Printable View
They're Here!
http://i174.photobucket.com/albums/w...ps2be1edbf.jpg
So many goodies in the last parts order! Decision time soon :highly_amused:
My .177 bolt is finally here... dang! What to do first :crazy:
Big thanks again to Eric- sorry for the ineptness on the new machine. It is now under control.
Great service as always!
Regards,
Doc Sharptail
http://i174.photobucket.com/albums/w...psec75edaa.jpg
Sorry the pic is so big. I wanted the guys to be able to see the extrusion ring in the factory stem seal, at left.
That stem seal saw approx. 80 shots @ 1600 PSI- no higher. It was passing air down through the trigger guard, on the shot cycle, the last time I used it. Referring to my notes on the 78-D, it saw about 3500 shots on CO-2, beforehand...
http://i174.photobucket.com/albums/w...ps4fcca1c5.jpg
Just had to get that .177 bee out of my bonnet- it was really eating at me :icon_mrgreen:
.22 at left, .177 at right.
Shot it on a couple of 12 grams, first, with the new delrin stem aboard. Every thing's bone-stock, except the delrin stem. 10.5 gr. Cr. Ultra Mag
1.) 514.4
2.) 506.3
3.) 511.1
4.) 506.6
5.) 508.5
6.) 507.7
7.) 508.0
8.) 510.1
9.) 504.4
10.) 509.8
Not bad, surprisingly flat.
http://i174.photobucket.com/albums/w...ps3e82cc88.jpg
They group like that at 12 Meters. Tasco 2.5-10X, at 4X.
Time to quit foolin around:
http://i174.photobucket.com/albums/w...ps16532ece.jpg
Factory bulk cap, with the male foster q/r fitting. Eric sells both. I pulled the rubber seal check sytem out of the brass body, as well as the aluminum end plug. I wanted the volume. Used the little brass grommet thingy from the check system under the foster, to keep the foster's check-rod from binding in the angled hole in the brass body.
850 PSI, with the Ultra Mags:
1.) 527.1
2.) 505.2
3.) 480.4
4.) 461.0
5.) 440.7
6.) 410.8
7.) 378.9
8.) 357.7
9.) Error #3 :icon_redface: the pellet passed under the front diffuser, and over the rear diffuser :highly_amused:
Test halted, before I could shoot my eye out.
1400 PSI, same pellet:
1.) 612.1
2.) 578.3
3.) 605.2
4.) 633.5
5.) 619.3
6.) 605.2
7.) 600.2
8.) 586.3
9.) 567.9
10.) 548.8
Yes! :eagerness: A little port restriction, and I'll have what I want! String's a little short, but that can be moderately remedied with a hair more pressure, and the port restrictor...
I am pumped over this. That .177 barrel appears to be lapped and choked, too.
Ran outta steam before I could get to the big rifle. Maybe Mrs. S. will let me have the bedroom for some AR-20-78A surgery, come morning!
Not all male foster's are created equally:
http://i174.photobucket.com/albums/w...ps3fb18a8c.jpg
Regards,
Doc Sharptail
I put a delrin stem into the 20-78 tonight, and still can't get a curve. Velocity isn't bad, upper 780's to start, and the fall off accelerates.
There is much trouble with the gun leaking. I finally got a water line t.p. in there that doesn't leak- after the 4th attempt- then the bolt o-ring started leaking. I was sort of expecting it- it came pretty rough from the factory. Replaced that o-ring, then the bbl shank o-rings started to leak, and now I'm outta the proper size. When it rains here, it's a blizzard. Lord help me keep my temper in check- in all seriousness. :go crazy:
I'm going to have to find a quality set of o-rings- like the solder-seal set we use at work. Those cheap chinese knock-offs from Princess Auto ain't gonna cut it on this rifle...
Did get the new scope on to the gun with the factory sight rail off. I'm pretty pleased over that. Once I get it shooting with some semblance of consistency, I'll bench with the new scope.
http://i174.photobucket.com/albums/w...psf86e6c1c.jpg
Slightly tighter cheek weld with the optical axis 3/16" closer to the bore...
Regards,
Doc Sharptail
First shot fastest and then decreasing velocity indicates too strong a hammer strike for the pressure.... Either reduce the hammer spring preload, or fill to a higher pressure, providing that is safe to do, of course....
Bob
Bob-
@ 2500, I can almost feel the gun "Wanting" to curve- eg: shot:
#3.) 759.3
#4.) 759.6
...and then it hits the skids from there.
I don't think the waterline t.p.'s are gonna be able to handle much over 2500.
Is relieving the t.p. hole in the breech to .25" a good idea? I realize it's going to make assembling the gun harder with the bbl. in the breech, but may make for a much better seal...
Regards,
Doc Sharptail
Drilling out the breech to the transfer port OD will mean that the TP will have to seal against the barrel.... Usually that means that you need a 1/4" OD flat on the barrel for the plastic tubing to seal against.... That makes the O-rings in the breech somewhat redundant, although I wouldn't remove them.... I assume you have a 1/4" OD recess on the top of the valve already?.... Here is the thread on my .25 cal.... I used a short piece of 5/16" Teflon rod with a 3/16" hole for a transfer port.... There is a corresponding recess in the bottom of the breech, and although I don't have a pic of it, I would assume the valve was similar.... and then a 5/16" hole through the main tube.... You are doing the same thing, except with a 1/4" OD....
http://www.canadianairguns.com/showthread.php?208
If you look about the middle of page 2 on that thread, there is a photo of the way I did the .22 cal valve and breech using a 1/4" poly port.... Both have a 1/4" OD pocket with a flat bottom to seal to the transfer port tubing....
Bob
Finally got time to look over this without being in a rush.
I like what you've done to the base of the breech. There shouldn't be much to prevent me from following this route. I didn't realize there was that much metal on the bottom of the breech.
What speed are you turning your mill cutter at? Am I correct in assuming that too low a speed is prone to chatter?
Regards,
Doc Sharptail
Use similar speeds that you would for drilling.... 800-1000 rpm on a 1/4" mill seems to work OK....
Bob