Try the RA4 Drag Model
Select Gate
READ GTA FORUM RULES BEFORE POSTING
GTA Forum Help Desk
GTA Announcement Gate
Dealer Area
GRIP
AirgunWeb Airgun Videos
Airgun Repository of Knowledge
Vendors and Vendor Videos
AirGun Expo 2021
Airgun Expo 2022
Contests and Giveaways!!!
Welcome New Members
In Memoriam
GTA Contributing Members
Shot Show Videos
Hajimoto Productions
Airgun Detectives
Air Gun Gate
BB Guns and Such
"Bob and Lloyds Workshop"
American/U.S. Air Gun Gates
European/Asian Air Gun Gates
PCP/CO2/HPA Air Gun Gates "The Darkside"
Air Archery
Vintage Air Gun Gate
Air Guns And Related Accessories Review Gates
Hunting Gate
Machine Shop Talk & AG Parts Machining
3D printing and files
Buyer's, Seller's & Trader's Comments
Bargain Gate
Back Room
Target Shooting Discussion Gate
Target Match Rules
Shooting Match Gates
Field Target Gates
The Long Range Club
100 Yard Match
Discussions By States
Welcome,
Guest
. Please
login
or
register
.
Did you miss your
activation email
?
1 Hour
1 Day
1 Week
1 Month
Forever
Login with username, password and session length
Home
About
Help
Old GTA
Gallery
Search
Stats
Login
Register
Advertise Here
GTA
»
All Springer/NP/PCP Air Gun Discussion General
»
Projectiles
»
Slugs/Solids/Bullets
(Moderator:
oldpro
) »
Try the RA4 Drag Model
« previous
next »
Print
Pages: [
1
]
Go Down
Share This!
Author
Topic: Try the RA4 Drag Model (Read 244 times))
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26956
GTA Forums Person of the Year 2017
Real Name: Bob
Try the RA4 Drag Model
«
on:
February 16, 2023, 08:55:02 PM »
If you are testing slugs to determine their BC, try using the RA4 drag model instead of the G1.... It is based on the .22LR bullet, and has virtually a constant Cd below Mach 0.8.... and that extends the furthest into the Transonic of any drag models we have.... This seems to be a better match for airgun slugs.... Here are the Drag Models....
Note that at Mach 0.75 (845 fps) the Cd is the same, no matter which drag model you choose.... By the time you get to Mach 0.9 (1013 fps), however, there is about a 25% difference in the Cd, so if you calculate the BC using the G1 model, by the time the slug slows down to Mach 0.75, the BC will be wrong by about that much....
Here is a 21 gr. Slug in .22 cal, with the BC plotted using the G1 drag model.... It is 25% higher at 955 fps than at 870 fps....
Here is the same Slug, same Chrony data, but the BC is calculated using the RA4 drag model....
Note that using the RA4 drag model, the BC is virtually a constant over this range of velocities.... If you use the RA4 model to calculate the BC, and then use it in your ballistics calculator when figuring your trajectory or wind drift, it will be much more accurate as the slug slows down.... Ideally, the BC should be constant, regardless of the velocity....
Bob
«
Last Edit: February 17, 2023, 02:03:41 AM by rsterne
»
Logged
Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
Print
Pages: [
1
]
Go Up
« previous
next »
GTA
»
All Springer/NP/PCP Air Gun Discussion General
»
Projectiles
»
Slugs/Solids/Bullets
(Moderator:
oldpro
) »
Try the RA4 Drag Model