Federal 6.5 Backcountry?

[diverc18]

I don’t know about you guys, but I’m more excited about the 153tmk being available in factory ammo than the velocity gain since I don’t reload and live in a state where you can’t order/ship ammo. I definitely not sad about the extra velocity gain either though lol. I may or may not have already sent my barrel to be chopped because of it.

 

[wyosam]

Margin of error for a young shooter. The whole discussion was initially based on a 12 year old...and the 6.5Creedmore bunnies turned it into something about them...as adults, who have hunted for years and probably killed several big game animals.

How much energy is required to make up for each inch of miss in this “margin for error”? I assume there is some initial requirement to make up for the .022” additional miss one accepts for not shooting a more appropriate adult sized cartridge?


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[Aussie Dan]

It has everything to do with a 6.5CM being in inappropriate for elk hunting until now

Are we really beating this dead horse again?
Its been proven, with pictures and necropsies that elk have fallen to much smaller calibres than 6.5 creed.

 

[bnewt3]

I think something we’re not considering is the blast and concussive force at the muzzle.

Take this from a guy who believes in suppressors. I believe that if I’m polite enough to put a muffler on my car, I should put one on my firearm.

That being said, the inherent problem for many will be that concussive force.

If you push higher pressure out of a shorter muzzle/barrel length (I’ll assume that a large measure of the “why” for the shorter barrel is to run suppressed while maintaining an overall package length that is handy enough to run around in the wild with), it begs the question whether the longer barrel at lower pressure or the shorter barrel + can + higher pressure equates to an overall improved operator experience.


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The YT video Backcountry Hunting Podcast put out shows this. He had a 22", 20" both suppressed, 17" unsuppressed......17" blast was serious.....and thats just what related through the video.

I would have liked to see what blast was like compared to brass though.

 

[Andouille]

I think something we’re not considering is the blast and concussive force at the muzzle.

Take this from a guy who believes in suppressors. I believe that if I’m polite enough to put a muffler on my car, I should put one on my firearm.

That being said, the inherent problem for many will be that concussive force.

If you push higher pressure out of a shorter muzzle/barrel length (I’ll assume that a large measure of the “why” for the shorter barrel is to run suppressed while maintaining an overall package length that is handy enough to run around in the wild with), it begs the question whether the longer barrel at lower pressure or the shorter barrel + can + higher pressure equates to an overall improved operator experience.


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Fair point perhaps for magnums, but is muzzle blast/pressure on a short suppressed 6.5CM an actual concern, and how does overall rifle length factor into "operator experience? I run a 19" barrel 6.5 CM with suppressor and its downright pleasant to shoot, and lots of folks here are happily shooting even shorter suppressed rifles.
With a good hunting suppressor, we're talking roughly ~130-140db 16-18" suppressed, vs 125-130db long suppressed, and >155db for unsuppressed 24". Add a few decibels for +Peak higher pressure ammo and a short suppressed 6.5CM is still more pleasant to shoot than a 30-06, 7prc, and larger.

Edit: for context, I also shoot 18" 30-06 suppressed, 7 prc 22" braked, and used to have a 20" 300WSM suppressed. A short 6.5cm suppressed is downright pleasant and mild in comparison to these.

 

[43.6N]

Fair point perhaps for magnums, but is muzzle blast/pressure on a short suppressed 6.5CM an actual concern, and how does overall rifle length factor into "operator experience? I run a 19" barrel 6.5 CM with suppressor and its downright pleasant to shoot, and lots of folks here are happily shooting even shorter suppressed rifles.
With a good hunting suppressor, we're talking roughly ~130-140db 16-18" suppressed, vs 125-130db long suppressed, and >155db for unsuppressed 24". Add a few decibels for +Peak higher pressure ammo and a short suppressed 6.5CM is still more pleasant to shoot than a 30-06, 7prc, and larger.

Edit: for context, I also shoot 18" 30-06 suppressed, 7 prc 22" braked, and used to have a 20" 300WSM suppressed. A short 6.5cm suppressed is downright pleasant and mild in comparison to these.

Cube root law of volumetric gas expansion:
After bullet exits muzzle, and pressurized gas is exposed to the open environment, it will expand decreasing its intensity by a ratio of distance cubed.

So longer barrel puts the point source of the shockwave further from our inner ear, allowing the shockwave to dissipate its intensity much more rapidly than someone would intuitively expect.

It’s still high pressure, and still painful. And bigger powder charges over tighter bore constrictions will give higher “uncorking pressures.”

Real life example: my 18” 6.5 creed. If I shoot without a suppressor, I get headaches and brain fog after 3 shots.
24” 6.5 creed shooting same load unsuppressed: I’m good for about 10-15 shots before feeling concussed.

 

[bnewt3]

Cube root law of volumetric gas expansion:
After bullet exits muzzle, and pressurized gas is exposed to the open environment, it will expand decreasing its intensity by a ratio of distance cubed.

So longer barrel puts the point source of the shockwave further from our inner ear, allowing the shockwave to dissipate its intensity much more rapidly than someone would intuitively expect.

It’s still high pressure, and still painful. And bigger powder charges over tighter bore constrictions will give higher “uncorking pressures.”

Real life example: my 18” 6.5 creed. If I shoot without a suppressor, I get headaches and brain fog after 3 shots.
24” 6.5 creed shooting same load unsuppressed: I’m good for about 10-15 shots before feeling concussed.

definitely not an engineer but wouldnt faster powders also drop in pressure much faster while still corked?
My smooth brain says with 24" barrel, there would(could? might?) be less pressure at bullet exit with +Peak than brass.

+Peak = more with short barrel, less with long?
Brass = less with short barrel, more with long?

I may be way off

 

[43.6N]

definitely not an engineer but wouldnt faster powders also drop in pressure much faster while still corked?
My smooth brain says with 24" barrel, there would(could? might?) be less pressure at bullet exit with +Peak than brass.

+Peak = more with short barrel, less with long?
Brass = less with short barrel, more with long?

I may be way off

Yeah, idk about that.
We are still talking 80kpsi.
I’m expecting these to be rowdy unless suppressed. And I think a lot more SciCo Scythes are about to start going in for warranty

 

[bnewt3]

Fair enough.

It might take more of a difference in barrel length for something like that to show up like 18" vs 30" or something like that

 

[KingOfTagSoup]

Interesting.....

 

[ckt3]

Real life example: my 18” 6.5 creed. If I shoot without a suppressor, I get headaches and brain fog after 3 shots.
24” 6.5 creed shooting same load unsuppressed: I’m good for about 10-15 shots before feeling concussed.

I appreciate this level of quantitative self-experimentation

 

[bnewt3]

I appreciate this level of quantitative self-experimentation

are you laughing at someone else's brain damage?

 

[shomi]

Interesting.....

Now I'm curious what a Barnes 90gr TAC-TX doing mach 3 from an 18" barrel will do to elk.

 

[43.6N]

I appreciate this level of quantitative self-experimentation

 

[nphunter]

I’m not sure what the draw is for the increased recoil in a small gun. Myself and many others are building small caliber rifles for long range to improve accuracy, spotting hits is a big part of that.

I can shoot a TMK out to almost 1K with a 16” barrel .243 at 6000’ elevation and still have adequate speed to reliably upset. I don’t see the point in adding more recoil for very little gain.

My kids both shoot 6.5cm Kimber hunters, they recoil plenty with regular ammo, they would be a bear to shoot with this ammo.

 

[Escalante11]

I’m not sure what the draw is for the increased recoil in a small gun. Myself and many others are building small caliber rifles for long range to improve accuracy, spotting hits is a big part of that.

I can shoot a TMK out to almost 1K with a 16” barrel .243 at 6000’ elevation and still have adequate speed to reliably upset. I don’t see the point in adding more recoil for very little gain.

My kids both shoot 6.5cm Kimber hunters, they recoil plenty with regular ammo, they would be a bear to shoot with this ammo.

Every review I've seen has noted that the recoil increase going from standard 6.5CM ammo to 6.5CM + Peak ammo was negligble. Certain of these reviews said that 6.5CM + Peak recoil was far less than 6.5 PRC

 

[bnewt3]

I’m not sure what the draw is for the increased recoil in a small gun. Myself and many others are building small caliber rifles for long range to improve accuracy, spotting hits is a big part of that.

I can shoot a TMK out to almost 1K with a 16” barrel .243 at 6000’ elevation and still have adequate speed to reliably upset. I don’t see the point in adding more recoil for very little gain.

My kids both shoot 6.5cm Kimber hunters, they recoil plenty with regular ammo, they would be a bear to shoot with this ammo.

For exactly the same reason plenty of people have historically chosen the tradeoffs of 270, 6.5PRC, 6.8W, etc over 6.5 Creed. More velocity, flatter trajectory.

The great part about +Peak is you have the option. Brass @ typical recoil or +Peak

AFAIK the recoil increase is simply from increased velocity so somewhere in the +10% range.

 

[RWT]

I don’t know about you guys, but I’m more excited about the 153tmk being available in factory ammo than the velocity gain since I don’t reload and live in a state where you can’t order/ship ammo. I definitely not sad about the extra velocity gain either though lol. I may or may not have already sent my barrel to be chopped because of it.

Do you live in the US? How are you unable to order or ship ammo.

 

[Chris in TN]

Anyone saying that +Peak is not needed for 6.5 CM is also implying that any larger 6.5mm cartridge (6.5 PRC, 6.5 RPM, 6.5-300) is also irrelevant.

Yes. That is ultimately my position.

A 16" 6.5cm with a 147eldm at 2500', firing at typical western elevations, will stay above 2000' out to perhaps 550-600 yards depending on exact environmental conditions. And you can do that with a 16" bolt gun with handloads. The 2660' I get from a 20" is, honestly, perhaps a bit superfluous.

I do not think more than 5% of western hunters can take advantage of field performance better than that.

I do still own a .280ai that I never shoot and I do still own a .45-70 and multiple bigger muzzleloaders that I hunt with during the appropriate season, but I do not personally believe the typical hunter, or even the guys from the middle of the bell curve of shooter ability all the way up to the last maybe 10% of the curve, 'need' more.

Of course, I happily agree that it's a free country and people can and should shoot whatever they want without worrying about what other people do. I'll also happily concede that less wind drift would be nice. And I'll happily concede that there are shooters with more skill than me, and some fairly small handful of them might be able to take ethical shots past that 600 yard mark, and there's certainly an argument that some of those guys can take advantage of more 'power' than a 6.5cm offers in a short length barrel.

But if we boil that down to generalities, yeah, a standard pressure 6.5cm is all you 'need'.

Every review I've seen has noted that the recoil increase going from standard 6.5CM ammo to 6.5CM + Peak ammo was negligble. Certain of these reviews said that 6.5CM + Peak recoil was far less than 6.5 PRC

This is generally going to be true and an unavoidable consequence of physics.

The smaller the case, the less powder it'll take to hit a given speed (speed, not pressure) and the lower powder charge means less total weight of bullet and expanding gas (aka 'ejecta mass').

Basically if you have two different caliber rifles that each weigh 10 pounds and one has a bullet plus powder charge of, say, 200 grains, and the other has a bullet plus powder charge of 210 grains (like a 6.5cm with a 153 and 47 grains of powder vs a 6.5prc with a 153 and 57 grains, just making numbers up)......the latter, even if they produce the same speed, will have 5% more recoil than the former.