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Author Topic: .257 cal Monocoque PCP  (Read 54057 times))

Offline Gertrude

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Re: .257 cal Monotube PCP
« Reply #20 on: November 13, 2015, 01:20:13 AM »
As usual, Very Impressive Bob !

so is it safe to say, this is not going to be your new "Grouse gun" ? ? ? LOL!
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Offline rsterne

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Re: .257 cal Monotube PCP
« Reply #21 on: November 13, 2015, 01:32:03 AM »
Maybe for taking their head off at 200 yards?.... It they'll keep it still instead of bobbing all over, that is.... *LOL*....

I hope I haven't bitten off more than I can chew, with this one....  ::)

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline sixshootertexan

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Re: .257 cal Monotube PCP
« Reply #22 on: November 13, 2015, 08:55:04 AM »
I think you can handle it Bob. Interesting design on the breech. How far do you plan on stretching it out?
  • Magnolia,TX
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Offline rsterne

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Re: .257 cal Monotube PCP
« Reply #23 on: November 13, 2015, 02:03:35 PM »
Realistically, I will find trouble getting a bench setup at even 200 yards where I usually shoot, let alone further out.... I may end up making a portable bench and target stand that I can take apart and put in the back of my Rhino SXS to take into the mountains to setup.... The plan is to sight in the gun at 100 yards, which by machining a 20 MOA downslope into the bottom of the Picatinny rail I plan to accomplish with the scope near optical center.... In the 6" long rail, that is about 0.035" slope on the bottom, which I will remove at the same time I machine it to fit the outside of the 1.25" Monotube.... If I can get the bullet into the upper 900s, with the BC that I hope to achieve, that should put me on target at the top of the bottom post in the reticle at 25 X at 200 yards.... If not, I can simply zoom out a bit, at 20X I will gain what amounts to one MilDot (ie 4 dots up at  20X the equivalent of dots up at 25X).... Resighting the gun for 200 yards will need about 18 MOA of "up" dialed into the turret, which is less than built into the rail, so no different than sighting in at 100 yards without the ramp.... To go further out, if the gun is shooting well enough, and I have the opportunity, I would use first the MilDots to get on paper, and then crank the turret up more.... When sighted at 200 yards, at 20X the top of the bottom post should be just over 300 yards.... Crank in another 20 MOA to recenter there (a total of ~ 38 MOA), and the post will put me at about 400 yards.... add another 22 MOA (a total of 60 MOA, now getting close to the end of the 70 MOA Elevation adjustment available in the scope), and by using the top of the post that would put me at about 500 yards.... Basically, the plan is to leapfrog one distance from the last, alternating using the MilDot to get on paper with adjusting the turrets.... Anything beyond that would require changing the slope of the Picatinny rail.... but let's face it, if I ever hit ANYTHING at 500 yards I'd be bouncing off the walls....   :o

So that's how I expect the sighting system to work out, and it's limitations.... Can I, or the rifle, ever do it?.... We can all dream, can't we?.... First let me get the gun built (a big challenge right there) and see how it shoots at 100 yards.... IMO, if you can't achieve 2 MOA at a given distance, there is no point in trying to get out further.... You're just fooling yourself....  ::) ... or maybe you're just having fun?....  8)

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline Rizen 1

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Re: .257 cal Monotube PCP
« Reply #24 on: November 13, 2015, 05:49:01 PM »
Very nice Bob!  I can't wait to see this one!!!
  • Strasburg Va.
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Offline Bill G

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Re: .257 cal Monotube PCP
« Reply #25 on: November 15, 2015, 11:30:38 AM »
Maybe for taking their head off at 200 yards?.... It they'll keep it still instead of bobbing all over, that is.... *LOL*....

I hope I haven't bitten off more than I can chew, with this one....  ::)

Bob

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  • Nicholasville KY
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Offline rsterne

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Re: .257 cal Monotube PCP
« Reply #26 on: November 15, 2015, 01:22:51 PM »
I liked the term Monotube, but since there is an air tube under it (making two tubes), it doesn't quite fit.... The upper tube takes all the loads keeping the critical parts (barrel, breech, and scope) aligned, like an Exoskeleton, so that makes it a Monocoque design.... From now on, I will be referring to it as my "Monocoque Design PCP"....

Bob
« Last Edit: November 15, 2015, 01:28:55 PM by rsterne »
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline rjorge

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Re: .257 cal Monocoque PCP
« Reply #27 on: November 15, 2015, 03:22:18 PM »
Great work so far! I am sure this will be another build where the experience shared and lessons learned will be very meaningful to those working with the .257 cal and FPE levels. I hope you exceed your goals! ;)
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Offline Tomg

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Re: .257 cal Monocoque PCP
« Reply #28 on: November 16, 2015, 11:19:03 AM »
Peaked my interest, dialed in:-)

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Offline LeadBreakfast

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Re: .257 cal Monocoque PCP
« Reply #29 on: November 16, 2015, 07:56:53 PM »
Very cool! Love that you designed it to work with your own bullets as well. I'll come along for this ride!
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Offline UCChris

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Re: .257 cal Monocoque PCP
« Reply #30 on: November 17, 2015, 02:35:52 AM »
This one is going to be epic. Subscribed.

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #31 on: November 18, 2015, 01:48:43 PM »
I have most of the materials coming to start work on this project.... I do need, however, a small block of aluminum for the front bipod mount.... I need a piece 1.5" x 2" x 2".... and 6061-T6 would be suitable, no need for anything fancier.... Anybody have a piece kicking around their shop you can spare?....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #32 on: November 18, 2015, 06:10:12 PM »
I have been looking at my supply of hammer springs for this project.... I needed a long, rather weak spring for the captive spring guide concept, and it turns out that using two QB (like) hammer springs riding on one guide should work perfectly.... The ones I have are actually 0.36" OD x 0.051" wire x 2.4" long, but they have the same spring rate and length as a QB spring.... Stacking two of them end to end gives a spring of the following specs....

LOA 4.80"
Rate 9 lb/in.
Max. travel 2.70"
Max. force 24 lbs.

There are two adjustments, the preload on the spring (set by the length of the spring guide, which is adjustable).... and the distance the end of the guide is clear of the inside of the hammer when uncocked (which sets the distance that the spring is compressed when the gun is cocked), also adjustable.... The hammer pulls back 1.50" from touching the valve stem to being cocked.... Here is a table of the various combinations....



The columns, left to right, are (distances in inches, forces in lbs.):
The distance the spring is compressed by the guide (preload);
The force required to do that (also the force at the beginning of the cocking stroke);
The distance the spring is compressed during cocking (the guide is clear of the inside of the hammer by 1.50" minus that distance) ("D") ;
The total distance the spring is compressed when cocked;
The force required to do that (force when cocked);
The average force over the travel of the hammer ("F") ;
The energy given to the hammer during the firing stroke (F x D / 12) ....

As you can see, I can vary the hammer energy from 1.0 - 2.0 FPE, and I am expecting to need about 1.4-1.5 FPE, so I should have no problem finding a setting that will work.... When I actually make the spring guide and adjuster I will post a photo of it....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #33 on: November 18, 2015, 10:07:55 PM »
Well, I made the first part today.... Amazing how something as simple as a spring guide and adjuster takes so long to make.... Here it is....



The spring guide is made from a piece of 1/4" drill rod 6.5" long.... It is threaded 1/4"-NF for 1.25" at the back, and carries two nuts, locked against each other, and a bumper made of a 90D # 108 O-ring.... The guide is also threaded at the front for another nut, which is held with Loctite bearing mount and then turned to provide a spring seat and fit loosely inside the hammer.... The adjuster is a 9/16"-NF bolt 2" long (which I had to anneal before machining) drilled through 1/4" and then counterbored to 3/8" for a depth of 1/2" to accommodate the length of the two springs, which total 4.8" long.... They are 0.36" OD x 0.051" wire.... As pictured, the spring is under 0.8" of preload (4" fitted length) and it takes about 7.25 lbs. to move it.... That is how hard the hammer would have to hit it on rebound to store any energy in the spring, so I think the chances of hammer bounce are very small.... It will take about 20 lbs. of force to cock the gun, which is high but certainly manageable.... The chart in the previous post shows the large range of adjustability....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline MJP

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Re: .257 cal Monocoque PCP
« Reply #34 on: November 18, 2015, 11:38:59 PM »
Nice design Bob, have been thinking something similar to avoid threads between frame and airtube.
One thing less to machine and when using stainless it's not so much fun cutting threads all the time.
Really looking forward seeing the finished gun.

Marko
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Offline dyotat100

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Re: .257 cal Monocoque PCP
« Reply #35 on: November 19, 2015, 01:19:30 PM »
I'm sure I have something close to what you need Bob. Have to check tonight or tomorrow though

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #36 on: November 19, 2015, 01:57:06 PM »
Hey, Doug.... I have a piece on the way, thanks!....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline Bill G

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Re: .257 cal Monocoque PCP
« Reply #37 on: November 19, 2015, 05:41:45 PM »
LOL I should have scrolled down a hair more and would have seen your post. disregard the PM.

Bill
  • Nicholasville KY
Engineering is the art of modeling materials we don't wholly understand, into shapes we can't precisely analyze, so as to withstand forces we can't properly asses, in such a way that the public has no reason to suspect the extent of our ignorance.

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #38 on: November 21, 2015, 07:17:25 PM »
My Christmas present from my dear wife came in today....



Millet 6-25 x 56mm SF.... Just another scope you say?.... well, yes, but this may give you a hint about what is different about it.... those are 1" rings for comparison....



Yes, the tube is 35mm, and the scope is 22" long with sunshade and weighs 2 lb. 13 oz. with the rings.... Here is it sitting beside a Leapers 3-9 x 32mm AO with sunshade....   :o



The scope is very bright and clear.... It focuses down to 15 yards, and has 140 MOA of Elevation adjustment.... I will be machining the Picatinny rail it mounts on to a 20 MOA angle on the bottom, which should put me on target at 100 yards with the scope still on optical center.... The 1/2 MilDot Reticle is calibrated at 25 X, and there is a mark at 12.5 X, which makes each 1/2 MilDot work out to a full MilDot, so that works out to a lot of holdover just using the dots....

Bad part is, I have to put it away until Christmas....   ::)

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline n4spd

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Re: .257 cal Monocoque PCP
« Reply #39 on: November 21, 2015, 08:50:17 PM »
wow. anyone allowed to be in your work around are really lucky.  good luck and thanks for sharing.  subscribed as well...
  • danville, ca