|
|
09-25-2017, 06:23 PM
|
Member
|
|
|
Join Date: Jan 2016
Location: The Villages, FL
Posts: 25
Likes: 1
Liked 8 Times in 6 Posts
|
|
Velocity Difference
I have an sd9ve with a 4” barrel and a shield with a 3.1” barrel. Shooting the same ammo from each shows about 50fps lower on the shorter barrel. Getting about 900 on the sd and 850 on the shield. Would that be typical difference? Shooting 145gr lrn with 3gr Titegroup. Thanks
|
09-25-2017, 07:03 PM
|
Member
|
|
|
Join Date: Aug 2005
Posts: 7,581
Likes: 4
Liked 8,930 Times in 4,139 Posts
|
|
You can figure to lose 25-30 fps per inch, but that's a very coarse guide. What is an sd?
|
09-25-2017, 07:33 PM
|
|
Member
|
|
|
Join Date: Dec 2009
Location: South Texas & San Antonio
Posts: 33,628
Likes: 241
Liked 29,141 Times in 14,091 Posts
|
|
There are many websites which discuss such things and provide experimental data.
|
09-25-2017, 07:39 PM
|
|
Member
|
|
|
Join Date: Mar 2012
Location: Eastern Pennsylvania
Posts: 1,033
Likes: 340
Liked 736 Times in 398 Posts
|
|
Besides length, the barrel itself can make a difference. And at these lengths powder choice can as well. So given the same ammo, there's at least 3 factors that could be contributing to the difference.
|
The Following 2 Users Like Post:
|
|
09-25-2017, 08:11 PM
|
Member
|
|
|
Join Date: Sep 2016
Location: Michigan
Posts: 165
Likes: 53
Liked 156 Times in 64 Posts
|
|
What Twoboxer said.
|
09-25-2017, 08:47 PM
|
|
Member
|
|
|
Join Date: Mar 2012
Location: Eastern Pennsylvania
Posts: 1,033
Likes: 340
Liked 736 Times in 398 Posts
|
|
Dunno what powder/bullet you are using, but being bored decided to run some stuff through Quickload. The loads below assume COL=1.12:
115gr PRN, Bullseye at max pressure, 4.0"=1247, 3.1"=1170, ie 77fps diff
115gr PRN, HP38 at max pressure, 4.0"=1186, 3.1"=1121, ie 65fps diff
These loads were chosen to generate ~900fps from a 4.0" barrel:
115gr PRN, Bullseye 3.4gr, 4.0"=907, 3.1"=840, ie 67fps diff
115gr PRN, HP38 3.5gr, 4.0"=895, 3.1"=828, ie 67fps diff
|
09-25-2017, 09:42 PM
|
|
Member
|
|
|
Join Date: Jan 2007
Location: Sandy Utah
Posts: 8,743
Likes: 1,590
Liked 8,897 Times in 3,548 Posts
|
|
There is typically 25-50 FPS per inch of barrel, usually closer to 25. That said, there are other differences that may allow the shorter barrel to actually be "faster" than the longer barrel. I have at least two 4" S&Ws that are actually faster than 6" S&Ws that I own, when shot the same day and with the same ammunition! You will only know if you buy a chronograph and do the testing yourself!
__________________
Gunsmithing since 1961
|
The Following User Likes This Post:
|
|
09-25-2017, 09:44 PM
|
Member
|
|
|
Join Date: Jan 2009
Posts: 338
Likes: 1,109
Liked 255 Times in 131 Posts
|
|
Wait til you find the load that shoots FASTER in the shorter barrel
|
09-25-2017, 10:18 PM
|
|
Member
|
|
|
Join Date: Dec 2012
Location: (outside) Charleston, SC
Posts: 31,000
Likes: 41,665
Liked 29,249 Times in 13,829 Posts
|
|
Even two guns.....
Even two guns of the same make and model can show large differences with the same load.
There is an article in my old Speer #9 manual called "What makes ballisticians get grey". They shoot the same loads out of a list of guns, many of them similar make and model. The results vary widely.
__________________
"He was kinda funny lookin'"
|
09-25-2017, 11:58 PM
|
|
Member
|
|
|
Join Date: Dec 2009
Location: South Texas & San Antonio
Posts: 33,628
Likes: 241
Liked 29,141 Times in 14,091 Posts
|
|
"I have at least two 4" S&Ws that are actually faster than 6" S&Ws that I own"
For revolvers, anything is possible. Differences in the barrel-cylinder gap width can make as big a difference in MV as different barrel lengths. Not difficult to imagine that a 6" barrel with a wide gap may produce a lower MV than a 4" barrel with a tight gap with the same load.
|
|
Posting Rules
|
|
|
|
|