The Lipsey's 480 Ruger 4-5/8" Bisley SBH arrived at the local emporium. Only one of them, and strangely enough I was there on the day it came in.
Just lucky I reckon, and impulsive ...

61*F today, Hornady 480 Ruger factory ammo, 325-grain XTP, 10 shots chronographed:

5-yard chrono average: 1204 fps, 10-shot Sd = 14 fps
BC = 0.150, correction to MV: add 14.2 fps

Summary for same ammo in three firearms:
4-5/8" SBH MV @ 61*F = 1218 fps: 10-shot Sd = 14 fps
7-1/2" SRH MV @ 52*F = 1273 fps: 5-shot Sd = 22 fps
20" Ruger No.1 MV @ 52*F = 1579 fps: 5-shot Sd = 7 fps

Better than I expected for the short "Bisley" revolver barrel.
Maybe the Bisley SBH is a little tighter at the cylinder gap than the SRH.

A cylinder gap does not seem to cause much velocity loss, but maybe it increases the Sd of the MV?

If I plot a line with the two revolver velocities versus barrel length, the Ruger No.1 is about 70 fps above that line for 20" barrel length.

If I plot John Taffin's data for 4-3/4" and 9-1/2" SRH barrels,
his revolver line and my revolver line intersect at about 1250 fps for 6-1/4" barrel.

I am not saying it is truly a linear relationship,
I only have two points on each line.
You can draw a straight line on any banana with two points.
Anybody got a 2" or a 20"-barreled 480 Ruger or .475 Linebaugh revolver?

Rip ...

Jeff Quinn's 2.588"-barreled 480 Ruger revolver (Alaskan DA),
shooting the 325-grain Hornady XTP factory load,
"high forties" F temperature,
assume 12' (4-yard) distance to chrono, his usual,
instrumental velocity = 1099 fps

Subsonic bullet, but probably pretty loud report.

Jeff Quinn's 6.5" and 7.5" velocities were higher than Taffin's or my numbers would predict.
And his 2.588" velocity is lower than we would predict.

But Quinn's 3 points are almost perfectly on a straight line:

1099 fps 2.588" Alaskan
1289 fps 6.5" Bisley
1332 fps 7.5" SRH

Plot that!

Within that barrel length range:
Quinn: 47.4 fps/inch, for 2.588" to 7.5" revolver
Taffin: 31.6 fps/inch, for 4.75" to 9.5" revolver
RIP: 19.1 fps/inch, for 4.625" to 7.5" revolver
RIP: 24.5 fps/inch, for 7.5" revolver to 20" rifle, just to mix apples and oranges for fruit salad.


Rip ...

Rip my Rossi 480 Ruger has a 20" barrel.

theback40,

Thanks for the reply.
Yep, I remember.
I was joking about the 20"-barreled revolvers to compare to 20" rifles.
Your rifle may figure into that "no-cylinder-gap" side of the comparison.
Jeff Quinn said his Alaskan 480 Ruger had a cylinder gap of 0.002".
Your rifle and mine have a cylinder gap of 0.000".

quote:

Originally posted by theback40:
Rip my Rossi 480 Ruger has a 20" barrel.

Your 1705 fps is fast compared to my 1579 fps, both rifles with 20" barrels..
Now that I have learned a little more about this, comments below in RED:

quote:

Originally posted by RIP:

quote:

Originally posted by theback40:
Rip,the same 480 ammo you show, gave me 1705 fps average in my Rossi 92 20" barrel.

OK, your velocity finding with the 480 Ruger factory ammo is as expected..
With 325 XTP you got 1705 fps from a 20"-barreled 480 Ruger.
You would not have the pressure loss that I do with shooting the 480 Ruger in a .475 Linebaugh 20-inch rifle.
Mine has 0.2" more throat jump just from the shorter brass of the 480 Ruger, let alone any other differences in throating between the two
chambers.

Still a factor, but how much that matters I still don't know.
Maybe your rifle is tighter in the grooves and lands, slicker finished rifling, etc.???

I got 1579 fps at 52 degrees F.
You got 1705 fps at what temperature?

Your temperature was guesstimated in the 70s*F.
I still do not know how much temperature affects the velocity of this ammo.

Besides my longer chamber, do we have a temperature difference in this comparison?

In the Super Redhawk with 7.5" barrel and cylinder gap, at 52 degrees F I got 1273 fps,
though that factory ammo spec is claimed to be 1350 fps.

Factory ammo spec was probably determined at a temperature around 70 degrees F, in a 7.5" revolver (?).

That factory claim may be with 9.5" barrel instead of 7.5" barrel.
Seems the Ruger Super Redhawk has been refined, in and out of production, year to year.
Early ones with 9.5" and 7.5" barrels and 5-shot cylinders, and case extraction problems,
later ones with 6-shot cylinders and no case extraction problems.
Hard to make sense of it all.
The earliest .480R/.475L Ruger No.1s had 22" barrels, later ones have 20" barrels.

I believe the handgun powders are pretty temperature sensitive, compared to the ThermoBallistic Independence of some rifle powders.

Maybe not so much of an issue.

Rip ...

Duh, I read to fast and it didn't click you wanted a 20" revolver!
I will have to figure out how to send you one of these boxes of Hornady 475 Ruger ammo.