velocity loss

[white eagle]

what would the loss in velocity be for going from say a 5.5" to a 4.5" barrel ?
100 fps or so ????[smilie=2:

[Walt]

It can vary a bunch. A slow 5.5" could be slower than a fast 4.5". I have chronoed more 1911 loads than anything else. I've found about 75 fps between the same full power loads in most commanders (4.25") and government models (5"0).

[44MAG#1]

After having chronoed barrels of different lengths with the same ammo back to back etc.. I have found that with most loads the velocity loss is 30 to no more than 40 fps with most running 30 to 35 fps. With a 10 inch 454 and a 7.5 inch 90 fps "just like FA said" was the rule with 300 gr and over bullets. Same for the 43/4 inch to 7.5 inch guns again just like FA said.
A 45 Colt with the typical loads will run an average of 30 fps difference with some loads almost no difference. 18.5 gr 2400 with a 260 to 280 Keith STYLE bullet will maybe hover around 30 to 35 fps.
These are no differences real considering a slow lot of powder in a 5.5 inch and a fast lot in a 45/8's inch can sometimes let the shorter outrun the longer. Same thing with changing lots of primers.
Until one gets to maybe a 150 fps difference do I consider it a difference. Even chroning the same load on different days can make a difference. That is the reason I chrono back to back when I want to find if there is a worthwhile difference.
And unless you chrono a load most shooter cannot tell a difference between a 1200 fps load and 1300 fps load.
I have a 45 ACP S&W revolver and using a typical 230 gr factory load and a Buffalo Bore load with a 250 at an actual chronoed vel. of 977 fps I can barely tell the difference. The difference is there but slight.
Again unless the difference is getting close to 150 fps i don't consider it.

[bigboredad]

There really is no set answer. I have a 5.5 inch that is faster than every 7.5 I have tested. Also it can depend on your forcing cone I know people who have lost velocity by going to a 11 degree cut. Also are both barrels fire lapped or is just one.

I've heard for years that with handguns you loose about 50fps per inch. But that's in a perfect world. If you are looking to get a 4 5/8 I can put your 5.5 in a loving caring home[smilie=s:

[BD]

The question as asked is too general to be answered with any validity. You would need to specify platform and cartridge to have any hope of a usefull answer. There is data addressing this for the .45 acp in my 1911s at castpics. 3", 4" and 5" using the same lot of Hydroshocks. On the other hand, if you're talking revolvers, the variations in chamber/throat/cylinder gap can easily outweigh velocity differences due to barrel length differences of several inches.


As an example I own a 4" .357mag DW barrel that is faster than my 6" DW .357mag barrel set to the same cylider gap, shooting the same load on the same day from the same cylinder. Go figure.
In one of the older speer manuals there is an article called something like, "Why ballisticians get gray hair", in which the author compares the velocity of 8 or 10 different .38 special revolvers with results all over the map irregardless of barrel length.
BD

[white eagle]

I was thinking of a 6" barrel vs a 4 3/4"barrel
in a s/a revolver chambered in 475 Linebaugh

[jwp475]

There really is no set answer. I have a 5.5 inch that is faster than every 7.5 I have tested. Also it can depend on your forcing cone I know people who have lost velocity by going to a 11 degree cut. Also are both barrels fire lapped or is just one.

I've heard for years that with handguns you loose about 50fps per inch. But that's in a perfect world. If you are looking to get a 4 5/8 I can put your 5.5 in a loving caring home[smilie=s:



Exactly, I have also seen shorter barrels that are faster than longer ones. A couple of years ago I chrono'ed a variety of factroy loaded 357 mag ammo in a 4" and a 6" barreled S&W M-19's some loads the 6" was faster, some loads were the same, and with some loads the 4" was faster. Only way to know for sure is to chrono

[PacMan]

White Eagle there are two things i would bet on.Two seprate bets same amount of money.
One is that the 6" will give slightly more velocity.
Two the 6" will be more plesant to shoot.
I know i would break even but feel sure i would be money ahead.