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PostPosted: Wed Jun 14, 2017 6:37 pm 
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Location: Coalmont BC
I have had a few guys ask about the idea of making a 6mm PCP, and it has aroused my curiousity, so I did some research.... I knew that LW made barrels in various twists (8, 9, 10, & 14") but I had never seen one in TJ's list, so I contacted Mike and it turns out that he has a mandrel to make them with 0.237" lands and 0.243" grooves, with a 10" twist.... They can be made in 1/2" and 9/16" OD, and he has a 9/16" in stock.... Then I started looking around for moulds to cast bullets, and I found these....

The first one is a Lyman 225107, interpolated out to a larger diameter by NOE.... It says it weighs 46 gr., but they currently have no stock in the store....

Image

The second one is a scaled down Lyman 257420, done at the request of Jack Bowman (Scandalous Airguns).... Aresenal have this mould available to order, listed at 60 gr....

Image

The third one is listed as a 73 gr., and is also out of stock at NOE....

Image

I scaled down my .257 cal 78 gr. BBT, and have sent the drawing to Al to add to the AirGun Discussion Section on the NOE Forum.... It looks like this....

Image

All of these should work just fine in Mike's 10" twist barrel.... According to my "lofty goal" PCP spreadsheet, with a 24" barrel at 3000 psi, and bore-sized porting, it should be possible to hit about 139 FPE.... In reality, that means you could probably do that with a 28" barrel, with the gun tuned to the max.... It should put the mid 900's within reach with my 65 gr. BBT with a 24-28" barrel at 3000 psi.... In other words, without going to ridiculous barrel lengths or pressures, any of the above bullets should be usable.... with the 46 gr. only requiring maybe 2200 psi or so....

Anyways, I thought I would throw this idea out there for everyone to chew on.... If there is enough interest, I'm sure we could get Al to put the BBT in a Group Buy, and the others into Inventory Runs.... I already started a thread at NOE to express your interest in the 46 gr. in hopes of getting an Inventory Run started....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Jun 14, 2017 8:23 pm 
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Very interesting!
But not very clear about the need of 6mm. Why not just make a solid slugs for a .25 ?

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Rifles: Horhe Jager .22 (LW barrel, 4500psi tube), Mp-512, Mp-60
Pistols: 46M, Zoraki HP-01 ultra, 2240, baikal drozd.


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PostPosted: Wed Jun 14, 2017 10:06 pm 
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Location: Coalmont BC
Just to be different.... There are already quite a few good bullets for .257 cal, the top choice, for most shooters, is the Lyman 257420, which casts at about 73 gr. in pure lead.... It works perfectly in the commonly available 25/20 barrels, with their 14" twist.... probably the most popular choice for long range airgunning at the present time.... The .224 cal would be a good choice, if you could easily get barrels with a fast enough twist, but the best combination easily available presently is a 37-41 gr. bullet in a 14" twist.... To build a really top notch .224 shooter, capable of handing 55-60 gr. bullets, would need about a 10" twist rate.... It is the availability of the 10" twist 6mm barrel, and bullets in the 60-75 gr. range to fit it, that makes this idea have merit, IMO....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Jun 15, 2017 12:17 am 
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Location: Winnipeg, Canada
Hard to read through this without thinking of the old P.P.C. 6mm powder cartridge :mrgreen:
Acronym reversal. Suppose someone will come up with a name for that...

-D.S.

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PostPosted: Fri Jun 16, 2017 6:52 pm 
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Location: Coalmont BC
I spent the day today drawing out a general arrangement of what I might build for a 6mm this winter.... Here is what I came up with so far.... I used my typical reversed tank block to keep the weight of the bottle centered.... and I may use a 1.25" OD x 0.095 wall 2024-T3 tube to keep the weight down....

Image

I have already ordered a tank from AliExpress.... its a 500 cc Carbon Bottle rated at 300 bar.... the plan is to have an adjustable regulator built into the tank block, feeding a 150 cc plenum at about 200 bar.... I would like to use 3mm thick carbon fibre sleeve on the 14mm OD barrel, so the OD will be 20mm (over 3/4").... which should make it VERY stiff.... The plan is to use a PRod trigger group and an AR style stock in line with the main tube.... That will put the adjuster for the SSG inside the buffer tube.... A Cothran valve will handle the air delivery, with it's 0.257"ports perfect for the job.... If I can arrange it, I will get two 10" twist barrels, one in 6mm and the other in .257 cal., both 28" long.... The goal is to drive my 2.5 cal long BBTs at 950 fps, meaning about 130 FPE in 6mm and 156 FPE in .257....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Jun 17, 2017 1:50 am 
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Location: Edmonton,AB.
Very interesting on the 73gr. Just might wonder how it would work for reduced loads in my Tikka T3.

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PostPosted: Sat Jun 17, 2017 1:56 pm 
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Location: P.G. B.C.
Noe is making .172" moulds now.

http://noebulletmolds.com/NV/index.php? ... j9hr3l0gm7

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Daryl


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PostPosted: Mon Jun 26, 2017 10:41 am 
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The 46 gr. and 75 gr. bullets above have gone to Inventory Run at NOE.... 5 signups and they will be run again.... GC or PB, and a Lyman HP pin available in 1 cavity....

http://noebulletmolds.com/smf/index.php ... 147.0.html (46 gr.)

http://noebulletmolds.com/smf/index.php ... 146.0.html (75 gr.)

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Profile  
 
PostPosted: Thu Jul 13, 2017 4:19 pm 
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Location: Coalmont BC
I ordered a couple of 1M pieces of Carbon Fibre tubing from China through eBay.... Excellent service, less than 2 weeks to receive them.... I can't believe how stiff this tubing is....

Image

It is 20mm OD and 14mm ID, so that means the wall thickness is nearly 1/8".... It is about the same stiffness as steel tubing at a fraction of the weight, and will make the barrel incredibly stiff.... I was talking to Mike at TJ's, and he thinks he can hammer the barrel down to 14mm to fit inside the tubing, I am sending him the 6" long piece in the photo as a sample....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Profile  
 
PostPosted: Thu Jul 13, 2017 8:31 pm 
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Posts: 2585
Location: Winnipeg, Canada
Interesting! I was just thinking about bbl. sleeves last night, by way of coincidence.

It looks like you've got plenty of hammer stroke in the above drawing. How long will that stroke be, if you know yet?
I'll be keeping an eye on this build...

Cool new avatar! Darth Cookie! :mrgreen: :mrgreen:

-D.S.

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PostPosted: Thu Jul 13, 2017 9:07 pm 
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Location: Coalmont BC
IIRC, the hammer stroke is about 7/8".... back of tube is like an MRod....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Aug 23, 2017 5:15 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
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Location: Coalmont BC
I got my barrels from TJs.... Mike did a fantastic job of hammer-forging them to fit the sample piece of 14 mm ID Carbon Fibre Tubing I sent him.... Both the 6mm and .257 barrels I ordered are a perfect slide fit inside the CF sleeve.... They are both a 10" twist, and the blanks are 29" long....

Image

I am slowly collecting the parts I need for this winter's projects, this was a big step along that path....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Aug 23, 2017 5:15 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8973
Location: Coalmont BC
Here is the stock I ordered from DHGate, along with the buffer tube (Mil-Spec).... The fit is perfect, with about 3" adjustment in the LoP, and almost an inch of vertical adjustment for the comb height....

Image

The stock / buffer tube assembly weighs just 1 lb. 5 oz.... and should look great with the PRod trigger group I plan on using on this build....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Profile  
 
PostPosted: Thu Nov 30, 2017 6:00 pm 
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Location: Coalmont BC
I got all my material for this build a couple of days ago, and decided the first thing to do was to turn down the back of one of the tubes to fit the stock.... I got a piece of 1.25" OD x 0.120" wall 2024-T3 tubing from Lloyd Sikes, which I plan to use for the .257 version, as I am going to build two guns at the same time.... The 6mm will be a regulated gun, using the 500 cc 4500 psi CF tank I got earlier.... and the .257 version will be an unregulated version having a 300 ccc reservoir that can be filled to 4500 psi.... I hope to tether it at about 3800 psi.... The straight tube, unregulated .257 version will look something like this....

Image

The tube is long enough, and a thick enough wall, that I was able to turn down the back 7" to 1.15" OD to fit inside an AR style stock.... It will be used directly over the tube, no separate buffer tube or threaded attachment required.... I used a steady rest on the lathe to support it (since it won't fit through my headstock) and turned down the butt end.... Here is a photo of the stock slid into place.... There is still 0.070" of wall remaining, so plenty of strength.... Note you can't do this with a 1.25" OD x 0.095" wall tube, because the remaining wall would be too thin.... so the 6mm version which uses that tube will have to have a conventional threaded adapter to hold the buffer tube assembly....

Image

With the tube slid in until the back of it hits inside the back of the stock, there is a bit under 1/4" of smaller OD tube showing, and the trigger will be mounted so that the LoP can be adjusted from 12 to 16".... At a 14" LoP it will look about like in the photo.... I have to mount a piece of aluminum barstock on the bottom of the tube to prevent rotation of the stock, and provide holes for the fore-and-aft adjustment feature.... The stock can be slid right off the back for access to the preload and gap adjustment of the SSG using a socket and/or screwdriver.... I will be using Prod trigger groups on both builds, with a taller sear supplied by Lloyd, which is intended for the 0.095" tube wall.... Since this tube is thicker, I will be milling a flat on the bottom of the tube and the top of the trigger group to get the correct sear engagement....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Fri Dec 01, 2017 8:26 am 
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Location: Caronport, Saskatchewan
Great projects, Bob! Looks great! Looking forward to your results.

Sent from my HTC One M9 using Tapatalk

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