My Hayabusa PCP - The Experiment Continues

[rsterne]

Actually, I load the bullet first and leave the gun uncocked until ready to fire, so I'm cocking it with the bolt closed.... I think I have enough depth in the breech under the bolt to hide the toggle, and I can always use a hairpin spring.... On the .22/.25 cal breech I could close the bolt with the hammer cocked, on the .30/.35 cal breech, which has 1.5" hammer travel, you can't rotate the bolt down to the locked position with it cocked.... At this point it's just a thought, anyway....

If the hammer toggle/bounce preventer in the Hatsan was really improving the efficiency compared too, say, a modded Disco at the same power level and pressures.... you would expect that the Hatsan would have much greater efficiency numbers.... It doesn't.... I am still of the opinion that a properly tuned PCP shouldn't need a hammer debouncer.... They seem to be useful if you are running too much hammer strike for the pressure.... eg. on the latter part of an unregulated shot string, or in a regulated gun running at maximum velocity for the pressure....

Bob

[SeanMP]

Oh boy oh boy oh boy......this is the part I've been waiting for.




Thanks for the kind words Bob....even if I made ya wait for months

Bad Sean...

[rsterne]

awwwwwwwww.... you just had a little Princess get in your way.... *chuckle*.... Now that's shes working as an Apprentice you'll be back up to speed in no time....

I meant every word I said about the quality of your work.... I'm embarrased, by comparison....

Bob

[rsterne]

Well mine's so tight I think I'll polish it a bit so that the bullet will slide in at least half way across the barrel port without any significant resistance.... I really have to lean on the bolt handle to seat the bullet past the port....

Might be a bit tricky mounting a sine plate in the vice on my milling attachment.... it's only 1" deep and opens to just over 2.3".... I wouldnt know how to use one anyway.... Besides, I can often turn the vise vertically and then swivel it for oddball angles.... like milling the slot for the bolt in a breech....

Bob

[rsterne]

I got the last few internal parts done today, assembled the reservoir, and it is currently sitting with 3000 psi of air in it and appears not to leak.... The plenum is shorter than the regulated version by the length of the regulator, so it is now 100 cc, making the air reservoir includng the 22CI tank a total of 460 cc.... Here are photos of the sub-assembly....





I still have to make the spring guides for the hammers, do a bit of work on the RVA, and make a transfer port from a piece of 3/8" Teflon rod, but otherwise it's very close to being able to be fired.... The first tests will be with the .224 barrel which is designed to shoot the 41.5 gr RWS bullets we purchased from Holland....

Bob

[rsterne]

I took SeanMP's advice and polished the bore with Bore Brite (red) today, and true to what he said, I picked up a few fps and the groups tightened up.... I tried the RVA at 2.5 turns out as well, with a 3000 psi fill, and got just about what I expected.... Although the first shot wasn't the fastest, the peak of the bell-curve was only at shot 5, and the efficiency was just under 1.0 FPE/CI.... so that's a little too hot.... I retested at 3 and 3.5 turns out, and the results of these three tunes are below.... All started at 3000 psi except the 3.5 turns out, which required only a 2800 psi fill....



The best tune is 3 turns out, which allows me to use a full 3000 psi fill and get 20 shots within a 4% ES and 13 within 2%, using an average of 44 psi per shot.... There are 16 shots within 25 fps between 1004 and 1029 fps, so that makes a pretty decent sweet spot using a 2900 psi fill and a 2200 psi refill, which works out to 1.13 FPE/CI at an average of 95 FPE.... If I was running the gun on a tether, I would fill to about 2700 psi, shoot a 5 shot group, and refill at 2500.... or use a regulator set for 2600.... That would give me 5 shots within about a 5 fps ES (0.5%) by running right at the top of the bell-curve....

When I shot the last string after I reset the RVA to 3 turns out after the days testing, I shot four 5-shot groups.... They were all just ragged holes, but one was exceptional.... It is the first time I have ever had a gun pass the "Feinwerkbau Test"....



I realize this was only at 20', but it's still the only time I could put a bullet in the hole made by a 5 shot group and have it remain in the single sheet of target paper.... The testing and tuning on this gun is now complete until I can get it outside to stretch its legs this summer.... The .257 cal barrel and my new bullet molds should be here this week, so the plan is to work on that next....

Bob

[rsterne]

It's finally time to start making some chips.... I spent a couple of days designing the breech and came up with a design that will work for all four barrels from .224 to .9mm.... The .224 and .257 will share a breech with a 1/4" loading tray and the .308 and 9mm will share a second one with a 3/8" loading tray.... The design for the tank block was done a year ago, so it was just a matter of printing it off, double checking it and making a few detail changes and notes, and then machining it.... Yeah, well it sounds a lot easier than it was.... It took me the entire day just to make the tank block, and I had to finish it after dinner.... Here it is....





The tank mount is the threaded portion of a 5/8"-18 NF Grade 8 bolt drilled out to 3/8".... The tank (sans regulator) seals directly to the rear face of the block with an O-ring.... The stub that goes into the 1" OD x 0.065" CrMoly main tube is located by three high tensile 10-32 low profile SHCSs and sealed by two O-rings.... The tank and tube nearly touch.... The larger hole in the stub is the air passage (9/32") which is larger than any of the ports I'll be using so basically all of the 475 cc of air is available to keep the pressure up at the valve seat during a shot.... The 1/4-20 NC tapped hole above it is for a long threaded rod that carries the valve spring.... On the left side of the block is a 3000 psi gauge (upper hole) and a male Foster fitting (lower hole) and on the right side is a 5K burst disc.... The vertical transfer hole is plugged on top with a flush 1/8" pipe plug.... The recess on the top front with the two 6-32 holes is for mounting a barrel band, and on the bottom is a 3-slot Picatinny rail....

Hopefully tomorrow I'll get to start on the breeches....

Bob

[Doc Sharptail]

Those bullets look suspiciously like the old 50 gr. Lyman for the Hornet. Might be worth it to keep an eye on gunborker and flea pay for an original mould. It'd be tons cheeper than having cast boolits shipped from Holland.

I had some Polar Biathlon's by Lapua that had a 41.5 gr bullet at 1075-1100 fps depending on temperature. They were extremely accurate, and expensive. If you can replicate that at even 1050 fps, good things are gonna happen- especially for small game hunting. I hope everything goes your way!

Regards,

Doc Sharptail

[SeanMP]

Absolutely brilliant. I like your work around on the probe. Are those made of O2? I have put some thought into probes in the past but have not had the time to really work it through. I would like to see a probe that retracts back into the body of the bolt. That way I could get a much larger bearing area on the soft lead and not have flow values fall into the toilet.

Loverly job threading the muzzle!

You have now jumped so far ahead of me its not funny. Production work has taken priority on the machines again.

[SeanMP]

This is getting exciting....almost there!

That is a HUGE amount of air. You wont have any problems with flow I dont think.

Sorry I came up bust with all the suppliers I use for gauges on the ship. None of them make a 1" gauge.

Thanks for the information. Now that I have a couple of springs in hand that will definitely work (25lb/in and 28lb/in) I can gain some mass back on the hammer. I drilled the pocket to accommodate every spring possibility. And I can get some of the waist area back as well. I should be able to come up to the 100gr ballpark. Of course this is just for the 308 build. In hindsight I should have moved the valve forward a 1/4"