FX Impact M3 .357, in the search for more umph

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7Green

7Green

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Jul 19, 2021
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Tuning - FX Impact M3 35 cal power destiny

A little history from my personal experiences thus far. Currently I have fired well over a 1200 rounds between 81 grain JSB's and 93 grain NSA's in the .357. When I first started, the gun came from the factory firing JSB's at around 880 fps and the NSA' were 790 to 800 fps. I began playing...
www.airgunnation.com www.airgunnation.com

Many of you recall my mission last summer. Well the mission continues.

I left off shooting NSA 93 grain slugs in a very accurate 860 to 865fps range out of the standard superior stx barrel.

I have taken small birds, rabbits, squirrels, turkey, and coyotes with this setup at some insane ranges like 200 plus.

Well last night I elected to open her up, now that some internal parts arrived.

I would also like to thank and give a shout out to cfs916 for assisting me with aquiring a tungsten hammer. He sells them on ebay and can make them to what ever spec your heart desires.

Installed now are:

-13.6 gram tungsten hammer. Head measure 3mm and is 30mm long. Total assembly weight is now around 33 grams.

-Huma power spring kit. The hammer spring is 56mm vs 52mm from FX.

-Power block

The new tungsten hammer allows me to adjust the micro dial to approx. 4.6 before it maxes. To get full rotation to the number 5 (I know I am picky) I either need a hammer that measures 1.85mm at the head and 30mm long or 28mm long and with a 3mm head. I am unsure if the spring is fully compressed or if the 30mm hammer bottoms out first. Future project I guess.

Chrono to come soon as I need to order more slugs. Pellets I have plenty of.

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If you notice the pink o-ring inside, it is slightly smaller and thicker than the original. The NSA slug probe works well with it and I find it may have a better seal. As I close the slug probe you can feel a slight resistance before it pushes through. I was using the same o-ring on the prior transfer port, so I know it works. I'm not sure the exact size because it is part of an airsoft kit I bought at the o-ring store.

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Well this week I have noticed my pressure has been ever so slowly dropping. Like a bar a day.

Put my ear up by where the tank screws in and could hear a slight burping sound, almost like a tick. Unscrewed the bottle and sound went away on gun and the bottle. Looked inside the bottle valve (where it screws in) and see a groove that appears like an o-ring should be there. Watched you tube and sure enough, yep. Some how that o-ring disintigrated from existance. Replaced and no more tick. Food for thought in case you ever need to hunt down a new leak.

I also attach my SCBA tank and dry fired a couple shots. 9 bar a shot drop. She must be breathing good now. I am really curious about the speeds I will see. Plan on launching some lead tomorrow.
 
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I was very impressed with the power level's after all the mods I have done, as 193fpe is no joke. Now I just need a tensioned slug barrel. Hurry up FX.

I plan on installing some other hammers to get full adjustability of the micro dial soon and will update with results, weights, and dimensions.

I would not doubt if close to 1000 fps with 93 grain NSA's is possible. To do that, the first reg may need to be deleted with the K&L kit or with setting both the first and 2nd reg close to eachother.

Mods to my gun are as follows:

-power block
-huma dual tranfer port with one size tighter oring installed inside
-huma power spring kit
-nsa slug probe
-13.6 gram tungsten hammer weight
-19.5 gram hammer
-huma 2nd stage extra high pressure regulator (135-200bar rated)

For new people who do not know the gun: Do not try this with the factory FX 2nd stage regs. I have a Huma high pressure reg installed.
 
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All the load and recoil is being held by a little 3mm rod with two holes drilled through it almost as large as the rod itself. I don't believe the impact is safe above 150fpe for that reason and that's why I sold mine. I was making stronger parts to replace the weak ones but I decided to go with a different platform rather than turn the impact into something it was never designed to be. I advise you to keep the butt plate in it's fully up position so that you don't end up with the pellet probe inside your shoulder when the charge rod (B19 reloading bar) gets enough fatigue.
 
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