375 H+H velocity lost if cutting barrel to 20"
- Thread starter gorky
- Start date
Roughly 25-30fps per inch. There are other factors that can have effect but that is te general rule of thumb for such medium velocity cartridges.
I remember Phil Shoemaker commenting on this subject in an article probably 10 years ago.
He was still getting 2500fps with 300gr A-Frames from the short barrel so call the 4" difference moot.
I remember Phil Shoemaker commenting on this subject in an article probably 10 years ago.
He was still getting 2500fps with 300gr A-Frames from the short barrel so call the 4" difference moot.
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- Lumby Town!!
If you search around for old posts you'll find that it's been debated here a few times....after the dust settled, the guys that have actually done it found that you don't loose much. I keep thinking of cutting mine too
velocity
It has been my experience after cutting off many, many barrels in all kinds of calibers that it is directly related to the burn rate of the powder in the equation. I played at length with a 35 Whelen which when cut from 26 to 22" lost 180 fps however changing powder burn rates we were able to recover 110 fps by going to a slightly quicker powder. You also cannot assume that a load that shoots from a 24" bbl will shoot from the 20" bbl, as it completely changes the vibration frequency of the bbl. If you are only shooting factory ammo, the only way is to chronograph. There as so many variables to consider, the only thing guaranteed is there will be a loss and it could vary from 80 fps to nearly 200 fps.
Douglas
It has been my experience after cutting off many, many barrels in all kinds of calibers that it is directly related to the burn rate of the powder in the equation. I played at length with a 35 Whelen which when cut from 26 to 22" lost 180 fps however changing powder burn rates we were able to recover 110 fps by going to a slightly quicker powder. You also cannot assume that a load that shoots from a 24" bbl will shoot from the 20" bbl, as it completely changes the vibration frequency of the bbl. If you are only shooting factory ammo, the only way is to chronograph. There as so many variables to consider, the only thing guaranteed is there will be a loss and it could vary from 80 fps to nearly 200 fps.
Douglas
Thanks for the experience related Douglas, but I must ask: is this a theory regarding unburnt powder?
There have been enough reports given on the subject of quicker powders finishing their burn and slower powders not etc. buy powder manufacturers and interested gun media persons that have proven that even H870 was finished burning in appropriate cartridges in the first 16" of the barrel.
There are other issues such as full gas development etc, that would create similar results, but relaoders need to stop buying into the wives tale of unburnt powder etc, in rifle barrels.
velocity
Not commiting to any one theory as to powder burn etc, just know what I have experienced. Suspect it has to do with pressure curves and peaks at longer and shorter distances down the bbl. We never did the "fresh snow" test for unburnt powder.
Another young man just bought his girlfriend a 16" bbl Ruger compact in 260 Rem, could not get it to group well at all 3-4" at 100 mtr with the optimum powders suggested in the books. I advised him to work closer to the faster burn powder end of the scale and lo and behold he was able to bring it in to about 1 1/4". He doesn't have a chronograph so velocities were not recorded (which means I'm off on a tangent somewhat), but just another factor in faster powders and short bbls.
Douglas
Not commiting to any one theory as to powder burn etc, just know what I have experienced. Suspect it has to do with pressure curves and peaks at longer and shorter distances down the bbl. We never did the "fresh snow" test for unburnt powder.
Another young man just bought his girlfriend a 16" bbl Ruger compact in 260 Rem, could not get it to group well at all 3-4" at 100 mtr with the optimum powders suggested in the books. I advised him to work closer to the faster burn powder end of the scale and lo and behold he was able to bring it in to about 1 1/4". He doesn't have a chronograph so velocities were not recorded (which means I'm off on a tangent somewhat), but just another factor in faster powders and short bbls.
Douglas
I admit I have no experience, but I too always understood that the fastest powders in long barrels would likely be the fastest powders in short ones, and that there was basically no way to get back the lost velocity resulting from shortening a barrel by changing powders.
Accuracy effects are another issue entirely, and can only be decided by doing it and shooting it.
Accuracy effects are another issue entirely, and can only be decided by doing it and shooting it.
Given that gases under pressure are what create velocity and that the burn rates of the powder are what creates that difference in velocity, I would think that accuracy and velocity would be effected by the barrel length. I beleive that Charlie Sisk has used pressure barrels to help better understand some of this, and with certain cartridges there are definite character spikes. We could pontificate that these could be due to the powders those cartridges normally use. I am running on memory here, but most rifles had their peak spike while the bullet was in the 4-5" travel range and then cartridges like the 7mm Rem Mag had another signifigant spike in the 15-20" range. Could be something there.
Anyway, back on topic for the OP unless this talk was what he was looking for.
I say cut the barrel and load RL15
Anyway, back on topic for the OP unless this talk was what he was looking for.
I say cut the barrel and load RL15
short 375
I agree 100% RL 15 gives great velocity in the old girl and very good accuracy. It is also a midrange burn rate for the H+H and should still give best velocities and consistency in the 20" tube.
I was unaware of the second spike you mention but it makes perfect sense, hence the fantastic muzzle flash and bang with certain powders, bbl lenghts and calibers.
Given that gases under pressure are what create velocity and that the burn rates of the powder are what creates that difference in velocity, I would think that accuracy and velocity would be effected by the barrel length. I beleive that Charlie Sisk has used pressure barrels to help better understand some of this, and with certain cartridges there are definite character spikes. We could pontificate that these could be due to the powders those cartridges normally use. I am running on memory here, but most rifles had their peak spike while the bullet was in the 4-5" travel range and then cartridges like the 7mm Rem Mag had another signifigant spike in the 15-20" range. Could be something there.
Anyway, back on topic for the OP unless this talk was what he was looking for.
I say cut the barrel and load RL15
I agree 100% RL 15 gives great velocity in the old girl and very good accuracy. It is also a midrange burn rate for the H+H and should still give best velocities and consistency in the 20" tube.
I was unaware of the second spike you mention but it makes perfect sense, hence the fantastic muzzle flash and bang with certain powders, bbl lenghts and calibers.
My buddy has a Sako in 375hh with a 20" barrel and over the last 30 years he's killed all kind of stuff with it all over Canada. Big grizzly bears, B&C moose, big elk, sheep etc. and he doesn't know how fast it shoots since he doesn't have a chronograph. He uses hornady and partitions and they have done it all. Point I'm trying to make is that it will still kill everything u point it at and will be a more nimble package.
