Where does 6.5 Creedmoor fall on this game chart?

[Koda]

Anything "Ackley Improved" is going to have a 40 degree shoulder.
Creedmoor has a 30 degree shoulder.

[/QUOTE]
260 Rem has the shoulder in the wrong place.

[/QUOTE]
"Headroom" is the ability to seat a long heavy bullet in the prime location (not sticking way into the case) and still be able to feed without single loading.
This principle is what most all of the new precision cartridges are based on.
[/QUOTE]
I was close... pointing in the right direction anyways. Isnt a 30 degree shoulder much steeper than most traditional cartridges?

Seems like all these improvements in case and cartridge design took off after the CM was introduced?
Except maybe for the 6.5 Swede of course.

 

[GrayGoose]

A longer throat is definitely important.

That's what she said. And I agree.

 

[DirectDrive]

I was close... pointing in the right direction anyways. Isnt a 30 degree shoulder much steeper than most traditional cartridges?

Yes.
30-06 for example is 17.5 degrees and designed to feed reliably in military weapons/machineguns.

Seems like all these improvements in case and cartridge design took off after the CM was introduced?
Except maybe for the 6.5 Swede of course.

I think it was a couple of benchrest shooters, Palmisano & Pindel (6mm PPC} that popularized the concept of added headroom with a sharper shoulder to create a more efficient combustion chamber.
6.5 Swede is an old school design.

 

[Koda]

I think it was a couple of benchrest shooters, Palmisano & Pindel (6mm PPC} that popularized the concept of added headroom with a sharper shoulder to create a more efficient combustion chamber.

Essentially, what PO Ackley did to everything. (exact shoulder angle notwithstanding).


I think the only thing the 6.5 Swede did right was the longer bullet.

It sounds like the PRC calibers are new inventions following on this case improvement longer bullet path?

 

[solv3nt]

That's what she said. And I agree.

It took you inebriates long enough.

 

[DirectDrive]

Essentially, what PO Ackley did to everything. (exact shoulder angle notwithstanding).

[/QUOTE]
Ackley was interested in getting more speed and curbing brass flow.
He straightened case walls to increase case capacity and the 40 degree shoulder increased case capacity.
The 40 degree shoulder also reduced brass flow, hence less trimming.
It's these new, long, high BC bullets along with modern powders that drive the modern cartridge designs.

Another way to look at is, Ackely modified existing cartridges.
These new-age cartridges are new designs.

I think the only thing the 6.5 Swede did right was the longer bullet.

It sounds like the PRC calibers are new inventions following on this case improvement longer bullet path?

Yep.

 

[Koda]

Ackley was interested in getting more speed and curbing brass flow.
He straightened case walls to increase case capacity and the 40 degree shoulder increased case capacity.
The 40 degree shoulder also reduced brass flow, hence less trimming.
It's these new, long, high BC bullets along with modern powders that drive the modern cartridge designs.

My guess is its possible Ackley wasnt aware of -all- the potential his innovation was producing. He improved case design, but if he had also improved [longer] throat and longer bullets he would have beat the Creedmore to the punch. And on the flipside, I still think the Creedmores inventors used Ackleys influence on the case.

Side note, I dont think Ackley went to true straight walls he just realized we didnt need as much taper as originally thought to achieve reliable extraction?

 

[DirectDrive]

My guess is its possible Ackley wasnt aware of -all- the potential his innovation was producing. He improved case design, but if he had also improved [longer] throat and longer bullets he would have beat the Creedmore to the punch.

I see the Ackley mission and the Creedmoor mission as two different things.

And on the flipside, I still think the Creedmores inventors used Ackleys influence on the case.

I don't. If I had to choose a mentor it would be Louis Palmisano and Ferris Pindell (22PPC/6mmPPC)

Side note, I dont think Ackley went to true straight walls he just realized we didnt need as much taper as originally thought to achieve reliable extraction?

Goes without being said.

 

[whiskeybill]

Ive never really heard anyone bash the creedmoor. I like that round. Very efficient. And fun to shoot.

What drove me crazy were they guys at the range telling tall tales about their 1K yard shots on trophy (You fill in the blanks). Then I look at their 100 yard targets and just shake my head. Way too much mythology sprang up around the cartridge / rifle. It's usually called "Hype". It's a damn fine tool in the right hands, but give it to a poor marksman / hunter, well you get that picture. No better or worse than any other cartridge. Seen plenty of elk fall to the old .270 Winchester (or the '06, or the 30-40 Krag, or the 35 Remington). Absolutely no reason the 6.5 CM won't work, save for the nut behind the butt.

 

[orygun]

Ive heard what the CM did right was throat the chambers longer for longer higher BC bullets.... something the 6.5x55 Swede already did what like 100yrs ago which is what made it famously accurate and deadly. Longer bullets also have better straight line penetration in large game which also made the swede famous for larger elk... and the CM is doing the same.

It is and thats not something that most traditional American calibers have done even today. The CM got this right from the start and hopefully it will start a trend but not that we need more new calibers we really just need to start throating new rifles in the traditional calibers with a longer throat and in some cases a faster twist rate.

It's not so much about the throat, although that's important.
It's about the shoulder location and the "headroom" it allows. That's why Creedmoor exists.
The competition shooters needed more headroom for their "long heavies" and Creedmoor has it.
Creedmoor is like a .260 Rem that went to college, got booksmart and then went out and applied it in the field.

All of these are valid points, but everyone is missing an important part. The throat of these new cartridges offers far less "slop" (clearance) between the actual bullet and the throat it fits in. I am NOT talking about headroom or a long throat. I'm talking about the fact that the throat is much tighter around the bullet keeping the bullet straighter as it leaves the case and engages the rifling. THIS is what I believe plays a very large part of the accuracy potential the newer cartridges.

 

[Koda]

All of these are valid points, but everyone is missing an important part. The throat of these new cartridges offers far less "slop" (clearance) between the actual bullet and the throat it fits in. I am NOT talking about headroom or a long throat. I'm talking about the fact that the throat is much tighter around the bullet keeping the bullet straighter as it leaves the case and engages the rifling. THIS is what I believe plays a very large part of the accuracy potential the newer cartridges.

Wouldn't that cause feeding issues, especially in gas guns?

I always assumed chambers had pretty tight tolerances anyways, if they were to tighten the tolerances on the throat dimension wouldn't they need to tighten the tolerance on the bullet OD?

 

[DirectDrive]

All of these are valid points, but everyone is missing an important part. The throat of these new cartridges offers far less "slop" (clearance) between the actual bullet and the throat it fits in. I am NOT talking about headroom or a long throat. I'm talking about the fact that the throat is much tighter around the bullet keeping the bullet straighter as it leaves the case and engages the rifling. THIS is what I believe plays a very large part of the accuracy potential the newer cartridges.

I think the benchrest guys were doing custom throats long before this new trend in cartridge design.
Chambers cut for a specific bullet.

 

[Konajay]

My son, who thinks he knows a lot but really doesn't, likes to bash me using my 6.5 CM to hunt deer. Funny thing is that rifle is a deer slaying machine. I've noticed the bashing has subsided quite a bit the last few years.

 

[Tlock]

My son, who thinks he knows a lot but really doesn't, likes to bash me using my 6.5 CM to hunt deer. Funny thing is that rifle is a deer slaying machine. I've noticed the bashing has subsided quite a bit the last few years.

I like to think it's the man behind the rifle, not the rifle it's self

 

[DirectDrive]

My son, who thinks he knows a lot but really doesn't, likes to bash me using my 6.5 CM to hunt deer. Funny thing is that rifle is a deer slaying machine. I've noticed the bashing has subsided quite a bit the last few years.

Think of all the deer taken with .243 Winchester.
6.5 Creedmoor has more power than that.

 

[orygun]

Wouldn't that cause feeding issues, especially in gas guns?

I always assumed chambers had pretty tight tolerances anyways, if they were to tighten the tolerances on the throat dimension wouldn't they need to tighten the tolerance on the bullet OD?

I was gonna be lazy and not look up the correct numbers, but it's a rare Saturday afternoon that I have nothing to do, so why not?
According to the SAAMI chamber and ammo drawings, here's what I find.
6.5x55 spec'd bullet dia .2644" with a tolerance of -.003" (.261 min dia)
chamber dimension for bullet .2693"
That's anywhere from .005" to .008" clearance.

6.5 Creedmoor spec'd bullet dia .2644" with a tolerance of -.003" (.261" min dia)
chamber dimension for bullet.2645".
That's .001" to .003" clearance.

THIS is what I'm talkin about.

I like to think it's the man behind the rifle, not the rifle it's self

There is always that. My wife would say it's the woman behind the rifle.

 

[orygun]

Oops! I forgot to add that the chamber dimension also has a +.002" tolerance, adding a potential two thousandths.

 

[Koda]

I like to think it's the man behind the rifle, not the rifle it's self

Anytime someone ribs me for using a "lesser" caliber, I waste no time blaming it on their rifle when they dont get one.


Of course all of that is nonsense from any caliber but all in good hunting fun and joking around.

 

[Koda]

I was gonna be lazy and not look up the correct numbers, but it's a rare Saturday afternoon that I have nothing to do, so why not?
According to the SAAMI chamber and ammo drawings, here's what I find.
6.5x55 spec'd bullet dia .2644" with a tolerance of -.003" (.261 min dia)
chamber dimension for bullet .2693"
That's anywhere from .005" to .008" clearance.

6.5 Creedmoor spec'd bullet dia .2644" with a tolerance of -.003" (.261" min dia)
chamber dimension for bullet.2645".
That's .001" to .003" clearance.

THIS is what I'm talkin about.

Since SAAMI specs are voluntary, I wonder if gas guns are made slightly larger chamber dia?

Or maybe the older looser chambers are no longer needed (or never were...)?

 

[Tlock]

Anytime someone ribs me for using a "lesser" caliber, I waste no time blaming it on their rifle when they dont get one.


Of course all of that is nonsense from any caliber but all in good hunting fun and joking around.

One of they guys in my elk hunting group has to have the newest and the best thing out there, last year it was a custom 30 nosler with a nightforce. He missed 1 bull and lost another.....I took 1 shot with my ruger american in 270 with a burris scope and put meat in my freezer