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PostPosted: Fri Dec 19, 2014 9:15 pm 
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Today I removed the breech and drilled out the barrel port and milled the transfer port recess deeper, completely through the breech to put the flat that it seals against in the barrel itself.... That allowed me to change to a 5/16" OD x 5/16" long Teflon Rod transfer port.... The stock porting (valve, transfer port and barrel) was a very stingy 0.114" (likely made for a .177) and I went to my usual 75% of the bore for the barrel port, which is a #20 drill (0.162").... The transfer port was the next size up (0.166"), and when I did the valve exhaust port later in the day, I used an 11/64" drill (0.172").... Here is a photo of the breech after machining, and the new transfer port sitting on top of it.... Note the beautiful job on the leade where it tapers into the rifling, visible through the barrel port.... The stock bolt probe seats JSB pellets nicely ahead of the (now larger) port, so no problem there....

Image

At this point I still had not modified the valve, but I wanted to see what I had gained (if anything) so I filled the gun and shot a string with the 15.9 gr. Exacts using the same 3 turns out on preload that I did on the last string for comparison.... It was shooting hotter, and I figured if I gained more when I drill out the valve port (and I should) I might be overpowering the Exacts, so I shot another string with the 18.1 gr. Heavies as well, same preload setting.... Here are the results....

Image

With the 15.9 gr. pellets I gained a solid 30 fps, lost a few shots, and the first shot at 3000 psi was more than 4% below the peak velocity, which had moved down from 2700 psi to 2600, but was now 935 fps.... I had 27 shots within my 4% ES, averaging 921 fps (30.0 FPE) at 1.35 FPE/CI.... With the 18.1 gr. pellets, the first two shots were too slow, and there was a nice long plateau from 2700 psi down to 2400 at just under 890 fps.... This was an exceptional string, I got 33 shots averaging 876 fps (30.8 FPE) from 2900 psi down to 2100, which works out to 1.45 FPE/CI.... That's pretty amazing in .22 cal at over 30 FPE, IMO....

Not wanting to stop there, I bled off the pressure and pulled the valve.... I was shocked when I saw the size of the valve spring, and how much preload it has, partly from the 1/8" thick brass spacer on the poppet.... The preload is so much I don't think the valve can even lift 0.1" without the spring going coil bound, which is likely the cause for the known poppet failures from shooting the gun at low pressure or dry-firing it.... The poppet was an interesting design, with a highly concave face that seals right around the outside edge, making the seal 0.41" OD.... At 3000 psi, that takes 396 lbs. to crack the valve, plus the force of that massive spring (another 20 lbs?).... so no wonder the hammer weighs a ton.... The throat of the valve is a generous 0.240", which seems totally out of place compared to the tiny 0.114" exhaust port.... The port is quite near the seat, but I determined there was lots of room to go to the size I wanted (in fact you could go to 3/16" for a .25 cal.), so I carefully positioned the valve in my milling attachment on my old Atlas lathe and drilled the exhaust port out, in 3 steps, to 11/64" (0.172").... I then eased the corners at the bottom to remove any sharp edges with a small spherical burr in the Dremel, cleaned everything up, (including the inside of the tube, it was filthy), replaced all the O-rings, added a small washer to prevent the check valve from damaging the brass filter in the fill fitting, and reassembled the gun.... I'm pretty sure I cured the leak, at least it's a LOT better.... Here is a photo of the drilled out valve and the poppet, valve spring, and spacer....

Image

I am in the process of topping off my Great White tank with my Shoebox compressor, so shooting strings will have to wait, but I had enough air in my SCUBA tank to get one fill to 3000 psi.... I still had the preload at 3 turns out, grabbed the 18.1 gr. JSBs and took a shot.... Hmmmmmmmmm.... 772 fps.... Valve lock?.... I continued shooting and the gun came alive at about 2700 psi and peaked at 2400 at.... are you ready for this?.... 1013 fps (41.3 FPE).... I refilled to 2900 and cranked the preload in a turn at a time, and it was still increasing at 2900 psi even at maximum preload, where it was doing about 980 fps.... I will be shooting some strings when I have my tank topped up, but it looks like I will eventually need more hammer strike to find out what the maximum is at 3000 psi.... After the next round of tests I will either increase the hammer travel more, remove some of the preload on the valve spring (or use a weaker one), or both, as the gun is already hard to cock at maximum preload.... Who would have thought that a gun known for too much hammer strike would need even more once the beast inside was unleashed?....

Bob

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PostPosted: Fri Dec 19, 2014 10:28 pm 
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A bunch of stuff is beyond me, Bob, what they are, the reasons why they work the way they do and what each part if doing for the 'whole' - but end performance I do understand. It would be wonderful to have a reliable 30 to 35fpe rifle for shooting rats with 16gr. Predators.

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PostPosted: Fri Dec 19, 2014 10:47 pm 
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Wow, that's really coming alive! What an odd collection of design choices they made inside there. Almost like it was designed by committee.

Great work as always, many thanks for sharing with us.

Jim


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PostPosted: Sat Dec 20, 2014 1:01 am 
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I took some time this evening to shoot some strings with the modded valve at several preload settings.... I used the JSB Exact Heavy 18.1 gr. pellets for all tests, and only those shots within a 4% ES were recorded.... Here are the results....

Image

To say this thing came alive when I drilled the valve out would be an understatement.... The highest velocity recorded was 1028 fps (42.5 FPE) at about 2500 psi with the preload at maximum.... The string is near ideal for a 200 bar (2900 psi) fill, but I can't max. the gun out at that pressure, there isn't enough hammer strike to find out what it would do with the JSB Heavies, let alone heavier pellets.... That string averaged 1012 fps (41.2 FPE) for 22 shots from 2900 psi down to 2120, for an amazing 1.40 FPE/CI.... At 3 turns out, I got 24 shots at 982 fps (38.7 FPE) average, from 2700 psi down to 1930 for 1.46 FPE/CI.... At 5 turns out the fill pressure was 2500 psi, returning 25 shots at 960 fps average (37.1 FPE), down to 1760 psi, for an efficiency of 1.51 FPE/CI.... At the minimum preload, 8 turns out, I still got an average of 931 fps (34.8 FPE) for 23 shots from 2200 psi down to just 1600, with an astounding 1.61 FPE/CI, it only used 600 psi to do that....

I particularly like the string at 5 turns out, from 941-973-941 using a 2500 psi fill to get 25 shots, the longest string.... I know the JSB Heavies are accurate at that velocity in other guns, and they were shooting one-hole groups during the Chrony session, which certainly looks promising.... However, it seems I can never leave well enough alone, so I'm going to pull the valve apart and remove some of the preload by thinning out that brass collar on the poppet.... I can't shake the thought that I can get the same performance without beating the valve to death with such a heavy hammer strike, I would really like to reduce that....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Dec 20, 2014 2:08 pm 
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Location: Rocky Mtn Hse Alberta
X2 9n that green string!

Very good results with a good shot count for sure!

Going to get me interested in those rifles again Bob.
Keep up the good work man

Walter

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PostPosted: Sat Dec 20, 2014 7:36 pm 
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Yeah - me too, Walter. I've got one of those as you know, but not the air-gun machining/tinkering skill or knowledge necessary to do this sort of work.

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PostPosted: Sat Dec 20, 2014 10:15 pm 
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Today I pulled the valve apart again, and worked on the poppet and spring.... I ground the ends of the spring flat, which decreased the length by 0.030".... I made a washer that reduced the preload by 0.095", so I shortened the preload by 1/8" from 0.200" to 0.075".... I had a spare poppet, so I tapered the sides slightly to reduce the seat diameter from 0.41" to 0.36", which doesn't sound like much, but that reduced the force holding the valve closed form 396 lbs. to 305 lbs., so combined with the spring change I reduced the effort to open the valve by 25%.... The changes also meant that the valve could open a lot further without the spring hitting coil bind.... Here is a photo of the old and new poppets, shim, and the spring with the ends ground flat....

Image

I reassembled the gun, and expecting it to need less hammer strike I set the preload to minimum, tethered the gun at 2900 psi, and fired a shot across the Chrony.... 1095 fps with 18.1 gr. JSB Heavies!.... REALLY !?!.... Wow, I guess it was driving the spring to coil bind before, I expected the same velocity at less preload, not another 60 fps!.... I tried all the hammer preload settings, and it really made no difference, the velocity was maxed even at minimum preload.... I stripped the back of the gun apart, took the plastic spring guide I had and turned 0.150" off the preload spacer and tried that instead of the metal one.... Now I could back off the velocity a little bit when I set the preload to minimum.... So, I went digging through my hammer springs and found a couple of likely candidates, and ended up with the ability to at least create a velocity curve.... I took that spring and "set" it by compressing it fully several times, and it lost about 0.1" in length, and I reinstalled it and ran one more test.... The results are in the graph below....

Image

You can see that even with minimal preload the stock spring was too strong.... The new, set spring was still capable of getting the gun to maximum, so I tried a few heavier pellets, with the following results at 2900 psi:

JSB Heavy 18.1 gr.: 1100 fps (48.6 FPE)
H&N Baracuda 21.0 gr.: 1053 fps (51.7 FPE)
EunJin Dome 28.4 gr.: 956 fps (57.6 FPE)
EunJin Point 32.1 gr." 933 fps (62.1 FPE)

This gun was no slouch stock at nearly 30 FPE, but I have more than doubled that now, putting it amongst the highest powered .22 cal PCPs.... I then hooked my Chrony up to my Netbook using Chrony Connect, and shot three strings with the JSB 18.1 gr. pellets, as in the graph below....

Image

At 4 turns out from my maximum preload setting (with the new lighter, set, spring) the string started nearly at the top and I only got 15 shots.... At 6 turns out, with a 3000 psi fill, I got a normal bell-curve 1004-1041-998 over 21 shots, averaging 1025 fps (42.2 FPE), at 1.19 FPE/CI.... and at 8 turns out (my minimum preload) I had to start the string at 2700 psi, and I got 20 shots ending at 1960 psi, 980-1015-979, averaging 1000 fps (40.2 FPE), at 1.31 FPE/CI.... The efficiency is down a bit, but still very good considering the power level.... I really like the MUCH lighter cocking force, it should be a lot easier on the gun.... If there is any drawback to the gun the way it is now, it is that I can't tune it down enough to get the JSB Heavies into the mid 900s.... There are two solutions, one is to fit a weaker hammer spring and drop the fill pressure down, the other is to fit a smaller transfer port and run the hammer spring at about 6 turns out, which gave me the 1025 fps string above.... From what I saw previously with this gun, dropping the power by dropping the fill pressure doesn't buy you many more shots, so I think I will try a smaller transfer port and see if that will flatten out the string.... I think something about 9/64" (0.140") should put me at about 35-36 FPE with those pellets, so I will start at 1/8", see what I get, and then try and work my way up until the gun is averaging ~ 950 fps where I know those Exact Heavies tend to still be accurate....

When I took a look at the diameter of the stock poppet I knew immediately why the B-50/51 had such a heavy hammer.... I figured that making it a bit smaller would ease the loads on everything, but I was surprised at just how effective it was.... The poppet could be made quite a bit smaller still, there is no reason the OD couldn't be reduced down to 5/16", maybe even 0.300", because the throat is "only" 0.240".... Doing that would, I think, necessitate making a much lighter hammer to compensate.... That's not a bad thing, but I have the idea in the back of my mind to convert my gun to a .25 cal, so the ability to flow lots of air isn't a bad thing, and I have the cocking effort under control just fine.... Oh, I also took some measurements on the hammer throw, and it can be nearly doubled over stock.... The way my gun was tuned from the factory the hammer travel was 0.52", and it is now 0.625".... I can go all the way to 1.00" by shortening the nose of the striker another 3/8", not that I plan to.... You can't machine off all of the nose right back to the shoulder, or that shoulder will hit the cocking pin when it rotates downwards when you rotate the bolt, but that is the limiting factor.... Even with that shoulder flush with the back of the side cocking slot, the back of the hammer is still behind the sear, so I see no reason that shouldn't work.... Increasing the travel to 1" would allow an even lighter striker and hammer spring.... You would just have to watch that with the valve fully open (to coil bind) that the sear didn't catch behind the hammer....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Dec 21, 2014 12:17 am 
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This last bit is excellent Bob, I was scared to touch anything in the valve. I tried to taper the poppet but only halfheartedly, I figured that the spring binding must have been responsible for all those broken poppets but I was guessing and never read anything conclusive when it came to adjusting the valve. Great work!

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PostPosted: Sun Dec 21, 2014 12:46 am 
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I didn't remove very much on the poppet, I figured if I needed to I could always go more.... It turns out I'm happy with it the way it is.... Now if I was building a .177, or even a mild .22 I would taper it more, and do a major lightening job on the hammer.... but if anything I'll be going up in caliber from here, not down....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Dec 21, 2014 8:14 am 
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I'm watching with great interest your process for getting the maximum out of that gun, but was wondering if you considered regulating it as well ?

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PostPosted: Sun Dec 21, 2014 1:15 pm 
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I very much dislike in-tube regulators for my shooting (hunting not target).... They are great for low-medium power use, but by the time you install the regulator far enough away from the valve to get the size plenum required for the kind of power I am interested in, you simply lose too much of the reservoir.... The 196 cc reservoir in this gun would drop to 130-140 cc with the room taken up by the regulator and plenum....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Dec 21, 2014 5:31 pm 
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Bob- the way you've found out what makes this thing tick, if I was to trade you barreled actions straight across, you'd have a fresh platform to re-build - asside what whatever has already been done. I have no idea what was modified, other than it works fine right from a 3,000psi fill.

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PostPosted: Sun Dec 21, 2014 6:06 pm 
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Last night I made a 1/8" transfer port and installed it, and this morning I determined that 1 turn of preload (from my minimum) gave a great string at the power I wanted with the JSB 18.1 gr. Heavies, so I shot strings starting from 3000 psi with five different pellets from 18 gr. and up at that setting.... I shot them through the Chrony at a target at 20' using 5 shot groups, not taking huge care, but good enough to assess the accuracy of the different pellets to do a "first cut".... The 18.1 gr. JSBs didn't disappoint, both types of EunJins, although still one ragged hole at that range, were nearly twice the group size on average, the Baracudas were in between, and rivaling the 18 gr. Heavies for top dog were the 25.3 gr. JSB Monsters.... Usually they shoot visibly worse than the Heavies, but this barrel appears to like them, more on that later.... Anyway, here are the shot strings, starting at 3000 psi, but only including the shots within a 4% ES, so the heavier pellets are missing the high pressure shots, as usual....

Image

Here is the summary....

JSB Heavy 18.1 gr.: 26 shots averaging 949 fps (36.3 FPE) at 1.31 FPE/CI
H&N Baracuda 21.0 gr.: 20 shots averaging 910 fps (38.7 FPE) at 1.37 FPE/CI
JSB Monster 25.3 gr.: 24 shots averaging 847 fps (40.3 FPE) at 1.37 FPE/CI
EunJin Dome 28.9 gr.: 22 shots averaging 811 fps (42.3 FPE) at 1.48 FPE/CI
EunJin Point 32.4 gr.: 22 shots averaging 772 fps (42.9 FPE) at 1.46 FPE/CI

This looks like a perfect tune for the JSB Heavies, and I have lots of preload available to get the Baracudas (and their cousins the Hunter and Hunter Extreme) up into the mid 900s with the small port.... I was quite interested in what I could get with the 25.3 gr. Monsters, and found that at maximum preload (8 turns in) I was getting 913 fps at 2900 psi.... I didn't test those pellets for maximum velocity yesterday when I had the big port in the gun, but I figured it should do closer to 1000 maxed out, so I pulled the gun apart yet again and put the 0.166" transfer port back in.... I tethered the gun at 2900 psi and added the preload data to the graph from yesterday as below....

Image

As you can see, this hammer spring is not quite maxing out the velocity with the 25.3 gr. pellets, there might be another 10 fps in it before it plateaus with the big ports, but 980 fps works out to 54 FPE, so figure the maximum with the stock hammer spring would be 55 FPE.... However, that matters not, because I had to back the preload out half way to 4 turns in from minimum to get a proper string starting from 3000 psi, and here it is....

Image

I'm impressed.... This is the strongest performance I've had from a .22 cal pellet shooter based on a production airgun, although I know there are stronger guns out there (eg. Condor).... I sure hope this pellet ends up being accurate downrange, it certainly is just making tiny ragged holes indoors.... From a 3000 psi fill I got a total of 17 shots averaging 935 fps (49.1 FPE) within a 4% ES, ending at 2180 psi for an efficiency of 1.23 FPE/CI, which I consider pretty amazing at nearly 50 FPE in .22 cal.... Not only that, but 12 shots were within a 2% ES (19 fps variation) averaging 941 fps (49.8 FPE), from 1950 psi down to 2350.... That would be plenty for a days hunt for nearly anything except ground squirrels, at least for me.... I'm pretty stoked that I have a .22 cal that does 50 FPE with a pellet that looks to have promising accuracy potential, and a good BC for great downrange performance.... It should deliver ~ 28 FPE at 100 yards....

With this thing shooting as well as it does, I'm shelving any plans to change it to .25 cal, at least until I have a chance to find out how accurate it is with these pellets this summer.... Unless I have a lightbulb moment, this project is done, at least for now....

Bob

PS, Nice try, Daryl.... :lol:

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Dec 21, 2014 7:00 pm 
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I haven't had much luck accuracy wise with cylindricals in .22 (or .177, for that matter) - Monsters, Silver-points etc.
I'm not driving them anywhere near as fast as you though- low to mid 6's, and I think that may be a large part of the problem.

The 10.3 gr JSB Heavy in .177 was a huge disappointment for me. I can't get it to group out of any bbl at any velocity. That one is a cylindrical too, if you look at it long enough :lol: .... I'm getting low on the ultra mag heavies from crosman, which have been more or less my go to pellet in .177 outdoors.

I'd be interested in seeing pix of your results.

Regards,

Doc Sharptail

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PostPosted: Sun Dec 21, 2014 10:17 pm 
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rsterne wrote:
Last night I made a 1/8" transfer port and installed it, and this morning I determined that 1 turn of preload (from my minimum) gave a great string at the power I wanted with the JSB 18.1 gr. Heavies, so I shot strings starting from 3000 psi with five different pellets from 18 gr. and up at that setting.... I shot them through the Chrony at a target at 20' using 5 shot groups, not taking huge care, but good enough to assess the accuracy of the different pellets to do a "first cut".... The 18.1 gr. JSBs didn't disappoint, both types of EunJins, although still one ragged hole at that range, were nearly twice the group size on average, the Baracudas were in between, and rivaling the 18 gr. Heavies for top dog were the 25.3 gr. JSB Monsters.... Usually they shoot visibly worse than the Heavies, but this barrel appears to like them, more on that later.... Anyway, here are the shot strings, starting at 3000 psi, but only including the shots within a 4% ES, so the heavier pellets are missing the high pressure shots, as usual....

Image

Here is the summary....

JSB Heavy 18.1 gr.: 26 shots averaging 949 fps (36.3 FPE) at 1.31 FPE/CI
H&N Baracuda 21.0 gr.: 20 shots averaging 910 fps (38.7 FPE) at 1.37 FPE/CI
JSB Monster 25.3 gr.: 24 shots averaging 847 fps (40.3 FPE) at 1.37 FPE/CI
EunJin Dome 28.9 gr.: 22 shots averaging 811 fps (42.3 FPE) at 1.48 FPE/CI
EunJin Point 32.4 gr.: 22 shots averaging 772 fps (42.9 FPE) at 1.46 FPE/CI

This looks like a perfect tune for the JSB Heavies, and I have lots of preload available to get the Baracudas (and their cousins the Hunter and Hunter Extreme) up into the mid 900s with the small port.... I was quite interested in what I could get with the 25.3 gr. Monsters, and found that at maximum preload (8 turns in) I was getting 913 fps at 2900 psi.... I didn't test those pellets for maximum velocity yesterday when I had the big port in the gun, but I figured it should do closer to 1000 maxed out, so I pulled the gun apart yet again and put the 0.166" transfer port back in.... I tethered the gun at 2900 psi and added the preload data to the graph from yesterday as below....

Image

As you can see, this hammer spring is not quite maxing out the velocity with the 25.3 gr. pellets, there might be another 10 fps in it before it plateaus with the big ports, but 980 fps works out to 54 FPE, so figure the maximum with the stock hammer spring would be 55 FPE.... However, that matters not, because I had to back the preload out half way to 4 turns in from minimum to get a proper string starting from 3000 psi, and here it is....

Image

I'm impressed.... This is the strongest performance I've had from a .22 cal pellet shooter based on a production airgun, although I know there are stronger guns out there (eg. Condor).... I sure hope this pellet ends up being accurate downrange, it certainly is just making tiny ragged holes indoors.... From a 3000 psi fill I got a total of 17 shots averaging 935 fps (49.1 FPE) within a 4% ES, ending at 2180 psi for an efficiency of 1.23 FPE/CI, which I consider pretty amazing at nearly 50 FPE in .22 cal.... Not only that, but 12 shots were within a 2% ES (19 fps variation) averaging 941 fps (49.8 FPE), from 1950 psi down to 2350.... That would be plenty for a days hunt for nearly anything except ground squirrels, at least for me.... I'm pretty stoked that I have a .22 cal that does 50 FPE with a pellet that looks to have promising accuracy potential, and a good BC for great downrange performance.... It should deliver ~ 28 FPE at 100 yards....

With this thing shooting as well as it does, I'm shelving any plans to change it to .25 cal, at least until I have a chance to find out how accurate it is with these pellets this summer.... Unless I have a lightbulb moment, this project is done, at least for now....

Bob

PS, Nice try, Daryl.... :lol:


Nice Bob, would be nice to see what they do at 40 or 50yrds for accuracy. With that power level. Even if its kinda wintery outside.
But winter is long and Im sure youll get that 25cal itch cause you can...lol...

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