Best short barreled 6.5 caliber??

[Terry Scott]

If you are building a bolt gun
Or want to buy a bolt gun the venerable 260 Remington would be a consideration
Lots of brass available and has the capability to push the 140 Berger to almost 3000 FPS
Sometimes I think we all get caught up in the marketing moment at least as far as the CM is concerned
The 260 is a very accurate cartridge and has better velocity than the CM

 

[Aldon]

6.5x55 AI on long action.

 

[rlspahn]

I am reading your posts and trying to understand your logic or science? If I am understanding what you are proposing is that barrel length has nothing to do with velocity, is that what you are suggesting here? Currently I am building a .270 Ackley Improved with a 26 inch barrel. I went the extra length (2 INCHES) to get the maximum MV out of the .270 AI due to the smaller bore diameter. What I have found is that the smaller calibers .257, 6mm, 6.5, .270 like that longer barrel to burn the powder for maximum performance; especially the magnums in these calibers. From what I have read unless you are shooting these magnum cartridges out of a 24-26 inch barrel they are not worth chambering a rifle for them. If this is the case how does what you have written in your responses work here? Shouldn't more powder mean that you have to have more space/area for the powder to burn in before exiting the barrel, otherwise it leaves the barrel behind the bullet? Logically for me if more powder means more velocity, it ought to have a place to burn in, without that space the powder leaves the barrel unburned. Isn't this the juncture where more powder is no longer efficient in a particular caliber and overbore applies? Where do you reach the point of diminished return? If what you are suggesting to be true, what would prevent necking down a 50BMG to .270 caliber and get 5000fps?

It's not about the powder burn per se but about the pressure created from the powder burn. Just because the powder stops burning doesn't mean the pressure goes to zero. You don't need 26" of barrel to fully burn most powders, but the longer barrel does allow the pressure to act on the bullet longer, continuing its acceleration in the barrel, and allowing it to reach a higher velocity. If you shorten the barrel, you reduce the amount of time that the pressure can act on the bullet and the velocity is lower, not necessarily how much powder is burned. Now at some point, you will get the barrel so short that the powder doesn't fully burn. That's how QL is predicting only a 1 to 1-1/2% reduction in powder burn (see post by yorke-1). So while there is not a lot of unburned powder exiting the muzzle, there is some wasted pressure that is expelled from the muzzle - what you would call muzzle blast.

 

[Michael Hathorn]

I have a 6.5 Grendel and love it! Have it in an AR platform with a pulsar 50 thermal on it and it gets results every time the trigger is pulled. Dead on also.

 

[Fred G Cook]

I have a custom Long Range Target 6.5x284. Running 48.5gr H4350 and a Berger 140 Hybrid with an average of 2822fps. I am new, and they are telling me I will get anywhere from 800-1500 shots out of that barrel with that caliber...

 

[Fred G Cook]

I have a custom Long Range Target 6.5x284. Running 48.5gr H4350 and a Berger 140 Hybrid with an average of 2822fps. I am new, and they are telling me I will get anywhere from 800-1500 shots out of that barrel with that caliber...

 

[MudRunner2005]

It's not about the powder burn per se but about the pressure created from the powder burn. Just because the powder stops burning doesn't mean the pressure goes to zero. You don't need 26" of barrel to fully burn most powders, but the longer barrel does allow the pressure to act on the bullet longer, continuing its acceleration in the barrel, and allowing it to reach a higher velocity. If you shorten the barrel, you reduce the amount of time that the pressure can act on the bullet and the velocity is lower, not necessarily how much powder is burned. Now at some point, you will get the barrel so short that the powder doesn't fully burn. That's how QL is predicting only a 1 to 1-1/2% reduction in powder burn (see post by yorke-1). So while there is not a lot of unburned powder exiting the muzzle, there is some wasted pressure that is expelled from the muzzle - what you would call muzzle blast.

As soon as the flame goes out, the gasses start cooling (simple physics), therefore pressure does rapidly start dropping. And once gravity overtakes inertia, the bullet comes to a halt.

Now, if you say it's all burnt up by then, that would mean that inertia is the only thing keeping that bullet propelling down the bore once burnoff has completed...Right? So, if your theory was correct, then there would be no actively-burning propellant gasses left in the bore as the bullet exits the barrel, right? If this is the case, then there would be no extensively loud muzzle blast, as all that superheated gas pressure would have been used up by then, and would not interact with the much cooler ambient atmospheric temperatures, creating the loud BOOM! we hear when a gun goes off. Sort of like how a subsonic round operates without a suppressor on it. There's still boom sound, but nowhere near the sonic boom crack of a gun that still has actively burning propellant in the bore. So, obviously, with anything loaded to supersonic capacities, there is still gasses being actively burned in the bore, up until the bullet exits the muzzle. That means most cartridges are still not going to put-out a complete burn in a 26" barrel, when pushed to supersonic velocities.

Also, barrel length is more dependent on cartridge capacity vs. bore diameter, than powder burn rate.

 

[rlspahn]

As soon as the flame goes out, the gasses start cooling (simple physics), therefore pressure does rapidly start dropping. And once gravity overtakes inertia, the bullet comes to a halt.

Now, if you say it's all burnt up by then, that would mean that inertia is the only thing keeping that bullet propelling down the bore once burnoff has completed...Right?

Nope. Just because the flame goes out as you say doesn't mean the pressure goes to 0 (atmospheric) instantly. As long as the pressure in the bore is greater than atmospheric pressure, there's a force to continue pushing the bullet. And as long as that force is greater than the dynamic friction between the bullet and barrel, the bullet's velocity will still continue to increase. While the gases may be cooling, both from direct heat transfer to the surroundings (i.e., barrel) and expansion (thermodynamics), the pressure still remains high enough to continue to accelerate the bullet. And there's enough "unused" pressure that we get muzzle blast once the bullet does exit the muzzle. We can argue whether or not the flame truly "goes out" before the bullet exits the muzzle - that's not really the point. From a thermodynamic perspective, QL is predicting that the bulk of the powder is consumed well before the bullet exits the muzzle, and that shortening the barrel length from 26" to 22" only changes the amount burned by 1% or so. My air gun pushes a pellet out the end of the barrel without any burned gases, it's just pressure from the compressed air that does the work.

None of this helps the OP with his original question. But as he can see, there are as many "best short-barreled 6.5 calibers [cartridges]" as there are folks posting on this board. We each have our favorites and rationale for choosing one over another. As long a we provide him that information, he can use that to help him decide which one is "best for him."

 

[MudRunner2005]

Nope. Just because the flame goes out as you say doesn't mean the pressure goes to 0 (atmospheric) instantly. As long as the pressure in the bore is greater than atmospheric pressure, there's a force to continue pushing the bullet. And as long as that force is greater than the dynamic friction between the bullet and barrel, the bullet's velocity will still continue to increase. While the gases may be cooling, both from direct heat transfer to the surroundings (i.e., barrel) and expansion (thermodynamics), the pressure still remains high enough to continue to accelerate the bullet. And there's enough "unused" pressure that we get muzzle blast once the bullet does exit the muzzle. We can argue whether or not the flame truly "goes out" before the bullet exits the muzzle - that's not really the point. From a thermodynamic perspective, QL is predicting that the bulk of the powder is consumed well before the bullet exits the muzzle, and that shortening the barrel length from 26" to 22" only changes the amount burned by 1% or so. My air gun pushes a pellet out the end of the barrel without any burned gases, it's just pressure from the compressed air that does the work.

None of this helps the OP with his original question. But as he can see, there are as many "best short-barreled 6.5 calibers [cartridges]" as there are folks posting on this board. We each have our favorites and rationale for choosing one over another. As long a we provide him that information, he can use that to help him decide which one is "best for him."

Who said the pressure went to zero instantly... That's just stupid.

 

[FEENIX]

None of this helps the OP with his original question. But as he can see, there are as many "best short-barreled 6.5 calibers [cartridges]" as there are folks posting on this board. We each have our favorites and rationale for choosing one over another. As long a we provide him that information, he can use that to help him decide which one is "best for him."

Agreed! There is no need to complicate it unnecessarily.

 

[smokey3]

My 6.5 PRC w a 22" proof bbl will run 2950 with 147's and 3035 w 140 vld's. My setup weighs 7lbs 7 ounces with optic and shoots very well. I also have a 21" 6.5 creedmoor that shoots the 143 ELDX at 2860 that weighs 6lbs 7 ounces all in.

That rifle with the Leupold is a very sharp looking rifle. You did well with that one.

 

[Crowe284]

Was with a buddy today shooting a 6.5 PRC W/ 22" proof barrel suppressed. The 143 eld x factory ammo trued at 2960 fps with less than 100 rounds down tube with sammi chamber and shot 1/2 minute at 1K. I have a 22" proof being chambered in 6.5 PRC right now by Straightjacket Armory as a bighorn origin shouldered prefit that will be here in a couple weeks. Positive I can get 3000 out of it when I handload with same bullet and H1000.

 

[nicholasjohn]

I am reading your posts and trying to understand your logic or science? If I am understanding what you are proposing is that barrel length has nothing to do with velocity, is that what you are suggesting here? Currently I am building a .270 Ackley Improved with a 26 inch barrel. I went the extra length (2 INCHES) to get the maximum MV out of the .270 AI due to the smaller bore diameter. What I have found is that the smaller calibers .257, 6mm, 6.5, .270 like that longer barrel to burn the powder for maximum performance; especially the magnums in these calibers. From what I have read unless you are shooting these magnum cartridges out of a 24-26 inch barrel they are not worth chambering a rifle for them. If this is the case how does what you have written in your responses work here? Shouldn't more powder mean that you have to have more space/area for the powder to burn in before exiting the barrel, otherwise it leaves the barrel behind the bullet? Logically for me if more powder means more velocity, it ought to have a place to burn in, without that space the powder leaves the barrel unburned. Isn't this the juncture where more powder is no longer efficient in a particular caliber and overbore applies? Where do you reach the point of diminished return? If what you are suggesting to be true, what would prevent necking down a 50BMG to .270 caliber and get 5000fps?

I have a 30-06 Ackley Improved, and the guy who built it put a 26" barrel on it, even though I had told him I wanted 24". It was close enough to hunting season that I just used it that way, and had him shorten it later. So, I had the rare opportunity to shoot a rifle with both a 26" and 24" barrel, with everything else being the same - same load, same barrel, same chamber, same chronograph, etc. The only change was taking two inches off the barrel, and velocities dropped by 100 feet/second. I had expected 25-30 fps/inch, like I had read in numerous publications. NOT SO - it was a full 100 fps slower, and accuracy was the same ( excellent.) So, don't believe everything you read about barrel length vs. velocity. Try it if you don't believe me - you may not get what I got, because there are other variables in the equation. Some of those variables we don't even know about. But that's what I got.

With your .270 Ackley, you will quite likely be glad that you went with the longer barrel, especially if you're building it on something like a falling-block single shot action. This will enable you to have a longer barrel on a rifle with the same overall length, due to the shortness of the action. I've worked with that concept, too - and have been pleased with the results. A 26" barrel is kinda cumbersome on a 30/06-length bolt action, but not on something like a Ruger #1 or Dakota Model 10. ( The Rugers are heavy; the Dakotas are not.) Anyhow, have fun with your .270 Ackley, and with 26" of barrel, you will probably find yourself feeling like you've got a .270 Weatherby. You may want to lean toward the slower-burning powders for that cartridge, since you have he barrel to burn it in. With the new slow-burners that have come out recently, you will have yourself a field day trying them out.

 

[rlspahn]

I have reopened the idea about making it a 6.5creedmoor. I saw a video by the DMR guys and they are pushing the 18" 6.5 creedmoors pretty fast. I think the creedmoor may be the ticket. If, and that's a big if, i can hit 2700fps out of my desired 20" barrel then that will get me to where I want to be for ME and fps at distance. After reading several other forums and posts from others on here, I think it might be possible to achieve. I think I may try it.

I have a 6.5 Creedmoor built by Defensive Edge using their +P throat. It has a 16.5" Proof barrel. In testing, DE was able to push 140 Bergers at 2750 ft/s. I shoot 124 gr Hammer Hunters at 2890 ft/s through a suppressor. Barrel plus suppressor length measures 24" from the face of the bolt.