Range Report Barrel Length's effect on velocity?

[Rotorhead407]

First post so please be kind. I've been googling all sorts of combinations of search terms trying to find the effect of dropping a couple inches on barrel length in terms of velocity/energy loss.

Specifically I'm trying to find a ballistics table that compares the same bullet for a .300 win mag at 400 yards. I've come across various 'rules of thumb' that all say different things like dropping 25, 50, and 100 fps per inch reduction in length. Is there a definitive answer to this? All the ballistic calculators I've come across have no place for the user to input their barrel length.

Thank you in advance.

 

[Lowlight]

Re: Barrel Length's effect on velocity?

It's all dependent on who's barrel it is,

Factory barrels are going to be slower than custom ones, tight bores, etc.

There is no one rule of thumb at 400 yards it won't matter much, they will all be more than fine.

 

[Rotorhead407]

Re: Barrel Length's effect on velocity?

Thank you for the speedy response. I'm attempting to create a very lightweight (20" barrel) rifle for elk hunting is why I asked.

 

[azimutha]

Re: Barrel Length's effect on velocity?

.300 Win Mag in a light rifle might be heavy on the recoil. FWIW, with two .308s I get 2650 fps out of a 20" barrel and 2725 out of a 24" barrel with the same exact load. I've killed three elk with the 20" .308 @ 220, 35 and 310 yards respectively. The .308 was more than enough. In fact, at 35 yards the first round penciled right through and I had to walk up and do a head shot. (Using Nosler 165 gr. Accubonds)

 

[MitchAlsup]

Re: Barrel Length's effect on velocity?

The only time the length of the barrel really comes into play is when you are trying to reach out as far as the caliber allows.

Properly loaded, a 308 is capable of 1300 yards with a 24" barrel but 'only' 1200 yards with a 20" barrel.

Thus, the last 4 inches of barrel are for the last 100 yards of supersonic distance.

However, in magnum calibers, the advantage of a longer barrel is that is simply weights more--this reduces recoil, and saves your ears.

 

[Greg Langelius *]

Re: Barrel Length's effect on velocity?

My view is not about how fast you can run the bullet, but how the same velocity in different length barrels affects the bore life. I like the longer barrels because I can usually run them out to distance with lighter loads.

Greg

 

[azimutha]

Re: Barrel Length's effect on velocity?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">My view is not about how fast you can run the bullet, but how the same velocity in different length barrels affects the bore life. I like the longer barrels because I can usually run them out to distance with lighter loads.

Greg </div></div>

That's why I have a couple rifles. The 20" barrel .308 is great for mountain hunting. The 24" barrel for longer range shots. I haven't had a chance to test the Berger Hybrid OTMs out past 600 yet, but because of their intentional design I'm inclined to think the sonic transition will be far less of an issue.

 

[Greg Langelius *]

Re: Barrel Length's effect on velocity?

My own rifles are tending to fall into this approach as well.

My LR 260 is 28", the barrel is being replaced with a 30BR 23" long, and the 260 slot is being taken over with a Savage Predator Hunter with a 24" barrel.

It should work well enough since the last 1Kyd venue that's inside my travel radius closed us Highpower/F Class guys out a couple of years back. Because of my health and my Wife's, I don't like to drive anywhere that puts us more than 2 hours away from each other anymore.

I'm just not as competitive as once I was; so the motivation to pack up the show and take it all on the road has waned somewhat. There is no issue here, I'm just trying to keep it all within my realistic capabilities.

Greg

 

[Dave inVA]

Re: Barrel Length's effect on velocity?

Dan Lilja did a study several years ago using a 338-378 Weatherby round. He started with a 46" barrel and cut 2" off at a time down to 24".
The article is at the link below.

http://www.riflebarrels.com/articles/bullets_ballastics/long_barrel_velocity.htm

Dave

 

[kraigWY]

Re: Barrel Length's effect on velocity?

This isn't a 300, but its a 308. Again all guns are different.

This is from my Granddaughters 8 grade science project. She wanted to determine the shortest barrel for convience yet still gice 1800 ft lbs of energy at 300 yards, the normal max for hunting elk.

First she went to the local stores that sold ammo. Determined that the 308 was the most popular, from what she found on the shelves. She picked the 180 grn Remington Corlocks.

I got her a 26' in barrel (douglas premium). Her goal was to cut it, 2 inches at a time. She cronogrphed 3 shots per cutting to get an average.

This is what she came up with:

Barrel Lenght 180 Vel Ke Vel KE
26 2826 fps 3,192 2240 2,005
24 2722 fps 2,961 2149 1,846
22 2713 fps 2,942 2141 1,832
20 2677 fps 2,864 2109 1,778
18 2654 fps 2,815 2089 1,744
16 2552 fps 2,603 2000 1,599

This just for an ideal what might happen. All gun/ammo combinations will be different.

Anyway, got her an "A", only gigged her because she and her friend had their faces in the pictures for the display, which ia a NO NO in Middle School.

 

[cali_tz]

Re: Barrel Length's effect on velocity?

@Dave, thanks for that link... great resource.

@Kraig, that is one helluva 8th grade project!