That is one way to skin the cat, another may be @ the rear 'plenum/regulator' gauge, the issue is making one that doesn't look goofy, and flows fairly equally to the porting used in the gun.
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fx impact x .25 Cal heavy over 880fps anyone?
- Thread starter Shinyknight
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That is one way to skin the cat, another may be @ the rear 'plenum/regulator' gauge, the issue is making one that doesn't look goofy, and flows fairly equally to the porting used in the gun.
So when you say bore the valve port and throat. Do you mean drill bigger hole in the valve hole and barrel transfer hole? So leave the bolt probe hole alone?
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Take that advice with a grain of salt, none of it is based upon experience with FX Airguns.
You won't get 880fps with an Impact 25 shooting 34gr through a 500mm barrel. But you should be able to with 600mm.
Try the easy stuff first. Like the hammer spring tensioner screw and let us know what your results are.
You won't get 880fps with an Impact 25 shooting 34gr through a 500mm barrel. But you should be able to with 600mm.
Try the easy stuff first. Like the hammer spring tensioner screw and let us know what your results are.
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Wrong. You don't know where my experience is or isn't...and it certainly is possible to hit 880 fps with a 500mm barrel out of an FX rifle with a 34 gr...just not in STOCK/OEM form...keep your ad hominems to yourself...at least have validity to an argument you're attempting to start...
No. The area in the bore MINUS the probe has to have equivalent CSA (cross sectional area) to that of the porting behind it, just as the valve throat CSA minus the valve stem CSA has to equal the porting forward of it. I highly recommend having one of Ernest Rowe's new "2019 power kits" installed when they come available, and you will without question hit roughly 880 FPS or more on the 500mm barrel...FWIW.
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By your own admission.
Seems you take every opportunity you can to bash the FX design when it comes to power output.
The OP's stock Impact doesn't need any of the mods you mentioned to get 880fps from 34gr pellets out of a 600mm barrel.
Others who chimed in with actual results have proven this. Heck my Crown can do it without your mods and the Impact makes more power than the Crown.
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H-I,
Great information I know Bob-O and I would dearly love to see a couple of pics of what that elongated Xfer port looks like as well as the probe tip. Maybe next time you tear it down?
By way of comment on pellet/slug speed; fastest isn’t always best when it comes to accuracy but I get that some ammo needs to be spun up to a certain velocity in order to get best ballistic performance and that seems to be particularly true when it comes to slugs. Now Bob’s been working with slugs but I’ve been enamoured with Ernest’s past comments about how fun it is to send 18gr pellets downrange with longer barrels at those kinds of speeds
All of which of course begs the question, have you had a chance to punch some paper with those HNs at that velocity?
Thanks bud!
George
PS H-I, RE: bore polishing...God help me but as soon as I read your post I was thinking about that little Harbor Freight metal lathe Ernest uses for polishing! Lol, how much are those? I’m just an Airgun-Ho.
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By your own admission.
Seems you take every opportunity you can to bash the FX design when it comes to power output.
The OP's stock Impact doesn't need any of the mods you mentioned to get 880fps from 34gr pellets out of a 600mm barrel.
Others who chimed in with actual results have proven this. Heck my Crown can do it without your mods and the Impact makes more power than the Crown.
Do you not understand English? Keep your ad hominems to yourself...Again, if you want to attack anything, attack the argument, not the person. Your initial statement only attacks me, and so does this one...which is a quote from MONTHS ago...
I mention how it is possible with a 500mm barrel and give the required specifications to do so because OP has 100 mm more barrel, and if it can be done with the mentioned specifications with 500 mm, then its without question that a 600mm barrel can obtain 880 fps with 34 gr.
The OP's question was can 880 + fps be obtained from an impact. Tell me again where I am wrong with my implications?
Because as far as I am concerned, anyone can undoubtedly hit 880+ fps with a .25 impact shooting 33.95 gr...with ease...
Furthermore...there is PLENTY of evidence on these forums of members hitting 880+ fps with .25 cal impacts shooting 33.95 gr...use the search function bub.
https://www.airgunnation.com/topic/got-my-crown-power-kit-very-disappointed/
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H-I,
Great information I know Bob-O and I would dearly love to see a couple of pics of what that elongated Xfer port looks like as well as the probe tip. Maybe next time you tear it down?
By way of comment on pellet/slug speed; fastest isn’t always best when it comes to accuracy but I get that some ammo needs to be spun up to a certain velocity in order to get best ballistic performance and that seems to be particularly true when it comes to slugs. Now Bob’s been working with slugs but I’ve been enamoured with Ernest’s past comments about how fun it is to send 18gr pellets downrange with longer barrels at those kinds of speeds
All of which of course begs the question, have you had a chance to punch some paper with those HNs at that velocity?
Thanks bud!
George
PS H-I, RE: bore polishing...God help me but as soon as I read your post I was thinking about that little Harbor Freight metal lathe Ernest uses for polishing! Lol, how much are those? I’m just an Airgun-Ho.
I haven't shot targets yet but I may do that today. I don't like the lathe method of polishing for fully rifled barrels, it doesn't get 100% of the bore.
Here is a pic of my .22 barrel inlet/transfer port. The little scratches to the right are from the carbide burr jumping out of the port. My hands aren't as steady as they used to be. The scratches don't hurt anything but pride. Couldn't get a clear pic of the pellet probe but the hole is larger than the port. With the probe lined up in the breach you can't see any edges through the transfer port. The port is only elongated toward the muzzle (pear shaped) but the entry is chamfered and blended. It doesn't have to look cnc cut to perform well.
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GJ with the DIY approach many are scared to take heavy-impact. 
I concur on the pride being the only thing harmed by those surface marks. The walls within the ports could use some contouring/smoothing...but ultimately have marginal effect on performance.
I concur on the pride being the only thing harmed by those surface marks. The walls within the ports could use some contouring/smoothing...but ultimately have marginal effect on performance.
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GJ with the DIY approach many are scared to take heavy-impact.
I concur on the pride being the only thing harmed by those surface marks. The walls within the ports could use some contouring/smoothing...but ultimately have marginal effect on performance.
Everything looks exaggerated in a high res closeup. I can't see those marks outside of the picture. Trying to take out tiny imperfections can lead to mistakes and removing too much material. I've learned to accept my limitations.
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H-I,
Hey thanks for the pix! That’s pretty much how I imagined One would go about the process. Did you leave any sharp edges on the barrel inlet? I’ve seen some porting where a edge was left “sharp” because the location would enhance the flow. Obviously one has to take care with “O” ring grooves
That’s an I nteresting comment about the thoroughness of a lathe approach. You’d think otherwise but I defer to your experience. Realistically speaking the lathe is “Out” anyway as I’d rather take $700 and apply it toward my Coltri purchase this summer. Besides I can afford a really good fiberglass cleaning rod as you described! Thanks for the help fella!
george
Hey thanks for the pix! That’s pretty much how I imagined One would go about the process. Did you leave any sharp edges on the barrel inlet? I’ve seen some porting where a edge was left “sharp” because the location would enhance the flow. Obviously one has to take care with “O” ring grooves
That’s an I nteresting comment about the thoroughness of a lathe approach. You’d think otherwise but I defer to your experience. Realistically speaking the lathe is “Out” anyway as I’d rather take $700 and apply it toward my Coltri purchase this summer. Besides I can afford a really good fiberglass cleaning rod as you described! Thanks for the help fella!
george
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NOW you're on point.
But you still failed to provide anything that would specifically help the OP with his issue.
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No sharp edges for me and the o-rings only seal on the outer side of their groove from the pressure. When you spin a rifled barrel against a stationary bore mop only the leading side of the rifling will get polished. They faster you spin it the greater the skip... like a tire going over a speed bump. The faster you go the harder it is for the tire to stay in contact past the high point. Back in the stone ages we used to cast a lead slug in the actual barrel to be lapped and then use the slug for lapping. Maybe Mr Rowe only used the spin method on ST barrels before the X came out.
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If this has been mentioned already then apologies. Before you do any involved work do this. I had the same problem. Got two inexpensive Huma gauges and found out the FX gauges were reading 20-40 bar high so I was shooting with reg pressure way low and hence at slow speeds. Now I’m at 905 FPS at 145 bar with 34 gen MK II. Gotta get the pressure reading right before you do anything. Then set reg pressure for tightest groups. Set hammer spring to match the regulator and you’ll be set. And you might be shooting better at lower speeds
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I have ordered a .25 Impact with 700mm barrel and 600 mm .22 kit plus a 600mm .22 B-liner to shoot jsb redesigned pellets. I am planning to achieve 940ish fps in both calibers. Going through this thread I think I'll be able to achieve my target velocity without any mods or will I need to do the modifications?
Thanks.
Thanks.
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