FX Do I need a slug power kit?

I’m not going to give you definitive answers to your questions but I will give you some advice that covers both of your questions. As you work with your gun and slugs, you will or might be lead in directions that tell you when you “need” something. The biggest mistake by Impact owners is throwing the kitchen sink at their guns and never learning the process of when you need to add something. Most wind up with a wonky hard to tune gun. You should never need a pin probe but if in your testing things get better as you hit 150b and you want to proceed, then you might have to add a weight or maybe just a shim. If you find bliss under 150b, you need nothing and are golden.

I Don't have the .25 but the H&N 27grs in .22 shoot very well out of my M3 600mm superior liner (@960fps) if my memory severs me right, like 1/2 inch at 60yrds. I retuned back to 18gr. pellets because I mostly shoot paper 50-60 yards. Just thinking you could try some H&N's.

I have shot both NSA 29gr and the 29.5gr out of the standard liner from my M3 25 700 with very good accuracy, the 29.5 was more accurate for me.
I did not have the slug power kit and I was able to shoot them at 960fps easily.
It has been a few years since I shot them, so best I can remember I had my 2nd reg at 125 or 135 bar.

spikex41 said:

Ok I’ll leave the slug power kit out for now, I’ll start out around 120 bar and go up by 5 at a time or so. Just gotta wait on a bunch of slugs to come in so I can start trying, I’ll prolly just order like 6-800 of one and test it then try the other if it’s not good. It takes so much Ammo to test all the reg pressures and diff speeds, I wish there was a quicker/cheaper way lol

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I'm no master of slugs or even air guns for that matter, but from what I have seen and heard most slugs like speeds from 945+. Seems about 970 is tops with most (not all) slug shooters I've watch on YouTube. Good luck and let us know how you come along.

spikex41 said:

Ok I’ll leave the slug power kit out for now, I’ll start out around 120 bar and go up by 5 at a time or so. Just gotta wait on a bunch of slugs to come in so I can start trying, I’ll prolly just order like 6-800 of one and test it then try the other if it’s not good. It takes so much Ammo to test all the reg pressures and diff speeds, I wish there was a quicker/cheaper way lol

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Unfortunately there is not. But when you get good at knowing what to look for as you shoot, you waste less lead. If it is taking you 6-800 to figure out if it shows promise, it’s probably not going to work. But this is why the Impact is the king of lead consumption. If all Impacts vanished, most airgun ammo manufacturers would have to lay off employees.

I would be inclined to buy 2-3 different slugs in the weight range you want to shoot. If they don’t perform to. Your satisfaction with the standard liner try the slug liner and higher speed. Somewhere in that mix you should find a combination that works.
When I first started shooting slugs 3 years ago guns were really sensitive to different slugs. Now it seems I can get different brands and weights to shoot better than I cold before.
As a note of reference, my Panthera 600mm 25 loves Zan 33 gr with the slug liner that came in the gun. It prefers higher speeds of 985 - 1010 fps. I shoot it at 985 to keep air consumption somewhat limited.

spikex41 said:

so the first time I tried slugs I spent a whole bunch of $ and got like 2-300 of every size and brand I could get my hands on, and never really knew what I was doing. I basically ran out of each ammo before I learned how to do it and gave up because pellets were so easy/accurate to 100 yards. Now I want to come at it again 2 years later and see if I can make them work or if I’m going back to pellets for another season.

I don’t think it’ll take that many but, I don’t wanna run out before Im done. if Im going to try 900-1050 fps in 5-10 fps increments at maybe 5-6 diff reg pressures it’ll take 500 for sure, mite as well get some extra in case I run into problems. If I find something close to half inch at 50 yards I’ll stop and try it at 100, 150 see how it holds out. Plus I have the 2 liners to try out. I almost feel like that’s not enough rounds for testing. Maybe once I get a good tune and see how it comes together I’ll be quicker at it but so far I’ve not had any success. pellets are easy. set the reg anywhere from 90-110 and aim for 870 fps and it’s good to go out to 100 yards it seems Almost every time, slugs not so much haha.

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Don’t feel bad. They and certain guns can be very frustrating.

I’ve burned through a lot of $ in slugs in the last 2.5 years, but it’s also been quality time with my rifle so not horrible.

Steve of AEAC has said “use the regulator as your primary throttle” which I take to mean don’t set it higher than needed, and “tune to the knee”.

I started with the lowest cost slugs because I’m cheap and if I find performance there why spend double? I do want ability in wind but heavier slugs cost more in lead, air, & upgrades so I’ve limited my .22 to 30 grains so far. I’ve spent 95% of my time with the standard liner vs the slug liner, so either that or the projectile weight has given better results with the standard which seems to like around 990 FPS with slugs.

If it’s not too windy it’ll hover around 1 1/8” to 1 3/8” at 100 yards. Sub shooter’s MOA at 100 has been rare but welcome. I feel confident out to 150 yards, but the difference between 150 & 200 is considerable. Maybe that’s projectile weight or my lack of wind reading ability.

Hopefully the above helps someone.

A lot of people have different processes of how they go about it. A lot of people have found satisfaction with their gun in a different state of tune compared to another person. An Impact is a tricky beast with slugs. For example, one way of tuning it has great numbers. But you can suffer from the first shot blues. Another way of tuning it you can get away from the first shot blues, still have decent numbers but the numbers start to suffer when you put a ton of shots through it during a shooting session. For the last 14 years I’ve looked at it this way. Shooting PCP’s is a hobby. Seven years ago I wanted another hobby to drain my wallet, so I introduced slugs. Just be happy you only have one gun to figure out. Unfortunately you chose a caliber that can be tricky.

Dont start at 120 bar if you are doing a .25 slug tune in my opinion anyway. Put the second reg at 140 bar - 145 bar. Mine wouldnt work at 150 bar with the stock hammer and valve spring yours might as some have said it will. Set valve adjuster fully open and use a pellet to find the plateau. The plateau should be fairly close to max if not max hammer preload if you dont have a heavy hammer installed. Once you have the plateau record the settings of the reg, macro and micro wheel.

Drop the macro wheel a couple spots and shoot a 5 shot group. Drop the macro another two spots and shoot another 5 shot group. Rinse and repeat until you hit the tightest group. move the macro back to the setting that got you the tightest group and start changing the micro by one click in both directions until group opens up. Do that to find the sweet spot again. Set micro back at the best setting. Then start slowly closing the valve by 1/4 turn until you see the best group again. Thats what worked for me. In my case it only took one or two clicks of the macro beyond the best group to see it open back up. Same with the micro it was pretty clear where I was getting the best group with each adjustment. Once I got to the valve adjuster the groups were fairly tight but I would get a .5 - .7 inch group with 4 shots and one would open it another .1 or a little more. As I adjusted the valve you could see the flyers starting to disappear and the over all group tightening up until the sweet spot was hit.

I did more fine tuning with the valve adjuster than the macro and micro wheels since it was very evident with one or two clicks of either that the groups were larger and not in the sweet spot. With the valve adjuster the groups just continued to get tighter as the flyers and over all group size tightened as I shaved the velocity with the valve adjuster.

spikex41 said:

I ordered some 26.8g nsa slugs

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I didnt get good results with nsa slugs in .25 or .30. I know allot of people do so it just depends on the barrel. I also had less than the best results with javelins in .25 and .22. The javelins came close to being the slug to use but just not quite good enough. In .22 the H&N heavy 34 gr. .218 were the ticket in my panthera and impact. I have H&N slugs coming in .25 that will get delivered wed. So this week if wind doesnt get in the way I will be doing my .25 tune with the H&N heavy 38 gr. and 40 gr.

spikex41 said:

If you use the reg as your primary throttle do you mean I have to get the reg set high enough to shoot so 920 fps then tune it down to 900 and try it? Then move reg up and shoot 910 fps then up and shoot 920? Etc…? I was told to go for reg high enough to shoot like 1000 then testing all speeds down to 900. Then try 5 bar higher and repeat, and keep doing it till 30-40 bar higher than required then look at the best groups and go back to that setting. i hate how every video I watch just shows people jacking the reg right to where they already know they need it and not going thru the process of finding that reg pressure,really doesn’t show the process at all lol.

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If you haven't seen it, I would suggest this video from Steve of AEAC. I keep watching, reading, and listening to whatever sources I can find to try to come up with a better understanding than yesterday. Lately I've felt that the rifle is more violent & maybe less accurate with a higher reg pressure so I try to use a tick over the minimum for the velocity I've verified as good.

It would be great if there were published a chart of all possible calibers and configurations of every rifle & every projectile, with settings & velocities for maximum performance of each, but it seems our toys are like fingerprints.

carlos_hathcock said:

Lately I've felt that the rifle is more violent & maybe less accurate with a higher reg pressure so I try to use a tick over the minimum for the velocity I've verified as good.

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with a reg you want to be on the knee. Find the plateau and drop the velocity 3 - 5% lower than the plateau by lowering the hammer pre load. That should get you in a pretty good spot and you can do some very fine tuning from there to get the exact velocity and accuracy. The hardest part with tuning is not knowing if the rifle will have a narrow velocity band it will be accurate in. If it has a very narrow velocity band for acceptable accuracy its harder to find. To make things even worse the slug you are trying may not shoot to your standards regardless of the amount of tuning you do to try and get accuracy. So far I am a believer in the H&N heavy slugs. My impact and panthera were both pretty straightforward and easy to get tight consistent groups with them. Thats in .22 but I will find out this week if it holds true with the .25.

A lot of great advice from these guys. I myself haven’t been impressed with FX liners in .25. But I’m a 500-600mm guy. I also have no desire to shoot over 32gr in .25. My reason is these are airguns and I like to use them for airgun things. I don’t want to get any closer to a rimfire because it’s just much more simple and lighter to use one. I like my slug guns to fill that void just below a rimfire and just above a pellet shooter. So I’ve completely abandoned the FX barrels on my two M3 .25’s. I did spend a year with two MKll .25’s shooting slugs out of superior liners. Both 600mm. What bothered me is they both could shoot fantastic groups but they just weren’t doing it all the time. The hero to zero three times a month finally got on my nerves.

Another interesting thing. I set up a 700mm Impact for friend with a heavy liner shooting heavy slugs. It was good with 41gr Zans. I tried to replicate that with one of my 600mm guns and it just wouldn’t match the accuracy. With Zan changing the design of the 41gr, I will be getting his gun back when he runs out of the original ones. And that’s another thing that sucks about slugs.

spikex41 said:

Hey guys I’m looking to try tuning my 700mm impact m3 in .25 cal for slugs again (tried before but never could get anything to shoot better than 1” at 50 yards). I was just thinking before I rip the gun apart and put the heavy hammer slug kit back in it is there any certain weight of slug that I can shoot without it? I was hoping to shoot something under 34 grains to keep my shot count up. hoping some of the nsa 29 or maybe the zans will be ok. I have both the stx and the heavy stx liners as well, is the pellet liner a better twist rate the lighter slugs?

anyways any help is appreciated, im just trying to get all my ducks in a row before I dive down the rabbit hole of slugs again lol

also how do you determine your second reg pressure? Some people are over 150 bar when I can get the same speeds at like 115-120 bar. Why set it so high If you don’t need to be?

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In my opinion the only time you would really need the slug power kit FX sells is if you are going to run super high reg pressures and heavy slugs. The tungsten hammer weight they use is way too heavy for an otherwise stock rifle. My MKII Impact is a 700mm Heavy Liner 25Cal running a Huma High Pressure reg, so when I set at 150Bar it isnt working very hard. Factory FX regs dont like to be turned up that high. I have the Huma power kit which comes with a stronger hammer spring and 3 hammer weights all a bit heavier than stock. I use Nielsen 34.9s and get them moving as fast as I want that day (~950-1050fps) without stressing out my rifle. I dont see how you can get the same speeds at 115-120Bar, but each setup is different. I also had to upgrade to a tensioned barrel and CF barrel sleeve to stop poi shifts.

If you have a stock Superior STX liner I would try a box of the light Nielsen slugs first before you do any upgrades. I have a few standard liners that do really well with light for caliber Nielsens. As far as speeds, slugs arent as limited as pellets. So long as your twist rate is good enough to spin your particular slug, the fps is just fine at slower speeds. You still dont want to go near the super sonic threshold so 700-1050fps is a good rule of thumb. The main thing is finding a slug and speed that is accurate in your setup. Speed is secondary since the bc on a slug is so much better and consistent when compared to a pellet.