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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Wed Mar 18, 2015 11:44 am 
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Location: Alberta Canada
Well congrats there Bob, :drinkers: your boolit design does show quite the ballistic accuracy. 205yrds for an airgun is looooong range shooting fir sure. :mrgreen:

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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Wed Mar 18, 2015 12:50 pm 
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Location: Central West River Nova Scotia
Congratulations Bob. Great bullet design. The shooter in that video is no slouch either.

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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Wed Mar 18, 2015 4:42 pm 
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joe hickey wrote:
Congratulations Bob. Great bullet design. The shooter in that video is no slouch either.

I agree great shooting.... 8)
I must say that must be putting out a lot of air to get that pellet out 205yrds...hens the straight hookup to the tanks..
first time I've seen some significant recoil on a pcp ....

congrats on the great design Bob :wink:

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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Wed Mar 18, 2015 5:56 pm 
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Location: Coalmont BC
Actually, he can get 2 shots at that velocity with a slightly slower 3rd shot, without the tether.... and if you notice, the tube is about the size of one on a QB or Disco (might be a bit bigger OD).... There is no reason that properly tuned you cannot achieve about 1.0 FPE/CI efficiency, so 200 FPE would use about 200 CI per shot, or 600 CI for three shots.... The gun is a Corsair, and he is tethering at 3500-3600 psi, and likely fills to a couple hundred more, so 3 shots should mean a pressure drop of ~ 1100 psi on a Disco sized tube (8 CI).... from say, 3800 to 2700 psi.... I don't know the exact details, but that would be my best guess....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
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Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Wed Mar 18, 2015 9:14 pm 
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The apple at 205 yards is very impressive. From an aim point of view, I make that roughly equivalent to a 5mm target at 10 yards (just a very rough estimate), but then add in all the moving air between muzzle and fruit. :shock:


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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Wed Mar 18, 2015 9:32 pm 
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Yep, and he was holding 1/2 MilDot off to allow for wind (and 4 Dots high)....

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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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Thu Apr 09, 2015 2:13 pm 
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Location: Coalmont BC
I finally, after a month, got the Metric O-ring I needed to seal the bolt into the thimble.... Last week I had the opportunity to cast some of my new 7mm Bob's Boattails, and that gave me the samples I needed to use the chambering reamer I got from Sean Pero to chamber the barrel.... Here are the results....

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In the photo above, you can see the system that retains the barrel into the breech, a threaded sleeve that presses against a collar threaded onto the barrel, the O-ring that seals the barrel to the thimble, the thimble itself, and the chambering reamer.... I ran the reamer in until when the bullet was properly seated the base was flush with the back of the barrel, which sits against a shoulder in the thimble just ahead of the transfer port.... The bolt pushes it home to that location.... Below is a closeup of the thimble, showing the internal 7.5mm x 1.5mm x 10.5 mm O-ring that seals on the OD of the bolt, and a bullet which has been chambered....

Image

You will notice that the rifling marks on the front driving band are approaching full depth, but the middle band is just entering the tapered leade.... There are no rifling marks on the rear band, it sits in the parallel section of the chamber, which is about 0.001" over the groove diameter of the barrel.... You can feel resistance for about the last 1/8" of bolt travel, but it is not hard to chamber, you are just aware of the bullet engaging the rifling, which I like....

My replacement ShoeBox Compressor (a Freedom 8 ) has been shipped, and with this work completed, I should be ready to test the 7mm version of the Hayabusa once I get it and top up my tanks....

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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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Tue Apr 14, 2015 5:28 pm 
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Location: Coalmont BC
I assembled the 7mm Hayabusa today and fired it for the first time.... I tethered it to a regulator at 2900 psi and tested the hammer spring preload to determine if I have enough hammer strike to max the gun out at that pressure, and I do....

Image

The velocity falls off slightly at the top end, not sure why, but I have seen it before.... It doesn't matter, as the gun would be an Air Hog at anything over 5 turns out from coil bind anyway.... The maximum FPE at 2900 psi was 193 FPE, which is right about where it should be using the 96.5 gr. Bob's Boattails, so I'm very pleased.... My new ShoeBox Compressor is at the Post Office and I'll be picking it up tomorrow, so within a few days I should have some shot strings to share with you....

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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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Wed Apr 15, 2015 3:57 am 
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Location: Alberta Canada
Sounds fairly sound there Bob. Await more of your testing. :D

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 Post subject: Re: 7mm Hayabusa Build
PostPosted: Fri May 08, 2015 12:02 am 
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Location: Coalmont BC
Got to send a few rounds downrange today.... 1" at 50 yards and just over 2" at 100 yards seemed typical.... I didn't get a chance to index the barrel, play with the tension, or the air stripper yet....

Bob

_________________
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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