Got A New 30 cal Barrel Kit for My Impact and...

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AirgunBill

Member
Nov 2, 2015
1,271
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Maryland, United States
A new pest target too 'Snapping Turtles' I got the 30 cal. to go after groundhogs with body shots if possible but today turtles were on the pest list. The farmer's wife was worried about the snappers eating the ducklings on the pond plus too many snappers can hurt the fish population. I wasn't sure how the shoot would go but it is next to impossible to range find off the water. For the most part the turtles were hanging near the bank where I could get a close range find distance. I was watching my direction for shooting as to not have any ricochets but the pellets seem to dive right into the water. The shoot was fairly successful and I saw some more snappers cruising around so more target are available. 

Oh I did some testing at fifty yards with the JSB 44.75 at 840 fps into ballistic gel. They did not expand at all as expected but did penetrate well which would be get for head shots on hard headed pests.. I then shot some 50 grain Varmint Knockers at 814 fps into the gel at 50 yards and they did okay expanding to about .360". I need to try and get more fps from them. By the way I got my barrel kit from SPAW and I had them open up the barrel port and probe. The barrel port was opened up on both sides so air flow should be good. Bill

PS I had just installed the power plenum on the Impact which was very easy with all the videos out there to watched.



https://www.youtube.com/watch?v=t_zuZsDpl5c&feature=youtu.be&ab_channel=GunPowder%26AirPower


 
Good shooting I'd bait the bank if I were you. Yo!
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When I younger my father and I would bait large hooks ( I forget what size ) with stew beef and tie them to a bank branch with nylon twine. Caught many a snapping turtle that way. I suggested that to to farmer that would be the best way to catch them but he of course does not have the time. Not sure I want to take the time either but know that would be the most efficient methods. Bill
 
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Where did you source the power plenum?

All those mods and your only getting 814fps with 50 grainers? You must have really low reg pressure and lovely shot count (at least compared to my .30).
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Utah Airguns. You will have to electronically sign a waiver with your rifles serial # that void your warranty. Bill

My initial settings was to only get the rifles shooting the JSB 44.75 to about 840 fps which Ted Bier said was the most accurate speed for that pellet. I do want to get the 50 grain Varmint Knockers to at least 900 to 930 fps. My present tune is at 125 bar, hammer spacing at 14.70 mm ( I believe about 13.40 would be about max and still be able to turn the power wheel ) valve at 9.00mm. The 4th line on the valve measures at 10.90 mm. If you have any settings that would get me in that fps range for the 50 Vk's I would appreciate the information. To tell you the truth I have never been able to get the velocities most get in their Impacts in my .22 cal but still pre- power plenum or my .25 Impact that came with the power plenum. Bill
 
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It would be nice to get some tune specs. so I know a ball park of settings I would need. Like about what regulator pressure do I need to get the fps I want and hammer spacing. It always seems I get to max. hammer spring adjustment and not get anymore fps like the hammer is not heavy enough to open the valve. Of course that was with other tunes when this rifle was in .22 cal. or with my Impact .25 cal with power plenum. I think I will go out know and do some tuning for the 50's and see if I can get at least 900 fps. Bill
 
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Good shooting I'd bait the bank if I were you. Yo!
Click to expand...

When I younger my father and I would bait large hooks ( I forget what size ) with stew beef and tie them to a bank branch with nylon twine. Caught many a snapping turtle that way. I suggested that to to farmer that would be the best way to catch them but he of course does not have the time. Not sure I want to take the time either but know that would be the most efficient methods. Bill
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OH if that's the case how's about baiting the bank itself draw them buggers out of the water. Less wasted 44gr JSBs... Go SAVING PRIVATE RYAN on them... Yo!
 
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Bill,

This is what I'd do:

Set your hammer spring adjuster screw so you get maximum compression/preload for the hammer spring.

Open valve.

Increase reg pressure by 5 bar and set hammer wheel to 1 and fire 3 shots over chrono. 

Repeat 3 shots on position 2 and look for increase in velocity. 

Repeat on position 3, 4, etc until you no longer get an increase in velocity. 

If not reached your desired velocity, increase reg pressure by 5 bar and repeat 3 shots starting from position 1 again.

At some pressure setting you should get the velocity you want.

Once I get 30fps to 50fps higher than my desired velocity, I use the valve to reduce to my desired speed.

Then I will harmonic tune.
 
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Bill,

This is what I'd do:

Set your hammer spring adjuster screw so you get maximum compression/preload for the hammer spring.

Open valve.

Increase reg pressure by 5 bar and set hammer wheel to 1 and fire 3 shots over chrono. 

Repeat 3 shots on position 2 and look for increase in velocity. 

Repeat on position 3, 4, etc until you no longer get an increase in velocity. 

If not reached your desired velocity, increase reg pressure by 5 bar and repeat 3 shots starting from position 1 again.

At some pressure setting you should get the velocity you want.

Once I get 30fps to 50fps higher than my desired velocity, I use the valve to reduce to my desired speed.

Then I will harmonic tune.
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Thanks Bob I will give that a try. Bill
 
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following
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Carscars go to this post where I go into more detail on the issue and resolving the problem at this point. It appears the lower fps I was getting can be resolved by putting the 57 mm OEM hammer spring back in the hammer. FX in addition to changing the hammer spring to 52 mm in the Power Plenum Kit may have change the hammer adjuster in the factory rifles to compensate for the shorter hammer spring. At this point my rifle is working and getting the fps I wanted. Bill

https://www.airgunnation.com/topic/why-cant-i-get-the-fps-out-of-my-30-cal-impact/
 
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