Author Topic: Anyone Neuter Their Bulldog? (Read 11990 times))

FuzzyGrub · « **Reply #60 on:** March 10, 2018, 09:08:33 AM »

Quote from: tkerrigan on March 10, 2018, 12:31:01 AM

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.

FuzzyGrub · « **Reply #61 on:** March 13, 2018, 08:00:05 AM »

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.

Shredmandan · « **Reply #62 on:** March 13, 2018, 11:14:49 AM »

Following...great info!

FuzzyGrub · « **Reply #63 on:** April 04, 2018, 01:28:06 PM »

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.

FuzzyGrub · « **Reply #64 on:** April 04, 2018, 08:15:49 PM »

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.

FuzzyGrub · « **Reply #65 on:** April 06, 2018, 11:18:34 AM »

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.

FuzzyGrub · « **Reply #66 on:** April 06, 2018, 05:12:30 PM »

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.

Tonycalves · « **Reply #67 on:** April 06, 2018, 05:55:43 PM »

Nervy looking down the business end!

YEMX · « **Reply #68 on:** April 06, 2018, 11:08:02 PM »

That is awesome!!

PCPhack · « **Reply #69 on:** April 07, 2018, 12:33:44 AM »

Quote from: Tonycalves on April 06, 2018, 05:55:43 PM

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.

FuzzyGrub · « **Reply #70 on:** April 07, 2018, 08:48:00 AM »

Quote from: PCPhack on April 07, 2018, 12:33:44 AM

Quote from: Tonycalves on April 06, 2018, 05:55:43 PM
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.

Rob M · « **Reply #71 on:** April 07, 2018, 11:10:28 AM »

awesome , whats the overall CC gain??

FuzzyGrub · « **Reply #72 on:** April 07, 2018, 11:46:16 AM »

Quote from: Rob M on April 07, 2018, 11:10:28 AM

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.

Rob M · « **Reply #73 on:** April 07, 2018, 12:34:23 PM »

Quote from: FuzzyGrub on April 07, 2018, 11:46:16 AM

Quote from: Rob M on April 07, 2018, 11:10:28 AM
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

FuzzyGrub · « **Reply #74 on:** April 07, 2018, 04:27:25 PM »

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.

YEMX · « **Reply #75 on:** April 22, 2018, 12:53:21 PM »

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!!

Rob M · « **Reply #76 on:** April 22, 2018, 04:43:43 PM »

Quote from: FuzzyGrub on April 07, 2018, 04:27:25 PM

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

FuzzyGrub · « **Reply #77 on:** December 28, 2018, 01:56:55 PM »

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.

FuzzyGrub · « **Reply #78 on:** December 28, 2018, 02:43:28 PM »

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.

FuzzyGrub · « **Reply #79 on:** December 29, 2018, 01:43:04 PM »

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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Anyone Neuter Their Bulldog?

Author Topic: Anyone Neuter Their Bulldog? (Read 11990 times))