Advise needed: Getting maximum shot count from FX Impact

[177er]

I have an Impact MKII
I want to tune it to get the 100's of shots as shown on the FX site.
4,5 (.177)

≈ 325 shots @ 18ft/lbs.
≈ 670 shots @ 12ft/lbs

Ideal scenario - 10gr pellets at 800-850 fps.

Current tune : Hammer Spring preload - set to very low. Hammer Spring - at Min - 1 (low).
Reg : 55-60 bar, Valve Adjuster - 1st line.

My current tune, I get about 150-200 good shots depending on if I set the Wheel from Min to Max. However, my tune works for both 177 and 22 and I only need to change cal to shoot 15 gr pellets at nearly the same speeds.

What am I missing?
I know how to tune from TOP down (highest approach) for the most power, and from Bottom up - start low, and keep increasing reg/HS to find a great tune.

 

[madeintheuk]

What size barrel? Shorter barrels are less efficient, and may cause lack of shots. Also, the hammer spring may still be overcoming the valve at that low pressure and maybe causing you to waste air. The impact isn’t really designed for such low power. I’m not sure if the hammer spring is the same in the sub12 impacts overseas. Maybe that could be a problem!

 

[NYmike]

If it's a stock Mk2 with the original small plenum, and you still have the manual that came with it, go to page 13 at the bottom...

"NOTICE-NEVER adjust the regulator below 100 BAR as damage to the system may occur and will void your warranty!"

Apparently, the Mk2 with stock plenum, non-adjustable internal valve spring and front valve travel limiting bumper needs at least 100bar reg pressure to function correctly. I agree with the previous poster that you are probably over powering the valve and wasting air.

 

[177er]

What size barrel? Shorter barrels are less efficient, and may cause lack of shots. Also, the hammer spring may still be overcoming the valve at that low pressure and maybe causing you to waste air. The impact isn’t really designed for such low power. I’m not sure if the hammer spring is the same in the sub12 impacts overseas. Maybe that could be a problem!

This is the stock 500 mm that was standard with the MKII . I am not sure if the hammer spring is weaker. I wonder if anyone knows if the sub12 HS is weaker? I agree - there seems to be inefficiency at a lower reg pressure. It's not affected the gun overall, it's been shooting really well and it's still a lot of shots.

If it's a stock Mk2 with the original small plenum, and you still have the manual that came with it, go to page 13 at the bottom...

"NOTICE-NEVER adjust the regulator below 100 BAR as damage to the system may occur and will void your warranty!"

Apparently, the Mk2 with stock plenum, non-adjustable internal valve spring and front valve travel limiting bumper needs at least 100bar reg pressure to function correctly. I agree with the previous poster that you are probably over powering the valve and wasting air.

No, this one is the MKII with the power plenum. I got this just before the M3 was released and it had the MOA rail and adjustable valve. Thanks for the info about the valve spring.

 

[NYmike]

No, this one is the MKII with the power plenum. I got this just before the M3 was released and it had the MOA rail and adjustable valve. Thanks for the info about the valve spring.

Yep, it appears the later model Mk2 doesn't have the minimum reg pressure warning in the manual. The parts diagram for the power plenum model still shows a valve spring inside the plenum but it also shows a spring under the forward adjuster like the Mk3s.

I still think you might improve efficiency by raising the reg a bit. I have an original Mk2 which I converted to a compact .177 with 500mm barrel and 300cc bottle. I run it at 120bar. Shooting H+N 10.6gr barracuda at 900fps I can get 5 mags per fill (150 shots). However, I generally only shoot 3 mags and refill from about 140-150bar. 

 

[Glem.Chally]

They gave MK1 manuals with MK2 guns, if you have an MK2 it also says in the manual not to adjust it down under pressure. This does not apply to the MK2 AMP reg. And neither does the never go under 100bar. I'd suggest 80 as a minimum for MK2s

I have 2 very early MK2s and neither of those rules apply (both came with small plenum) as they have the AMP reg. 

 

[nugria]

Hi All,

I've a low power Impact (early) w/o the power plenum, .177. I've set it up for low power shooting. My limited research indicated the low power Impacts used the same hammer spring but a different hammer. My guess was that the counterbore where the hammer spring fits is deeper in the 12 ft-lb versions. Being impatient and not wanting to order/wait for a 12 fpe hammer, I increased the depth of the counterbore on the hammer an additional 6.35mm. Lighter hammer, less preload on the hammer spring.

It is shooting much better but still has excessive hammer spring for low regulator pressures (55 bar). In other words if I increase the regulator pressure with the minimum hammer spring it increases the velocity. In a "high efficiency" tune the velocity would drop with an increase in regulator pressure. BTW, I'm shooting 5.71 gr Trophy Greens. Very light pellets.

With that said it is starting to settle down. This is a rested group. I pulled one shot at 9:00.

I plan to get the regulator pressure set on the other side of the hump one of these days. It is certainly not tuned for efficient use of air but a 200 bar --> 55 bar session is in the 350-450 shot range with a 480cc bottle. IIRC, it is running about 10 fpe.

The OP is looking for about a 15 fpe tune in .177? There are some airgun efficiency calculators that can be used to get some idea on actual shot counts taking into account bottle size, fpe, change in bottle pressure. I've never reached the numbers advertised in efficiency. The FX advertised numbers may not be realistic in a particular gun, caliber, transfer port size and barrel length.

Enjoy,

Nugria

 

[NYmike]

They gave MK1 manuals with MK2 guns, if you have an MK2 it also says in the manual not to adjust it down under pressure. This does not apply to the MK2 AMP reg. And neither does the never go under 100bar. I'd suggest 80 as a minimum for MK2s

I have 2 very early MK2s and neither of those rules apply (both came with small plenum) as they have the AMP reg.

Ah ha, that explains the lack of anything with Mk2 on it in my manual. I'm afraid not adjusting the reg down under pressure is such an ingrained habit now that I'll probably never do it any other way. LOL. Thanks for the info.

 

[177er]

I still think you might improve efficiency by raising the reg a bit. I have an original Mk2 which I converted to a compact .177 with 500mm barrel and 300cc bottle. I run it at 120bar. Shooting H+N 10.6gr barracuda at 900fps I can get 5 mags per fill (150 shots). However, I generally only shoot 3 mags and refill from about 140-150bar.

Thanks - I'll give that a go.

They gave MK1 manuals with MK2 guns, if you have an MK2 it also says in the manual not to adjust it down under pressure. This does not apply to the MK2 AMP reg. And neither does the never go under 100bar. I'd suggest 80 as a minimum for MK2s

I have 2 very early MK2s and neither of those rules apply (both came with small plenum) as they have the AMP reg.

This is the MKII with the large plenum and AMP reg. I'll check in with a higher reg pressure / shot count ratio.

It is shooting much better but still has excessive hammer spring for low regulator pressures (55 bar). In other words if I increase the regulator pressure with the minimum hammer spring it increases the velocity. In a "high efficiency" tune the velocity would drop with an increase in regulator pressure. BTW, I'm shooting 5.71 gr Trophy Greens. Very light pellets.

With that said it is starting to settle down. This is a rested group. I pulled one shot at 9:00.



I plan to get the regulator pressure set on the other side of the hump one of these days. It is certainly not tuned for efficient use of air but a 200 bar --> 55 bar session is in the 350-450 shot range with a 480cc bottle. IIRC, it is running about 10 fpe.

The OP is looking for about a 15 fpe tune in .177? There are some airgun efficiency calculators that can be used to get some idea on actual shot counts taking into account bottle size, fpe, change in bottle pressure. I've never reached the numbers advertised in efficiency. The FX advertised numbers may not be realistic in a particular gun, caliber, transfer port size and barrel length.

Great info here. I already have a 15FPE-18FPE tune, the idea is to get more shots. You said you're getting 350 shots, and technically, I should get the same amount. While not 600 shots, at least 300 would be a good starting point from 250 bar to 100.
The hammer spring could be overpowering the valve even at minimum is the assumption here.