Home Forums Reloading Big Game Rifles Barrel length question?

I know longer barrels add to your FPS.

My question is 2 parts.

1. How many FPS per inch do you loose on average?

2. How does barrel length affect max load pressure? Does a longer barrel with the same load have higher pressure or is it affected?

This may help answer #1.
http://www.accuratereloading.com/223sb.html

#2 Pressure is unaffected by barrel length.

Thanks. That is pretty cool.

the older reload manuals used to state that on average you lose 50 ft./per sec. per inch of barrel.........

............I have performed a considerable amount of testing, comparing my own compact with longer barreled rifles chambered in the same round using the same identical reloads.

Unlike that 223 Remington example, I didn`t start out with a 24" barrel, then cut it down in 2" increments to what I have now. Cutting down the same barrel, I suppose would be the most accurate way to figure the fps per inch loss from any particular barrel.

Since that wasn`t possible, the next best thing to do was to recruit a rifle or two chambered in my same cartridge, put a pretty good wide variety of identical reloads together and then chrony the rifles side by side at the same time. This experiment took a few weeks to complete.

Interestingly, between my friend`s two 24" 300 WSM rifles and my own compact 300 WSM, the average velocity loss per inch was between 16.4 and 19.5 fps using identical reloads. With another set or sets of the same rifle combos, it could very well average lower at 15, even at about 20, or more at 25, 30 fps per inch or maybe even 35 fps per inch depending on the whether the bores are slower or faster and which rifles had either.

From a percentage standpoint, the 16.4 fps and 19.5 fps per inch #s, broke down to overall velocity losses of between 4.2% and 4.5% with these three individual rifle combos.

Like that same 223 Remy example, I would be very interested to see someday, that same barrel cut down experiment in 2" increments with a 300 WSM as well as other cartridges.

It has been done!
One of your gunsmiths over there did it a few years ago on a number of cartridges. I think Charlie Sisk was his name.
He concluded that lopping 6" off any barrel would only reduce velocity on average 100fps! Of course there is a limit to how short you can go!

He also discovered that the long held belief that faster powders made up for the velocity loss in shorter barrels to be false, the slower powders still had an advantage, even in barrels of 16.5"!

He didn't include the 300WSM, I think it was before it was invented, but he did extensive testing on a 300WinMag, from a 27" barrel he got 3115fps with 180's, and from the barrel being cut to 22" he got 3001fps, I don't see the WSM being much different.

The "old rules" said 30-40 FPS/inch if you were in the 2700 FPS range of velocity. Thats why a 24 inch 30-06 does not make sense to me, then nor does a 16.5 inch 30-06 unless you just hate your hearing.

416RigbyHunter is correct.

Below is Charlie Sisk's September 14, 2002's post indicating the results of his tests of muzzle velocities as he shortened the rifles' barrels.

Strength & Honor...

Ron T.



Charlie_Sisk
Campfire Ranger


Reged: 02/21/02
Posts: 1321
Loc: Dayton, Texas Been doing a little more experimenting.........
#88566 - 09/14/02 03:15 PM Edit Reply Quote



For a long time I have wondered about how barrel length affected velocity. I had always been told you need a certain length barrel for certain calibers. I have read when folks compared one gun to another with different lengths but I always thought that was not an apples to apples comparision. So I did a few test myself.
All these were Shilen barrels. I used the same brass through out the whole test. All weighed to with 1 grain. Bullets were tested on the Juenke machine. Powder charges were weighed to .1 grain. The same rest, chronograph, Redding press, primers all from the same lot, bullets for the same box, same lathe, same crowning tool, same cutoff tool, and each rifle done from start to finish on the same day. Ambient temperature was the same because I shoot from inside the shop. I held the rifle the same way on the rest every time. I shot ten rounds first to break in the barrel. Then cleaned with Sweets and fired one fouling shot. Then shot five rounds and took the average. I used a midrange load fron the Nosler book, not too hot but certainly not a reduced load. Here is what I got.

22-250 Hodgdon 380 34 grains Federal GM210M Remington brass 55 grain Ballistic Tip
27 inches 3469 fps
26 3451
25 3425
24 3407
56 fps from highest to lowest

270 Winchester Hodgdon 4350 54 grains Federal GM210M Winchester brass 130 grain Sierra
27 inches 3115 fps
26 3093
25 3071
24 3054
23 3035
22 3027
21 3001
114 fps from highest to lowest

300 Winchester mag Federal GM215M Winchester brass 74 grains of Reloder 22 180 grain Partition
27 inches 3055 fps
26 3031
25 3024
24 3003
23 2984
22 2960
95 fps from highest to lowest

340 Weatherby Federal GM215M 250 grain Sierra
81 grains Reloder 22 Wby brass
27 inches 2837 fps
26 2817
25 2809
24 2791
23 2777
22 2755
21 2731
106 fps from highest to lowest

I think I will do a little more thinking before I recommend a barrel length in the future. What do you folks think ?
Charlie



.338 Winchester & .257 Roberts

Here is the info about the 338 Win and the 257 Roberts.
338 Win mag
Winchester brass
Federal GM215M primers
Reloder 19....73 grains
250 grain Partitions
27 inches.....2806 fps
26 inches.....2787 fps
25 inches.....2761 fps
24 inches.....2743 fps
23 inches.....2716 fps
22 inches.....2697 fps
21 inches.....2676 fps
20 inches.....2656 fps
150 fps from 27 inches to 21 inches

257 Roberts
Federal GM210M primers
Remington brass
H-4350....45 grains
120 grain Partitions
27 inches.....2860 fps
26 inches.....2834 fps
26 inches.....2815 fps
25 inches.....2815 fps
24 inches.....2798 fps
23 inches.....2775 fps
22 inches.....2760 fps
21 inches.....2739 fps
20 inches.....2717 fps
143 fps from 27 inches to 20 inches

I want to test this on the next 450 Marlin I build and on a 222 Remington. If I get the same results with those, in my mind the test is over. I think this will be enough data to support the findings. Are there any folks out there who have a degree in this sort of thing ? Maybe explain how many data points would be needed to be able to say this would work with the majority of calibers ? Someone with experience in statistical (spell check) quality control?
Charlie



--------------------
Sisk Rifles
400 County Road 2340
Dayton, Tx 77535
www.siskguns.com
charliesiskguns.com
1-936-258-4984

The data and opinions contained in these posts are the results of experiences with my equipment, componentry, and testing methodology ONLY. As your equipment, componentry, and methodology is different, NO CONCLUSIONS SHOULD BE DRAWN FROM ANY DATA PRESENTED, nor should any data presented form the basis for any load development. DO NOT, UNDER ANY CIRCUMSTANCES, ATTEMPT TO REPLICATE THESE RESULTS, as doing so could be extremely dangerous.

I`m going to write this thread down!........ The next time people think I`m full of it (aka crap), when I state I lose only about 4.5% from my 300 WSM compact vs the 24s using the same reloads, I`ll refer the skeptics to this particular thread.

The 300 Win above, loses 95 fps from a barrel 5" shorter which equals 19 fps per inch,,,OR,,,a total of 3.11% points. My 300 WSM loses between 4.2% and 4.5% from its 16.5" barrel, which is 7.5" shorter than a 24" tubes I`ve chronyd.

Won`t mention their names, but I hope they come across this thread!!!..........

Had pretty much varying results on this issue, but not much approaching the loss of velocity some would have you believe.
My best present example is a Rem. M7 in 22-250 with a 20 inch Bbl..
Clocking a 53 gr. TSX @3573fps....

Not too bad...least wise the deer don't notice....

Ingwe

BTW!...........Thanks Ron T and 416RigbyHunter!!!!!!!!!

Dad's 7mm is 24 1/2" long & my 264 Win Mag is just over 26". You wouldn't think the extra 1 1/2 would be much of an issue in the field, but I find it somewhat clumsy & awkward compared to Dad's 7mm, especially going through light bush.

1 1/2" shorter on a 264 Win Mag shouldn't make much difference?

Ron T - Thanks for this post it is helpful - especially since my head begins to leak when I get too much data stuffed in there. Rooster

I have tried longer barrels on three 270 Win. The first was a Lilja cut to 25" and the second was a Kreiger which started at 26". Both seemed too long compared to a 22" so I started cutting them in one inch increments. The load was a maximum charge of H4831sce and 130 grain bullets. The average loss was about 22fps per inch. Both ended up at 22.75" because that is what balanced just right for me.