Author Topic: Question for the Mad Scientists here (Read 10522 times))

dyotat100 · « **Reply #60 on:** December 28, 2016, 08:48:17 PM »

Is that 357? That is way low

MJP · « **Reply #61 on:** December 29, 2016, 04:40:12 AM »

Oh man, how come they effed up the design like this, I thought it was another copy / version of Robert Lane design where the case mouth is the effective port.
That's just plain poor and will never give good performance IMO.
The Lane cartridge has small chamber that the firing pin opens to back off the piston to open the cartridge valve.
Marko
Edit: picture.

Gippeto · « **Reply #62 on:** December 29, 2016, 09:17:40 AM »

Agreed. Lane cartridge is more what I was expecting when I heard it was a dump valve cartridge. Turns out it's essentially the same valve design as Crosman uses in the 1077 and 357 co2 guns....and not a blow open or dump valve at all.

Lane cartridge is very similar to the Saxby cartridge.

https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US4531458.pdf

Al

Privateer · « **Reply #63 on:** December 29, 2016, 11:59:01 AM »

Pulled the barrel off to inspect it.
I found a lot of lead packed near the breech end so I suspect that some bullets are getting shaved in that area.
That build up would allow a gap that could be leaking air on firing.
I'll get it all cleaned out and shoot again with a bit smaller bullet to see if that helps.

rsterne · « **Reply #64 on:** December 29, 2016, 01:08:21 PM »

So the Lane (and Saxby) cartridges have a small pressure chamber at the back that holds the main valve stem forward.... Firing pin vents that and dumps the air and the main stem is driven back by the air pressure to open the valve at the front?.... Sensible design....

Bob

Privateer · « **Reply #65 on:** December 29, 2016, 01:41:55 PM »

Same cart filled to 4000 PSI with a 98 grn smaller diameter bullet.
647 FPS

Gonna fill again to 4000 PSI and try a JSB .35 81 grn
Rick used those for his reviews.

rsterne · « **Reply #66 on:** December 29, 2016, 03:24:11 PM »

Five years ago I was doing 116 FPE with 78 gr. EunJins with a modded Disco on 2400 psi....

Bob

MJP · « **Reply #67 on:** December 29, 2016, 04:50:41 PM »

Yes Bob, I like the Lane design, pretty much same as the old brocok BACS system. But this Mac air cartridge is pretty much the stupidest design of any cartridges I have seen. And the lack of power pretty much proves it.
I would use the base the cylinder and coupling on this and make new innards for it.
The transfer port in the stem is too long and too small, takes forever to flow the amount of air in the cylinder.

Marko

rsterne · « **Reply #68 on:** December 29, 2016, 07:09:07 PM »

I think the ID is the problem way more than the length (barrels are much longer).... but we agree that the passage inside the transfer tube is way too restrictive....

Bob

MJP · « **Reply #69 on:** December 29, 2016, 08:04:14 PM »

The length is dead space that eats volume from the cylinder and needs to be filled during a shot. Any port volume between the cylinder and projectile is bad when you have so little volume to begin with.

rsterne · « **Reply #70 on:** December 29, 2016, 08:23:51 PM »

True Dat!....

Bob

Privateer · « **Reply #71 on:** December 30, 2016, 07:57:46 PM »

Maybe a sabot of some kind in the tube?
I have some 1/4" Peek 1000 on the way for other projects so may give it a try.
Don't drill the tube out.
That was a total fail.

It didn't collapse but it did bend and jammed.

rsterne · « **Reply #72 on:** December 30, 2016, 11:22:52 PM »

Where did it bend and how?.... How big did you go?....

Bob

MJP · « **Reply #73 on:** December 31, 2016, 03:43:32 AM »

Did you drill it in a lathe?
Would be fun to play with one and see how much improvement can be had with different internals.
Maybe we'll see my version of the Mac rifle in the future...

Marko

Privateer · « **Reply #74 on:** December 31, 2016, 02:16:13 PM »

.257 barrel is back on it and I'll try some of KnifeMakers bullets in 70 grn 1st.
4000 PSI same cart.
640.3 FPS

rsterne · « **Reply #75 on:** December 31, 2016, 03:35:25 PM »

Really kinda sad, huh?....

One thing I'm learning from this, however.... is how to use smaller transfer ports in Lloyd's program to predict FPE levels.... Still working on it, but every piece of data helps....

What are your barrel lengths?....

Bob

Privateer · « **Reply #76 on:** December 31, 2016, 04:37:28 PM »

Quote from: rsterne on December 31, 2016, 03:35:25 PM

Really kinda sad, huh?....

One thing I'm learning from this, however.... is how to use smaller transfer ports in Lloyd's program to predict FPE levels.... Still working on it, but every piece of data helps....

What are your barrel lengths?....

Bob

Sad in that the Stated specs don't match up. But that's the norm now days.
Never expected it to being Honest.
I can say it's pretty accurate at 50 yrds no matter what round I'm shooting so far.

From their web sight...

.257
The barrel is precision hammer-forged moly steel and is 26" long. It is rifled (6 grooves) with a 1:14 RH twist with a bore of .250" and grooves of .257"

.357
The barrel is precision match grade molychrome steel and is 28" long. It is button rifled (6 grooves) with a 1:18 RH twist with a bore of .351" and grooves of .356"

I can tell you the .357 bullet samples I have are .358 or so.
KnifeMaker sent me a sample of .257's and the ones I've checked so far are .257 or so.

I got some 126 grn .357 Bob's Boattails here.

Privateer · « **Reply #77 on:** December 31, 2016, 05:31:55 PM »

sorry. the .257 is about 80 grn.

rsterne · « **Reply #78 on:** December 31, 2016, 05:40:56 PM »

That brings me within 2 fps of your 640 with that bullet using Lloyd's spreadsheet.... more data needed to confirm, of course....

Bob

Privateer · « **Reply #79 on:** January 01, 2017, 01:48:03 PM »

I picked up a digital scale to weight the bullets. Would a more exact weight help?
I can also shoot the different bullets at different pressures.

2 FPS is darned close!!

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Question for the Mad Scientists here

Author Topic: Question for the Mad Scientists here (Read 10522 times))