Author Topic: 45 caliber Big Bird Big Bore Build (Read 22403 times))

BigBird · « **on:** August 14, 2019, 10:27:20 PM »

I've been doing my 15 - 30 minutes of work here and there on my barrel and will be proceeding with a 45 cal. deer airgun that I will be working on over the course of maybe 6 months to a year. So updates will be farther between. This time may be good for planning and getting suggestions.

I'd like to have a 45 caliber deer gun that will operate similar to a Quackenbush (.458 Long action outlaw) in that I am going for a few good shots (declining or top of parabola) with shots 1 and 2 being higher velocity. Probably 3000 psi since I only have a hand pump.

Barrel (previous to more work)

I have a Bergara 45 cal muzzleloader barrel, (1 in 28" twist) that has about 27" of bore. I took off the welded on lugs via dremel and it was quite easy.

Lug on

Lug off

It has a 5/8" x 18 x ~1" threaded female breech plug area on the end that I will use for attaching the other half of the breech so breech and barrel are one unit. The barrel is 1" at breech and 7/8 (was) at the muzzle and I will continue to taper back to the breech.

Working breech end

Ugly Muzzle (I'll clean that up)

So right now I'm looking at a513 DOM steel tubing for the pressure tube and need advice. I dont see the benefit of 4130 with its lower yield point. I like 1" x .083 but if it doesn't work for this setup then I can go to 1-1/8" x .095.

Also, everything will be pinned (fill end, valve) as opposed to a real Quackenbush

I was using the calculator here with 3.5 SF
http://www.engineersedge.com/pipe_bust_calc.htm

Here is size, length for ~10 CI, weight, which is also a concern.

1x.083 = 0.834 ID
25" x .81 lbs per ft = 1.6875 lbs weight for 10 ci

1.125x.095=0.935
23" x 1.0452 lbs = 2.0033 lbs for 10 ci

Please bare with me, it may look like muppets from Sesame Street are making it.

BigBird · « **Reply #1 on:** August 19, 2019, 08:32:40 PM »

Took a couple hours to do the final profile on the front half of the barrel. Still need to polish out shallow file marks but it has a nice transition from 0.838 to 0.692.
I think it is going to be a light sporter profile.

Still looking for a tube. Any suggestions?

Madd Hatter · « **Reply #2 on:** August 19, 2019, 11:57:47 PM »

IMHO, Don't want you your yield strength to close to your ultimate strength.

BigBird · « **Reply #3 on:** August 20, 2019, 09:38:39 AM »

Quote from: Robert Feddeler on August 19, 2019, 11:57:47 PM

IMHO, Don't want you your yield strength to close to your ultimate strength.

Yes. 4130 does have a wider difference. The real benefit is the UTS in the 90k's psi. I guess it would be good for engineering a fail in the design so it leaks before it breaks (Something like outboard orings or orings near a tube hole). That would be a benefit over other tubing. Or use a burst disk.

I am worried about testing to deformation. I know Lloyds testing of the Crosman barrels yield happened pretty early (around 7k? IIRC). I read Bobs use of 1"x .065 for a tube in 4130 and that would be a great size for my application.

I am always on https://www.makeitfrom.com/ doing comparisons. It shows 1020 does have a wider difference than any of the popular lightweight tube alloys (2024. 7075). Maybe 1020 is a "tweener"?

BigBird · « **Reply #4 on:** August 21, 2019, 01:09:30 PM »

So, based upon all the feedback and suggestions I ordered a 4130 - Round DOM Tube 1.125" x .083" x 36"
with 24" of 1144 and some other a513 tubes for my 30 caliber and future projects.

BigBird · « **Reply #5 on:** August 23, 2019, 02:46:36 AM »

Burning the midnight oil. Maybe I can get this done for this deer season?

The original small portion of muzzle that remained had to come off so I could put the barrel through the 22mm spindle hole. I didnt want to just lop 1/2" to 3/4" off so I inserted some random soft round rod (from a power wheels axle IIRC) that must have been 3/8" or maybe metric cause it fit perfect with some plastic around it. I drilled and tapped a 8-32 in the front of the barrel (the non rifled - bullet starter portion) into the rod and then cut the screw off (so I could use the carbide cutter to cut through it without the head hitting the bit). Chucked it into the lathe and turned down the muzzle to about 0.78 then cut the screw portion off. It wasnt concentric (big kids on the Power Wheels) but it didnt matter because now it fit through the spindle hole. So I put it through and worked on the muzzle and turned it down "all concentric like". It still needs some final finish but it should be much easier from here on out.

Lopped off portion (cut through tapped threads) on top of native muzzle. Not to be confused with the original front sight hole (further back from the end of the muzzle). It only amounted to about 1/8" and the portion that was not rifled.
, to be removed anyway.

Muzzle looking almost finished

Mark Davis · « **Reply #6 on:** August 24, 2019, 08:53:46 PM »

Quote from: BigBird on August 21, 2019, 01:09:30 PM

So, based upon all the feedback and suggestions I ordered a 4130 - Round DOM Tube 1.125" x .083" x 36"
with 24" of 1144 and some other a513 tubes for my 30 caliber and future projects.

Are you using the 1144 for end caps?

BigBird · « **Reply #7 on:** August 25, 2019, 12:06:23 AM »

Quote from: Mark Davis on August 24, 2019, 08:53:46 PM

Quote from: BigBird on August 21, 2019, 01:09:30 PM
So, based upon all the feedback and suggestions I ordered a 4130 - Round DOM Tube 1.125" x .083" x 36"
with 24" of 1144 and some other a513 tubes for my 30 caliber and future projects.
Are you using the 1144 for end caps?

I may use it for end caps. I read that Bob used it for a valve and was hoping to do that as well. It has a good machinability score and strength. Not sure about how it polishes for making a good seal.
Otherwise my 1.25" 303 SS is available but it is hard to work with with my makeshift lathe motor and there is a lot of diameter to take off. I am open for suggestions.

I went through some worry about the barrel when I couldnt find my center. Every way I put it, it would wobble. Somehow it worked and it was turning fine. I reduced the breech side down and now it is just file work to get it smooth and to make sure the profile looks good. I found some USA made used files for $1 a piece and bought 10!!! Oh man do they work nice compared to dull HF from the bad parts of China. I have fine and coarse now and I can get it real smooth before sanding.

Difficult to do work in a black hole but then you'd see my "visual organisational skills". I have no time for clean up and work in a small space

BigBird · « **Reply #8 on:** August 26, 2019, 09:58:43 AM »

Previous to last picture.
I had to turn down the breech side barrel which included this welded area for the front stock/cleaning rod lug.

Also in reply to Mark Davis because you may have implied a different question....

Quote from: Mark Davis on August 24, 2019, 08:53:46 PM

Are you using the 1144 for end caps?

Yeah, it is less than the diameter of the tube but who said all endcaps need to be tube diameter? Check out "Bontrager" big bore. Ill probably use a large screw for the rear end cap if it will work but the front will be a little better steel like 1144 or 303.

BigBird · « **Reply #9 on:** August 27, 2019, 08:34:29 PM »

UPS said yesterday but got lost or something but finally delivered tubes and a 1144 rod today. Here is the barrel (&1/2 of breech) on top of the tube. The 1" x .083 steel a513 looks like a very good size for the project too. There is a 7/8" x .065 x 24" as well. I'll have some on hand anyway.

Finger shows the end of the breech at about 31" for the tube size.
Stock is the take-off from my 1917 Enfield. I'd have to fill a couple holes in the stock (doable) if I used that but it gives a little perspective.

Finished barrel (need to work on the breech part to attach the rest of the breech)

Breech attachment (hopefully what I was thinking anyway...)

Barrel weight

BigBird · « **Reply #10 on:** August 28, 2019, 02:55:45 PM »

Sending back the 1-1/8" x .083 as it had some issues on one side.

The drawing process was dirty and it only happened to one side so someoone didnt watch the feed or maybe there was scale.

I tried to clean ot off but it is in some pits.

BigBird · « **Reply #11 on:** August 30, 2019, 11:06:23 PM »

Ok. Bad luck with this supplier. This was a replacement tube, hand picked but it still has a couple gouges and a damaged end from poor packing.

These people dont care about Safety!

BigBird · « **Reply #12 on:** September 02, 2019, 11:33:26 PM »

I am getting bored/irked waiting on a response about a refund for the crabby tube (s).

So I started working on the 1-1/4" 303 round rod that I have been saving. I hobbled along but after several meager passes it worked.

I may use it for a 1-1/4" x .095 tube.. I have a 12" piece to play around with.

I figure I only need about a 20" tube for the volume I want. It would be a little heavier but places the center of gravity nearer to the fore hand and allows more room for a moderator if possible.

Tube calculations:
20" for 17.65 ci
Area = 0.8825 x 3000 = 2647.5 lbs force on internals (?)
Not sure if countersunk 1/4 SHCS screws would be enough.

Weight
1.172 lbs / ft = 1.953 lbs for 20"

BigBird · « **Reply #13 on:** September 05, 2019, 03:12:56 PM »

Worked on extending the breech using the 1144. It's some tough stuff and took a little longer to reduce down but it should be much stronger for the breech connection than 1018.

I had to make a 1" threaded section that was 5/8" x 18 to connect to the breech plug area of the barrel.

I made it a little longer than I needed so I would have enough to play with. I'll only need about 3". There is a rebated area in the breech end that I will use for a little more strength. I'll turn down a little more of the 1144 rod to fit into it..

Mark Davis · « **Reply #14 on:** September 05, 2019, 11:51:49 PM »

I just asked about the 1144 because I use it for punches, and keep some pieces around for different projects.
Reading your post made me realize it could be useful for end caps on pressure vessels.

No plans to build an air gun yet, but still interested in suitable materials.

BigBird · « **Reply #15 on:** September 06, 2019, 12:44:00 AM »

I was wondering if it takes a shine. Polishability index is not in the properties listed on makeitfrom.com (it may be called something else). Also they could add a cold bluing index to the properties too. Although I think I have two different indexes on this breech and it will need to get cerakoted.
I think there are a lot of metals that can be used. The reason I chose it was the machinability index and this supplier had it fairly cheap ($6.10/ft). I was hoping to use the 1144 for the breech and valve until my tube supplier couldn't get me a good defect-free 4130 tube in the size I wanted. I went up to a 1-1/4" in 1020 tube (2 coming tomorrow) and had to use a different rod due to the 1.06 inside diameter.

Gippeto · « **Reply #16 on:** September 06, 2019, 02:59:24 AM »

JM .02, but would not make the valve body from steel. Any corrosion on the seat from the air will likely cause a leak...might get away with it if you go with an inserted seat, but you'll almost certainly be fighting corrosion at some point down the road.

Quite a few folks seem to like aluminum (inexpensive and easy to machine), have seen a few done in stainless (I'm not overly fond of tapping small holes in stainless...can't imagine why lol). My go to material for valve bodies is brass 360...easy to get and easy to work with...just costs a bit more than aluminum.

We now return to our regularly scheduled program....

Al

BigBird · « **Reply #17 on:** September 06, 2019, 09:29:18 PM »

Quote from: Gippeto on September 06, 2019, 02:59:24 AM

JM .02, but would not make the valve body from steel. Any corrosion on the seat from the air will likely cause a leak...might get away with it if you go with an inserted seat, but you'll almost certainly be fighting corrosion at some point down the road.

Quite a few folks seem to like aluminum (inexpensive and easy to machine), have seen a few done in stainless (I'm not overly fond of tapping small holes in stainless...can't imagine why lol). My go to material for valve bodies is brass 360...easy to get and easy to work with...just costs a bit more than aluminum.

We now return to our regularly scheduled program....

Al

Thank you. This is my first build like this so I am indebted. I was going off some other builds and saw the 1144 used there. I did ask when I was trying to source the internals. I had read about aluminum corroding in some crosman guns and also saw a lot of the big bores are made with SS (416) or an unknown steel (stainless).

Gippeto · « **Reply #18 on:** September 07, 2019, 02:42:04 PM »

Reading through, I see where you asked. Do you have other threads on this build so I can get right up to speed on it?

Do you have a scaled drawing of the moving bits.. receiver and valve/striker portion of the pressure tube? I find it helpful, but some folks prefer to wing it or copy something already existing. Easier to get good help if they can see where you're heading as well.

I use normalized 4130 tubing from Aircraft Spruce and Specialty. For a few bucks extra, you can get a copy of the material test report if desired. In Canada at least, they seem to treat their tubing with some respect.

I have read about corroded aluminum valves, but never seen one. Most likely is a galvanic corrosion, which requires something more than you would typically find in clean, dry air. Possible culprit is inadequate cleaning after bluing the steel bits leaving some caustics or acids behind and un neutralized.

Stainless isn't hard to work with, but you need to pay attention, and keep it cool. Once it work hardens, things can go down hill quickly...more so it seems if a fellow is tapping the bottom of a hole.

Brass just turns so nice with HSS or carbide. No work hardening, no build up on the tools, no coolant mess, nice chips almost irrespective of speed and feed. Nothing here to not love.

About all I want to type on the phone. Keep at it.

Al

BigBird · « **Reply #19 on:** September 08, 2019, 02:13:38 AM »

I will be matching the upper half to a Quackenbush so it should be proportional at least with the holes and TP. That was what I set out to do originally (have a .45 caliber upper). I'm not sure how the breech will line up with the Quackenbush though because two halves will be screwed together (extending the muzzleloader breech with the 1144).

I wanted a longer barrelled .45 than a 20" .45 because it is a smaller diameter than a .58 (all things being ~equal I think smaller surface area bullets should have more time in the barrel and subject to pressure). I wanted a .45 to shoot better BC for range (dont get me wrong, I do like my .58 though!). I want this one to be a deer gun too.

I won't be using the Quackenbush for a blueprint of the lower half as It isn't a pinned valve and the spring is anchored in a way I wouldn't anchor it (I've haven't disassembled mine yet).

I was thinking of building it like a QB valve except longer to accept the front trigger screw on bottom and with more flow through front half of the valve (spring "housing") similar to what I saw on one of Bob's valve (an internal expanding retainer). Pinning screw locations I was thinking of using Two 1/4 x 28 on the sides (in same cross section as the TP), I will turn down a 1/4 or 5/16 Socket Shoulder Bolt to use as the lower pin (opposite the TP) and also as a stock mount screw. Screw holes will go through and see "lower" pressure.

I would probably add 2 more pinned screws on the side of the breech side of this longer valve I was thinking of using 4 pins in front of the TP like the "Bontrager Big Bore" but if I'd rather put them like above since the valve is extended toward the breech anyway.

https://www.gatewaytoairguns.org/GTA/index.php?topic=160665.0

I built a .30 cal valve with 303 SS and did not use coolant and it felt like 304 sometimes. I will use coolant on this. I may drill in water.

I was planning on following that build with a sculpted out concave valve face and screw on springhousing. (If I can thread 1" or 3/4"). If I want to make a balanced valve later it makes it esier too. Traditional 1/8 or 5/32, O1 tool steel, delrin poppet.

I could not find the right size 4130 on Aircraft Spruce as they skip some common wall sizes.

I just recieved some 1.25" x .095", 1020, a513 and some flat 1/2 x 2" 1018 for the trigger attachment and maybe barrel band. They were supposed to send the mill certification and I will get those. These "look" very good. I will test these with my hydraulic hand pump.