FX FX MK4, .25 Cal. A little disappointed?

[USMCShooter1]

Hi Guys,
First, I’ve been in the adult Airgun world for 20 years now. While I was still on Active Duty, and had some time on my hands, I had a side business repairing and tuning everything from cheap Chinese Springers to Daystates. I was involved with a couple of other guys working the bugs out of the Gen 1 Marauders when they first came out. My first PCP was a BSA Hornet in .22…I can pull it out of the safe today and shoot dimes at 50 with boring regularity.

As a retirement gift to myself when I retired from the Marine Corps 11 years ago, I bought a Kalibre Cricket and hunted the hell out of it…over 3500 squirrels and countless other species. The only repair it’s ever needed was a leaking air pressure gauge o-ring about a month after I bought it. I added a power plenum to it about 5 years ago, and it’s a beast…I run 26gr JSB’s at 955 average. I hadn’t shot it in nearly a year, pulled it out yesterday…velocity spot on, 6 FPS ES….just a hammer.

My wife bought me an FX MK 4 in .25 in September (was supposed to retire from civil service, but wound up working remote another 6 months). I mounted an Athlon Talos on it, sighted it in across the chrony with 26gr JSB’s…out of the box it was running 880 with what appeared to be a conservative tune.

Yesterday I finally had a chance to spend 7 hours with it. I’d bought some 34gr slugs, as well as some 39gr. I expected to be able to run any of them at around 950…didn’t happen. Best I could get out of it with the 39’s was 810 average. The 34’s ran about 870.

That being said, it ran the 26 grainers at 1050 with it turned up…lol! I turned it back down to 950, and a far more efficient tune…72 shots on the reg set at 130.

So I got to wondering about the Cricket…out of the box, it was sending the 26gr JSB’s at 1170…had to turn it down a lot…lol! So I shot some 34 grainers…817 average…so I started turning in the hammer spring…at about a full turn, they were running 980.

I loaded some 39 grainers…875 out of the gate…1/2 turn on the hammer and 960. Just for kicks, went on other 1/2, and turned the power plenum reg up 30…1030 FPS.

On the FX, I turned the reg up to 150 (book says don’t go over 170), valve open max, macro on 16, micro at 5.

Did I miss something? Slug accuracy was horrible (Cricket was still wadding them up), but I understand FX has a dedicated slug barrel?

Did expect too much? Did I miss something in the tune? I didn’t just open it wide open and run it…I went in steps…again. Spent 7 hours with it

Open for any input.

Jamie

 

[Jlowe]

If I read this right, FX superior liners are good up to 34 grains in 25cal, after that go up to a heavy slug liner. I just changed out a 22cal liner in my Maverick to shoot 33 grains in my 22cal. Anything over 25 grain in the 22cal superior standard liner doesn't shoot well. I have a 25cal Wildcat BT Sniper with the standard liner that shoots 33.49 JSB's MKII's really well. Your 39 grainers need the heavy liner. Should be an easy fix.

 

[Gerry52]

What he said . Probably just the wrong marriage of liner & weight of slug. The gun is certainly capable with the correct combination.

 

[MongooseV8]

You are probably running out of hammer strike, in regards to your speeds. And as far as accuracy goes, its always a gamble with slugs. A lot of people have wasted piles of money and time trying to find some combo that works only to give up.

If your Impact has a heavy liner it should be able to stabilize 39g slugs, but may not give good accuracy. If FX installed a Standard STX liner then most will run out of enough rpm in the mid 30s range.

And thank you for your service

 

[extradrygin2001]

On my M3 the barrel has 2 ports. One that is restricted and one that is wide open.

To change the port you have to rotate the barrel 180 degrees. Do this buy pulling the barrel out about 2-3 inches rotate it 180 degrees and slide it back in.

I had the same problem with mine in .22 trying to get 25 grain pellets to come out at a decent FPS,

 

[6gun]

Hi Guys,
First, I’ve been in the adult Airgun world for 20 years now. While I was still on Active Duty, and had some time on my hands, I had a side business repairing and tuning everything from cheap Chinese Springers to Daystates. I was involved with a couple of other guys working the bugs out of the Gen 1 Marauders when they first came out. My first PCP was a BSA Hornet in .22…I can pull it out of the safe today and shoot dimes at 50 with boring regularity.

As a retirement gift to myself when I retired from the Marine Corps 11 years ago, I bought a Kalibre Cricket and hunted the hell out of it…over 3500 squirrels and countless other species. The only repair it’s ever needed was a leaking air pressure gauge o-ring about a month after I bought it. I added a power plenum to it about 5 years ago, and it’s a beast…I run 26gr JSB’s at 955 average. I hadn’t shot it in nearly a year, pulled it out yesterday…velocity spot on, 6 FPS ES….just a hammer.

My wife bought me an FX MK 4 in .25 in September (was supposed to retire from civil service, but wound up working remote another 6 months). I mounted an Athlon Talos on it, sighted it in across the chrony with 26gr JSB’s…out of the box it was running 880 with what appeared to be a conservative tune.

Yesterday I finally had a chance to spend 7 hours with it. I’d bought some 34gr slugs, as well as some 39gr. I expected to be able to run any of them at around 950…didn’t happen. Best I could get out of it with the 39’s was 810 average. The 34’s ran about 870.

That being said, it ran the 26 grainers at 1050 with it turned up…lol! I turned it back down to 950, and a far more efficient tune…72 shots on the reg set at 130.

So I got to wondering about the Cricket…out of the box, it was sending the 26gr JSB’s at 1170…had to turn it down a lot…lol! So I shot some 34 grainers…817 average…so I started turning in the hammer spring…at about a full turn, they were running 980.

I loaded some 39 grainers…875 out of the gate…1/2 turn on the hammer and 960. Just for kicks, went on other 1/2, and turned the power plenum reg up 30…1030 FPS.

On the FX, I turned the reg up to 150 (book says don’t go over 170), valve open max, macro on 16, micro at 5.

Did I miss something? Slug accuracy was horrible (Cricket was still wadding them up), but I understand FX has a dedicated slug barrel?

Did expect too much? Did I miss something in the tune? I didn’t just open it wide open and run it…I went in steps…again. Spent 7 hours with it

Open for any input.

Jamie

There's still harmonic tuning and valve impulse for projectile /barrel length and finding the accurate velocity from your gun. It will do anything you want if you're willing to put a bunch of time in it. Slugs can be a finicky mistress. It's a bit more than dial a power number up and shoot it, especially if you have a 700mm barrel. It took me a while to step away from desired on-paper velocities or fpe numbers and just find the precision tune and let her rip. Precision is worth more than power after a while.

The ground squirrels were more anchored by a 15 fpe 177 than they were a 43 fpe 25 strictly by shot placement yesterday

 

[jps2486]

Out of the box, FX rifles come with pellet liners. And yes, accuracy with slugs will suck most likely. You may have a defective barrel too, not unheard of. I hate shooting slugs. My Wildcat Mk3 VP is deadly at 100 yds with 25.4 gr pellets, so why screw with success?

 

[Jman4183]

Sounds like a couple of things going on. First thing is hammer weight. If you aren’t getting the speeds you are looking for having done this myself I can’t recommend going to the tungsten hammer in an impact highly enough. In .357 I was having issues getting the 93 grain nsa slugs running past 800fps. Now it’s running much quieter and calmer at a more conservative tune. I have a tack driver now at 920fps. I am a little surprised that you couldn’t get a 36grain moving fast enough tho? I would talk to the dealer you got it from. Or contact Utah air guns directly as they handle your FX warranty. Tell them what you’re trying to do and since you just bought it they may just hook you up idk. It’s not super expensive anyway. You also should get the slug liner for sure. Faster twist rate to stabilize and also they put more aggressive rifling on the outside of the liner. They also add a special kind of choke/crown on slug liners.

Now all this to say, I have a .25 fx drs classic and yes it has the slug liner. However with minimal hammer spring tuning I was able to get it shooting 36grain patriot slugs at 930fps. I also tend to find fx guns “settle in” to whatever tune you put them on, so try and stay with the same projectile if possible.

Thank you for your service this Memorial Day!

 

[DesertSilver]

Another thing does your rifle have a pin probe or pellet probe! The pin probe allows more airflow than the pellet probe. If you buy a slug liner get the slug kit. It will have the heavy hammer and hammer spring along with the adjustable pin probe.

 

[USMCShooter1]

Thanks for all the info guys…learning the higher-dollar game…lol! With the Cricket smoking slugs out accurately, I’ll probably just use it for my coon/coyote hammer.

I’ll probably still give the guys at UA a call, just to talk possibilities.

I’m a sow’s ear/silk purse type. I like taking underrated guns and making them run with the big dogs…I’ve got a gen 1 .22 Marauder with an LW barrel that gets 43 shots at 950-ish with Predators…I see now they’re making refs for them, but I’m not sure without a lot of valve mods it would run that fast any more efficiently.

The Cricket and MK 4 were both splurges to see how the upper crust plays. They’re both impressive in their own right, and proof that you get what you pay for.

I’m learning that money still doesn’t buy miracles…lol!

Jamie