Ideal barrel length for 450 Marlin

[Mike Sr.]

I've been wondering if the new XLR, 24" barrel lenght might be too long for attaining a max velocity for this round...longer the barrel, longer the drag on heavy bullets...I think the 18.5 is too short!

What about 20inch or 22-inch barrel for optimum velocity..?

 

[No_Brakes23]

I am curious myself.

 

[MachIVshooter]

I've been wondering if the new XLR, 24" barrel lenght might be too long for attaining a max velocity for this round...longer the barrel, longer the drag on heavy bullets...I think the 18.5 is too short!

For the friction to actually start slowing the bullet down, you'd have a barrel as long as your house. That said, the feasible gain in velocity of the .450 Marlin begins to taper off with more than 22 or 24 inches. Each cartridge and each load have certain barrel lengths that get teh most out of the cartridge without being too long to be practical. For most rifle cartridges, that length is 20-26 inches. Shorter sacrifices too much velocity, but longer makes the rifle too cumbersome for the marginal gains.

Concerning the .450 Marlin, the 24" XLR will give a substantial increase over the 18 inchers (I would hypothesize ~150 FPS with 350-405 gr. pills). But it is not as handy if you are on horseback or fighting your way through dense underbrush.

 

[44AMP]

Rule of thumb

A general rule of thumb is 35-70 fps per inch, shorter or longer than "standard barrel length. However, this rule is only for average, as each different caliber and load combination varies. And, the individual rifles can vary that much or even more.

I have seen three different guns with the same barrel length, firing ammo out of the same lot give 100fps difference in velocity. Not the usual case, but not unheard of either. Some guns are "faster" than others, to a measurable degree.

two inches over standard (24 vs 22 in) should give you about 150fps more velocity, with the possible exception noted above. This would translate to about a couple of inches less drop at longer ranges. (I don't have any data for the .450 Marlin), but using .45-70 tables, this would be about right.

So, it all boils down to what you are willing to put up with, to get what you want. 24" isn't noticably longer than 22" in most situations. 26" is noticably longer. So, do you want the rifle to hit as hard, and shoot as flat as practical, or will you sacrifice a little bit of downrange performance for a handier package? Long range magnums benefit more from longer barrels. Woods rifles get their utility from shorter ones. Your call.