Thank you to our advertisers!







Author Topic: Dual Tank Benchrest Rifle  (Read 1976 times))

Offline sb327

  • Expert
  • *****
  • Posts: 1528
  • yes
  • Real Name: David
Re: Dual Tank Benchrest Rifle
« Reply #20 on: September 21, 2022, 05:51:34 PM »
.
  • USA, OK, Stigler
Dave

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #21 on: September 21, 2022, 08:51:09 PM »
Pretty kewl!.... Would it be possible to use the steel bonnet from the HP reg. and make a piston to suit for the Flex?....

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 sb327

  • Expert
  • *****
  • Posts: 1528
  • yes
  • Real Name: David
Re: Dual Tank Benchrest Rifle
« Reply #22 on: September 21, 2022, 09:01:43 PM »
It should, I was gonna try but Iíve got the hp aired up for shooting tomorrow.

Dave
  • USA, OK, Stigler
Dave

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #23 on: September 22, 2022, 06:46:48 PM »
By special request, Hajimoto has agreed to make me a Flex (adjustable) Ninja Regulator with a steel bonnet, set up for a maximum of 3600 psi.... Ninja won't verify that it is OK, but the body and steel bonnet are both rated at 4500 psi MSWP.... I did the math for the CGA 320 threads on the adapter.... and I can use 2024-T3, but will use 7075-T6 for even more strength....

Al has confirmed that he will be making the mold for the .183 cal. 39 gr. bullet (eventually), so I just have to confirm I can get the barrel into Canada....

Bob
« Last Edit: September 22, 2022, 06:54:19 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 Scotchmo

  • GTA Senior Contributor
  • ******
  • Posts: 2227
  • Real Name: Scott Hull
Re: Dual Tank Benchrest Rifle
« Reply #24 on: September 22, 2022, 07:13:31 PM »
By special request, Hajimoto has agreed to make me a Flex (adjustable) Ninja Regulator with a steel bonnet, set up for a maximum of 3600 psi....

I have never opened up my steel bonnet Hajimoto HP regs, so I donít know what piston size is used. Do you know if your special request Flex will have a large or small piston?
  • Los Osos, California

Offline sb327

  • Expert
  • *****
  • Posts: 1528
  • yes
  • Real Name: David
Re: Dual Tank Benchrest Rifle
« Reply #25 on: September 22, 2022, 07:29:06 PM »
Pretty kewl!.... Would it be possible to use the steel bonnet from the HP reg. and make a piston to suit for the Flex?....

Bob

Sounds like Haji is going to get you fixed up. Between shooting today, I swapped the steel bonnet onto my flex, using the piston I made. Works fine. I left the bonnet backed off just a bit because my piston is a little long (to compensate for the washer I used in the flex bonnet).

Dave
  • USA, OK, Stigler
Dave

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #26 on: September 22, 2022, 07:56:35 PM »
Scott, I don't think they make the Flex with a small piston, I will ask Haji....

Dave, thanks for that info.... How much range of adjustment do you have on the Flex with small piston?....

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 Scotchmo

  • GTA Senior Contributor
  • ******
  • Posts: 2227
  • Real Name: Scott Hull
Re: Dual Tank Benchrest Rifle
« Reply #27 on: September 22, 2022, 08:05:13 PM »
Scott, I don't think they make the Flex with a small piston, I will ask Haji....
...

Bob

OK. But do they make a steel bonnet with a large piston? I would think the smaller diameter piston would be better for an HP output reg.
  • Los Osos, California

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #28 on: September 22, 2022, 08:16:47 PM »
I have a steel bonnet with the large piston, in fact a couple of them, so yes, they do (or at least did) make them.... He said he could supply a Flex with a steel bonnet, and I have asked him if it takes the large or small piston (hoping for the small)....

The basic difference between the large and small, when used at 3000 psi, is that the large piston requires 0.032" Bellevilles in four sets of three (108 psi/thou), whereas the small piston uses ten x 0.032" as singles (43 psi/thou).... This means with the small piston, there is much more travel, and a far softer spring rate, and so it should open further (and refill quicker) for a given pressure drop in the plenum....

Bob
« Last Edit: September 22, 2022, 08:20:47 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 sb327

  • Expert
  • *****
  • Posts: 1528
  • yes
  • Real Name: David
Re: Dual Tank Benchrest Rifle
« Reply #29 on: September 22, 2022, 08:39:08 PM »
Bob,

I didnít check max and min.

I do know where I had it set when airing it up was ~3200 and I adjusted from there to 3950. I have more adjustment left.

Dave
  • USA, OK, Stigler
Dave

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #30 on: October 07, 2022, 02:16:22 PM »
My tanks have arrived from AirgunArchery Fun in Saskatchewan....



They are gorgeous, and I love the long slender profile....  8)

I have ordered the 4130 CrMoly tubing for the main tube, and some 2024-T3 for internal parts....

Bob
« Last Edit: October 07, 2022, 02:25:03 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 bear air

  • GTA Senior Contributor
  • ******
  • Posts: 2862
  • yes
  • Real Name: Chris
Re: Dual Tank Benchrest Rifle
« Reply #31 on: October 08, 2022, 06:40:44 PM »
What a great project!
  • Sioux City IA, USA
Psalm 107:14  He brought them out of darkness and the deepest gloom and broke away their chains

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #32 on: October 14, 2022, 05:20:29 PM »
It turns out that I will also be getting a .22 cal LW pellet barrel with a VERY slow twist, compliments of Mike Niksch of Thomas Benchrest Rifles.... I helped Mike decide what to get for shooting 25.4 gr. JSB Monsters at 100 yards (he is trying to beat rimfires) and it is working well, so he is sending one as a thank you!.... Here is a 25 shot group he shot at 100 yards (looked like he pulled one)....  :o



I decided I will make up an upper to either fit on this gun, or since I have a pair of SIG 450 cc, 250 bar bottles, I might make another lower for it.... In any case, I borrowed the concept from my Monocoque .257 and came up with this unique way of marrying the barrel and breech....



I have a meter long piece of 16mm ID CF tube (to fit the LW barrel) with a 20mm OD, and I have ordered a piece of 5mm wall CF tubing a meter long, 20mm ID x 30mm OD, to slide both it and the breech into.... Barrel in green, breech in blue, bolt in red above.... The breech will be 20mm OD, turned from 2024-T3, and sealed to the barrel with an O-ring.... The resulting assembly should be about the same stiffness as a 1-1/8" OD steel barrel, at a fraction of the weight....

Sidetracked, maybe, but this should be fun!....  ;)

Bob
« Last Edit: October 14, 2022, 07:16:03 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 sb327

  • Expert
  • *****
  • Posts: 1528
  • yes
  • Real Name: David
Re: Dual Tank Benchrest Rifle
« Reply #33 on: October 14, 2022, 09:11:14 PM »
Excellent barrel! It should be a relief going into a build not wondering if your barrel is gonna be a shooter or just ho hum.

Canít wait to see some build pictures.

Dave
  • USA, OK, Stigler
Dave

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #34 on: October 15, 2022, 08:29:09 PM »
I have been thinking about a change to my balanced valve for this gun.... Here is a drawing, although the dimensions show a 5/16" throat (from my 6mm), which I can reduce to 1/4" for these smaller calibers, and reduce all the other dimensions proportionally if desired.... That would make the valve easier to open.... The balance chamber is 50% of the area of the poppet seat.... reducing the force required to crack the valve by that much....



The valve body is in black, the poppet and front spider are in blue, the balance chamber is in red, and the O-rings in magenta.... The valve spring (green) is outside the balance chamber instead of inside it.... This allows the chamber to be much shorter, and therefore a lot less volume.... The balancing force is basically only going to reduce the force holding the poppet closed.... Once it opens 1/3rd of it's diameter (it may never get that far), the poppet (actually the buffer O-ring on it) hits the end of the balance chamber, which can slide 1/8" forward, driven by the momentum of the hammer.... As the balance chamber fills with HPA from the valve throat through the vent in the poppet stem, the closing force increases.... This allows the dwell to be tuned with the hammer strike....

If I need a larger balance chamber, I can move the balance chamber forward by tightening the screw that holds it in place in the spider.... That would reduce the hammer strike required as the valve would have a longer "blow open" period.... The balance chamber dimensions can be changed if a larger alteration in operation is needed....

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 sb327

  • Expert
  • *****
  • Posts: 1528
  • yes
  • Real Name: David
Re: Dual Tank Benchrest Rifle
« Reply #35 on: October 15, 2022, 09:28:41 PM »
Thatís gonna allow A LOT of tuning ability over a set amount of blow open. And I believe it to be easier on spiders.

Dave
  • USA, OK, Stigler
Dave

Offline rsterne

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #36 on: October 31, 2022, 02:18:17 PM »
I just received my Carbon Fibre barrel sleeve from Amazon.ca....



30mm (1.18") OD x 20mm ID, shown with my normal 20mm OD barrel sleeve inside it!....



Anybody need a metre long CF Crowbar?....  ::)

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

  • Member 2000+fps Club
  • Bob and Lloyd
  • GTA Senior Contributor
  • *****
  • Posts: 26188
  • GTA Forums Person of the Year 2017
  • Real Name: Bob
Re: Dual Tank Benchrest Rifle
« Reply #37 on: November 01, 2022, 01:59:10 PM »
I have a question for those who have made successful benchrest rifles.... I am not talking about a "lead sled" mounted in it's own recoil carriage like the PB guys use with 6mm.... I am talking about a gun to be shot from bags, bipod or a forward rest, sitting on a bag against your shoulder (legal for NUAH rules, EBR, etc.etc.).... I know I can make a virtually rigid upper including the scope mount, something that will keep the barrel extremely well aligned, and immune from harmonics, relative to the scope.... How rigid does the attachment to the lower, which contains the valve, trigger, bipod mount and stock need to be?....

For example, could you use multiple barrel bands (eg. 2 or 3) to fasten them together?  I'm talking about beefy ones that would rigidly clamp the two tubes together, at the rear, near the valve transfer port, and maybe another one further forward, possibly at the front tank block.... I guess what I am really asking is could you replace a bulky, hard to machine receiver, with a couple of clamps?.... Your thoughts?....

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 subscriber

  • GTA Senior Contributor
  • ******
  • Posts: 5970
  • yes
Re: Dual Tank Benchrest Rifle
« Reply #38 on: November 01, 2022, 06:07:48 PM »
Bob,

A one piece receiver should be stiffer and more robust against abuse than a modular one, but that depends on the stiffness of each part, and the integrity of each junction.  As always, the devil is in the details. 

Also, as you are not going to attach a bayonet and joust with this air rifle, "less robust" may not matter.  Just don't use it as a crowbar.

The modular design of the RTI in the video below may serve as inspiration:

  • USA

Offline subscriber

  • GTA Senior Contributor
  • ******
  • Posts: 5970
  • yes
Re: Dual Tank Benchrest Rifle
« Reply #39 on: November 01, 2022, 06:31:09 PM »
If you need more inspiration, consider that aircraft fuselages and wings are made from flexible, light weight parts, that are fixtured into position and riveted together, to form precisely shaped robust parts. 

As you would not be making many air rifles, the fixturing aspect would not be required, but there would be more consideration of the placement and alignment of parts during assembly.

If the pressure in the air tank was kept in a narrow range (tethered bench gun), then the variation in air tank swell and stretched length is unlikely to spring the barrel and cause the POI to drift during a session, or between sessions.  You could even do the final torqueing of some barrel band screws after pressurizing the air tank, so there is no stress between tank and barrel at normal operating pressure.
  • USA