FX Impact PP question

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bigHUN

bigHUN

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Jan 16, 2020
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Looks like my Impact .25 700mm MK2 PP reached the limits.

Would the larger 720cc Plenum (vs stock 650 cc) provide more juice for heavier slugs, let say 45 or 49 grains?

The chart below is only for my own researching the Plenum, I know that the performance still need further investigation, what slugs likes what speed also not all barrels likes all speed.

My question is only with purpose to justify my expense....



PP limit.1636571009.JPG









 
My guess is you will have to do some valve mods.

I tried to shoot slugs with a stock mk2 25cal 700mm

I didn’t do any mods besides the slug kit.

You might find short light slugs that perform well, but the real game with slugs is the longer heavier one. And the gun just doesn’t have the juice to push them. 

Thats my opinion…if you want to shoot slugs .22 is where it’s at. 
 
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Have a Mk1. I added a 1.25mm brass shim to my hammer spring, ported the barrel, shortened the valve spring two inches and added one of Michael's Plenums and was shooting extremely accurately at 74fpe on 135bar

Had the 700mm Slug A barrel shooting 33.5, 36, 36.2, 38.5 NSA and 34gr VK slugs at 740fps and 960fps they were < MOA @ 100 yards. The JSB 33.95 pellets did very well on the same tune. 85FPE was easily attainable without regular adjustment. So you can do more with less. After all of this I went ahead and installed an external valve spring to make the gun easier to tune.



https://www.airgunnation.com/topic/never-ending-mods-on-the-gen1-5-impact-x/?referrer=1


 
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I seriously doubt a larger plenum would do any good. That's probably not necessary until you go over say 95 FPE. Did you replace the valve spring with the lighter one from the Slug Power kit? That makes a difference. I'm shooting the NSA 43.5 grain at about 900 FPS with 135 bar reg pressure, and stock hammer weight and stock spring. Ernest transfer port and NSA pin probe.
 
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Hmmm, let me just rewind the history...all these changes were back in time (last winter) I was tinkering jumping to cal .30, but today with all these shortages I may be lucky I didn't, started shooting slugs instead.

Rear block hole elongated/slotted (inside) from 6.5mm into 7x9 mm slot; Valve body transfer hole enlarged from 6.5mm to 7.2mm and a new peek poppet 9.2 mm; Huma V2 transfer port and Huma pellet probe (not a pin); Hammer weight replaced from 6 gram (steel) to 7.5 gram (brass from that guy on ebay) + 2 mm spacer washer; Hammer Spring replaced from 52.8 mm to 57.5 mm (Huma); Valve Spring replaced to Huma;

I have not installed the kit with a pin, I sourced the springs individually, at the time of these upgrades that kit was on backorder for a long time.
Last week I have seen the C3 black delrin puck is compressed (1mm shorter) but I left it there until next time I am working there locally, I have a spare new in my box may replace this week.

What I did not checked is..........the gate alignment between the pellet probe and the Huma dual port. Couple weeks ago I had to replace the SaberT ambidextrous cocking handle was hitting hard on the front block and I put a thin spacer there also replaced the rubber balls...this is my last chance for a human error, checking it right after this typing.



Edit:

The pellet probe to Huma port - gate alignment is visually correct.

If the C3 worn=compressed for 1mm vs new, that means the valve is open for 1mm longer, so scratching this one as well.

The valve peek poppet (9.2mm) may not have enough room around the circumference (inside 10mm valve housing) for larger volume of air can pass through? I am not opening that one until breaks.



Edit #2

I am wrong, kind a stupid sometimes...

If the C3 worn=compressed for 1mm vs new, that means the valve is open for 1mm shorter so not enough dwell time. Luckily I have a spare Hammer with C3 and replacing it now. I will have to source the C3 to be made from peek.
 
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Hmmm, let me just rewind the history...all these changes were back in time (last winter) I was tinkering jumping to cal .30, but today with all these shortages I may be lucky I didn't, started shooting slugs instead.

Rear block hole elongated/slotted (inside) from 6.5mm into 7x9 mm slot; Valve body transfer hole enlarged from 6.5mm to 7.2mm and a new peek poppet 9.2 mm; Huma V2 transfer port and Huma pellet probe (not a pin); Hammer weight replaced from 6 gram (steel) to 7.5 gram (brass from that guy on ebay) + 2 mm spacer washer; Hammer Spring replaced from 52.8 mm to 57.5 mm (Huma); Valve Spring replaced to Huma;

I have not installed the kit with a pin, I sourced the springs individually, at the time of these upgrades that kit was on backorder for a long time.
Last week I have seen the C3 black delrin puck is compressed (1mm shorter) but I left it there until next time I am working there locally, I have a spare new in my box may replace this week.

What I did not checked is..........the gate alignment between the pellet probe and the Huma dual port. Couple weeks ago I had to replace the SaberT ambidextrous cocking handle was hitting hard on the front block and I put a thin spacer there also replaced the rubber balls...this is my last chance for a human error, checking it right after this typing.



Edit:

The pellet probe to Huma port - gate alignment is visually correct.

If the C3 worn=compressed for 1mm vs new, that means the valve is open for 1mm longer, so scratching this one as well.

The valve peek poppet (9.2mm) may not have enough room around the circumference (inside 10mm valve housing) for larger volume of air can pass through? I am not opening that one until breaks.



Edit #2

I am wrong, kind a stupid sometimes...

If the C3 worn=compressed for 1mm vs new, that means the valve is open for 1mm shorter so not enough dwell time. Luckily I have a spare Hammer with C3 and replacing it now. I will have to source the C3 to be made from peek.
Click to expand...

Sounds like you b set up pretty well already. Your C3 and check your C1 measurement is about all I could have added.

Oh, and you can adjust your valve past line 4 to what would be line five as well if you have not done that already.
 
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C3 replaced, the C1 measurement is off because that is driven by a larger peek poppet siting on the gate.

Next I suspect that I over loaded the longer hammer spring (Huma # 1308) with two extra washers and this may lock the valve, I could see the hit marks on Valve Stop (A17) edges and I did some radius to C1.

Going to test this latest change right after writing this.

If this latest C3 change doesn't show me an extra speed jump = that means the peek poppet is way too large inside the hole and restricts the flow. And that is a different ball game going further.

As is I am well pleased with the FX Impact performance, my tinkering has only one purpose - exploring the limits beyond ordinary ;)


 
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I need to explain something. So what is my problem?

At my place the wind is pulsing in waves, couple small with a speed and then a big one with different speed.

To be transparent to waves in ocean vs waves on the lakes. Both are waves but the current under the surface is different. I like surfing and paddling on board and I know the difference.

Same with winds, some geographical areas have swirling, some gusting, at my place is pulsing. Now transferring this picture to my gun club where I shoot airguns only.

We have channels for each distance = shooting lanes and both side tall trees. I can hear the wind is coming just by listening the tree leaves and the grass start moving and the game is going on.

But a problem is ones I put my earmuffs on, that cuts off the frequency. earmuffs? Right beside me a guy with a long range precision rifle is playing he's game....

I tried many magic to learn to read the wind and NFG...this why I am looking into heavier projectiles maybe I find a cure, at least partially.

Currently with 37 grain slugs the wind is tossing them around, the groups are acceptable not bigger then 1.5 MOA and down to 1 MOA, but off the center X.

Today 23 Km/hr (14.2 mi/h) wind which I call almost normal, but the winter is coming and will last usually to April
 
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HMMM, I hit 1,024 FPS on 150 bar using JSB 44.75gr pellets. I did this with the slug kit, 54cc PP and modified OEM pellet probe. No need to worry with C3 anymore as it is part of the hammer. I did use the two extra hammer weights as well. This was also with 0.299" sized and silicon lubed JSBs using a 700mm STX liner. The barrel port was also opened up more. I never have installed the dual port Huma I have as I didn't see the need to install it. My liner was also mirror polished and then I used Trewax as the final prep. I cannot reach this speed with slugs in similar weights. My belief is too much blow by occurring.
 
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Replacing the worn out C3 (part of a Hammer) did make a difference, not much but still.

The results proving me I have a restricted air path, and that is a 9.2mm peek Valve poppet. Winter is coming and looks like it will be long enough for this project.

I am happy with these numbers, this is only to show the pool of available power and doesn't mean that I am a speed freak :)

The remaining balance is that I am ordering some 44 and 48 grain slugs, and I will try to match to me Superior Heavy liner liking, whatever it takes.



PP limit 02.1636655810.JPG

 
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I agree, whatever the most accurate is with a good power balance with efficiency is the way I like to tune. I run my .25 cal liner (600mm STX Superior) between 65 to 70 FPE, the 30 (700mm STX) between 85 to 90 FPE for the best efficient accurate thump. I cast my own slugs in .25 cal, so can't really help any. Now, I will say that the .30 cal at 1,024 FPS was the most accurate in testing, but was not at the balanced efficiency I wanted.
 
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I am shooting at a gun club, if I say 2-3 hundred shots a week that will be modest. Beside other commitments in my house/family I have no time casting my own slugs.
Click to expand...

For me, I couldn't shoot at the high volumes I do without casting. The cost would be prohibitive. Once setup and going, I can now churn out hundreds of slugs well within .5 grain weights or less in just a few hours. The sizing is the easiest and fastest part. No weighing needed, typically This did take many hours of practice and learning though to get to this point. I also cast pellets and slugs in .25, .30 and .357 calibers. This does take time, but I have lots of ammo in the thousands count stored up and can dial the ammo in per bore diameter. So, I don't have to cast in unpleasant weather temps. I also shoot into rubber mulch filled totes/bins out to 70 yards (my home range limit) to reclaim the lead to do it all over again. Yes, I am retired so have the time to do all of this when I feel like it. I do have plenty of commercial projectiles as well, but I save those just incase. I have read a lot about ammo shortages, but I am not affected by those with over a 100 pounds of sheet lead on hand.

These are just a couple of small samples of what I cast in .30 and .357 calibers. The molds and equipment expense has long paid for itself many times.




 
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I never researched where can I source lead, in rods I would assume. I watched some videos but I already have so many hobbies and I cannot feed them all.

Semi retired but working around family almost like a full time. The company I worked for stopped the production because of equipment supply issues.
Click to expand...

Rotometals is a commercial source, and is how I got started, but there are some scrap metal places you can find lead pipes at from roofing and such. You just want to make sure it is pure lead. Mine came from an X-ray room door. Once you get into it you'll find lead sources. Casting is a hobby in itself just like anything else. I enjoy casting about as much as I enjoy airguns and shooting. Just another hobby/challenge to take on which actually has some benefits outside of the enjoyment. Not for everyone, like anything else.
 
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