Optimal speed with slugs.

This question is another example of why slugs can be frustrating. We all look for proven data because we want shortcuts. Plain and simple. I have slug guns in two calibers but really focused on one caliber for maybe 5 years now. Glem and Motorhead gave pretty broad speed ranges but no definitive data and here’s why. I have a .25 barrel that has no choke. The gun shoots very well at 960fps. Probably better than most guys slug guns. But I know that my slug stats and speed are slow for my twist rate so I push the speed upwards and things get better. I’m not happy about how fast the gun is and how hard I’m pushing it but one would think, ok this is solid data. A shortcut. The thing is in 30 minutes I can slip a FX barrel back onto the gun and produce great accuracy that goes against everything the other barrel taught me. The slug is going way too slow for what the twist rate is telling me. I had a gun and slug combo that always wound up at 935fps. Didn’t matter what transfer port mods, reg pressures from 125-150b, after twisting knobs and turning screws when I found great accuracy and sent a couple across the chronograph, 935fps. For me, definitive data is barrel, gun, and slug specific. There is very little that I will paint with a broad brush when it comes to slugs except you can hope to get lucky, buy a gun with a proven leade that likes a particular slug or you have your work cut out for you depending how picky you are. How picky am I? Just so you know when you read my posts, if slugs in my guns won’t match or exceed a pellets accuracy and just as important consistency, they are worthless. Not worth the aggravation of not knowing if you’re shooting Dr. Jekyll or Mr. Hyde every time I grab the gun.
 
Is there a consensus on twist rates and what weights are appropriate for each twist rate in .22cal? I know in the PB world, lower twist rates stabilize heavier bullets and vice versa. Is it the same with airguns shooting slugs? Sorry, I'm a newb when it comes to slugs. Hopefully I'm not derailing this thread and maybe I should start a separate one.
 
Speaking specifically about Airgun Technology Uragans… I can tell you that speeds do not need to be particularly fast for extremely good accuracy out to 200 yards.

I hunt ground squirrels , starlings doves n pigeons at the following speeds:

.177 13 grain knouts 800 fps. Accurate to 175 and very very accurate to 140 yards

.22 H&N 21 grain .217 and .218 @ 840 fps. very accurate out to 185 yards.

.25 NSA 34.9 882 fps accurate past 200.

The .22 H&N is the most accurate of the 3

Faster speeds or even slower may be better…. But these work beautifully for me and give huge shot counts in .177 an .22
 
Speaking specifically about Airgun Technology Uragans… I can tell you that speeds do not need to be particularly fast for extremely good accuracy out to 200 yards.

I hunt ground squirrels , starlings doves n pigeons at the following speeds:

.177 13 grain knouts 800 fps. Accurate to 175 and very very accurate to 140 yards

.22 H&N 21 grain .217 and .218 @ 840 fps. very accurate out to 185 yards.

.25 NSA 34.9 882 fps accurate past 200.

The .22 H&N is the most accurate of the 3

Faster speeds or even slower may be better…. But these work beautifully for me and give huge shot counts in .177 an .22
I have notice with my Vulcan 2. 25 Cal and with the Uragan in. 22 that with pellets accuracy is better under 90 yards, but farther away 140 yards accuracy is much better with slugs.
 
My Bullshark will only shoot fx hybrids at 880-900 1/4in groups at 50 yards any slower or faster and the group starts to open up. Every other slug I have tried in that gun it hates, go figure it likes one of the most expensive ones. Rti profit compact with there slug barrel loves the nsa 17.5 at around 920. With slugs it just seems to be trial and error to figure out what's best for a particular barrel.
 
from 930 fps to 1.003 fps, just changing fill probe (made myself), 177 slug 14g, Tranfer port - High, Hammer - 1, OP 125 bar.

fill probe slug.jpeg
 
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