FX FX 1:16 superior slug liner, which slug?

[Vince]

Which slug do you guys use in your .25 slug liner?

Best I can get out of my 600mm King .25 at the moment is an inch at 50 yards, 115-120 bar, large wheel 19, small wheel 2.75 plus one or 2 clicks, with .250 H&N 34 grain.

(tried a bunch of others, all lighter than 34)

At 35 yards various slugs will go hole in hole, but at 50 is where the trouble starts, they start to go off course.

If shooting at a clear background I can clearly see them spiraling wildly. I'm thinking perhaps the twist rate is just too fast for them.



Go heavier?

 

[CanMike]

What speed are you shooting?

I shoot the h/n slug hp II in my 1:16 reximex barrel and they are very tight at 40-60 yards. Im shooting at 860-870 FPS.

I’m waiting for new hammer spring. I can’t get faster currently but the lighter ones shoot 900+’and don’t group.

My external REG is at 170-180 BAR. Rifle is not regulated.

 

[dgeesaman]

At 120 bar I imagine you're shooting at the very low end of velocity for slugs. I think those 16 twists are intended for higher velocity (and higher spin rates)

 

[Impact701]

H&N .250 40gr Heavys shoot MOA from my M3 and my DRS.

 

[Vince]

Think I'm onto something

.250
37 ZAN
38 H&N

140 bar.

TINY groupings at 35 yards!

Tried 40 grain H&N as well, seems to be grouping a little bigger but too early to tell, might just be a matter of tweaking the current settings a bit.

Still have to fine tune with chronograph and long range testing, but it's looking very, very promising. (now power wheel on 23 & quick tune on 3.5, I'm guessing 900 - 950 FPS with the 37's)

Liner is firelapped and recrowned.

Crown made by FX was rough.

10x .251 slugs with 220 grit, and 10x with 320 grit.

When I got the slug liner liner I checked for bore consistency and observed a tight fit for the first 3-4 inches, then a good even consistent fit till 2/3's in, then a very loose spot, followed by a rather abrupt .247 choke.

Tightest spot in bore before choke is .250

After this little bit of lapping the choke is still .247, but bore feels more consistent when pushing a pellet through, and choke is less abrupt..

Stopped there since it shoots so well at 35 yards now.

Slugs lubed with Hornady One Shot.

 

[Vince]

Ok, tried at 50 yards. Calm, hardly any wind.

No chrony, but tuned below the knee. 140 bar, large wheel 23, quick tune on 3.5.

Couple of observations;

'Cold bore' / first shot is a good bit lower, gun needs 1 or ideally 2 shots to become consistent. My guess is combo of valve stiction as well as reg creep (about 5 bar according to reg pressure factory gauge).

That disqualifies it for a hunting gun in this current setting (for me). My goal is now to get that cold 'bore shot' closer to the group.

Slugs used ;

.250 37 ZAN
.250 38 H&N
.250 40 H&N


Started with 37 zan,
first shot low, then 5 in bottom group. Quick tune wheel 2 clicks up, adjusted scop for bullseye, then I shot the top group. That looked promising;

38 grain H&N at same setting did OK , not spectacular, but not horrible;

Then onwards to H&N 40 grain.


Bottom and top group = 40 grain H&N, middle group 38 grain H&N;

Thought I was there, but the darn 'cold bore 'shot (giving the gun 10 minutes or so before shooting the next group) showed up again, even after just 10 minutes. Less then 5 bar creep according to pressure gauge.)

This is what's repeatedly happened, 1 low, other 4 touching;

Tried upping the hammer spring tension via a couple of click on the quick tune system, but that incease caused larger groups. Back to original hammer spring tension setting.

I then thought to lower the reg pressure by 5 bar without touching the hammer spring setting, to see if accuracy remained and at the same time solving the cold bore shot situation. This resulted in the groups opening up, so no joy there either.

The sweet spot is found, but it's only there after a slow cold bore shot....

Overall impression for now is that this gun can shoot, but it's super sensitive to even minute pressure differences. Don't know if the thin liner is that sensitive, or if it's something else. Also wonder if the .25 is more sensitive than the .22.

I'll pull the reg for a good polishing, see if that helps getting the consisteny to where i like it to be...

 

[Vetmx]

Welcome to the FX Impact life. You’re not doing anything wrong so don’t beat yourself up. All the chasing only to find out it didn’t help or made it worse is normal. Your thought process while troubleshooting is also spot on. It’s the side of that gun that nobody talks about. They just live with it and claim their gun is just fine.

 

[Centercut]

I’d give the .25 Altaros ATP Smooth 49.5 grain at 885 to 890 fps. Micro at 3.5, reg pressure at 135 bar. Macro wheel - doesn’t matter. I get SubMOA at 100 yards and good accuracy out to 300 yards.

 

[Xcaliber]

You need a chronograph to check velocity and to help with tuning, they're cheap, just get one from Amazon for like $50.

 

[Vince]

Have one, problem is with first low velocity shot after not shooting gun for a moment. Consistent velocity is there after the first one or 2 shots. There's a bunch of threads related to this. Seems to be quite the thing with FX guns..