Tuning Continued Confusion with Reg pressures

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Drumsnguns

Member
Jun 14, 2016
959
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North Carolina, United States
Hi all,

I posted a question before asking if High reg pressure or Low reg pressure was preferable for slugs. I think that my question was somewhat confusing, So I want to try again.

I watched Matt Dubber's video where he is cranking up the reg pressure for slugs, (like 170 Bar). He is also using the lighter valve spring, included in the FX power kit, which as he says will allow the valve to stay open longer for more power with very heavy slugs in his .22 Impact w power plenum.

OK, on my .25 cal Impact with the Power Plenum and 700 mm Slug A set up, I have the dual Transfer Port and the FX Pin probe ....and the 57 mm hammer spring, shooting 33.5 NSA.. I also plan to try 36.2 and 38.5 gn as well. But that's another story.

Because of these add on's , I am able to achieve High velocities at low reg settings which is what I wanted to conserve air. But I can get the same velocity with either high reg pressure or low reg pressure. For example, I can achieve 920 fps at 100 Bar with the valve knob all the way out or I can also achieve the same speed with say 130 Bar with the power wheel on 1, and the valve knob turned in. Which is the best setting for this particular velocity?

Matt says he uses the lighter valve spring and he turns his valve knob in all the way and gets 1000 + fps with 30-34 gn .22 cal. slugs. I'm sure he's got his hammer spring cranked in but he doesn't mention it.

So I'm wondering two things:

Should I be using the lighter valve spring that was included with the power kit? I tried it and it was POWERFUL even at low reg pressures but I had the valve out all the way. I went back to the original valve spring.

And is it better to take the reg up then control the velocity with the valve knob, HSTA etc.?

I know I'm probably over-thinking things but my brain really hurts wondering which is the best way to go. Sometimes I hate all of the these adjustment options...just too many.

I'm shooting slugs right now at 900-920 with reg at 100 and power wheel on 3-4 with 33.5 NSA slugs. I've only been able to shoot once or twice with all of this bad weather. Groups look OK at 60 yards.

Thanks for any input
 
Hi all,

I posted a question before asking if High reg pressure or Low reg pressure was preferable for slugs. I think that my question was somewhat confusing, So I want to try again.

I watched Matt Dubber's video where he is cranking up the reg pressure for slugs, (like 170 Bar). He is also using the lighter valve spring, included in the FX power kit, which as he says will allow the valve to stay open longer for more power with very heavy slugs in his .22 Impact w power plenum.

OK, on my .25 cal Impact with the Power Plenum and 700 mm Slug A set up, I have the dual Transfer Port and the FX Pin probe ....and the 57 mm hammer spring, shooting 33.5 NSA.. I also plan to try 36.2 and 38.5 gn as well. But that's another story.

Because of these add on's , I am able to achieve High velocities at low reg settings which is what I wanted to conserve air. But I can get the same velocity with either high reg pressure or low reg pressure. For example, I can achieve 920 fps at 100 Bar with the valve knob all the way out or I can also achieve the same speed with say 130 Bar with the power wheel on 1, and the valve knob turned in. Which is the best setting for this particular velocity?

Matt says he uses the lighter valve spring and he turns his valve knob in all the way and gets 1000 + fps with 30-34 gn .22 cal. slugs. I'm sure he's got his hammer spring cranked in but he doesn't mention it.

So I'm wondering two things:

Should I be using the lighter valve spring that was included with the power kit? I tried it and it was POWERFUL even at low reg pressures but I had the valve out all the way. I went back to the original valve spring.

And is it better to take the reg up then control the velocity with the valve knob, HSTA etc.?

I know I'm probably over-thinking things but my brain really hurts wondering which is the best way to go. Sometimes I hate all of the these adjustment options...just too many.

I'm shooting slugs right now at 900-920 with reg at 100 and power wheel on 3-4 with 33.5 NSA slugs. I've only been able to shoot once or twice with all of this bad weather. Groups look OK at 60 yards.

Thanks for any input
Click to expand...

Hi Drums, 

We are sorry to hear that your having difficulties understanding how to best tune your gun. Just wanted to inform you that we have technicians during the week that can help walk you through these steps, troubleshooting, or just for more knowledge of how your gun best works. Please feel free to reach out Monday - Friday 9 AM - 4PM either by phone or E-mail. 

E-mail : [email protected]

Phone: (866) 639 - 0772

Regards 

FX Airguns USA
 
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drumnguns , I a week ago added a power plenum and huma regulator, also I have opened the tp and probe in my impact mk2 25cal. I am also still waiting for the weather to improve to do more tuning and testing. The gun is shooting great @125bar and hammer spring is just about maxed out to get 910-920fps with nsa 36.2 slugs my only problem is it’s much louder than the original stock setting @160bar ? The other thing is if I go with the slug power kit will gain FPS with less noise and maybe a little less regulator setting? I have been paying attention to your results and again waiting for the weather to cooperate . Good luck and I will be following your results.
 
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My preference personally is low Regulator pressures. I have nearly the same setup as you just for reference. Higher reg pressures do a couple things that I don’t like. 1 - typically higher wear on parts, so potentially shorter life span. 2 - higher reg pressures also typically mean louder and the gun is a lot more jarring when fired at higher reg pressures making the gun more hold sensitive. 

If I can get the velocity required at 110 bar why tune the gun at 140 or higher for the same velocity. Especially with the valve adjuster on our guns. We can make them efficient (as possible) and also not worry about the valve staying open after the slug leaves the barrel, possibly introducing turbulence around/behind the projectile. Just my 2 cents.

I am convinced Dubber runs those Reg pressures purely to get the kind of velocities required to reach out beyond 150 yards with a heavy .22 slug. He shoots heavier slugs in .22 than I do in .25!

If you don’t have a carbon fiber liner sleeve on your slug liner try one out. They have done wonders for accuracy with my Dreamline and my Impact especially with slugs.

I’d love to hear other opinions on your question as well, I’m not an airgun or ballistics ‘expert’ by any means.
 
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My preference personally is low Regulator pressures. I have nearly the same setup as you just for reference. Higher reg pressures do a couple things that I don’t like. 1 - typically higher wear on parts, so potentially shorter life span. 2 - higher reg pressures also typically mean louder and the gun is a lot more jarring when fired at higher reg pressures making the gun more hold sensitive. 

If I can get the velocity required at 110 bar why tune the gun at 140 or higher for the same velocity. Especially with the valve adjuster on our guns. We can make them efficient (as possible) and also not worry about the valve staying open after the slug leaves the barrel, possibly introducing turbulence around/behind the projectile. Just my 2 cents.

I am convinced Dubber runs those Reg pressures purely to get the kind of velocities required to reach out beyond 150 yards with a heavy .22 slug. He shoots heavier slugs in .22 than I do in .25!

If you don’t have a carbon fiber liner sleeve on your slug liner try one out. They have done wonders for accuracy with my Dreamline and my Impact especially with slugs.

I’d love to hear other opinions on your question as well, I’m not an airgun or ballistics ‘expert’ by any means.
Click to expand...

Agree. High reg pressure means more HST and more stress on the components. It may also mean a low valve spring tension, causing air wastage + noise. To quote B Sterne, leaving the valve open too long means creating pressure when Elvis has already left the building.

Give me a good balance between air pressure, valve spring tension, and HST any day.

🐦
 
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So I'm wondering two things:

Should I be using the lighter valve spring that was included with the power kit? I tried it and it was POWERFUL even at low reg pressures but I had the valve out all the way. I went back to the original valve spring.

And is it better to take the reg up then control the velocity with the valve knob, HSTA etc.?
Click to expand...

I have a similar setup: FX Impact X 700mm 25 cal, upgraded with FX Power Plenum + Slug Power Kit + Huma Dual Port V2

I have it setup to shoot the JSB 34gr at about 910fps, with reg set at about 105bar. 

I initially installed the lighter valve return spring included with the Slug Power Kit, but realized it was too soft at low reg pressures and did not provide sufficient spring tension for valve return adjustment. I have since reverted back to using the Power Plenum's stiffer valve return spring. 

I prefer to shoot at the lowest reg pressure that will get me the speed I want to shoot at. This allows me to use softer hammer spring tension, which in turn leads to quieter hammer strike and less stress on the entire system. It also leads to more shots per fill since you can shoot to a lower bottle pressure before having to refill.


 
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I agree with what y'all are saying. I'm getting very high speeds at 100 bar and I even have the HSTA backed out to 19.50 mm, the aftermarket add-ons are helping with that. I think my question was more to do with reg pressure and harmonics but at this point I don't know what to think.

I'm out today and shooting at my current settings and at zeroing at 30 yards and at around 900-910 I'm getting the makings of a one hole group and then shots are changing course and hitting an inch away at say 10 o clock or two o clock. 

I changed scopes and thought that might have been my problem. But as is with the Impact one day it's dead nuts and the next day it like a scatter gun. I think I'm almost to the point of giving up on slugs because I just don't know which direction to go. I waited all week to shoot. The weather is great but after just three targets I packed it up and took it inside.

Obviously something is not right but like I said, there are so many variables, I just don't know what to try. I keep seeing guys shooting with the same set up and slug just getting great groups I have a decent shooter one day and a shotgun the next.

Totally frustrated.

Using the Slug A but the Superior Heavy I have isn't any better.

BTW JSB MKI pellets shoot great out of the setup and at this tuning.

I might try swapping barrels to my Gen 1 Impact and see what that does. Seems I've always had accuracy troubles with this Gen 2. 

Oh well. Thanks for the input guys. As always, much appreciated. 
 
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Ceasar, I have heard some talk about the carbon fiber sleeves but really don't know where to go to get some go info about where to buy and how to set up. If it needs any kind of machine work to do it then In SOL. i don't have a shop or the means to do that where I live.

Would be an interesting thing to try as I'm totally stumped. Wish they would come with the sleeves from the manufacturer.
KP
 
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I'm out today and shooting at my current settings and at zeroing at 30 yards and at around 900-910 I'm getting the makings of a one hole group and then shots are changing course and hitting an inch away at say 10 o clock or two o clock. 

I changed scopes and thought that might have been my problem. But as is with the Impact one day it's dead nuts and the next day it like a scatter gun. I think I'm almost to the point of giving up on slugs because I just don't know which direction to go. I waited all week to shoot. The weather is great but after just three targets I packed it up and took it inside.

BTW JSB MKI pellets shoot great out of the setup and at this tuning.
Click to expand...

Are you also getting the occasional flyers with JSB pellets as with slugs? If you are getting flyers with slugs, but no flyers with pellets, then your barrels may not like the slugs you are shooting with.

I had "flyers" issue using the pin probe on stock FX transfer port. Installing the Huma Dual port V2 with the center guide eliminated the flyers - shooting JSB 34gr MK2. Haven't tried slugs. (https://www.airgunnation.com/topic/pellet-probe-tube-cylinderstandard-probe-versus-pin-probe/)

As a test, try reinstalling the original FX cylinder pellet probe to see if it eliminates your "flyer" issue. If the stock cylinder FX pellet probe does eliminate the flyers, then you know your pin probe/dual port is not chambering your ammo consistently.


 
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Frank320, Good questions.

I didn't get a chance to shoot pellets with the remaining time I had yesterday, But I did take the the 700 mm slug A barrel off of my MK2 Impact, (the rifle this topic is about), and put it on my Impact MK1. The MK1 is running at 140 Bar with the standard probe. Since the Huma Dual TP is on the 700 mm barrel it of course was transferred as well. It was shooting 901 fps on power wheel setting 5 so roughly the same velocity for both guns. I got some real interesting result and I don't know exactly what it means.

One would think that there is something going on internally with the Impact 2's action. Here are the two targets from yesterday. I used a rangefinder for the Impact 2's target but walked off for the Impact 1 (and I'm usually within 1 yard when I walk it off so that's why I put 60-65y on the Impact 1's target.

So same Ammo; same distance; same velocity; same barrel/liner and the same scope on both rifles for the comparison.

Impact 2_700 mm_NSA 20210110_19222885.1610376449.jpg




Impact 1_700 mm_NSA 20210110_19241402.1610376478.jpg


The Impact 1 has been rebuilt and upgraded to the MK 2 level with exception of the plenum. It still has the original plenum on it.
 
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well, if i read your post and test above correctly, your Impact 1 has the stock FX cylinder pellet probe, while your Impact 2 has the pin probe. 

That "could" be the reason for the groupings above. You might need to adjust the pin probe on your Impact 2, and also check to make sure that the pin probe is chambering the ammo smoothly and consistently as it exits the magazine. Try reinstalling the stock FX cylinder pellet probe into your Impact 2 and see if the groups improve. 

I adjusted my adjustable pin probe to chamber my ammo at the same depth as my stock Impact cylinder pellet probe as a starting point.
 
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Frank320. You read correctly

Trying the original probe will be my next move. Just ran out of time the other day.

I'm really not sure how to properly adjust the Pin Probe since the main problem you run into is adjusting it where the magazine can be inserted. Doesn't leave much wiggle room after that..

I will mark the pin probe at the barrel in the full closed position then remove the probe assembly and see where the slug is in relation to the TP off the gun. I tried loading the slug then removing the barrel but the slug is so loose it slides around when removing the barrel. 

I marked the probe when I first installed and it looked like I had it set right but I'll recheck

Stay tuned.
 
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As I understand it the gun with the higher pressure is in this case in a better hamonic tune, as it seems to group better. While the gun with the lower pressure is more in what we call a speed tune, where you have the needed pressure to achieve the needed speed. If you harmonic tune with regpressure, you can not go lower on the reg if you do not want to go lower on the speed. An opposite way of doing it might be to drop speed some, on either hammer spring force, or valve adjuster, where you also end up with higher pressure than you need, to achieve a specific speed.
 
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Tor47....this is why I posted this question. Higher reg pressure or lower reg pressure for the same velocity? 

BUT with this particular MK2, I have tried other settings. No matter where though, it tricks me into thinking on day 1 that yep, this is the harmonic tune....but then on day 2 its all over the place. 

I've had it at 140 and the last tunes were at 120, 125 and 130.

I'm getting tired of chasing tunes. That's when I get out my old Cricket and just have fun shooting. Always shoots the same.

I mean right now my scope is on it's way back on a warranty claim....I probably wasted shipping charges and it's probably not at fault.
 
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Well I am not a expert, but as far as I know slugs are more sensitive to the harmonics of the gun, than pellets. I do not really know why, but maybe it is because slugs are generally heavyer than pellets? If trying to shoot slugs in the same velocity range or faster, than lighter pellets, maybe the gun simply vibrates more, and becomes more sensitive? Maybe espesially heavier slugs have a more narrow velocity range as they do not self destabilise as pellets? Shooting them to slow, and they do not spin enough, and shooting them to fast the gun itself becomes the issue as vibration is more pronounce? I
 
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Yes, I agree what Matt posted was a successful result. No problem there.

But I and I'd imagine many others have spent a lot of time with their guns looking for the sweet spot. I have really spent a lot of time on this MK2 and slugs, literally going up and down the scale. But there are almost an infinitesimal number of combinations of variations. That's why I come to the forum....to see if someone can point me in the right direction.

Funny how after many hours and lots of money in slugs....(all sized for that matter), I can slap the barrel on a different Impact body and Voila....nice tight groups.

Guess which set up I'm going to be using from here on out. I'm going to talk to FX after I re-check the pin probe on the MK2 and see if we can't get to the bottom of things. Very strange this gun.
 
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