Caliber conversion 60fpe .25 to a 37 fpe .177 ... O'baby !!

[Motorhead]

    Been wanting to try this for quite a while now ( well sense finishing my bottle fed exotic M-rod ) See: https://www.gatewaytoairguns.org/GTA/index.php?topic=169004.msg155898655#msg155898655
So today after servicing 2 customer guns took a bit of time for my own project.
The rifle linked to above ONLY changing barrel & probe in the mechanical set up along with cranking up the reg pressure from 2K where we shoot it in .25 cal, the Weeee little .177 started to wake up @ 300/400 psi higher where I found the best compromise not wanting to change hammer weight or spring settings was at @ 2400 psi.

Barrel put in a 22" TJ .177 liner with 4 land/groove and no choke specs.  Transfer post an elongated .140 x .250 slot. Transfer port in the rifle prior a tapered one at .250/.180" specs & kept it intact.
Oddly the gun sounds similar to the .25 set up and likely due to the transfer port specs and the barrel now at similar spec tho longer it acts similar


*Here just a quick condensed sample of speeds shot while fiddling around.

2400 PSI regulator set pressure, projectile & weight as listed ...

Nielsen 15.5 Slug @ 1035 fps w/ 36 fpe
Nielsen 18 Slug @ 975 fps w/ 37 fpe
Nielsen 21 Slug @ 850 fps w/ 37.6 fpe
JSB Monster 13.4 @ 1090 fps w/ 35 fpe
H&N Sniper Mag 14.97 @ 1055 fps w/ 37 fpe

Went high as 2800 psi on the reg pressure and only gained @ 40/50 fps across the board & muzzle report went way up ... Not enough barrel length my best guess ?
So ... there we have it a .177 ( Not .172 ) caliber SLUGGER ! that can shoot production .177 slugs or the heavyweight pellets with some decent power. Sadly only have the remains of a Nielson .177 sampler pack and not able to shoot any groups yet.  When Nick gets the high speed machines cranking out .177 slugs we will pick this project back up once more.

WOOF !!

[nervoustrigger]

Ah yes, that's a brutal icepick for sure   Looking forward to seeing how it likes some of these heavy projectiles. 

[bear air]

I love hearing these success stories Scott. I really love that it's a maruader platform you have been doing it with.

[Rallyshark]

Nice!  I'm very curious to see how that TJ liner does with the slugs!  What is the twist on that one?  I've had my best results with the NSAs(in every weight) around 1000-1025 fps in the unchoked poly barrel, which is 1:17.7.  Granted, the TJ barrel is different land and groove diameter too, right?

Either way, you got the power to push them, so the odds are in your favor so far

[Motorhead]

Just went out and did a bit of informal trials with the 2 heavy pellets … Shooting against a dirt bank at @ 80 yards aiming at random walnut size stones the JSB Monsters were not real happy and scattered in an estimated 3-4 inch random pattern.   The H&N Sniper Magnums were tight and was able to shoot marble size stones one after another !

This thing is crazy how flat it shoots & also very odd the JSB and H&N when shot sounded completely different ? The JSB's were a crisp SNAP and the H&N a more subdued POP

Perhaps the speed being 30fps or so closer to supersonic ? or there softer lead and less bore drag … don't know but it was obvious enough to mention.

 

That works ( Sniper Mags ) being I've got 2 full tins and a partial to tide me over until slugs become viable.

[scion19801]

kinda funny how this turned up. i am in the process of doing the same thing on a gauntlet. going from .25 to .22 versus all the way down to .177. Hoping it will sling slugs mainly. parts to do the swap are reasonably cheap and no machining needed. well kinda, got a funny feeling that the lead in the .22 barrel will need to be worked as i'm sure it has a 90 degrees step versus a nice taper into the bore.

[Ribbonstone]

Looking forward to your tests with slugs.  Have much more of an interest in a standard .177 barrel than a custom .172.

Tried the fast/heavy .177...not as fast as yours (BAM 50),but managed 30-32 foot pounds. Better shot count (unregulated rifle) back down to 25-27 foot pounds.

OF the pellet-pellet choices, the 15gr. H&N Sniper MAgs / 16.2 Gr. JSB Beast/ 16.1gr. EunJin (now Seneca) worked pretty well out to 75 yards.

(Alas...viral situation and lack of spare parts made me combine the BAM 50 and the BAM 51....but I kept the total upper of the .177 BAM 50, so a "top swap" would work.)

Lock-down/social isolation pretty much keeps me at home....so while I could revive that experiment, thinking now is not the time.

[Motorhead]

kinda funny how this turned up. i am in the process of doing the same thing on a gauntlet. going from .25 to .22 versus all the way down to .177. Hoping it will sling slugs mainly. parts to do the swap are reasonably cheap and no machining needed. well kinda, got a funny feeling that the lead in the .22 barrel will need to be worked as i'm sure it has a 90 degrees step versus a nice taper into the bore.

It take a LOT OF POWER to get the smaller bore guns up to big power and not that easy IMO.   This rig I'm working with has a HUGE valve .280 throat & .250 transfer and in a Balanced configuration on top of this.
As a .25 cal with 34 grain JSB's a 60 FPE rifle and with a .30 cal fitted and 44 grain JSB it musters just shy of 80 ft lbs !!
  Dropped down to .177 cal specs it levels out as set @ 37 ft lbs which is a SERIOUS loss of efficiency of the pressure moving a far lighter projectile because the bore diameter has far less area.

You may see 800 fps with 15 grain slugs, surprised if it manages to make more

[nervoustrigger]

Scott, this project is interesting to me and is rather timely because this past weekend I was enjoying my little 12fpe .177 LW QB79 and was rummaging around and came across the OEM barrel and some other bits and pieces.  I’ve been wanting to assemble a .177 with a bit more oomph—not because I have any particular use for it but just for the fun of it.
 
I considered taking the mothballed B50 and going unregulated and see what madness it will yield with the benefit of a 3000psi fill.  But after some deliberation, I decided to try a modest but more useful approach which is to see what a 1500psi regulator setpoint will give me from the QB79 platform.  Just start with standard porting and see what happens.  If the barrel turns out to be a good one and it does well with the JSB 10.3 and 13.4, maybe move up from there.  Bump up the porting, go with a long tube for more plenum volume.
 
So I started gathering up parts.  Turns out I have most everything I need, including a valve but no poppet.  Needing a stem, I got after a piece of 2mm W1 rod with a torch and proceeded to quench and heat treat it caveman style.  That seems to have worked because the emery wheel struggled to chew through it when it came time to cut it to length.  Then over to the lathe with a stick of PEEK to make the poppet.  My lathe-fu is still white belt so I followed up with some smoothing against a simple jig and then final lapping in the valve.  Last night I did a quick pressure check and I’m pleased to say it sealed great with 1000psi.
 
Still have several other things to do (RVA, MDS hammer, etc.) before I’m ready to assemble but with any luck, this weekend I’ll have it together for initial testing.

[Rallyshark]

Scott, I could be crazy here, but...  I'm thinking you'll do better with a bore sized transfer to reduce the pressure drop between the valve and projectile.  What do you think?  I know a while back when I started playing around with the high power .177 setup, I swapped a .177 barrel/probe to a gun that was ported for .22 and power was pretty good.  I actually picked up a little more power when I built a gun ported for .177 though.  I may have done some other changes, so I could be "misremembereing"   The two different guns were identical models, fwiw. 

[Motorhead]

Scott, I could be crazy here, but...  I'm thinking you'll do better with a bore sized transfer to reduce the pressure drop between the valve and projectile.  What do you think?  I know a while back when I started playing around with the high power .177 setup, I swapped a .177 barrel/probe to a gun that was ported for .22 and power was pretty good.  I actually picked up a little more power when I built a gun ported for .177 though.  I may have done some other changes, so I could be "misremembereing"   The two different guns were identical models, fwiw. 

Typically i would agree 
This build because it is so unconventional having HUGE valving that easily runs a .30 cal & use of the balanced valve where I've already found strangling the transfer path via TAPERED transfer tubes the setup we have is being strangled via only a .177" bore.  The transfer size is at .180" at the tubes outlet which sits right under the barrel.  The elongated port I've got in barrel .140" x .250" is just making sure all my choking can be controlled via the tubes outlet size.  * It very well may change to something smaller ?  But for now I was wanting to see what the gun would do running wide open at @ Bore spec.

* Because the throat is so large at .280" & deep, transfer path leaves throat at .250" I'm already WAY PAST a place where achieving any sort of bore spec area behind poppets sealing surface and seeing optimal effeciency. It simply IS NOT HAPPENING !!

Plus ... set up as such i can put the .25 or .30 barrel with a probe change in 2 minuets, reduce regs set point and shoot !!  Easy peezy !!     This .177 is an after the fact using a platform I've already got dialed in 

[Rallyshark]

That makes sense to me!  I wouldn't change it either, given your quick caliber/tune swap ability   Now we wait for target time!

[UnderPressure]

This rig I'm working with has a HUGE valve .280 throat & .250 transfer and in a Balanced configuration on top of this.
As a .25 cal with 34 grain JSB's a 60 FPE rifle and with a .30 cal fitted and 44 grain JSB it musters just shy of 80 ft lbs !!

Is the .30 barrel Lothar Walther like the .25?

unchoked barrel?

[UnderPressure]

Nice!  I'm very curious to see how that TJ liner does with the slugs!  What is the twist on that one? 

+1.

[Motorhead]

This rig I'm working with has a HUGE valve .280 throat & .250 transfer and in a Balanced configuration on top of this.
As a .25 cal with 34 grain JSB's a 60 FPE rifle and with a .30 cal fitted and 44 grain JSB it musters just shy of 80 ft lbs !!

Is the .30 barrel Lothar Walther like the .25?

unchoked barrel?

The .25 cal barrel a LW Poly w/ choke
The .30 barrel a TJ non choke
The TJ .177 best I can measure it a 1-18 twist ( Thought originally a 1-22, but it's not that slow )

[Motorhead]

Follow up on the transfer port getting smaller W/O hurting power and Helping efficiency .....
Made another tapered port today exiting at .157" ( #22 drill )    Same power & lower muzzle report.
Port choking even here in .177 cal works like it does on larger calibers !!  Could likely go even smaller based off previous testing ... going to leave it for now, these tapered ports take @ 20 min to lathe manufacture.
Previous port choking thread here: https://www.gatewaytoairguns.org/GTA/index.php?topic=165159.msg155844248#msg155844248

Scott

[Nvreloader]

Scott
Following along, very interesting............ ,
by any chance will this be your next FT rifle, if you have the accuracy needed?   

Don

[Motorhead]

Scott
Following along, very interesting............ ,
by any chance will this be your next FT rifle, if you have the accuracy needed?   

Don

No, my primary FT rifle will remain my RAW TM-1000 in .20 cal with a HW barrel.
Tho at the club level its a dang shooter or until it can equal the TM it is showing potential with some tweaks to be used as a primary FT rig.  As currently set up it is very accurate with most folks likely viewing it as the most accurate shooting gun they have experienced.
Sadly as a post National FT champion my personal standards are rather high and these guns are likely going to need some tweaks from as delivered OEM specs to equal purpose built equipment.

[Nvreloader]

Thanks Scott

I know you have the Moxi to get it done,
it'll be very interesting to see the final results for that .177.     

Don

[Motorhead]

Oups ...

This thread is about the Bottle Marauder and Not the JSAR Raptor mini is which I was speaking of 2 posts above.  Same technology used in both rifles, but there tuned very differently at vastly different power levels.
This bottlerauder is a HIGH POWER hunting gun by design recently converted from a .25 to .177 where the Raptor mini is DE-TUNED down to 20 fpe for field target duty.