GTA
Airguns by Make and Model => Benjamin Airguns => Topic started by: FuzzyGrub on May 22, 2017, 08:39:29 PM
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While many push to get more power from their Bulldog, I'd like to optimize on the 81g JSB pellets. I'd like to get a 4% Es @ 130FPE average. It looks like 10 shots will be doable, but like to explore SSS or TSS options, and maybe push the boundaries to 15 shots? Dreaming?
I have run strings with 5.5, 6.5, and 7.5 Turns out from full clockwise. The 6.5T looks the most promising, at 855-910-853fps (57Es), 2.9-2.1Kpsi. Along with springs, may look into using a BSB, and also conventional tune with a smaller TP. Am I plowing new ground, or have others blazed a trail? I couldn't find any info, but would like to hear others experiences.
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Following ;D
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Done and done.
I've regulated mine down to 200FPE . That's down from a max of about 260
I've also put a bigger reservoir on it and i fill mine to 4500psi. I can get 13 regulated shots at 200fpe with an extreme spread avetage of 8fps. That is with the airbow res. Im redoing it right now to make a res that goes all the way to the end of the moderator. That will be a 50% increase.
You could probably just use the airbow regulator and get close to what you are wanting. And if you made an adaptor to use the airbow reseroir and for sure get your 10 shots.
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Done and done.
I've regulated mine down to 200FPE . That's down from a max of about 260
I've also put a bigger reservoir on it and i fill mine to 4500psi. I can get 13 regulated shots at 200fpe with an extreme spread avetage of 8fps. That is with the airbow res. Im redoing it right now to make a res that goes all the way to the end of the moderator. That will be a 50% increase.
You could probably just use the airbow regulator and get close to what you are wanting. And if you made an adaptor to use the airbow reseroir and for sure get your 10 shots.
I saw some of your reg results, other work and videos. They will certainly help me on my first dis-assembly. :) Do you have a part schematic for the airbow? I didn't find any on crosman's site.
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The oem spring is the same OD as the Mrod at 0.480", but a half inch longer, at 3", using 0.069" wire. Anyone know what its spring rate is? I ordered a spare today, and they also had a "detune" spring, so got that as well. It is part# 20-R3571-039. With the oem spring, you can't back it off to remove all preload. Even if it did, the curve won't be what I'm looking for, based on the 7.5 T data. I have a good selection of Mrod springs and additional ones that fit inside it to try the equivalent of SSS/TSS.
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Done and done.
I've regulated mine down to 200FPE . That's down from a max of about 260
I've also put a bigger reservoir on it and i fill mine to 4500psi. I can get 13 regulated shots at 200fpe with an extreme spread avetage of 8fps. That is with the airbow res. Im redoing it right now to make a res that goes all the way to the end of the moderator. That will be a 50% increase.
You could probably just use the airbow regulator and get close to what you are wanting. And if you made an adaptor to use the airbow reseroir and for sure get your 10 shots.
I saw some of your reg results, other work and videos. They will certainly help me on my first dis-assembly. :) Do you have a part schematic for the airbow? I didn't find any on crosman's site.
Here's a link to the schematic download(under the downloads):http://www.crosman.com/airguns/airguns-airbow/benjamin-pioneer-airbow (http://www.crosman.com/airguns/airguns-airbow/benjamin-pioneer-airbow)
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Here's a link to the schematic download(under the downloads):http://www.crosman.com/airguns/airguns-airbow/benjamin-pioneer-airbow (http://www.crosman.com/airguns/airguns-airbow/benjamin-pioneer-airbow)
Thx Joe! :) Checking it out now.
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I'm a bit surprised that they didn't use compatible air tubes, but I guess that would be too easy.
I did see an o-ring (#50) between the airbow hammer and valve. I'm betting it is just a bumper and not a BSB though. ;)
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I was very surprised too. I was really hoping i was gong to be able to just screw them together.
I think number 50 is a seal that comes in from the valve side to keep air from going around the valve guide when the rifle is fired. But I'm not positive. I have not taken a airbow apart.
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I think number 50 is a seal that comes in from the valve side to keep air from going around the valve guide when the rifle is fired. But I'm not positive. I have not taken a airbow apart.
It would have to be on the other side of #51 to do any sealing, and the poppet steam is not sealed, which is where any air would come. It isn't on the Bulldog. Maybe the drawing is in error? The airbow schematic is also not showing the valve body. Maybe that is integral to the receiver?
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Get in touch with Al at Aeromagnum. He is having a Bulldog tuned for optimal power and shot count and having an airbow reservoir installed on his so he might be able to shed some light on your questions.
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Get in touch with Al at Aeromagnum. He is having a Bulldog tuned for optimal power and shot count and having an airbow reservoir installed on his so he might be able to shed some light on your questions.
I saw what he had posted on website. Looked more like power mods, but will keep an eye on for updates.
While a bigger res and reg may be mods down the road, looking to do some benign testing/adjusting while it is still within the 30 day.
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Yes, he is going for max power but my thought was that the man that he has doing the mods for him might be able to take you the other direction that you're interested in. Good luck with your mods.
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I also noticed that the airbow is using twin hammer springs and different guides.
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Badgerfarm, He's having me do it.
I would give my contact but it seems the moderators don't want me to say anything about what i do. I even got my post changed for saying "gracious" to "Gracious" and someone else video link removed. I must have perturbed someone off. Sorry.
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And we are not going for full power on Al's he just has an exact speed he wants to push his bullet at and so thats what we are going for. Should be right about 230fpe with 10 regulated shots
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Badgerfarm, He's having me do it.
I would give my contact but it seems the moderators don't want me to say anything about what i do. I even got my post changed for saying "gracious" to "Gracious" and someone else video link removed. I must have perturbed someone off. Sorry.
The GTA takes safety very seriously, as we all should. If I went forward with a longer airtube and reg, would still maintain 3Kpsi fills.
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Thats not what they edited out but i get what your saying.
It is funny that Ataman and some others do it but they gave me heck about it. But i do totally understand. that's why i tested it to 10k.
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Get in touch with Al at Aeromagnum. He is having a Bulldog tuned for optimal power and shot count and having an airbow reservoir installed on his so he might be able to shed some light on your questions.
I saw what he had posted on website. Looked more like power mods, but will keep an eye on for updates.
While a bigger res and reg may be mods down the road, looking to do some benign testing/adjusting while it is still within the 30 day.
OK, I must be a tad dyslexic ::) I was referring to Magnum Airpower LLC https://www.magnumairpower.com/gun-gallery.html (https://www.magnumairpower.com/gun-gallery.html)
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From Matt's work, the airbow res is the wrong threads for the bulldog adapter. :(
Does anyone know if the airbow adapter, item #57, part #SWFA301, will thread into the bulldog receiver? I'm guessing not, but hoping yes! ;)
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No they won't. It's a huge difference too.
I can take a picture of both tonight and show you if you like. I was hoping the same thing so i bought one.
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I'm still awaiting some parts from crosman. Not much to update:
- The throw measures about 0.9" from sear latch to poppet stem impact.
- OEM Spring is 3.25" long, think I said 3" earlier.
- The oem spring uses too thick of wire, to insert my 0.36" OD springs.
- Trying to find equivalent oem spring, to estimate spring rate, seems to indicate somewhere in the 20-25 lb/per inch.
- I have a 12.5lb outer and 14.8lb inner (27.3lb) that I will try, but made my first hammer guide too long and bottomed out. ::)
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Well, the oem spring is about equal to my pair of springs mentioned above. So, ordered a few more from MC to experiment with. I did find one that will fit inside the oem. Still waiting on the crosman order. Small orders that go USPS seem to take awhile with them.
I plan to use my Mrod cross-flow depinger that has been sitting in the parts bin since all the Mrods have regs. I got a larger cross-section o-ring, such that it should stay centered in the larger BD air tube. The current inlet is 0.4" diameter with four 0.2" diameter cross-flow holes. It looks like I can open it up to 0.5" and 0.25". I will also use an aluminum pipe stand off. Anyway, that's the plan.
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Update: the crosman order came yesterday and the MC spring will be here today.
FWIW:
- The "detune" spring is same OD and length as the oem, but has 0.056" dia wire, vs 0.066".
- TP measures 0.300" OD x 0.500" L x 0.195" ID
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- I have a 12.5lb outer and 14.8lb inner (27.3lb) that I will try, but made my first hammer guide too long and bottomed out. ::)
With zero preload, this only produced 450fps with the 81g JSBs. Need more spring.
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good to know.
You gonna try a stiffer spring?
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good to know.
You gonna try a stiffer spring?
Yes. The next step is a shortened oem spring plus an inner 15lb spring. If that isn't enough, will add a third spring.
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Awesome!!! can't wait to hear how it does.
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The MC springs arrived. I do have to make a different spring guide given the smaller ID of the inner spring. Also, if I need to go to three springs, will need to come up with a guide/sleeve.
First tin of four JSB's is empty, so ordered another 4 tins from PA. Comes to 14 cents a pellet. ;)
FWIW: I did clean the barrel and lube with FP-10, before firing first shot, and have lubed the pellets with krytox chain wax.
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The two springs you now have should be perfect if you increase the TP to .250 which is what Id call the minimum for that bore size to be efficient. I like to see most TPs to be 70% of the bore size as a standard and with so much area base to push on(357) you really need that instant volume to be filled quickly otherwise youll end up over dwelling the valve to get the breakaway speed up and thus using to much air. So my suggestion is open TP to .250 and use the twin spring in free flight and you should be golden.
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John did you get any new data? Call me curious.
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John did you get any new data? Call me curious.
Yes, I was home for part of the weekend, and was able to get some basement chrony time while it was raining on Sunday.
I'll provide more data this evening, but here is a general description:
- The twin springs with no preload, started in low 700fps @ 3kpsi, and peaked at 2kpsi and then dropped quickly.
- I shimmed the inner spring so about 1/4" was in preload. I have a string with 9 shots within 4%, compared to 7 shots with oem alone.
At this time, not doing any TP changes, but will latter. I think I can squeeze 10 shots out of it with some more tweaking. I need to do some 50yd accuracy testing next.
Thx for your input.
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Original String:
OEM spring
6.5T out from full CW
3Kpsi
--- 818
--- 855
01 875
02 901
03 906
04 910
05 902
06 889
07 874
--- 865
--- 853
--- 837
2kpsi
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Twin Spring: Outer: cut oem + 15lb rate inner, shimmed out 1/4"
Adjuster flush
3Kpsi
--- 796
--- 814
--- 836
01 852
02 868
03 875
04 883
05 884
06 878
07 876
08 866
09 856
--- 837
--- 827
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Getting there. Reduced the shimming on the inner spring from 1/4" to 1/8". Virtually within the 4%.
Twin Spring: Outer: cut oem + 15lb rate inner, shimmed out 1/8"
Adjuster flush
2.8Kpsi
01 854
02 868
03 879
04 881
05 887
06 884
07 876
08 864
09 860
10 850
2kpsi
Ave: 870
Ave FPE: 136
From Lloyd's calculator, using a 340cc res, get: AVE FPE/CI of 1.19, 80 psi per shot
Also got this string from turning the preload out 1/4T from above:
2.7Kpsi
01 840
02 851
03 856
04 875
05 877
06 875
07 870
08 861
09 855
10 841
2kpsi
Ave: 860
Ave FPE: 133
AVE FPE/CI of 1.33, 70 psi per shot
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Very respectable.
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Thx, I think I will stop there for now. I would like to get a bit better on the Es.
Cracked open tin 3 yesterday. Four more should arrive by Thursday. Hopefully, it will stop raining and can get back to getting groups. The local farmers need a break in the weather to get their first cutting in.
I'll post some pics and details of the TS set-up with guide and shims. I think it would not be hard to make the inner spring externally adjusted (no shims), but will put that out as a possibility for the future.
If it keeps raining, will work on DIY LDC, but can't post details about it here. It is a 2" X 6" from three Trident silicone grease containers. I don't know if it is going to hold up. I'll let you know if successful or not.
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I will be picking back up the Bulldog soon. Plan to open the ports, like many have done, but also fit a Huma reg, lighten the hammer, and lighter valve spring. A front mounted air fill is suppose to arrive today. Stay tuned.
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Looking forward. GL
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Fuzzy i just received my order of Regulators from Huma so i've got them in stock.
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Fuzzy i just received my order of Regulators from Huma so i've got them in stock.
Good to know, Matt. I have a prod reg and other stuff coming from Huma along with just a universal reg to fit the BD tube. It has been paddling itself across the pond. ;) I'm planning on a much smaller plenum than yours. targeting 130fpe w/ 81g JSB, and then make things as efficient as possible. Everyone seem to take the BD in the other direction for maximum power. For me. iIts my heavy duty pellet plinker. :)
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...A front mounted air fill is suppose to arrive today.
Did you have this made, or is it available somewhere??
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...A front mounted air fill is suppose to arrive today.
Did you have this made, or is it available somewhere??
I got one from another airgunner, but there turned out to be an issue with it, so in the process of making my own, after one flawed attempt.
Another possibility, but I'm concerned it is different threads is to try the airbow fill probe assy. If it did fit the BD airtube, it would be nice to have the gauge. I believe some trimming on the clam shell stock to get it to fit would be required.
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...A front mounted air fill is suppose to arrive today.
Did you have this made, or is it available somewhere??
Another possibility... is to try the airbow fill probe assy.
Oooh!! Please update when you can! It would not surprise me if Crosman did change the threads up, however- there's a chance that Crosman did the right thing and made the threads the same... *CROSSING FINGERS*
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I have been told that the air cyl do not interchange. That would have been great. The airbow cyl is about 4-5" longer. Also told the airbow adapter does not fit the BD receiver. :( The airtube O-rings are slightly different sizes, too. So, I'm betting it is unlikely. If I fail on my next attempt, then I might try the airbow fill assy. Worse case, I'd be out the return shipping.
Matt sells a extra long BD air cyl. For my plans, a bit too long. But for those extra number of power shots, something to look at. It is designed to fit with one of his LDCs.
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I have been told that the air cyl do not interchange... The airbow cyl is about 4-5" longer. Also told the airbow adapter does not fit the BD receiver.
Matt sells a extra long BD air cyl. For my plans, a bit too long. But for those extra number of power shots, something to look at. It is designed to fit with one of his LDCs.
Perhaps the airbow cylinder is just different at the receiver end. So I'll hold out hope that the airbow's end cap will work. I might be interested in a longer cylinder for the BD, if I go with a 32" barrel...
Is there enough room on the receiver to enlarge the barrel bore? I was kicking around the idea of a sleeved barrel- I would only need 1.25" in depth (longer is better, of course). I really need to get one of these in my hands...
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FWIW: The airbow cyl does have a vent hole drilled in it for the reg.
I don't know if there is room to enlarge the barrel. I briefly looked for barrel blanks for 25 and 30 caliber, but they were not large enough and would need to be sleeved.
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Yeah I was very disappointed that the threads and adapters were not the same threads. BOO CROSMAN!!!
I made several adapters to put the airbow tube onto the bulldog but in the end i just quit because If i just made my own tube i could get more air and make it fit whatever i wanted.
I'm out of material long enough to make a full length tubes but i have a few pieces that are just an inch short so If you want me to make you a custom length tube just give me a length and i'll make it happen. I've got the Airbow end caps and fill ports in stock too.
And i understand turning it down to make it a plinker. I think its a fun gun to shoot but with as much power as it comes stock with it's way too much to punch holes in paper and shoot in a normal backyard.
I plan on turning one of mine into a version of what your doing and then taking another one to as much power as i can possibly get. I'm hoping to push the 600 FPE mark with Helium.
But admittedly, what you are wanting to build will be MUCH more fun to shoot.
YMEX the threads are on both ends of the airbow tube are different than the bulldog tube.
And yes the Airbow tube does have a vent hole in it for the regulator at about 7" from the valve.
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Paper puncher NOT! ;) But it does smack those metal rimfire targets with authority! :)
A Pm coming shortly.
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From Matt's work, the airbow res is the wrong threads for the bulldog adapter. :(
Does anyone know if the airbow adapter, item #57, part #SWFA301, will thread into the bulldog receiver? I'm guessing not, but hoping yes! ;)
Sorry to dash your hopes and dreams but no it will not. I have one i ordered to try out and it doesn't fit.
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YMEX the threads are on both ends of the airbow tube are different than the bulldog tube.
Wow... way to go Crosman, way to go. ::) >:(
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Modified Bulldog shooting Nielsen Specialty Ammo 180gr. slugs at 909 fps. 330fpe.
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180gr.
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Thats the opposite of neuter. Great job! Who made the shroud and LDC?
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Modified Bulldog shooting Nielsen Specialty Ammo 180gr. slugs at 909 fps. 330fpe.
That looks so much better!!! How about sharing some of your mods to get to 330FPE.
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Back to the BD today. Opening up the ports. Going to 17/64" (0.265"), which is a little smaller than what you see the power tuners doing. They are usually going to 9/32" (0.281"). I'm trying to get more efficiency with a shorter dwell, and will be adding a Huma reg coming up. I might go to the 0.281" when I install that.
Existing ports:
- Valve Pocket: 0.372"
- Valve exhaust: 0.200"
- TP ID: 0.196"
- Barrel Port: 0.220"
Well, I did end up "going all the way" to 0.287" on the ports.
Maximum poppet travel is 1/4". I inserted a 115 square o-ring that will limit travel to a hair more than 1/8". Using it more as a limiter than like a BSB. The airbow has an o-ring in the same location. It will also cushion the hammer from making any metal impact.
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...will be adding a Huma reg coming up.
I just looked at HuMa's site... I don't see any regs that are built for larger than .30 and regulate higher than 170 bar... What pressure were you looking at running the reg at?
I never thought to even try to run a reg w/a big bore. Thanks for the idea!!
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...will be adding a Huma reg coming up.
I just looked at HuMa's site... I don't see any regs that are built for larger than .30 and regulate higher than 170 bar... What pressure were you looking at running the reg at?
I never thought to even try to run a reg w/a big bore. Thanks for the idea!!
It is a "standard" regulator that is sized for the BD tube. and for the BD you need to drill the vent hole. Keep in mind, my plan is shooting 81g pellets at 130FPE vs a 200FPE+ bullet shooter, so if I have to set it higher than 2400psi, I messed up on the plenum size! ;)
One complication with reg'ing the BD, is you need to add a fill port on the front. Matt at Pitbull is helping out with that. A custom air tube that will add 6" along with an airbow fill port and gauge. The extra six inches should cover the air loss from my planned plenum and reg displacement. BTW, he also sells the Huma regs with a plenum designed more for higher power/bullets.
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...my plan is shooting 81g pellets at 130FPE [not] a 200FPE+ bullet shooter...
...BTW, he also sells the Huma regs with a plenum designed more for higher power/bullets.
Yeah, you're right- I forgot you are trying to focus on the .357 pellets... The Pitbull reg kit should fit your needs perfectly!
I'm not sure a touch over 2500 psi (175 bar) will cut it for my build though. But thank you FuzzyGrub! Regulation is definitely something to consider for my build!!
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I don't have my Bulldog handy to look at right now, is there a chance that the hammer can be modified to have a low power sear catch position? If the sear slot is at the butt end of the hammer it wouldn't work I'm thinking. The bolt might not pull back far enough to load ammo also. Regards, Tom
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I don't have my Bulldog handy to look at right now, is there a chance that the hammer can be modified to have a low power sear catch position? If the sear slot is at the butt end of the hammer it wouldn't work I'm thinking. The bolt might not pull back far enough to load ammo also. Regards, Tom
I think it catches on the front edge. Slotting the hammer wouldn't be easy for me. I think I would try to remove the small nose on the hammer and drill and tap it for an adjustable striker, before trying that.
I do have a spare hammer that I plan to try to "lighten up", which isn't going to be "easy" for me either. ;)
The valve spring is very easy to compress, but being conical, hard to find a stiffer one that fits both ends. Might figure out a way to shim it, ie give it more pre-load.
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I think I have a endcap with fill that will work to test the oem BD tube w/reg. I have been going through some plenum/air res calculations. More reverse engineering from a "desired" plenum size, vs bottoms up. Anyway, because the new tube will give me 6" of additional air space, trying to keep plenum/reg close to that volume.
With a 5.5" plenum, that gives me about 90cc's. With my 130FPE goal, that works out to 0.7cc/FPE. If I consider shooting the 81g pellets at 900fps, then a 145FPE would be like 0.62 cc's/FPE. Using that 5.5" plenum, with oem tube should leave me almost 240cc of air res.
So, until I'm confident on plenum size/reg pressure, don't want to drill the vent hole. The huma reg only has less than 1/2" between O-rings, which is not much flexibility in plenum adjustment. My thought was to set the reg pressure to 2400psi, maybe higher, but on the fill, start at 2000 psi and test a shot, keep upping the pressure a few hundred psi, and retest. My thought is, I'd get a valid test, without any reg creep.
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Following...great info!
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I received my air tube and parts from Matt at Pitbull, yesterday. :) It had dis-appeared into a USPS black hole for a little while, but it did pop out the other side and everything was wrapped extremely well. Matt included some nice "extras" such as a single shot tray and some rail sets. I appreciate it.
I hope to install this weekend and will provide pictures along the way. I'd like to get the first plenum test complete.
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The air tube is shorter than Pitbull's standard air tube. It will be just shy of the end of the oem muzzle. It is threaded for the Bulldog receiver tube on one end and the airbow fill assy on the other. I will have a gauge on the res and on the plenum. It does mean the use of the airbow fill probe and will remove and plug the oem foster fitting on the receiver.
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Started the conversion this AM. Some pictures below comparing the 26.5" tube to the oem 21" one.
I will be testing a 5.5" plenum (91cc) which is about 0.7cc/fpe for my desired 130fpe. The plenum is reduced to 5" because the fitting into the receiver provides 1/2" of plenum. I also drilled three vent holes in it such that no air can be trapped behind it. Added a couple of thin O-rings to keep the spacer centered in air tube.
Reg has been set to 2400psi, which is higher than I hope to go. This is just to test the plenum size before making the final choice on where to drill the reg vent hole. When I fill, will be starting at 1900psi and test in 100psi increments upto the 2400.
I haven't modified a hammer to make it lighter yet. I will be stopping at the H/W store today to find some shims for the conical poppet spring. Ie increase the preload to compensate for the lower running pressure, for now.
I need to dremel out the front of the stock for the longer air tube.
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Well, when I went into town, left the part on the counter. ::) Ended up getting a spacer a tad too larger in diameter, so sanded it down. Only provided about 1/8" additional preload.
The stock mod was uneventful. Did the ruff cut with a bench grinder. Finished up with an aluminum tube/sand paper. Fits nice.
With the tube exposed in the front, means the bottom rail will not fit and would be useless, anyway.
Next up, will be some testing.
Dining room table back to normal, just before she is due home. ;)
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Nervy looking down the business end!
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That is awesome!!
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Nervy looking down the business end!
No joke...I would only ever check it from an angle once pressurized. Cool project, and the gun looks great.
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Nervy looking down the business end!
No joke...I would only ever check it from an angle once pressurized.
Yes, it can be easily read from an angle without looking down the barrel. :)
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awesome , whats the overall CC gain??
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awesome , whats the overall CC gain??
The stock tube calculates out to about 340cc. The new tube calculates out to about 430cc, or about a 90cc gain. Matt's "standard" air tube is longer and mates with his LDC. I think it is around 500cc's.
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awesome , whats the overall CC gain??
The stock tube calculates out to about 340cc. The new tube calculates out to about 430cc, or about a 90cc gain. Matt's "standard" air tube is longer and mates with his LDC. I think it is around 500cc's.
this is great. so your shot count will be through the roof compared to stock.. I also think 130 fpe is enough for most applications ( outside larger game
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A little testing today. I filled via my guppy and left the tank installed. After every shot cracked the valve back open and topped it back off.
Initially, tried a single spring at 2kpsi. At zero pre-load only got 534fps. At full 6 turns in, got 835fps.
I switched back to my twin spring set-up. At zero preload got 869 fps. At a minus half turn, 852 fps, which is my target. Topped it off a few more times to reconfirm results. Also went to 3.5T and got 873 fps, so I'm below the knee. Note: with my twin springs it goes into coil bind before getting to 4 turns in.
So it looks like with the 90cc plenum set at 2k will give me the power I'm looking for. Next test is to set reg to 2K and do a string from a 3K fill, to get approx. shot count. Not sure how much creep will occur without having the vent though.
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Most excellent work FuzzyGrub!! I think I'm going to take a page from your book for my build. It's a Brod, not a bulldog, but the same principles should apply... Keep the great info comin!!
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A little testing today. I filled via my guppy and left the tank installed. After every shot cracked the valve back open and topped it back off.
Initially, tried a single spring at 2kpsi. At zero pre-load only got 534fps. At full 6 turns in, got 835fps.
I switched back to my twin spring set-up. At zero preload got 869 fps. At a minus half turn, 852 fps, which is my target. Topped it off a few more times to reconfirm results. Also went to 3.5T and got 873 fps, so I'm below the knee. Note: with my twin springs it goes into coil bind before getting to 4 turns in.
So it looks like with the 90cc plenum set at 2k will give me the power I'm looking for. Next test is to set reg to 2K and do a string from a 3K fill, to get approx. shot count. Not sure how much creep will occur without having the vent though.
the adjustability range of your gun is very impressive also , even if not the goal
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Picked up the bulldog today. Fixed the reg leak and did a test string. Pushing the 82g JSB's to 801fps until coming off reg set point. Goes to 890 fps and then declines. Reg setpoint was at 145 bar.
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Dropped the reg set-point 200psi. Huma set-point = 132 bar, but my gauge says 2000psi. I got 3 mags (15 shots) at 890fps. 4th mag went from 877 - 835fps.
I did see some fluctuations that I assume is because I haven't drilled the vent hole yet.
Next step is to open more gap/adjust my twin spring system to bring the power down to 850-860fps range.
That produced 3 mags at 855fps ave, but when it went off reg, it climbed back to 890fps. Need to decide to drop set-point some more or reduce the plenum size some.
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Shortened the plenum from 5" to 4", and still getting to 870+ fps. I don't feel comfortable going lower, so going to go ahead and drill the vent hole. There is only 1/4" between O-rings on the reg, so not much adjustment after that.
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Ok, still at 4 mags, with three on reg, 1 off. Going to leave it there for now.
Reassembled gun. One thing of note to adding a longer air tube that is close to the end of the shroud or past it, the button head cap screw on the bottom of the end cap will not clear the air tube or in my case, the gauge. It also needs to be only 1/4" in length or it will be in the projectile path. I used a set- screw for now, that sits flush with the shroud.
I'm looking at the possibility of moving the shroud forward about 1", by doubling up on the shroud mount, part #R3571-007. Adding an inch infront of the muzzle might help quiet it some. My DIY LDC is 2 1/4" OD by 4" length, two chambers. Not something that would hold up under 200FPE conditions, though. ie made of plastic.
The DIY LDC does block reading the fill pressure. Not really needed, but the next time I depressurize, will rotate the gauge 180 degrees.
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It has been a while since I have shot this gun outside of the basement range. These pellets put a great "smackdown" on those metal 22 long rifle targets @ 50yds. :)