Author Topic: XS60C PCP Repeater project (Read 456088 times))

stalwart · « **Reply #260 on:** April 23, 2014, 02:42:34 AM »

The first experimental .25 bolt. I'm not sure if it's worth it to shape the inside of this nose to aid flow, but I'm tempted to fill the nose halfway with epoxy, and mill a nice curve with a ball end mill (that I don't yet own).

rsterne · « **Reply #261 on:** April 23, 2014, 12:11:29 PM »

Nice, but was it necessary to reduce the diameter of the portion where the barrel port will be that much?.... I assume the larger OD is where the O-ring is?.... If the nose can be larger, so can the flow-through hole, right?....

Bob

stalwart · « **Reply #262 on:** April 23, 2014, 03:51:20 PM »

Yes, the larger portion fits the ring, and begins at the rear of the port. On the .25, that reduction matches the play of the bolt. To go bigger without interference, and get that last bit of speed, will require either a liner, a sleeve or a custom bolt. The nose could be tapered, and the mag's wheel could be chamfered, I suppose.

I'm seeking a good universal (and cost effective) fit, first. Then, we head for the bleeding edge.

I'm always open to ideas here...

rsterne · « **Reply #263 on:** April 23, 2014, 07:04:34 PM »

If the problem is feeding through the mag, possibly just a radius on the front edge to start it?.... As long as you can get a 3/16" hole through the bolt it probably won't matter anyway....

Bob

stalwart · « **Reply #264 on:** April 23, 2014, 09:56:13 PM »

What the heck... let's try it. The tube wasn't cheap, but there's 7' 10 3/4" left of it.

The 1st one slaps home, just the way I like 'em. We'll go bigger until that changes... see where we end up.

stalwart · « **Reply #265 on:** April 24, 2014, 04:46:56 PM »

.190 port, and .197 passage. This is the limit... any bigger passage (smaller bevel) turns it into a hole punch. You can feel it contact the mag's wheel, but it still slaps home.

.25 guys will get both this and a probe. The probes will probably be faster, but the flow thru seat any pellets perfectly. There's just enough room for a slotted receiver port, so I can slot the bolt port to match.

As Bob knows, when I said there was barely room for all this, I wasn't kidding.... but, enough is enough!

StevenG · « **Reply #266 on:** April 24, 2014, 05:43:20 PM »

Will this stuff fit a second gen XS60C or only the first gen?

rsterne · « **Reply #267 on:** April 24, 2014, 05:57:03 PM »

What is your goal for port sizes on the exhaust port and barrel port?.... any throat work?....

Bob

stalwart · « **Reply #268 on:** April 24, 2014, 07:34:31 PM »

Quote from: rsterne on April 24, 2014, 05:57:03 PM

What is your goal for port sizes on the exhaust port and barrel port?.... any throat work?....

Bob

Funny you should mention that... the limit appears to be .190 x .240 for a slot, and I have a crazy idea for throating these (somewhat) cost effectively. More if it works... tooling is the thing right now.

What do you think is the max port we could actually put to use?

Quote from: StevenG on April 24, 2014, 05:43:20 PM

Will this stuff fit a second gen XS60C or only the first gen?

Gen1, Gen2, and Umarex Fusion. Frankly, I'm surprised no one has asked about building a .22 Fusion repeater. It's on my bucket list.

BTW, if anyone wants to put a prebuilt Bobcat, or MRod set up on a credit card... I have orders gelling for PA, McMC, and Little Machine Shop. We could work something out that would happen very quickly. I built spares of everything.

rsterne · « **Reply #269 on:** April 24, 2014, 08:23:23 PM »

You need at least 3/16", more than that is gravy.... On my Hayabusa I managed boresize porting straight through, but that is a 130 FPE in .257 cal.... You can't utilize that much power in .250 cal.... the bullets aren't heavy enough....

Porting is one of those strange things.... open it up lots and you gain power but lose shots, and lower the pressure of the peak velocity.... Adding hammer spring then increases the power even more as you move the peak to higher pressure, but of course even fewer shots.... It's all a balance....

Bob

stalwart · « **Reply #270 on:** April 25, 2014, 08:04:38 AM »

Is there any reason a flow thru bolt, with replaceable noses with graduated ports, couldn't be used to tune?

StevenG · « **Reply #271 on:** April 25, 2014, 10:05:02 AM »

.22 Fusion? We might be able to work something out. I want to go the other direction. Take the barrel and LDC setup from a fusion and put it on an XS60C pcp. Mostly for the fact that making it a PCP is done and I like the wood stock better.

How much is a bobcat? If you don't want to answer here just email me, or pm or I can email you.

stalwart · « **Reply #272 on:** April 25, 2014, 10:18:54 AM »

The Bobcats are .22 only, as the PRod mags are only available in .22.

I have some Mrod set ups that are cut and coated, and a few cut and still raw (you smooth and paint). You can choose to have a fixed or removable barrel. Turnaround is pretty quick now, thanks to the early buyers. Email me if that would work for you.

stalwart · « **Reply #273 on:** April 25, 2014, 10:02:05 PM »

It occurred to me that an alternative to graduated noses for the bolts, for tuning, a threaded nose with the largest possible opening could be shimmed (or lock-nutted) to "misalignment" with the exhaust port in accurate amounts to restrict the flow to whatever is best.

Is this a dumb idea?

avator · « **Reply #274 on:** April 25, 2014, 10:09:20 PM »

Have you honestly ever had a dumb idea?

rsterne · « **Reply #275 on:** April 25, 2014, 10:28:55 PM »

Similar idea to my probeless retracting bolt with a screw adjuster so it can't be fully retracted.... I was able to dial the power down to about 5 FPE from over 100.... No reason that rotating the nose of the bolt to gradually choke off the barrel port can't work the same way....

I don't suppose you could just vary the angle of rotation of the entire bolt by changing how far the handle drops down in the slot?.... Maybe not enough height to be 100% effective and still lock reliably?....

Bob

stalwart · « **Reply #276 on:** April 25, 2014, 11:17:13 PM »

Quote from: avator on April 25, 2014, 10:09:20 PM

Have you honestly ever had a dumb idea?

I would say no... but there is a divorce lawyer, an easy dozen ER docs, and countless bystanders who would vehemently disagree with me. Putt on over to my shop sometime, Bill... it's becoming a museum of huh??

Quote from: rsterne on April 25, 2014, 10:28:55 PM

Similar idea to my probeless retracting bolt with a screw adjuster so it can't be fully retracted.... I was able to dial the power down to about 5 FPE from over 100.... No reason that rotating the nose of the bolt to gradually choke off the barrel port can't work the same way....

I don't suppose you could just vary the angle of rotation of the entire bolt by changing how far the handle drops down in the slot?.... Maybe not enough height to be 100% effective and still lock reliably?....

Bob

Just checked. You guessed it... takes too much of the throw.

When I grow up, I want to try a retractable bolt like yours. Elegant.

stalwart · « **Reply #277 on:** April 25, 2014, 11:23:31 PM »

Then when we start to vary the port location there will be room for a bolt with a thumbwheel (and detents) to allow quick, easy adjustments. We could stagger a couple detents for fine tuning, or just make it a 4 speed.

rsterne · « **Reply #278 on:** April 25, 2014, 11:31:04 PM »

How about a 2-speed.... Plinking and WFO.... An insert to restrict the flow for plinking....

Bob

stalwart · « **Reply #279 on:** April 25, 2014, 11:36:06 PM »

A .190 port goes from open to fully closed in roughly 90*. Lots of room for graduating. A fine thread wouldn't allow much extension in 90... not enough to worry about.

What's the max port for a .177? Maybe a 3 speed?

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XS60C PCP Repeater project

Author Topic: XS60C PCP Repeater project (Read 456088 times))