Impact X .30 700mm Mods, The Quest For 120 FPE

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heavy-impact

heavy-impact

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Sep 13, 2018
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The title says it all. Mods so far for 100 fpe...

Huma extra high pressure regulator.

3.25gram 4.47mm thick lead weight added to the hammer.

4.47mm hammer spring preload from the lead weight.

Delrin washer in place of the hammer bumper o-ring.

5.8mm valve seat from Earnest Rowe.

Ported valve housing, rear block transfer port, barrel transfer port and pellet probe.

I only get a tiny gain above 165 bar because I need more hammer weight. Right now The gun makes 100 fpe at 165 bar. I did some testing today under less than ideal conditions to see if the mods have harmed accuracy and the answer is, I don't think so. Shooting off the bipod at 60 yds in 4-12 mph winds blowing towards 2 o'clock with the target being 12. I got the same pre-mod groups that are normal for me. The best I can do is pull the trigger when the crosshair moves over the center, without a machine rest. The 5th shot opened up my .295 center to center group to .544. I was actually 2 fps short of 100 fpe with the average being 944 fps shooting JSB 50.15gr

1543877337_9817321235c05b2d9e55d95.14865321_100fpe1 -.jpg
1543877337_9078592535c05b2d9a0f386.14182421_100fpe .jpg


I have a High power kit coming from Earnest Rowe at FX in a couple of weeks or whenever he has time to make it. I have no idea what it consists of. I also have 2 more pellet probes and barrel transfer ports coming in the same order. The pellet probe is the most restrictive part. The one I'm using right now has the floor removed where it contacts the pellet. I'm not sure how much more radical I can go on the probe without causing feeding problems. I'll update as I gain performance.

Please share your FX Impact tuning tips and tricks.... and opinions on this subject.

I'll include the OEM hammer and spring specs for reference.

1543879035_13057056685c05b97be98196.49196368_Impact H&S -.jpg



 
I'd love to have 100-120 FPE out of my Impact. I'll be watching your developments with great interest. 

Been wondering if FX Sweden has any plans to develop and offer a ground up production gun with this power potential. Their offerings so far have pretty well covered all the other bases. I see a growing interest in high power slug guns for medium and large game. Surely FX has noticed it too. Were FX entertaining the notion, I'd be content to wait for it and add it to my arsenal and leave my Impact in it's stock configuration because it already covers a need that I have. 

Anyway, thanks for sharing your developments.

BeemanR7
 
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jwrabbit123,

If you're asking me, I'm shooting slugs at coyotes out to 80 yards, and hopefully out to 100 yards soon. But I'm using a hotrod AirForce Condor in .25. of 100 FPE. I'd much prefer to have that capability with an FX Impact because my Condor is too long to suit me and my weak back. A high powered bullpup like the Impact would be much better for me.
 
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IMO, what you need to achieve your goal, is as close to full bore (.3") porting as possible, and roughly 180 - 185 bar....or 2600 - 2700~ psi...and a 60~ grain projectile...provided you have a big enough plenum and the pressure drop during the shot isn't greater than 5%~.



I will definitely follow with interest to see what it takes and if you hit your goal! Good luck! Should only require 10-20% more hammer weight than you currently have to get the valve to open up. If you're currently at 22.6 grams, that would make an ideal weight of around 26 grams IMO.



-Matt








 
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what are you shooting with it ? like if you get to 120fpe what slug?
Click to expand...


I like the 51.2gr hollowpoint in my avatar cast by Loren. As for game I'd like to be able to adjust the gun up or down and use whatever projectile is appropriate for whatever I'm hunting. As soon as FX releases a slug barrel I'll have one of those.
Click to expand...

Are those the Bob's Boattails that Loren is casting? I cast 60 grain Bob's Boattails for my 120fpe .30 Long Flex and they look like those. 

I agree, it takes a heavier projectile to get to where you are going. 
 
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Well, you've saved me some typing. I was going to start a very similar thread this morning about the .22 cal version, shooting 30 gr NSA slugs, but since the mods are pretty much the same, I'll just hang out here instead :)

I've been working pretty much in parallel with what you've done. The only thing on your list that I didn't try yet is the Delrin washer in place of the o-ring for C3. Did you happen to measure how thick that was? I do have more hammer weight, and see increases up to 190 bar, which is the highest I've tested. 

I had wondered about modifying the probe to possibly have less restriction. The end of the probe is hollow, with the TP hole in it. I've wondered about cutting off the hollow end, then drill and tap a small hole in the center for a small set screw. The set screw would extend forward to push the projectile in from the center, rather than around the edges like the probe normally does. This "may" be less restrictive, but might also cause feeding issues and/or projectile damage. If you really want to find out whether the probe is causing any significant restriction, you could cut one probe off as a test. Use a normal probe to position the projectile, then swap it with the one that was cut off. That would allow you to test zero probe restriction.

For the barrel TP and probe, there's also the option of a double port. Ernest posted a picture of one that looked much less restrictive. That's something I'd like to test eventually.

I opened my valve seat up from the stock measurement of 5.6mm to 6mm. At the same time I also slotted the valve tube, and rounded the back side of the valve tube outlet port. The results for those two mods was pretty disappointing for the work involved, maybe 10 fps. If you calculate the area for airflow, the valve seat, minus the diameter of the valve pin is about half the standard valve tube outlet port. It's clearly the biggest restriction by a wide margin, and I don't see how it can be significantly improved.

At this point, I'm convinced that the biggest gain remaining is to enlarge the regulated air chamber via an external tank like Ernest has shown. I sometimes use an external digital gauge, and a Tee that allows me to compare my analog gauge to the digital test gauge. The adapters add maybe 1/10 of the volume that Ernest added with his tank, and even with that small volume increase, my fps goes from 923 to 947 for 30gr at 180 bar. I saw 961 fps at 190 bar with the external plumbing. I'm in full out search for a pressure rated, off the shelf option for an external tank. I'm assuming you'll be getting one in your high power kit, and I may have to contact Ernest directly to see if he has anything available. Otherwise I might cobble up a purely ridiculous test with a small air tank adapted to the gauge hole. That would show me the max potential of the mod.

Cheers,

Rusty 
 
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Well, you've saved me some typing. I was going to start a very similar thread this morning about the .22 cal version, shooting 30 gr NSA slugs, but since the mods are pretty much the same, I'll just hang out here instead :)

I've been working pretty much in parallel with what you've done. The only thing on your list that I didn't try yet is the Delrin washer in place of the o-ring for C3. Did you happen to measure how thick that was? I do have more hammer weight, and see increases up to 190 bar, which is the highest I've tested. 

I had wondered about modifying the probe to possibly have less restriction. The end of the probe is hollow, with the TP hole in it. I've wondered about cutting off the hollow end, then drill and tap a small hole in the center for a small set screw. The set screw would extend forward to push the projectile in from the center, rather than around the edges like the probe normally does. This "may" be less restrictive, but might also cause feeding issues and/or projectile damage. If you really want to find out whether the probe is causing any significant restriction, you could cut one probe off as a test. Use a normal probe to position the projectile, then swap it with the one that was cut off. That would allow you to test zero probe restriction.

For the barrel TP and probe, there's also the option of a double port. Ernest posted a picture of one that looked much less restrictive. That's something I'd like to test eventually.

I opened my valve seat up from the stock measurement of 5.6mm to 6mm. At the same time I also slotted the valve tube, and rounded the back side of the valve tube outlet port. The results for those two mods was pretty disappointing for the work involved, maybe 10 fps. If you calculate the area for airflow, the valve seat, minus the diameter of the valve pin is about half the standard valve tube outlet port. It's clearly the biggest restriction by a wide margin, and I don't see how it can be significantly improved.

At this point, I'm convinced that the biggest gain remaining is to enlarge the regulated air chamber via an external tank like Ernest has shown. I sometimes use an external digital gauge, and a Tee that allows me to compare my analog gauge to the digital test gauge. The adapters add maybe 1/10 of the volume that Ernest added with his tank, and even with that small volume increase, my fps goes from 923 to 947 for 30gr at 180 bar. I saw 961 fps at 190 bar with the external plumbing. I'm in full out search for a pressure rated, off the shelf option for an external tank. I'm assuming you'll be getting one in your high power kit, and I may have to contact Ernest directly to see if he has anything available. Otherwise I might cobble up a purely ridiculous test with a small air tank adapted to the gauge hole. That would show me the max potential of the mod.

Cheers,

Rusty
Click to expand...

If you change the pellet probe to a pin I don't think the magazine will function correctly. I think you'd just have to remove the top and bottom to leave two pins for proper feeding.

You commented on my external plenum in my other thread https://www.airgunnation.com/topic/larger-plenum-test-on-impact-x-30-700mm/

I haven't revisited the external plenum yet. It's too bulky.

1543930633_2076947355c06830972ebc9.61462896_1.jpg
1543930633_9422528215c06830999a700.88777826_2.jpg
1543930633_9079650295c068309b76c59.37771945_3.jpg

 
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If you change the pellet probe to a pin I don't think the magazine will function correctly. I think you'd just have to remove the top and bottom to leave two pins for proper feeding.

You commented on my external plenum in my other thread https://www.airgunnation.com/topic/larger-plenum-test-on-impact-x-30-700mm/

I haven't revisited the external plenum yet. It's too bulky.
Click to expand...

I admit that I hadn't even considered the function of the magazine. The slugs I'm shooting don't fit, so I haven't used a magazine in quite a while. I really don't know why the pin wouldn't work though, but the threads would be sawing into the rotating part of the magazine, so probably a bad idea for magazine use. 

Thanks for the link to your other thread. I swear I searched for this yesterday and didn't find it. 

Rusty
 
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No need for threads on a pellet probe, just drill a hole and press it in.
Click to expand...

The idea for threads was a variable length to compensate for the difference between a flat base slug and a diabolo pellet. I seriously doubt the probe is costing much speed at this point, but every little bit helps. 

After the reminder of what you used for your external chamber test, I ordered a similar air-oil separator unit to try. If nothing else, I can use it for it's intended purpose, though I have a much better unit for my tank fills. I also emailed Ernest, so we'll see if he has anything to offer.

Rusty


 
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Are those the Bob's Boattails that Loren is casting? I cast 60 grain Bob's Boattails for my 120fpe .30 Long Flex and they look like those. 

I agree, it takes a heavier projectile to get to where you are going.
Click to expand...

I believe they are, he said he machined the mold down to get them where they are.
Click to expand...

Those are good bullets if your barrel likes them. Both of the TJ barrels on my Flexes like them (17” with 1:24 twist and 24” with 1:16 twist). But most other people who have tried them on my recommendation with non TJ barrels haven’t had good results to my knowledge. I also have the same bullets in .457 and it seems like my .45 Texan SS likes them. 
 
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I would opt for full bore and a retracting bolt probe...unfortunately for FX or any side lever rifle, that is more of a challenge than a bolt action. Port size matters and may make or break or goals or require you to up the pressure to undesired levels...



For a .30 cal at 90% bore porting (.27") your bolt probe will have to have the equivalent area of a .131" 'pin' style bolt probe. For a full blown flow through style, you would have to subtract the wall thickness *2 from the bore size. To get to 90% bore porting with flow through you would need a wall thickness no greater than .015" on the probe, which IMO is very skinny...my probe runs from .035" to .015" radially for an average of .025", and its a half circle flow through style (like a waning crescent moon), so .25 - .025 = .225". I have no loading issues with this config. Hope this helps



-Matt 


 
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Has anyone considered varying the thickness of the Delrin C3 hammer bumper? Thinner would mean more velocity when the hammer strikes, but less cushion, and less potential opening distance. Thicker would give more cushion, and more potential opening distance. Of course if it's already reaching the max distance either way, then I'm not sure how much difference the thickness would make. I'm going to make some to try, and I guess I'll start with the stock C3 thickness.

Rusty


 
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Has anyone considered varying the thickness of the Delrin C3 hammer bumper? Thinner would mean more velocity when the hammer strikes, but less cushion, and less potential opening distance. Thicker would give more cushion, and more potential opening distance. Of course if it's already reaching the max distance either way, then I'm not sure how much difference the thickness would make. I'm going to make some to try, and I guess I'll start with the stock C3 thickness.

Rusty

Click to expand...


I've got different material washers to try, all around 1mm thick, even carbon filled peek. 4mm x 8mm is the id/od. I think the main purpose of that bumper is to reduce metal fatigue and noise. Thinner or harder material should produce more noise and possibly more fatigue. The bumper I'm using now is a M10 delrin sealing washer from my yong heng pump spares. It's pretty thick and about 2mm larger in diameter than needed but I think that will prevent deforming as fast. Let me know your results.
 
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