Impact .25 ST vs STX comparison

[PerkyVal]

For those curious how a new Impact with no changes, or tuning yet perform with the standard ST barrel, and the new STX barrel system with the X liner this will interest you.


Description: Fx Impact out of box ST 25.4gn
Notes 1: Stock, ST barrel, 25.4gn
Notes 2:
Distance to Chrono (FT): 7.00
Ballistic Coefficient: 0.036
Bullet Weight (gr): 25.400
Altitude (FT): 0.0
Temp: 68 °F
BP: 29.96 inHG
Shots
# FPS FT-LBS PF
15 907 46.40 23.04
14 900 45.69 22.86
13 897 45.39 22.78
12 897 45.39 22.78
11 899 45.59 22.83
10 902 45.89 22.91
9 904 46.10 22.96
8 897 45.39 22.78
7 899 45.59 22.83
6 896 45.29 22.76
5 893 44.98 22.68
4 904 46.10 22.96
3 896 45.29 22.76
2 896 45.29 22.76
1 898 45.49 22.81
Average: 899.00
StdDev: 3.78
Min: 893
Max: 907
Spread: 14
True MV: 919.05
Shots/sec: 0.25
Group Size (IN): 0.00


..and the STX



Description: Fx Impact out of box STX 25.4gn
Notes 1: Stock, ST barrel, 24gn
Notes 2:
Distance to Chrono (FT): 7.00
Ballistic Coefficient: 0.036
Bullet Weight (gr): 25.400
Altitude (FT): 0.0
Temp: 97 °F
BP: 29.96 inHG
Shots
# FPS FT-LBS PF
15 924 48.16 23.47
14 922 47.95 23.42
13 919 47.64 23.34
12 923 48.06 23.44
11 918 47.54 23.32
10 920 47.74 23.37
9 918 47.54 23.32
8 917 47.43 23.29
7 923 48.06 23.44
6 921 47.85 23.39
5 922 47.95 23.42
4 919 47.64 23.34
3 917 47.43 23.29
2 922 47.95 23.42
1 920 47.74 23.37
Average: 920.33
StdDev: 2.29
Min: 917
Max: 924
Spread: 7
True MV: 940.86
Shots/sec: 0.24
Group Size (IN): 0.00

 

[Michael]

Are ST & STX barrels the same length?
Are settings kept the same & just barrel change? 

I would've thought the BC would've changed a bit. How did you calculate BC? Or was it just at the muzzle?

 

[PerkyVal]

I used the same shroud although I didn't hold them next to each other. As far as the BC is concerned i just used the number that chairgun had, so the accuracy of it is ballpark.

 

[Michael]

"PerkyVal"I used the same shroud although I didn't hold them next to each other. As far as the BC is concerned i just used the number that chairgun had, so the accuracy of it is ballpark.

Cool, I'm looking forward to doing some comparisons myself. Thanks for sharing 

 

[Eaglebeak]

That is a significant gain in velocity and consistency from just a barrel change, are the transfer ports the same? It will be interesting to see if you achieve similar results with the heavies. Perhaps they are using less choke on the fully rifled X barrels?

 

[mag_de_mars]

concerning choke i can confirm on .30 barrel it seem there is no choke 

 

[wolfie]

Hi, yes illuminating

No mention of fill pressure but temp on first string said 68 degrees F second string showed 97 degrees F.

Assume p/l max and tp 3

Chronograph, Caldwell 

Is that correct!

safe shooting

 

[PerkyVal]

Temp was 68 on both, I just didn't change it in the software for the one string.

I filled the gun to 230bar before both strings

 

[Tomiboy]

Have you shot for groups yet?

 

[Drumsnguns]

Since there's already a topic for barrel comparison I will add my initial findings to this data base.
I got the 600 mm ST-X barrel this weekend. Before I say anything else I will say that the wind has been blowing non-stop since March here in NC. It's either wind or rain or windy rain. I don't think there's been 6 days where we've had calm conditions in all these months

OK, having said that, the past couple of days have been no exception.

I got the barrel from Utah Airguns, cleaned it then installed it on the Impact. Below are targets from the first and second day and I included a target from the ST standard barrel for quick comparison. I zero'd at 30 yd and shot about a magazine's worth to lead-up the squeaky-clean barrel then got a couple of very impressive groups. The first day I had a cross wind and today I had the wind at my back at a 45. Winds feel like 7-10 mph
I won't list chrony numbers but:

Velocity: 837 Ave., with King Heavies, MK II.
Extreme spread: 11
Standard deviation: 3.
Regulator is 120 bar and hammer spring at max.
The old ST barrel shot at 855 fps ave. with about the same ES and SD but Ernest had enlarged the TP on the standard barrel.

I want to get out to 100 yds but the wind is just going to have to die down before I can do that in all fairness to the ST-X.
All targets are at 55-57 yd with 8-shot groups ea., shot off Atlas bipod with rear bag.

First target/ST-X

 Second day ST-X

Original ST barrel shot on 5/25

Temperatures and weather conditions are similar for all targets and all have been shot within 10 days. The gun was left at original settings for all.

I'm impressed with this barrel shooting like this right out of the box. It isn't even broken in. The first target above was Pellets #17-25. The original barrel did not shoot this good out of the box. Looking forward to more testing and calmer days.
BTW, Utah Airguns are really nice folks to deal with. 
KP

 

[Drumsnguns]

I want to clarify some things. The POI difference between the first and second ST-X targets is owing to the fact that on the first day I had very limited time to shoot and I didn't chrony so, I just guessed using the data for the original barrel, (855 fps), in Strelok.

This morning I entered the new velocity into Strelok but they went a hair high. I shot this second target when there was a momentary drop in the wind. I pumped out 8 shots as fast as I could before the wind started back up. 

The guys at Utah told me that from their tests they believe the X and standard barrel to shoot similarly out to around 50 yd....it's not until you get out further, say 75 and beyond where the X takes over the lead. Let's hope so. Can't wait to find out.

I'd really like for Ernest to enlarge the TP on this new X barrel but I'm afraid those days are over. Ernest?

KP