APTA Butterfly

[@tghoffmann]

Hi Paul, great questions … from a shooter. Let me offer some random comments on this that might be useful. 1) I did not “sight in” with “live ammo” … too many variables Instead I did a mechanical zero, as if I was setting up iron sights to a barrel. 2) I started with a retired BSA red dot and it worked fine. I later stepped up to a Bushnel to get a brighter reticle on a bright sky. I found it helpful but more because of my poor eyesight than any deficiency in the BSA. 3) To mount it, use a Picatinny rail with a curved, not flat, back. If the radius of the back is smaller than the radius of the barrel, the rail will self-center mechanically along the pipe. 4) To mount the rail, don’t use anything that penetrates the pipe; even an empty hole will cause the throw bag to abrade. I used thin stainless steel wire, wrapped in a tight clamp around the barrel and through the grooves of the rail. Check out www.clamptitetools.net. Perfect for this application: strong, tight and reliable with a clean look. 5) To get a reliable mechanical zero, I set the barrel horizontal in a pipe vice with a 12” laser level on it. The level also had a radiused bottom and, by luck, the distance from the laser beam to the barrel was almost identical to the standoff height of the mounted optic. I used a clamp to hold the level tight to the barrel (magnet was useless on aluminum) and marked a spot on a wall about thirty feet away. Then I removed the laser, looked through the BSA and adjusted windage and elevation to the wall spot. Sounds complicated but it only took a few minutes. Over nearly a year, I re-checked this setup several times and it was completely repeatable. 6) To “zero” with live ammo, I tried to lock down as many variables as I could think of: same weight bag, same manufacturer, same throwline, same firing position, same position of my throwline bucket, directly under the barrel and in line with the shot. With the chamber dimensions given in my videos, I discovered that, to a first order approximation, air pressure in psi corresponded to shot height in feet. Useful. 7) All in, this work essentially eliminated aiming error with the butterfly APTA and shooting from the mortar position. The biggest variable left that would determine the practical success or failure of a shot was the judgement of how much “loft” over a branch to aim into the shot. Typically, “success” means you’ve just zinged the shot a foot or two over the branch … can’t be under and shouldn’t be so high that you have to do a lot of isolation work. 8) If I were going further with this, I’d try to publish a chart of firing angle, air pressure and branch height that give one (1) “loft” number … ie “aim 7.5 feet high”. With the red dot and the device improvements, you really can draw a bead with that kind of precision BUT the “loft” variable is BIG. Right now, you ;pick that up with experience. Good luck. Let me know what you learn on this. Regards, Tom

[@mike660r1]

Tom, thank you for the information on this tool. I was able to build my own after ordering parts from multiple states and suppliers. The hardest part was finding someone that had a thread die large enough to cut the 1 1/2" threads on the barrel. Thankfully, someone in my family had a large adjustable unit. The only concern I ran into is the 1" jam nut above the butterfly valve. In order to get the jam nut spun all the way down on the 1" nipple, it requires the use of a wrench to get it there. It doesn't release easily either to tighten it up against the barrel. It isn't a major issue, but I'd still like to have the ability to adjust the red dot site more easily. I think I can find a balance once I get the scope perfectly aligned. It was such a joy building this project. Launching throw bags had me chuckling like a kid. Good stuff!

[@bigmanbs1]

Another well made, high quality video! thank you very much for making this video. Now I know how to improve my first gen APTA. I always thought the trigger lever was way harder to pull than it should be, and now i know what i can replace it with to improve performance.

[@mmoseleywpi]

Now you've got me thinking... if you wanted to get really, really fancy, replace the control valve with an air opened angle piston valve, with a pilot line plumbed to the pressure chamber with 1/8" stainless tubing and an air button valve in line to act as the trigger. Haha, of course that's probably a $200 upgrade, which doesn't fit your cheap or simple philosophy! Would be pretty sweet to have push button operation though. Might improve aim even more.

[@NHlocal]

OK Tom, you've sold me on "upgrading" my APTA. Excellent video showing the upgrades and performance. I have been thinking about changing out the ball valve, now I know I am. I know you gave the specs on the air chamber and butterfly valve, but do you have them listed anywhere? What is the cost of these upgrades? Are they easy to do? Thank you for taking the time to gather all this information and most of all doing the work to get video and share it. Randy

[@tghoffmann]

+NHlocal Hey, Randy. How you doing up there, neighbor? PM me on the Board, send me your email, I'll send you some links that could be useful to get the parts together.

[@NHlocal]

+Tom Hoffmann Doing great up here, "starting" to cool off. ;~) Tom that would great if you send those links. I "assume" you are talking about the KZbin "Board"? Thanks again Tom! :~D

[@critant]

Hello Tom, nice ideas good engeneering. Can you please send me a link where you find the butterfly valve.

[@ryanalbright6510]

Mr. Hoffmann Why don't you talk to Fredrick Axilton of FX Air Rifles in Sweden. He is an air gun engineer who is amazing. He loves a challenge.

[@mmoseleywpi]

Just one word of caution, and this is not probably anything big to worry about, but if that close hex nipple is stainless and the reducing coupling is stainless (or the jam nut), you might want to put some anti seize on the threads. Stainless on stainless threads, particularly tapered threads like pipe thread, are prone to galling and seizing up hard as you like... I know from experience.

[@tghoffmann]

+Marc Moseley Thanks for the SS threads tip ... didn't know that. About the inflator, search "Zefal EZ Adaptor" on eBay. About the pushbutton stuff, you're as crazy as I am! I actually experimented with a solenoid valve, I I have it in in the basement ... 1)the shooting dynamics change dramatically when you trigger through a small-bore hole and 2)the whole idea was just too much non-sense. We both should have our heads examined.

[@mmoseleywpi]

+Tom Hoffmann Haha, not the first time I've been told that. Just out of curiosity, what size solenoid valve did you use? You can get air angle piston valves at least 1" if not bigger. The pushbutton valve would just be inline with the 1/8" pilot line that would open the piston valve. And you're right, all of that is so much nonsense.

[@mmoseleywpi]

+Tom Hoffmann The other reason I mention the bike tube cartridge inflator is it can be nice to be able to use threaded or threadless cartridges. Many times you can find the threadless cartridges even cheaper, especially by the bulk.

[@aaronmcgarity2112]

Hi Tom! I have an original 1st generation APTA and I'm would love some information on where you found the parts to upgrade/how much it cost you. I can't get the accuracy I want, so unfortunately leave the APTA in the truck and hand throw more often because pumping up the APTA anywhere from 5-10 times is not very fun.

[@darylbarton9024]

Hey Tom, love your videos, very informative. My questions are about the fittings you used. Most low pressure fittings are only rated to 150 psi. Are you using high pressure fittings? Also, the fitting with the jam nut, is it a straight thread or a pipe thread? Thanks for what you do and keep up the good work!

[@MrSingleJack]

Nice work Tom.

[@tghoffmann]

+JB Holdway Thanks, Jack. Always nice to hear from you.

[@Logjam5]

Lefty! Nice looking spot.

[@wjsx4399]

Hi, Tom. Great videos on your APTA customizations. Extremely informative. With the aluminum pipe from Online Metals for the pressure chamber, did you cut your own threads or were you able to purchase it already threaded? I don't have the means to cut my own threads. Thanks for whatever advice you may have.

[@tghoffmann]

+wjsx I did my own threading with a hand threader but any plumbing supply place can do it for you. Or homeDepot. I used Online Metals too, but I bought "PIPE", not "TUBE", T6 Sch40

[@wjsx4399]

+Tom Hoffmann Thanks, Tom. Wondering what you think of going with a 4-foot aluminum chamber as you did with your previous steel pipe version. I was thinking of ease of use in the "mortar" position. Appreciate the guidance.

[@wjsx4399]

+Tom Hoffmann Sorry for all the questions. Online Metals has 1" OD 6061T6 tube in a whole range of wall thicknesses, from 0.035 up to 0.25. Sched 40 evidently applies to pipe, and an approx 1" OD pipe has a sched 40 wall thickness of 0.113. Is that about the wall thickness you used? Thanks again.

[@tghoffmann]

+wjsx No, actually, just the opposite. Going with a longer pressure reduces performance. On the pump, you have to pump more strokes to get to equal pressure but you get no benefit. On the cartridges, you get distinctly less pressure and reduced bag height. I think the 31cuin. chamber (1x36 sch40) is best.Where I have evolved, but I haven't published, is to go to;a 3-foot ;barrel;I get SL:IGHTLY belter range and SLIGHTLY better accuracy, but the improvement is only marginal. I keep it only because I get the "free space" in my gun case already carrying the 3-foot pressure chamber.

[@tghoffmann]

+wjsx Sorry, brainfart. Corrected above. PIPE not TUBE. Don't worry about wall thickness, just spec Sch40.

[@danielschneider2080]

If I may ask, what is the length of those tubes? Looks like 20"+45" or something? I only recall something about the optimal chamber pressure... Great video and thank you very much for sharing!

[@tghoffmann]

+Daniel Schneider The barrel is stock TS, the chamber is 1x36" 6061-T6 aluminum, schedule 40, from onlinemetals.com.

[@EarthshipFreedom]

+Tom Hoffmann does the chamber come with threads? also. do you think the barrel can be ordered from there with threads? dimensions? thsnks!! love your videos and enthusiasm.

[@tghoffmann]

+EarthshipFreedom You know, that's not a bad idea. TreeStuff is very flexible to customer requests for specials. Yes, the barrel comes with threads (1.5" nom. NPT) but you'd have to ream out the muzzle.

[@EarthshipFreedom]

+Tom Hoffmann ok. what dimension would the muzzle need to be reamed?

[@EarthshipFreedom]

+Tom Hoffmann ok great. what is the length of yhe barrel. so many questions i have! im a welder and fabricator, so building this is right up my alley. cant wait to try it out! i have dome dead trees that are very dangerous and im going to get a rope in them anf give thrm a tug with the tractor.

[@NHlocal]

.....also Tom, which red dot sight do you have, and what case is that you're "packing" it in? Thanks!

[@tghoffmann]

+NHlocal Case is a Plano single scoped rifle case, private labeled Sig Sourer. $15 used/perfect at my local gun shop. About $30 new, everywhere. Flimsy for guns but fine for the APTA.I had two RedDots, liberated when I upgraded my long guns. BSA RD42 and Bushnell Trophy 730135 . The BSA is a wider field of view and it's very inexpensive. I like the Trophy: it's closer to the barrel, much brighter, choice of easy-to-see reticles and has a long sunshade that's perfect for pointing into the trees.

[@RhysFransen]

You should try a harrision rocket weight they are the best i have used last the longest too they are handmade

[@tghoffmann]

+Rhys Fransen Thanks, Rhys. Do you use them in an APTA? If so, what size? What seems to make them last longer?

[@RhysFransen]

+Tom Hoffmann Yes i tap the end on the ground to seat it, 10oz they hand stiching quality is incredible they very consistent and the shot on the inside doesn't move around so much

[@bigkid2302]

Tom the part that allows the CO2 cartridge to be attached to pipe thread. Where is that acquired, if you don't mind?

[@tghoffmann]

Search "Zefal EZ Adaptor" on eBay.com, $10 incl ship.

[@bigkid2302]

+Tom Hoffmann so the schrader is still being used wether filling with air hose, or CO2 cartridge. I was under the impression that you were leaving the cartridge connected to the OFE/APTA! :-)

[@tghoffmann]

+DahBulldog Yes, the Schrader is the primary valve with either the pump or the cartridge. There is no valve in the Zefal connector, just the piercing pin. But I do leave the cartridge connected during the shot ... I just don't care to unscrew it while under pressure. Similarly, if I'm shooting from the mortar position, I leave the bike pump connected, just lying on the ground near the tail of the APTA. If I have to take a second shot (God forbid), I'm ready to start pumping immediately, no fussing to re-connect. You can't do that with the rifle or the bazooka.

[@mmoseleywpi]

+Tom Hoffmann As cycling is one of my many hobbies, another option is to buy a cartridge inflator meant for road side inflations. You can find them fairly reasonable, many will take threaded or threadless cartridges, and you could then leave just the schrader valve on the APTA so you could switch from cartridge to bike pump with no adapter. e.g. of one such product: www.rei.com/product/851753/genuine-innovations-ultraflate-plus-co2-tire-inflator?cm_mmc=cse_PLA_GOOG-_-8517530001&CAWELAID=120217890000786640&lsft=cm_mmc:cse_PLA_GOOG

[@eliassalas2654]

hello tom im trying to actually build this apta upgrade. im having trouble finding fittings and also the pressure chamber. I tried the website wher you got yours but I called and they've asked me for measurements on the thickness of wall . would you get back to me regarding this please .

[@tghoffmann]

+elias salas Contact me at [e-mail] and I'll try to help.

[@eisiator]

hey tom my name is phili, like your mods on the apta and i try to build my own. some how its really hard to find that butterfly valve!!! maybe you can help? greatings from germany

[@MountainCrestFarm]

Some WAY overkill here. The red dot sight is pissing money away as it doesn't improve accuarcy a bit. For it to improve accuracy it would need a rifled barrel and close AND repeatable tolerance between the barrel and the projectile.