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SwedeNelson
Not my first air gun – but is my first big bore
Not anything like the old model 94 Daisy I got on my 8th birthday!Getting set up so we can get the chronograph working across the back of the shop.
Will be posting velocities and do some expansion test in the near future.Have a 357-150-FN bullet in the works that we hope will shine out of a Bulldog too.
The first one to use a tip similar to a Ballistic Tip but made out of aluminum.
More testing to do but this should be a great platform to do it on.Bullet maker, maker
Al Nelson
SwedeNelson-
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michaellovett
Had a little time to play with the bulldog last night.
Wanted to see what adjustment was with the hammer spring.
It has real easy accesses – remove the butt cover about like a
Tupperware lid and use a 1/4″ Allen wrench to turn it.
Stock mine was set about flush with the housing.
Tethered the gun to a 3000# scuba tank and shot 5 shots with
each full turn of the wrench.
This is with our 357-150-FN (Bulldog) bullet in its hollow point configurationStock setting (Flush)
646 FPS
652 FPS
650 FPS
650 FPS
640 FPS
Average 648 FPS1) one turn in
705 FPS
713 FPS
705 FPS
707 FPS
691 FPS
Average 704 FPS
Increase 56 FPS2) two turns in
723 FPS
736 FPS
727 FPS
725 FPS
728 FPS
Average 728 FPS
Increase 24 FPS3) three turns in
758 FPS
757 FPS
757 FPS
754 FPS
759 FPS
Average 757 FPS
Increase 29 FPS4) four turns in
772 FPS
767 FPS
769 FPS
770 FPS
769 FPS
Average 769 FPS
Increase 12 FPS5) five turns in
771 FPS
771 FPS
770 FPS
770 FPS
770 FPS
Average 770 FPS
Increase 1 FPS6) six turns in
This is the bottom of the adjustment.
Screw is bottomed out.
771 FPS
770 FPS
771 FPS
770 FPS
770 FPS
Average 770 FPS
Increase 0 FPS
Looks like 3 1/2 to 4 turns will get you all you can get.
Need to run the same test but this time
just charge the rifles tank at the beginning of each string
And see how it falls off.Bullet maker, maker
Al Nelsonrsterne
Congratulations, Al, you have just discovered the “knee” of the curve of velocity vs preload…. It typically looks like this….
Different bullet weights and springs will have different curves, but provided you have enough preload available, all of them will produce a plateau…. The further up the plateau, the more air the gun uses and the noisier it is…. At the other end, as you back the preload out you get a downslope…. the power drops and the gun gets quieter as the efficiency goes up…. Where the two (more of less) straight lines meet is the “knee”…. That is where you want to tune for (nearly) maximum power at that pressure with decent efficiency….
However, the Bulldog isn’t a regulated PCP, so you can’t tune it that way, because as the pressure drops the velocity will also drop…. You need to tune with less preload to produce a “bell-curve” for the velocity as the pressure drops…. You’ll see what I mean when you try it….
Bob
tomkerrigan
Sure, remove the air chamber from around the barrel by removing the button screw at the rear top. Then just forcibly slide it off. Then remove the outer skin and loosen set screw next to fill nipple to drain air. Unscrew air tube and set aside the tapered valve spring. Remove barrel and look down through the rear set screw hole. There may be a plastic sleeve in the port, just take it out and leave it out. Find a bit that will just fit the port. Place in milling machine or drill press and clamp receiver so that drill bit will slide up and down without too much friction truing the port with the axis of the DP or MM. Replace bit with about a “J” bit or so, about .275″ and drill through the port into the air valve. You can look through the front of the air valve to see the bit come through. Do the same procedure to line up and drill the barrel. Remove burrs and reassemble and you are done. Point gun up when filling from empty and don’t forget to cock it. Now you will have the power to shoot longer bullets and accuracy should improve. If the farmer quits working his field behind the shop, I will try some 160gr that I got a 5/8″ group with 4 bullets at 50Yd a couple of months ago. Any problems don’t hesitate to call me at 541-979-1717. I’m retired so I’m usually available. Regards, Tom
After the above post I sent the Bulldog to Travis at jsairrifles.com/ as he needed a rifle to build a new balanced valve for. It came back about six months later shooting at 330fpe if I overfilled it to 4000psi just for a test. Shot at about 280fpe using normal fill pressure. And about 50% easier to cock. He has it again now, said something about working on accuracy, so will see how it does in six months or so. Regards, Tom
I would like to point out that filling a 3000 psi gun to 4000 psi is NOT recommended (and I realize you know that, this is for the benefit of those who don’t)…. The Bulldog has a rather weak cocking lever which has been known to bend, and the math on the tube ends shows that 3000 psi is the Maximum Safe Working Pressure for the design…. Yes, you may get away with overfilling it once or twice, but doing that on a regular basis will be stressing the parts to the point that fatigue will creep in, and the likelihood of an early, and catastrophic, failure increases dramatically….
Bob
darrellsteenwyk
Hugh Kuhns
michaellovett
Rizen 1
rsterne
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