My Hayabusa PCP - The Experiment Continues

[SeanMP]

I initially drilled the .250" counterbore in the .224 barrel with a stub drill.... turned out fine, nicely centered, (I didn't go very deep) but the (118*?) shoulder was too steep and with the tightness of the chamber it was actually shaving the bullet when I pushed it in.... Soooooooo, I changed to using a center drill with a 60* taper, I had one that was 1/4" OD.... I drilled in until the taper stopped about 0.030" from the barrel port, and then polished the .250" section and the taper with 400 grit, paying particular attention to where the taper met the .224 chamber to smooth and round the edge so there was nothing to shave the bullet.... I think you might want to polish the chamber a bit more if your barrel is as tight as mine.... When I push a bullet in, it polishes the driving bands just going through the section aft of the barrel port, let alone in front of it.... It's pretty difficult to load, actually, requiring quite a lot of force to seat the bullet, especially by the time you get the base flush with the front of the barrel port.... My bolt probe is actually leaving a dent in the base of the bullet, that's how tight it is....

Bob

Hmmm That's bloody odd. I actually got the chamber to the point where the bullet would drop in and settle just before it's final position. Spent hours lapping the two barrels to get them to the point shown in the other thread..........I wonder if the port work displaced at bit of metal??
But yes both barrels are gnat's arse tight.



I wouldn't hesitate to incorporate the 60* taper on the reamer. The LW QB's are done this way because of the multiple steps on the factory bolts.

I would say that 99% of everything you would ever want to do can be handled by the square and hex block. Make a sine plate for everything in between.

[rsterne]

A couple of days ago I started working on two hammers, but set them aside until today when I got a chance to drill the main tube for the valve and rear cap, and slot it for the trigger sear and cocking handle.... Once that was done I was able to lay out the location for the cocking handle on the hammers, drill and tap them, and face them to final length.... Here is the tube and hammers.... The front of the hammers is at the bottom of the photo, near the tube....



I was VERY pleased with the accuracy achieved on the valve port and mounting screws and the matching holes in the main tube.... They lined up perfectly, the advantage of the 5C collet holder.... I laid out the cocking slot from the matching slot in the .30/.35 cal breech and milled it 1/4" wide.... It is long enough to allow the hammer to hit the back of the valve (at 1/4" lift) and pull back far enough to go about 1/16" past the trigger sear for cocking.... I made two hammers, the one on the right is for the .30/.35 cal and has a travel of 1.50" and weighs 113 gr. with handle.... The one on the left is for the .22/.25 cal, has a travel of 1.25", and a weight of 94 gr. with handle.... The handle is made from a 2" long 1/4"-28 NF bolt with the head rounded.... I still have to make the spring guides, which will thread into the hammer and move with it, adding a bit more weight.... The trigger sear engages on the crosswise ledge (cut at 22* to match the sear) just behind the large flat, ie the hammer sticks out ahead of the sear when cocked.... The cocking location is 1/4" further back on the .22/.25 hammer, hence the reduced travel.... The larger hammer has a 1/4" wide slot 0.10" deep milled into the bottom to clear the sear during the shot.... The front part of the slot tapers to meet the bottom of the hammer at a 30* angle, and this allows the hammer to draw back over the MRod trigger sear during cocking.... The taper on the waist of the .22/.25 hammer accomplishes the same thing.... Here are photos showing the breech / hammer / trigger assembly....



The above photo shows the hammer in the cocked position.... The cocking handle just clears the front of the shaft of the bolt handle.... and is just inboard of the knob....



In the lower photo, the hammer is shown in the uncocked position (ie sitting against the valve stem).... You can see there is 1/4" of travel remaining to allow for the valve lift.... Both the bolt handle and the cocking handle clear the MRod stock I use just fine.... They seem to feel nice to operate, I'll know better once I put in a hammer spring.... I still have to cut the main tube to length and drill the front to mount the tank block, and then make the holder for the valve spring.... plus make the spring guides, a new, longer RVA, and then I should be ready for initial assembly and leak testing.... I hope to have my .257 barrel any day, I may wait until that is machined to fit before doing any assembly....

One other note.... I got some of the new .30 cal FX 46.3 gr. Pellets (JSB Exacts) in the mail today from AirGunSource.... I slid one through the LW barrel I have, and it was a disappointingly loose fit.... The head of the pellet had virtually no rifling marks on it, although the skirt, of course, did.... I would be surprised if they are accurate.... If they won't work in an LW barrel, JSB may have made a big mistake making a pellet that won't work in the standard size 0.308 groove 0.300 land barrels used by LW and DAQ.... Time will tell....

Bob

[rsterne]

Sean: RE polishing the barrel with Bore Brite (red).... I pulled the barrel and did the chamber area until the felt pucks weren't quite so tight in the bore (maybe 20 strokes).... I then assembled the rod full length, added fresh paste, and did 20 strokes full length, not quite out the muzzle, then reloaded it and did 30 more.... I then removed a section of rod, reloaded with paste and did 15 more, took off another section, reloaded and did another 15.... So, the full barrel got 50 strokes, and the breech end about 100.... I still have yet to clean it and reassemble.... Any suggestions RE the method I used?.... How often should I do this?.... I probably shot about 100-150 rounds already (1 bag)....

Bob

[rsterne]

I'm actually not crazy about the stock it's from a Benjamin Marauder, cut down.... it's VERY heavy.... This gun duplicates the ballistics of a .22LR target velocity load, and the bullets are made by RWS, they appear to be a copy of their R-50 (?) target bullet, so I assume they are swaged.... This gun was built because of the success of these bullets in Holland (where Sean ordered the bullets) where they shoot outdoor bench rest at 100m (110 yd.).... I have seen published 5-shot groups as small as 12mm (just under 1/2") at that range.... They use .224 Hornet barrels with a 1 in 14" twist to stablize them, and I bought two of them (1/2" OD liners from TJ's) and had them shipped to Sean to work his magic on them.... He did a beautiful job installing the Carbon Fibre stiffener tube, and machining the ports and muzzle for the Hatsan stripper....

Bob