to make for a decent comparison - to say nothing of varying brass, bullets, COAL and barrel length.

Very few good comparisons can be made.

Secondly, the SLR case isn't an "improvement" in the typical sense, because it nets a decrease, rather than an increase in case capacity. Altering a shoulder angle from 20º to 30º is not going to net you ~150-200fps.
 
The 260 Improved I was looking at has a 30 degree shoulder, the one Whitley created not Ackley. I know his has to be fire formed, let me go to his site and read a bit. Its been a while since I compared the two, but I came across some benefits mentioned some where.
 
What is the difference between a SLR and the 260 Ackley Improved? Assume the 260AI would have a 40 degree shoulder which would mean more room and more efficiency than the SLR and the 260?

260AI makes the shoulder diameter a little larger (decreasing body taper - increasing case capacity), while at the same time blows the shoulder forward and sharpening the shoulder to 40º (again increasing case capacity).

Meanwhile, the SLR doesn't change body taper, and pushes the shoulder back to 30º, resulting in a longer neck and sharper shoulder, as well as decreasing case capacity slightly.

The key difference between the two is the the location of the shoulder/neck junction of the AI stays (essentially) in the same place as the parent cartridge, while the body/shoulder junction moves forward. On the SLR, the body/shoulder junction stays put, and the neck/shoulder junction moves back.
 
The 260 Improved I was looking at has a 30 degree shoulder, the one Whitley created not Ackley. I know his has to be fire formed, let me go to his site and read a bit. Its been a while since I compared the two, but I came across some benefits mentioned some where.

Whitley also has a 260 - 30º improved, which is essentially halfway in between a 260 and a 260AI. It doesn't alter the body taper as does the ackley, and it only blows the shoulder to 30º.

The AI has more case capacity.

Still more, is the 6.5 LRP, which nets as much case capacity as the parent case can provide - minimal body taper and the shortest (reasonable) length neck.
 
With my quick little search I'm coming up with all kinds of numbers. But, I did find that Water capacity for the Creedmoor is stated at 53.5gr. and the Super LR/S is at 55.5gr. of water. Now this is where I'm confused because the stated fired case capacity of the 260Rem case is 53gr. With that said I guess the first two are unfired brass. But, even with the stated number for the Creedmoore and the consistent velocity people are getting with the round ( compared to the larger capacity of the 260Rem.) you can kind of make a guess of standard velocity for the 6.5 Super LR/S. Standard with no pressure signs at all, not mild bolt lift issues. I may have to exercise my brain now.
What is the difference between a SLR and the 260 Ackley Improved? Assume the 260AI would have a 40 degree shoulder which would mean more room and more efficiency than the SLR and the 260


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