Tune your AirForce Texan for max velocity and maximize air efficiency. If you like the information I've provided, I'd be grateful if you would take the time to give me my first "Professor" ranking as a forum contributor who is providing good and accurate information.
You have a chrono… great! The chrono is mandatory to properly tune your rifle. I also hope you have a good regulator as well. Proper tuning can be achieved without the regulator, but it will take significantly longer to complete the rifles power adjustments.
Below you will find my personal spreadsheet to enable you to tune your rifle like a pro, following the guide below while documenting your results on the provided spreadsheets will enable you to tune your Texan for max velocity while maintaining your best possible air efficiency. This information is shared freely and was developed solely by myself over the course of hundreds of hours of testing with thousands of rounds down the pipe. Following this procedure will give you the best possible shot to shot accuracy, especially helpful when you reach out to touch targets that are several hundred yards out. If you share this information, I'd appreciate it if you only forward the link to this post. No Joe Biden like plagiarists on my work is authorized.
Start with your tuning session at the maximum rated pressure for your rifle and with your ammo of choice.
I have attached my personal testing spreadsheet for your use and included the results from one of my tuning sessions, this info should serve as a good visual reference for what you should expect when following the tuning directions I've provided. Note: MY RIFLE IS HEAVILY MODIFIED, DO NOT USE MY MAX PRESSURE SETTINGS ON YOUR STOCK RIFLE, USING MY MAX PRESSURE ON A STOCK RIFLE WILL DAMAGE THE RIFLE AND VOID YOUR WARRANTY... OR WORSE! If you have excel to open the attached spreadsheet, great, if not, I have attach a pdf. file you can print.
Equipment needed for tuning: Air and lots of air, slug of choice, Chrono, Air regulator for tethering your rifle is a big help,
did I forget to mention you will need lots of air?
Tuning step #1: I start by testing with 3 shot groups at each pressure for averaging, you can switch to 5 shot groups for final testing if you like, this tuning can be accomplished with just one shot at each pressure setting with adequate results.
1. Set your hammer spring tension to max... See picture attached above in previous post dated 5/6/24.
2. Begin testing at your rifles maximum rated air pressure.
3. Now shoot each of the pressures listed and note your speeds after each shot.
4. If you are shooting slugs that are under 400gr., you will likely hit a sweet spot where velocity increases at a pressure reading that is lower than the maximum rating for your rifle.
*The pressure where you achieved maximum velocity is where you will begin “Tuning step #2 second step of tuning.
Tuning step #2 a) Set your rifle up on the pressure that gave you the greatest velocity with the hammer spring set to maximum.
b) Shoot three rounds to verify your readings.
c) Back off your power wheel 180 degrees, moving your power wheel (Hammer spring tensioner, (1/2 turn, moving is slightly to the left, which is moving it away from the rifles action and fire one round, taking note of the velocity and write it down on the spreadsheet provided.
d) Back of your power wheel another 1/2 turn and fire one round, taking note of the velocity, and writing it down on the provided spreadsheet. Repeat this procedure until you achieve a consistent 10fps drop from your max velocity.
e) Now turn your power wheel back in, increasing the hammer spring tension until you regain 5fps of the 10fps you lost. Save this setting for the specific ammo you have chosen, if you change ammo weight and want to maintain maximum performance, you will need to tune your rifle each time you change your slug weight. Following this procedure will give you the tightest possible shot to shot spreads with no wasted air behind the slug chasing an empty barrel. Air efficiency is very important on big bore rifles, especially when out hunting and you’re unable to top off your rifle between shots.
A day of proper tuning will give you a great performing rifle and years of fun.
Daniel Carr-DG
View attachment Pressure fps tuning chart_AirgunNation share.pdf View attachment Pressure fps tuning chart_AirgunNation share.xlsx 
