300RUM From 26" To 24"???

wonksy

wonksy

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Just wondering guys whats your take on cutting a 26" RUM down to 24".
I know you dont lose much FPS per inch of bbl, but does this theory still hold true with the RUM's, Or would I be sacrificing more?
A Smith guessed I would lose roughly 100fps, just wondering if anyone has done it yet or if I'd be better off leaving it at 26".
Thanks
 
50-100 fps, but the only way to know, is to do it.

Before anyone jumps in - some "Myth-Busting". The 300 RUM and other "overbore" cartridges, do not "need" long barrels. They gain and lose more velocity per inch of barrel added or removed, but will always be faster than smaller cartidges, such as the 300 Win Mag, 30/06 etc. You will not need to use a faster powder with the shorter barrel either..........

Most people buy a 300 RUM (I have one) for long-range shooting, and that's why they tend to have longer barrels - it's not because it "needs it". The handling advantges of a shorter barrel are irrelevant when your shots are 300 yds+. To be honest, if shots are at 300 yds or closer, the 300 RUM is overkill, but you can't "over-kill" an animal.

I'd say leave it at 26" unless that length affects its use in the field.
 
Andy said:
Before anyone jumps in - some "Myth-Busintg". The 300 RUM and other "overbore" cartridges, do not "need" long barrels.
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See now the Smith I talked to told me the complete opposite of this. He said they need the longer barrels to burn the high volume of powder they require.:confused:
 
wonksy said:
See now the Smith I talked to told me the complete opposite of this. He said they need the longer barrels to burn the high volume of powder they require.:confused:
Click to expand...

and it begins..........:popCorn:

All of the powder that will be burned, is used up in the first 3-4" from the boltface. What remains is heat, gas and the products of that combustion. There will only be unburnt powder if the pressure was below the optimum operating range of that powder.

Several tests have been conducted, one going back over 50 years (I have the article), in which the muzzle velocity of loads using several powders of differing burn rates (from quite fast to quite slow) were measured as a barrel was cut back from about 30" to 12". The load that produced the highest MV at 30" (the slowest powder) did the same at 12" - so much for shorter barrels requiring faster powders and slower powders requiring longer barrels.
 
wonksy said:
See now the Smith I talked to told me the complete opposite of this. He said they need the longer barrels to burn the high volume of powder they require.:confused:
Click to expand...
He is right in a sense. What Andy is saying is that a 24" RUM will still be faster than a 24" 300WM or 30/06.

A longer tube will take full advantage of all that gas caused by burning that big pile of powder.

.
 
You're going to lose velocity and increase noise, how much velocity depends on the load used.
In reality, the 2" less really won't be that noticable for handling. You'd have to go with 22" or so to make a real difference in feel, IMO. That's when you may as well go to a 300 Winmag or WSM.
Generally overbore calibers need a long barrel to obtain max velocity, I would say 26" is usually considered minimum for ones like the 7mmSTW,257 Wby, 30-378 Wby,etc.

I've done some chrono testing in a 300 Winmag from 26" to 24" and using the same load the loss was just under 100 fps. I would guess the RUM is similar or more.
 
wonksy said:
I understand that Paul.
What would you do?
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Since you don't handload, I suggest selling it & buy a 30/06. A 30/06 would be easier to shoot, easier to carry and ammo is WAAAAY cheaper so you will be able to shoot it more.

What else you got for BG rifles these days?

.
 
SuperCub said:
Since you don't handload, I suggest selling it & buy a 30/06. A 30/06 would be easier to shoot, easier to carry and ammo is WAAAAY cheaper so you will be able to shoot it more.

What else you got for BG rifles these days?

.
Click to expand...

Handloading will hopefully start someday, biggest problem right now being I have no room in the house for it. 2 rooms in basement, but 1 is being used for spare room(Guests) and the other is the lil girls toy room.

As For Cals These Days...
300RUM,300WSM,45/70govt,35Whelen,270win,30-30win and 22-250
(which will be sold if NB ever follows NS and gets rid of its stupid ancient varmit cal rules:rolleyes:)
 
wonksy said:
As For Cals These Days...
300RUM,300WSM,45/70govt,35Whelen,270win,30-30win and 22-250
(which will be sold if NB ever follows NS and gets rid of its stupid ancient varmit cal rules:rolleyes:)
Click to expand...
I'd sell the RUM and keep the WSM. You could sell the WSM as well and still be covered with the 270. Spend the $$ on loading stuff.

.
 
Get a 300WSM if you need 24" barrel, leave the 300RUM at 26"

Bad idea since RUM use huge quantities slow burning powders so you'll get:
  1. huge muzzle blast
  2. increased recoil

The muzzle velocity loos is not such an issue but muzzle blast and recoil will be one.
If you want a 24" 300 Magnum, get a 24" 300 WSM!

Alex
 
Andy said:
All of the powder that will be burned, is used up in the first 3-4" from the boltface.

...the muzzle velocity of loads using several powders of differing burn rates (from quite fast to quite slow) were measured as a barrel was cut back from about 30" to 12". The load that produced the highest MV at 30" (the slowest powder) did the same at 12" - so much for shorter barrels requiring faster powders and slower powders requiring longer barrels.
Click to expand...

I don't know how anyone can do a test that shows all the powder is burnt in 3 or 4 inches from the boltface. That would mean with case length of over 2 inches, the powder would be burnt within 2 inches of bullet travel... I don't believe it.

Your statement about faster and slower powders with shorter and longer barrels does not relate to all cartridges with the choice of powders we have today either....
 
guntech said:
I don't know how anyone can do a test that shows all the powder is burnt in 3 or 4 inches from the boltface. That would mean with case length of over 2 inches, the powder would be burnt within 2 inches of bullet travel... I don't believe it.

Your statement about faster and slower powders with shorter and longer barrels does not relate to all cartridges with the choice of powders we have today either....
Click to expand...

TY Dennis!
:cheers:
 
guntech said:
I don't know how anyone can do a test that shows all the powder is burnt in 3 or 4 inches from the boltface. That would mean with case length of over 2 inches, the powder would be burnt within 2 inches of bullet travel... I don't believe it
Click to expand...

Here's how: you look at the pressure curve. You will notice that pressure peaks in just a few microseconds, at a point where the bullet will have travelled only a few inches. After that, the pressure curve shows a drop which indicates that the burn has completed. You will also notice that the shape of the curve is consistent with a pressure curve produced when a piston moves down a pressurized cylinder, i.e. pressure is reduced in a consistent fashion as the volume increases.

guntech said:
Your statement about faster and slower powders with shorter and longer barrels does not relate to all cartridges with the choice of powders we have today either....
Click to expand...

You're going to have to explain that statement, because it makes no sense to me.

wonksy said:
TY Dennis!
:cheers:
Click to expand...

Feel free to pipe in!
 
Andy said:
Here's how: you look at the pressure curve. You will notice that pressure peaks in just a few microseconds, at a point where the bullet will have travelled only a few inches. After that, the pressure curve shows a drop which indicates that the burn has completed.
Click to expand...

I have also read about 'tests' where un burnt powder was collected from in front of the muzzle on large clean sheet that was placed for that purpose... after it had the chance to burn in a 24 inch barrel... so not all powder burns within 2 inches... there is a point where more powder simply becomes a projectile with less velocity. I have personally measured this with a 338-378 and a 28 inch barrel. (Using an Oehler 35P)

With the choice of powders offered today a hand loader can compensate somewhat using a slightly faster powder in a slightly shorter barrel for a higher velocity than a slower powder may give. There is no set rule, cartridge capacity and bullet weight and diameter and the barrel length all affect this.
 
Guntech, I experienced this with the 375RUM you shortened from 26" to 21" for me standard loads that worked great in my 26" barrel had a velocity drop of appr 150fps if not more I switched to RL17 powder and was able to produce exactly the same top velocities/pressures as the original 26" barrel length gave me.

CC
 
Camp Cook said:
Guntech, I experienced this with the 375RUM you shortened from 26" to 21" for me standard loads that worked great in my 26" barrel had a velocity drop of appr 150fps if not more I switched to RL17 powder and was able to produce exactly the same top velocities/pressures as the original 26" barrel length gave me.

CC
Click to expand...
Did you try RE17 in the 26" bbl before cutting it? It might have given the best velocity then as well.


.
 
Camp Cook said:
Guntech, I experienced this with the 375RUM you shortened from 26" to 21" for me standard loads that worked great in my 26" barrel had a velocity drop of appr 150fps if not more I switched to RL17 powder and was able to produce exactly the same top velocities/pressures as the original 26" barrel length gave me.

CC
Click to expand...

Same velocity in 21" bbl. as RL17 gave you in the 26"? ;)
 
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