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

[Motorhead]

Another week of being locked down at home .. More fiddling around with this .177 slugger conversion.
The original valve used was a JSAR Gen 2 SS body with custom balanced guts. Throat a huge .280", poppet head @ .350" having an exiting transfer port of .250", hammer a fairly heavy 40ish grams.

I was having good results and rifles been shooting well enough, but listening to the muzzle report I knew dwell and general state of tune was not being optimized for the little .177 caliber application.
Took the gun apart pulling the complete valve, hammer too and set aside the SSG set.
In its place went back to an original WAR valve body that has the replaceable seat, where I selected the smallest one i had ... .250" throat with an @ .210" transfer exit.  * This seat/ poppet set is an aluminum core peek shell design that is lapped onto the thin seats sealing rim. Poppet O.D. dropped to just .290" being A LOT easier to open !  Balance chamber specs remained the same.  My poppet to chamber ratio lower yet.  EASY to open !!

Reassembled and started testing ... WHOA !! too much hammer with gun going FULL AUTO for 2-3 seconds making 1000+ psi air dumps.  Pulled the hammer, made a new one from 100% mds nylon weighting just 14 grams.  Tested again having no problem making the same power ( This H&N Sniper magnum 15 grans ) to 1050 fps at @ 2300 psi.    Still tho I could hear the dwell was too long and air use was still not in check.
Hammer out a few more times with the final configuration having a DESTROKE nose on the hammer REDUCING stroke by a full .550" !! .... Active stroke now looks to be @ .350" +/-   SHORT STROKE !!
Doing so had to cut the 6# m-rod factory spring @ 3/8" and reset the SSG overall length which also added a bit more spring preload. Assembled with @ 1/16" of free flight the gun now fires with a sharp SNAP and still produces the 1050 fps at the same pressure.
Cocking the gun is ODD being breech opens up with no effort what so ever except for the last @ 3/8" or so.  Single finger easy too !

When crunching the new size specs threw the system it is far better suited now for high power .177 use & likely would do well in .22
Throat area minus poppet stem is an equivalent .200" ..... Exit from throat goes into a Tapered transfer tube at .210"/.165" specs. Barrel port an elongated slot offers full bore specs.

Doing some informal accuracy testing certainly lost nothing and feel it gained some from having far less hammer weight with less stroke. Shot cycle is snappier and rifle moves less when fired.


I'm really liking this small caliber flat shooting monster 

Scott S

[Rallyshark]

That's good stuff right there!  Progress is always fun   One thing I've really loved about the .177 slug shooter is how quiet it is!  Whenever I shoot it, people just look at me and wonder how that super quiet gun is pinging targets at 150-200 yards,lol!  While I have to crack the valve the old fashioned way(with lots of hammer spring/hammer), your porting is very close to what I settled on with mine.  I've got the PEEK valve seat at .215(minus the thin valve pin diameter), so I'm in the same ballpark(without doing too much math) with the valve exit, and the transfer is bore sized with a .165-.170 equivalent oval barrel port.  I've got mine tuned to shoot the 15.5 NSAs at 1000 fps, with the regulator around 2100 psi.  I suspect I could do a wee bit better with efficiency, if the reg were at the 2200-2300 range.  Right now I'm around 2.5-3% below the knee.  The ES is pretty great though.

I look forward to seeing how your gun does when you can get some real target time in, so you can fine tune the gun for the speed the chosen slugs like!  I will say, I think the BC of the NSA .177 slugs is a bit higher than listed.  I think they are listed at .062, but based on my long distance holdovers they are closer to .080+.  Without a doubt, I enjoy the .177 slug gun more than any other gun.  It is so quiet, accurate, and deceptively powerful on long range targets and critters  

[Motorhead]

Woo WHOOOO ….. just received a few 100 pre-production NSA slugs off the high speed machine.  12-15-18-21 grain hollow points ALL with dish bases.

 

but it's hot "dang" HOT right now and not sure when I physically can endure being out in this heat and do some testing …. too be continued

[oldpro]

Woo WHOOOO ….. just received a few 100 pre-production NSA slugs off the high speed machine.  12-15-18-21 grain hollow points ALL with dish bases.

 

but it's hot "dang" HOT right now and not sure when I physically can endure being out in this heat and do some testing …. too be continued

Same here buddy, pretty much doing same thing as you except im using a Raptor with TJ .177. Its smoking hot so not much going on today either, I did shoot the new 12 grain and they shot really well. Im going to get up early tomorrow to beat the heat and give it a go. Your project looks awesome by the way!

[Rallyshark]

I'm still waiting on you guys to let us know how those slugs end up shooting for you!  We don't get to see a whole lot of .177 slug shooting on here, but I think we should.  The .177 slugs are among to most interesting to me right now, because the barrel options for them aren't "known" like they are for the .22.

[Motorhead]

Well .... got to shoot all 4 weights in BOTH my higher power .177 PCP's late in the day today.

In my M-rod with the JSAR air tube and a balanced valve of my own design the results were encouraging  with all 4 weights when shot at 50 yards having the 12.5 grains @ 940 fps and the 21's @ 640 fps.  * This threw a LW standard rifling w/ choke 21" barrel.

In my Bottlerauder and balanced valve of my own design the results were Horrid !  All 4 weights were all over the place with the 21's actually KEY HOLING     12.5's shot @ 1070 fps and the 21's @ 700 fps.   * This threw a TJ's 4 groove w/o choke 22" barrel.   
Odd thing here is with H&N Sniper magnum PELLETS @ 1060 fps the TJ barrel shoots sub 1/2" groups all day long.


Took the TJ's out of receiver having the bare barrel in hand ... tried to push some of the pre production NSA snugs down the bore  Holey molely what a tight fit !!  WAY TOO TIGHT !!  When slug exited muzzle it showed signs of full GROOVE contact and obviously full land contact as well.
Did the same with the LW barrel .... Great fit and good Land witness marks and able to pass threw the choke w/o much extra push.

So it looks that in my situation of wanting to use the excellent TJ's that shoots heavy pellets so well ... for NSA .177 slugs at this point is a BIG no go in that barrel.   So, my efforts will be to see how the LW barrel in the other rifles does when I can get back out and shoot some more.

NICE SLUGS with a deep hollow point being very well formed .... so far so good NSA wise 

Dang it's HOT !!!!  Saw 105* today

[KnifeMaker]

To the too hot to shoot situation, working with HOT Steel taught me to work at night. this translated to testing at night very well. I use a 2400 out the front gun mounted light and this allows me to actually see how the slugs are fling. Any wag, siirleing or other wony filight patterns are instantly seeable. I don't even set up the bench until around 2:00 AM in the morning. But lately, that is still too hot her in central Texas. GRRRRRR!!!


Sounds it is time to think about sizing those slugs for the TJ's. Even with slugs that fit, such as in the L/W barrel, I find tweaking the size by as little as .0001" can sometimes pay huge dividends in accuracy .


Yes, there is an investment. Press and dies to start with. However, once set up, die inserts from NOE are only 9.95 US each. I buy several at a time and slowly hone them to different sizes. It is amazing the differences it can make. This is something pellets shooters are not familiar with. However, we powder shooters are very use to it. And lets face it. Slugs/bullets are after all, pb tech. So we must adapt.  With sizes available at .001 differences, it misses the opportunity of guilt edge accuracy unless we are willing to go the extra distance to really bring out what can be achieved in accuray.


For those not interested in top accuracy, fps and fpe can be enhanced as well. I often see a 25-35 fps difference in just a .0001 to .0002 difference in size. 


Mike

[Rallyshark]

I suspected the NSA slugs were going to be a no go in the TJ's, given the barrel specs.  I'm sure they'd do better, if sized down for that barrel, but it is a tight barrel by .177 numbers.  In my playing with the NSA slugs(both new and old), the unchoked LW poly barrel has definitely been the winner.  I've tried the NSAs in a standard choked LW, a choked LW poly, and an unchoked LW poly.  The choked poly was slightly better than the standard choked, but I never was able to get either of the choked barrels to really dial in with the slugs.  I tried them at almost every conceivable speed, but I just couldn't find a combo that was more than just average accuracy.

The unchoked poly is another story.  It is speed dependent, but I was able to find a speed with every slug that worked.  The original NSA slugs still prove to be the most accurate for me though.  I'm able to make every weight pretty dang accurate, and they work well in a 50+fps window.  That window is generally 975-1050fps, with them really hitting their stride from 1000-1025fps in all weights.  The 15.5 seem to have the largest window, with it getting smaller as the weight increases. 

I'm nowhere nearly as experienced with the slugs as you guys are, but I'm thinking an unchoked LW with a 1:15-1:16 twist would be the bees knees, especially with the 18 and 21 grain slugs.  I bet it would prove accurate at lower velocities, negating the need to push the slugs in 1000 fps range for sure. 

I've also tried the Griffin .177 slugs, and I got key holing on almost all of those.  I only tried those in 19-24 grain weights.  I think they may be worth trying in that TJ barrel.  They were running slightly smaller in diameter than the NSA slugs, so who knows...

[Motorhead]

UPDATE ....
Bottlerauder is now set up as a .22 using a 23" HW 6 groove No choke barrel shooting in the @ 47-48 fpe range which does heavy pellets and 23-25 grain slugs excellent !!  It is IMO the ideal balance in power and air use for this rifle.  * can be turned up to shoot harder, but as set is in the sweet spot.

The .177 slugger was trial tested in my JSAR mini that had been the prototype FT gun all year.  Found that running a .177 at really high FPE just uses too much air and sorta defeats it being practical.   The JSAR tested sporting a 18.5"  LW .177 standard choked barrel.  Balanced valve, LW hammer & SSG
Power is sitting right at @ 29 fpe able to shoot 16.2 gr JSB Beasts @ 900 fps, JSB 13.4 Monsters @ 990 fps & NSA 12.5 gr Slugs @ 990 fps.
Efficiency is stellar and accuracy is spot on having now shot it sub 1" at 100 yards.  This is IMO also the ideal balance in power and air use as well being set in the sweet spot.

While a Temporary set up in the JSAR .. it will likely end up there eventually.  Tho for now still my FT gun for the 2020 season.

While the JSAR too can make the previous 37 FPE .... at that power it is is an air hog relative to a slightly more conservative tune where it is at now at @ 29 fpe.
The LW barrel shoots heavy pellets as well NSA slugs equally well.   As for the TJ .177 it is in the barrel box for another day.

[Rallyshark]

I have to agree with that move there.  MOA with a .177 ain't nothing to sneeze at.  My .177 slug gun generally lives in the 30-34 fpe range for shooting the 12.5 and 15 grain slugs.  I just adjust the HS accordingly, and leave the reg where it is.  It is a ton of fun at that "lower" power level, and gets a decent shot count for the lighter NSA slugs.  It's is my go to gun at that tune in most cases for long range plinking and pesting.  A good strong .177 gets over looked too often IMO.  People don't realize how much you can do with them, and VERY quiet to boot!   

Admittedly, I just pulled the reg and upped the power for a "special" purpose this weekend.  I have it running around 45 fpe with the 18/21 grains slugs, which are no longer available   I've been saving the heavy ones for special uses, but I'm hoping NSA will add a heavier slug to the new high speed runs soon.  I need the extra juice to poke a deeper hole at the moment, but it will be right back at the lower regulated power afterwards though  

I'm sure you'll have plenty of good times with that 29 fpe tune, when you do set the gun to stay there.  That is a great tune on that gun, no doubt!

[oldpro]

 Going to make a double tank bench rest .177 Raptor slug gun for squirrel season this spring!

[Motorhead]

Well .... The Bottlerauder this thread started with became a @ 50 fpe .22 slug shooter and the .177 spec slugger ended back into JSAR raptor mini ... here: https://www.gatewaytoairguns.org/GTA/index.php?topic=181014.msg156102180#msg156102180