Home Forums Hunting & Shooting Ask The Gunwriters velocity drop question 24" vs 22" brl

Hi
Would like to get a reasonable estimate of the approx muzzle velocity drop I would expect on my 22" barreled rifles from the 24" test barrel data I see, and therefore understand when I am probably approaching max pressure. (across my chronograph)

I have 2 rifles, both with 22" barrels, that I reload the most: (both bolt guns)
- 30-06 165gr or 168gr spitzer using a powder like IMR or H4350 (ruger 77 mkII)
- 6.5x55 swede 140gr spitzer using a powder like IMR or H4350 (Howa 1500)

I have looked online and see wildly different data on this, so wanted to find out what you folks actually have experienced.

What does your experience tell you on this, and I understand it would be a rough estimate, and it is my responsibility to be checking all the other signs of pressure and not just be relying on the chronograph!

Thanks much for any thoughts on this.

I'd be surprised if the Swede dropped much different than about 24 to 26 fps, per inch , from my experience sporterizing model '96's. I was of course using military barrels which does not apply to your commercial barrel maybe?
As a sidebar, I got great accuracy results going down to 20" on three of those sporters (made them into fullstock carbines). Too many powders to list here, they all worked well, but accuracy honors always went to faster powders than the experts recommend. Near max published loads of 3031, 4895, 4064 and 4320 with any good 140 gr flat base. When I shifted to Barnes 130 gr, all I did was reseat the copper bullets over the same powder charges for wonderful accuracy and very similar ballistics, not that I am a long shooter.
No experience shortening '06 barrels.

Thanks flintlocke, great info!

Have a super weekend.

My experience has taught me two things.

1. Every rifle/chamber/barrel is different

2. Chronographs eliminate guessing.

25-30 fps per inch is my guess for both those rounds, probably 50-60 fps total. It's usually not as much as people think.

In the vast scope of things, does a few fps really make that much difference? I've had barrels from 18.5 up to 24" and where and how I hunted made more difference than 2 inches of barrel length. Climbing trees with that 7 RM and 24" barrel was a chore because the barrel hit or caught every branch on the way up or down. The 18.5 inch barrel shined in that application. A 20” on a bolt action has been the best compromise for me and if the holes go in the target where I want them, it works well for me. No one I know has ever shot through a chronograph, but that’s just me.

My only data is from shooting my two 7mm Weatherby Magnum rifles with 24” and 26” barrels respectively. There is about 20 fps difference between them with the same load of Norma MRP and 150 gr TTSX bullets. One is a hammer forged Howa barrel and the other is a button rifled Krieger Criterion barrel. Obviously two very different barrels but actual velocity differences can really be shown by cutting off a barrel inch by inch and measuring the same load speeds. I think this method has generally shown 20-25 fps per inch. I would think that different powders with different pressure curves might be a factor also. MD has several articles on this subject. Happy Trails

I have 2 Win M70 SS Classics in 300Win. One has the factory 26"bbl, the other has a BOSS bbl that I cut back to 23". Doing some load tests w/R-26 last week there was a 25FPS increase in the 26" rifle vs. the 23" rifle. Same FL size brass with the same number of firings, same primers, same 3.34" seating depth to match the mag box.

The 26" rifle has considerably more rounds through it than the 23".

Using IMR 4831 and 200gn TSX, the difference in velocity between the same 2 rifles identified above is under 10FPS using a LabRadar multiple times over the course of ~50 rounds through each rifle.

I hope this clears things up.

+1

About what I usually see too,but there are also some barrels that are faster and slower than others as well.The only way to tell is use a chronograph.I wouldn't load without one anymore.They are not that expensive and well worth it.Another thing you can do is play with different powders.Sometimes you can gain that extra velocity difference between a 22" and a 24" barrel by using a different powder on that shorter barrel.

rifleshooter.com

Test of a few calibers, speed check @ 24-26", chopping an inch off at a time & re checking speed. Good charts & sometimes multiple types of ammo chacked during the process as well.

Super informative.

Obviously, different chamberings & different guns will behave a little different, but here's a test that will show the basic tendencies.

MM

Barrel Length Effect on Velocity with 224 Valkyrie

Thanks to all for the great info you provided.

I appreciate it!

https://rifleshooter.com/2015/04/7mm-remington-magnum-7-rem-mag-barrel-length-versus-velocity/

Here's an article on a 7mm Rem Mag test with velocity loss documenting per inch. Different cartridge, but I think you'll see slightly less loss due to smaller case capacity of your cartridges. His average loss with the 7mm Rem Mag per inch was 26fps.

Cut 4" off my 24" 22-250 barrel. Chronographed before and after, using same load showed a loss of 30 fps per inch.

From what I've read the more overbore a cartridge the more gain in FPS for every inch of barrel. What I've read in loading manuals depending on the powder burn rate, between a 22" and a 24" barrel there's about a 60 FPS difference in the two. I have a .270 with 22" barrel and with a 130 grain SGK on top of 56.7 grains IMR 4831 through my Chrony I get about 3050-3070 FPS depending on ambient temp. For me that's smokin' ass hot.

Charlie Sisk testing, an oldie but a goodie.

https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/5886778/1

20 FPS/inch seems like a reasonable prediction

There would be several ways to find the velocity of a cartridge.
The most popular of coarse is to shoot over a Chronagraph in oder to get the information.
Armed with the velocity information we can now use one of the many sites in order to obtain information needed to create an elevation chart needed in order to add the correct number of clicks on the scope for various distances.
Its always advisable to confirm the information by actuall shooting at at least some of the distances.
While not all of us have a chronagraph, we can at least shoot at various distances and then count the amount of clicks added to the scope and compare that to the program in order to get the velocity number.

My Berger manual has information on velocity difference with different barrel lengths in all the cartridges they have data on.

I don't know how they arrived at this information but I would expect it to be close.

Chopped a '96 Swede down from 24 to 21" - lost 33 fps per inch.......with 120s......mv loss with lighter bullets is often greater than loss with heavier bullets. Good info above.