Velocity Lost with 2" shorter barrel

[hunter24605]

Is there an approximation of how much velocity is lost over book data listing a 24" barrel and using a 22" barrel? Specifically 280 Rem 140 Gr bullets..I realize there is a bunch of variables to consider, just looking for an approximate loss. I have been using the 1% per inch rule.
Thanks

 

[OU812]

I have heard 30 fps per inch of barrel but like you said lots of variables to consider. Shooting across a chrono is the best way to know.

 

[sockeye]

I hear 20-25 fps per inch, but you are correct in there are many variables such as powder burn rate, bearing surface to name a few. If your shortening and re-crowning, you may be more accurate. I would think a .280 with a 22" barrel that's accurate would be as good an all around cartridge as there is. Mike Bellm has a good read on barrel length on his website BellmTC's.

 

[DrMike]

As others have already noted, there is a differential with changes in barrel length. I anticipate 25-35 fps differential for each inch of barrel.

 

[hunter24605]

Well, I guess I was pretty close..Of the three I checked using the 1% rule, they calculated reductions of 28.5, 29.8, and 30.2 fps per inch.
I was asking because shooting across the chrono and figuring a 30 fps per inch reduction, a lot of the data published by powder manufactures seems to be faster than I'm achieving. However, data published by bullet manufactures seems to be more inline with my results.

 

[Blkram]

You're definitely in the right neighbourhood! 20-30 fps per inch of barrel is a good average, while some may get less, and others more variance.

No animal is going to be able to tell the difference that it was killed cleanly by a bullet travelling 100 fps more, or less, than what the manufacturer claimed it should be doing, at reasonable ranges (400 yards or less).

Data published by the various powder and bullet manufacturers will always be somewhat different than what we will get due the following variables:
1) powder lots are not consistent from batch to batch
2) no two barrels will provide the same results due to various tolerances in chamber, rifling, metal density, barrel length, barrel harmonics, bedding, lapping, chryogenic treatment, etc. Resulting in "slow" or "fast" barrels
3) elevation and atmospheric condition variances between where they developed their data and where you are developing and shooting your loads
4) consistency in calibration and accuracy of scales used for weighing components used to make their loads vs your equipment and settings of dies for assembling components into cartridges for testing (I.e. c.o.a.l and jump to the lands, etc.
5) variances in shooter's bench rest shooting equipment set up techniques (I.e. Distance from muzzle to chronograph)

Any time we can be within 100 fps of the published data, and are achieving good groups and velocities, consistently, we should be happy with the results. Some barrels need a "break in" period to settle in and start producing better velocities ( some immediately, while others can take 300-400 rounds before seeing the results that we expect ).

The real proof is the confidence that your load produces for you in that particular firearm and its performance on the game that you harvest with it.

 

[Thebear_78]

I think the ratio of bore diameter to volume of powder has a lot to do with rate of velocity loss. For example a 375 h&h will lose around 20 fps an inch down to 20", then increases as you drop below 20", a gunsmith buddy cut one down from 26" and graphed the loss. The 264 Winchester lost 60-80 fps and increased each inch.

Since your 280 is fairly small bore and medium volume I'm betting 35-40 fps per inch. Faster or slower powders could also have an effect


Sent from my iPhone using Tapatalk

 

[TXbaldhunter]

You really cannot tell,it depends on the barrel.I have two Ruger no.1's in the 7mag.One has a 24" barrel,the other has a 26" barrel.The 26" will shoot the same load around 200fps faster.I also have two Remington 7mags.One has a 24" barrel and the other a 26".The 24" is a Douglas barrel,the 26" is a factory barrel.The 24" will shoot the same load 50fps faster than the 26".So out of four 7mags shooting the same load from the slowest to the fastest it goes like this,24" Ruger,26" Remington,24" Remington,26" Ruger.I've learned it is what it is,if it shoots good,just live with it.

 

[baltz526]

Different powders react differently to barrel length. One powder may lose 15fps per inch another 80fps per inch. The only way to find out is chronograph as you chop off inches.

 

[TXbaldhunter]

Kinda what I was thinking.Short barrels may get better velocity with a faster burning powder than a slow burner.

 

[Silent Sam]

You can't lose what you never had... :wink: If your barrel was the same length assuming that you would get the same velocity would be just as much a guess.

"I think the ratio of bore diameter to volume of powder has a lot to do with rate of velocity loss."
This I agree with - aka expansion ratio - but won't help you much in your case.

"Short barrels may get better velocity with a faster burning powder than a slow burner."
I disagree here. Assuming you are using appropriate powders I bet the highest velocity load in a long barrel will still be the fastest as the barrel is shortened.