Barrel length vs. Velocity

[Obtunded]

There is an excellent article on 6mmBR regarding the correlation between barrel length and velocity. Although this compares a single type of cartridge, I think it holds true that there is a popular misconception that shorter barrels unduly impact velocity. It is an interesting read.

Short & Heavy barrels are less impacted by whip, harmonics, and heat warping. TR shooters will tell you that a long barrel does however make a rifle far easier to aim unsupported.

 

[guntech]

There is an excellent article on 6mmBR regarding the correlation between barrel length and velocity. Although this compares a single type of cartridge, I think it holds true that there is a popular misconception that shorter barrels unduly impact velocity. It is an interesting read.

Short & Heavy barrels are less impacted by whip, harmonics, and heat warping. TR shooters will tell you that a long barrel does however make a rifle far easier to aim unsupported.

This test did not really use a short barrel... cutting from 33 inches to 28 inches with a 6mm BR case would give much less velocity loss than if you were use a 30-378 and cut the barrel from 28 inches to 22 inches... I guess it depends on what you call short and the cartridge used....

but 28 inches isn't really short...


.

 

[X-fan]

With this particular cartridge I'd be more interested what happens from 24-28 inches?

 

[tps50701]

This test did not really use a short barrel... cutting from 33 inches to 28 inches with a 6mm BR case would give much less velocity loss than if you were use a 30-378 and cut the barrel from 28 inches to 22 inches... I guess it depends on what you call short and the cartridge used....

but 28 inches isn't really short...


.

Don't exactly have the link, but Tac-ops out of California - famous for it's rifle building skills, short barrelled rifles and accuracy guarantee - did an exact experiment to determine this.

I believe they came to the conclusion that the velocity only dropped like 60-80 FPS from 26" down to 18" with a .308 700 barrel.

They cut and crowned the barrel at 1" intervals down to 18" with no appreciable loss of velocity. They actually don't really build any rifles over 22" unless the customer specifically want it.

It really is just a matter of looks for you at this point.

Cheers, Carl

 

[Finger Toes]

The big boomers like the Weatherbys and the other over bores are supposed to be the ones that suffer the most fps loss from inches removed right? The 308 family cases in the larger calibers would lose much less no? Most manufacturers have longer tubes on the mag cals, not just for extra weight.

 

[crout]

Good article. what i get from that is a 6mmbr is a great round and you can use a 28" pipe and don't have to spend the money on a longer pipe to try and get higher velocities. not true for a lot of other calibers(well maybe with those lengths of pipe)

These are results from a 223rem showing velocity loss from progressivly shorter barrel(same gun same barrel, same powder/brass/primer bullet weight)
Powder --- 20.0 H 4198
Barrel Length started at 22" all are 5shot averages for velocity
2771 fps
2741 –
2713 –
2659 -
2645 -
2594 -
2555 -
2484 -
2431 -
2377 -
2337 -
2292 -
2247 -
Barrel length ended at 10"

I wish i had more data for a longer barrel. it would be interesting to see when the velocity realy slows down. even if we assumed the same velocity gain of 30-50fps per inch of barrel a 26" barrel would give us about 200fps more. that's huge and very beneficial.

I have another example but all variables are not the same but gives a good idea.
6.5x55swede 140gr sierra matchking and r-19
22.5" barrel average 5shot velocity with 50gr of powder 2828fps
26" barrel " " " " " " " 3056fps

 

[Obtunded]

You're right Dennis, I guess I did imply that 28 is "short". I take a large number of orders for 30 and 32" 6mm barrels and I can't really figure out why... rather like why there is an obsession with 1:10 twist barrels for 308 rifles since I don't know very many people that shoot 220 and 240 grain bullets from a 308

 

[RifleDude]

Accurate Reloading did this with a .223 Rem chambered Sako at one time. Detailed measurements with a variety of hand loads can be found here: http://www.accuratereloading.com/223sb.html

 

[crout]

Accurate Reloading did this with a .223 Rem chambered Sako at one time. Detailed measurements with a variety of hand loads can be found here: http://www.accuratereloading.com/223sb.html

That's where my above data comes from

 

[ffwd]

There is an article on the Lilja website. 338-378 Weatherby, Geske action, 46" to 24" in 2" increments.