300RUM From 26" To 24"???

[Andy]

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.

Who needs pressure testing equipment when we have white sheets.

If you read carefully, I stated that the pressure needs to be appropriate for the powder, i.e. high enough, and that not neccesarily 100% of the powder will burn regardless of the pressure and barrel length. Now is stuff on the white sheet really "unburnt power" or is it "products of combustion". When I clean a 32" bore after using a load with Bullseye powder (I've done it), is the soot "unburnt powder"? Does that indicate that I need a faster powder or a longer barrel to get a comlete burn?

I already addressed your second point (knowing it would come up). It's just not true, and was proven 50 years ago, and more recently even with new powders. That notion has entered reloading folklore and will forever remain there.

 

[Andy]

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

So you tried Re17 with the 21" barrel and it was as fast as "standard loads" with the 26" barrel. What conclusion do you draw from that? Did you try Re17 with the 26" barrel as well?

The powder that will develop the highest MV's with a long barrel will do the same with a shorter barrel, and that could well be Re17 for the 375 RUM.

 

[Camp Cook]

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

No I didn't and yes I wish I had tried it out but didn't know that I was going to have to do a powder search to get velocities back up at that time.

CC

 

[AlexF]

Take a look at this: Barrel Length vs. Muzzle Velocity
http://www.loadammo.com/Topics/October05.htm

Simply put you lose velocity when shortening a barrel because the expanding gas stops pushing on the bullet.
As long as gas pressure x bullet area is greater than bullet friction you get better velocity.

Two other very interesting muzzle velocity vs barrel length
For very long barrel in 338/378 Weatherby
http://www.riflebarrels.com/articles/bullets_ballastics/long_barrel_velocity.htm

For short to super short 223
http://www.accuratereloading.com/223sb.html

This pretty much covers everything about muzzle velocity vs barrel length.
Another issue is muzzle blast and concussion when shooting cartridges which use slow burning powder.

If you want to have some fun, shoot a short 243 Win or a short 270 WSM with a case full of Retumbo at night (you might need sunglasses )

Alex

 

[Northman999]

Back to the OP.

I would not cut your barrel, no way.

The whole point of a 300 RUM is velocity, period.

As soon as you do anything to reduce your velocity, you are working counter to what the cartridge was made for. Even cutting 2" and losing "about" 100 fps, is still a loss no matter which way you slice it. If you were willing to trade velocity for a lighter, quicker handling rifle, you bought the wrong caliber in the first place, no offence.