Air Gun Home :: View topic - New Old Project - Hayabusa PCP

rsterne · Moderator

It is in the next to last post.... 9 lbs. 14 oz. with sight....

Bob

Bob La Londe · Veteran Member

rsterne · Moderator

Lengthening the valve stem will not make the valve open further, I already have 1/4" of lift available.... All it will do is shorten the hammer travel, reducing the available hammer energy and momentum.... PCP valves only open about 1/4 of the throat diameter most of the time, that is where they reach their maximum flow rate.... If they ever open more than 1/2 the diameter they are only wasting air through excess dwell.... The gun already has 3/8" porting and a 13/32" valve throat....

Bob

Bob La Londe · Veteran Member

rsterne · Moderator

It turns out I had another hammer spring here to try, which allowed me to examine what the maximum performance was.... It was actually two 3" long springs of 0.062" wire instead of the single 4.5" long spring of 0.072" wire.... This gave me about the same force when cocked, but instead of having no preload when uncocked it had a preload of about 10 lbs.... That gave more hammer energy, so I was able to find out where the velocity plateau was at 3600 psi.... It turns out the gun maxes out at about 870 fps (340 FPE).... I couldn't back the preload adjuster out far enough with the long spring to get down under 800 fps, but by using the original spring I was able to plot the velocity profile.... Once I established that the best place to tune the gun was with the original spring maxed out, I then shot a string, recording all the shots within 5% of the peak....

The best choice for a hammer spring would be one about 5" long, made of 0.062" wire, and I can get a 10" one from Trakar and then cut it in half, which is the eventual plan.... However, I was able to get 9 shots with 5%, of which 7 shots were within 3% ES.... The average velocity for those 7 shots was 819 fps (302 FPE), and I would refill at about 2500 psi, and the efficiency is 0.76 FPE/CI....

I think this will prove to be an effective short range Grouse gun.... It doesn't have the smack of a powderburner, but if I can get decent patterns with the #8 shot I think it will do the job....

Bob

rsterne · Moderator

Today was quite a day.... After a couple of years of planning and a year of work, I shot my Hayabusa .457 for the first time today, and saw over 550 FPE.... I tested three kinds of ammo, found the maximum that the gun would do at 3600 psi with all three, and found two great shot strings.... The bullets used were a 143 gr. roundball, and two Lee bullets, a 216 gr. RN and a 336 gr. FN.... In order to find the velocity plateau I had to use the two 3" hammer springs like I did on the .410 shotgun, and here are the maxed out results....

143 gr. RB - 1101 fps (385 FPE)
216 gr. RN - 993 fps (473 FPE)
336 gr. FN - 859 fps (551 FPE)

Needless to say, all the work and frustration has paid off and I've got a pretty big smile right now.... I put the 4.5" long 0.072" wire spring back in and shot the following strings....

With the spring just shy of coil bind the roundball showed the first shot fastest at 1070 fps.... The 216 gr. RN had the 2nd shot fastest at 960 fps.... Both bullets had 5 shots before falling more than 4% below the peak.... With the 336 gr. FN bullet I got a very nice 7 shot string peaking at 815 fps (496 FPE).... That string averaged 800 fps (477 FPE) with an efficiency of 0.96 FPE/CI.... I then backed the preload down a turn and shot another string with the 216 gr. RN and got 8 shots peaking at 929 fps (414 FPE) and averaging 913 fps (400 FPE) with an efficiency of 0.99 FPE/CI from 3600 psi down to 2400....

To say I'm pleased with this performance is an understatement.... I was hoping this gun would break 500 FPE, I never though it would break 550, nor did I think it would give me 8 shots at 400 FPE on a fill.... Time to just bask in the glow of satisfaction for a while.... I need a break.... and a drink.... Mr. Green

Bob

Mentolio · Veteran Member

Congrats, that is freakin' awesome! Isn't 550 foot lbs entering powder-burning pistol energy? Really impressive work, and thank you for the Marauder info. I will try to make adjustments based on your info ASAP.

rsterne · Moderator

It's about the same power as a .45 ACP with the 216 gr. bullet.... more with the 336 gr....

Bob

Mentolio · Veteran Member

What kind of "effective range" do you expect with the .457 at over 550 foot lbs? I have read that "air power" cannot push a slug as "efficiently" (effectively?) as powder can, but how different can 551 foot lbs at 859 FPS "air power" and 551 foot lbs at 859 FPS from a powder burner be? Once leaving the muzzle, how can "powder power" be any different than air?

rsterne · Moderator

It isn't any different.... once a bullet leaves the muzzle you are only dealing with the aerodynamics and physical properties of the bullet and the air.... The power source no longer matters.... That bullet, starting at 550 FPE will still have 480 FPE (800 fps) remaining at 100 yards....

Bob

AirGunEric · Site Admin

rsterne · Moderator

This will give you an idea of the power.... I taped four clear Cedar 2x4s together and it blew through two of them and imbedded completely in the third....

This was the 336 gr. Lee FN travelling at 792 fps (468 FPE), which is the first shot of my 7 shot string.... Here are the exit holes and bullet in the third 2x4 (edge view)....

The 2x4s were a foot long and taped tightly together at both ends with duct tape, and the 3rd one where the bullet stopped was split from end to end.... They were against a solid backstop to prevent movement....

Bob

Mentolio · Veteran Member

YOWZA...really impressive results!

Bob La Londe · Veteran Member

I don't know if you have worked on your shotgun application in a while, but one of the articles I read a while back about one guys successful air shotgun used a quite uncomfortably long barrel. My guess would be that it simply required longer to accelerate those loads up to the speeds most shotgunners wanted. With a slug settling for slower speed doesn't matter because the energy is huge, but for shotgun applications speed is important because the small shot doesn't carry much energy even at much faster speeds.

rsterne · Moderator

Yes, a longer barrel would be preferable, a 50% increase (from 24" to 36") would increase the potential FPE by roughly that amount, and the velocity by ~ 22% in theory.... and assuming you could get enough valve dwell to take advantage of the longer push....

Bob