Some thoughts on .357 vs .45 & .50

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billzweig

billzweig

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Aug 21, 2019
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BC
There is some ambiguity when it comes to "airgun power". Projectile energy is proportional to the bullet mass and its velocity and is usually given for specific guns as muzzle energy; close the muzzle. So a 0.45 heavy bullet can produce some 500 ft-lbs at 700-800 fps a short distance from the muzzle. But the smaller calibre can not only can achieve higher muzzle velocity, but will keep it at a longer distance, and since the energy is proportional to the square of velocity it could have a higher energy than the larger calibre at the same distance (and is often more accurate). I am now designing and building a big bore gun and trying to choose the optimum calibre for a longer range shooting and hunting. For example when hunting (in BC, Canada) at high elevations the distances are often 300 yards or more. Any suggestions? Thanks.


 
Since the mass of the projectile is contributing to fpe, how about a long, heavy, boat-tail .357 slug that is selected from those already available on the open market. Select the barrel design for a specific bullet that gives the best long-range accuracy, much like FX designs their liners around specific pellets, optimizing twist rates and chokes for that round. As you have seen with the Airforce Texans, air consumption will be high, might want an oversize or dual-bottle design... There are guys tuning and hot-rodding Texans to do higher performance, but designing and building a big bore from scratch would be whole different level of effort. Would be interesting to create a long-term build thread on the project.
 
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I would think a .257 or .303/.308 would best suit what you describe. If you can wait, and want to drop some money, then a .452 from american air arms would be the best thing you could do for power, range, and accuracy.

In .257 there are some proven builds shooting 1200 yards. Custom builds for sure, but that's an extreme example.

air force texans are reaching out there too, in .357 mostly, but .45 is a really popular caliber.
 
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Since the mass of the projectile is contributing to fpe, how about a long, heavy, boat-tail .357 slug that is selected from those already available on the open market. Select the barrel design for a specific bullet that gives the best long-range accuracy, much like FX designs their liners around specific pellets, optimizing twist rates and chokes for that round. As you have seen with the Airforce Texans, air consumption will be high, might want an oversize or dual-bottle design... There are guys tuning and hot-rodding Texans to do higher performance, but designing and building a big bore from scratch would be whole different level of effort. Would be interesting to create a long-term build thread on the project.
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I was thinking along similar lines.I do have good experience with boat-tail bullets in firearms (one of my favourites is the 6.5 mm Swedish.) The 178 gr HP-BT, 35 calbre could be a good start, though I do not mind making, and experimenting with, "wildcats". The idea to make my own design come through observing the basic flaw in the air delivery system and air flow geometry in practically all current air guns. As mechanical engineer I was often dealing with complex pneumatic systems design and analysis. The design of a radically different gun was my long awaited goal. Now, that I am retired and in a possession of a very well equipped machine shop, I do hope it shall come true.


 
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Now, this sounds like a noble quest! To take down big game at that range in the mountain winds you will need a slug with sufficient B.C., coupled with velocity and accuracy . I'm guessing a slug from 30 to ..45 caliber. Best of luck on your project and don't allow naysayers ruin your fun. Experimentation, is where progress begins!
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Thank you, Yoopper. I'll experiment with both .357 and 0.45. It will be nice to switch from my Swedish Mauser to an air rifle - even when I certainly cannot expect the same performance. But I do hope to significantly increase the power over existing air rifles. Or at least this is what is showing (at the instant of firing) in computer simulation. One thing that I have difficulty finding is the impact velocity at different distances for big bore air rifles. This data is commonly available for regular ammunition. My own measurements will have to wait as at 250 yards I got a perfect bullseye in my shooting chronograph...

In any case I am close to finishing the design and to start machining. This is what it will likely look:

1567727459_7185817795d719f638a4433.31345523_PCP-rifle.jpg

 
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Strelok or Chairgun will give you ballistics data given inputs like muzzle velocity, bullet weight, BC ....etc.

How much FPE are you expecting at the muzzle?

if you haven’t come across them, there are several good articles on Hardairmagazine.com written by Bob Sterne about some basics on PCP theory ...etc c
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What I would like to see are actual field measurements of velocity (or energy) vs distance for real airguns. This data is commonly available for firearms, for example:

1567746451_10275271595d71e993b7cd01.47181093_Hornady.png


As for my design: it is difficult to simulate or to calculate the velocity. Conservatively I hope to get some 40% increase - compared with same size bullet in commercial guns available today. This translates roughly to the doubling of the energy.
 
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Shooting targets at 300 yards is one thing cool in fact but

hunt game with Airguns at those ranges is going to result in bad shots and wounding more than you take.

You are not taking into account the amount of time it takes a 900fps at muzzle projectile to travel 300 yards At 300 yards it's difficult enough to hit a 6 inch plate that doesn't move little on a live animal. Add in mountain ranges with thermals, crosswinds, downdrafts and on and on that challenge some of the best long distance fire arm shooters and your asking for trouble 

Speaking as Texan where Airgun game laws has just opened up I cringe every time I see a post like this.

As an archery Hunter who has had deer do the matrix thing and duck an arrow (jump the string) at 50 yards I really don't see any ethically means for an Airgun to be used to take game at those kind of ranges.


 
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Hey Billzweig,

Remember what I said about naysayers (see Willie's post). Just because they think something is impossible or can't do it themselves , they discourage others from even trying. I'll bet it wasn't that long ago if someone said he was going to try 4,000 psi in a air rifle some guys cried, you'll blow your head off! Breakthrough is brought on by experimentation. Go for it! 
 
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Shooting targets at 300 yards is one thing cool in fact but

hunt game with Airguns at those ranges is going to result in bad shots and wounding more than you take.

You are not taking into account the amount of time it takes a 900fps at muzzle projectile to travel 300 yards At 300 yards it's difficult enough to hit a 6 inch plate that doesn't move little on a live animal. Add in mountain ranges with thermals, crosswinds, downdrafts and on and on that challenge some of the best long distance fire arm shooters and your asking for trouble 

Speaking as Texan where Airgun game laws has just opened up I cringe every time I see a post like this.

As an archery Hunter who has had deer do the matrix thing and duck an arrow (jump the string) at 50 yards I really don't see any ethically means for an Airgun to be used to take game at those kind of ranges.

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I completely agree with you. I certainly would not attempt this with existing airguns and so far have been using my 6.5x55. And this is exactly why I am trying to make an air-gun with higher velocity - and unless proven to work well I shall stick with the firearm. As I've indicated I did the design, calculations and computer simulation as well as some shop tests and it looks promising enough for me to continue. Still a long way.
 
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Hey Billzweig,

Remember what I said about naysayers (see Willie's post). Just because they think something is impossible or can't do it themselves , they discourage others from even trying. I'll bet it wasn't that long ago if someone said he was going to try 4,000 psi in a air rifle some guys cried, you'll blow your head off! Breakthrough is brought on by experimentation. Go for it!
Click to expand...


Thank you again for the encouragement. As mentioned before this is a radically different approach that possibly can allow 1300-1400 fps with 0.45 or 0.357. I did reach those velocities in a test setup (the so called "proof of concept"...) but making a practical gun is a different story and I am aware of it. Meanwhile I do appropriate comments, suggestions and criticism
 
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Take your .357 bullet and let's say you can push it to 1350 FPS at the muzzle and let's use this bullet for example 205gr with an estimated BC of .24. That gives you 825 FPE at the muzzle, which would be just HUGE HUGE power from a .357 AG. The Texan is listed at 300 FPE with a 190gr as a reference. But let's say you get there with your BHAG (Big Hairy Audacious Goal)

1567983744_20240317135d758880331903.03616967_N.O.E._Bullet_Moulds_360-214-HP_GC_U3_Sketch.jpg


You are starting out at Mach 1.21 AWESOME!!! , but at 125-135 yards your bullets has slowed to Mach 1....Bad news from there. Between 135 and 160 yards your bullet has dropped below Mach 1 and is now hitting that nasty transonic speed zone that will destabilize the bullet and there goes accuracy out the window.

But let's dial it back a bit. You said 40% more power than commercially available AG's. Again let's use the Texan in .357. at 300 FPE That would make your BHAG 420 FPE.

Now that same bullet at that energy would have a muzzle velocity of 962 FPS, which is good because it keeps the bullet out of that nasty transonic zone...right?

The bullet will then have 129 inch of drop at 300 yards and 9 inches of wind drift (with a 5 mph 90 degree wind) and it is dropping like a rock at this range. Miss your yardage by 10 yards and the POI changes by 12 inches.





Not raining on your parade, but pointing out the realistic physics of an AG

The balance has to be found between Speed, Bullet Weight, and BC.

Again Chairgun software (It's Free) is a great tool for running what if cases in your design. This is not like powder cartridges where there is a load data book and published data for cartridges at different loads. It is more like building wildcat loads, just no brass or powder....lol

https://www.hawkeoptics.com/chairgun-and-x-act-end-of-life.html


 
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Billzweig,

It seems like the big obstacle to your goal is the limit of available air pressure to drive your slug at sufficient velocity. How about a pressure booster that gives you the pressure necessary to drive a slug at say, 2000 fps. Pressure boosters are currently used to transform 120 psi to 4000 psi to pump up air tanks, it just the ratio of the low pressure piston to the high pressure piston. I attempt to send you a sketch of the booster mechanism. Please let me know what you think.

Thanks, Howard 

download.png
1567989714_9965537045d759fd2da6d01.84402723_20190908_00001_001.jpg



 
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Thank you both Loren and Yoopper. I really appreciated you comments and input and indeed this was my hope when starting this topic; to listen to suggestion and criticism from more experienced members. All the comments you are bringing are very valid and some I've been considering as well. I am using the Chairgun software as well as other ballistic programs that I was using for many years for my reloading and wildcat experiments (for example using the ELD Match Hornday 6.5mm bullets as well as custom machined and sabot bullets) and I hope this experience will help me here too (and there are significant differences in the results between the programs predictions and the field measurements. That is why I would like to see actual airgun ammunition speed as measured at various distances - that is much easier to obtain with firearms)

So on one hand I hope to design a low drag bullet suitable for my air-gun, possibly a machined two-metal bullet, and on the other hand to use my already (mostly) developed air system that can create a momentary intensified pressure through the air flow geometry. This combined with the timely release of the bullet at the moment of maximum pressure buildup hopefully can give me good results.

I am sorry for not explicitly disclosing all the design details, but before that I would like to work the details and to actually make a working gun that should offer some improvement over existing models, though possibly below my original, ambitious goal.


 
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Hey Billzweig,

Remember what I said about naysayers (see Willie's post). Just because they think something is impossible or can't do it themselves , they discourage others from even trying. I'll bet it wasn't that long ago if someone said he was going to try 4,000 psi in a air rifle some guys cried, you'll blow your head off! Breakthrough is brought on by experimentation. Go for it!
Click to expand...

Shooting targets at 300 yards is one thing cool in fact but

hunt game with Airguns at those ranges is going to result in bad shots and wounding more than you take.

You are not taking into account the amount of time it takes a 900fps at muzzle projectile to travel 300 yards At 300 yards it's difficult enough to hit a 6 inch plate that doesn't move little on a live animal. Add in mountain ranges with thermals, crosswinds, downdrafts and on and on that challenge some of the best long distance fire arm shooters and your asking for trouble 

Speaking as Texan where Airgun game laws has just opened up I cringe every time I see a post like this.

As an archery Hunter who has had deer do the matrix thing and duck an arrow (jump the string) at 50 yards I really don't see any ethically means for an Airgun to be used to take game at those kind of ranges.

Click to expand...

I completely agree with you. I certainly would not attempt this with existing airguns and so far have been using my 6.5x55. And this is exactly why I am trying to make an air-gun with higher velocity - and unless proven to work well I shall stick with the firearm. As I've indicated I did the design, calculations and computer simulation as well as some shop tests and it looks promising enough for me to continue. Still a long way.
Click to expand...

As mentioned I live in Texas so yes I am a little gun shy about posts like this and other 300 yard posts when hunting is mentioned I wasn't trying to rain on your parade.

If the fear of shooting my chrony (again)...and explaining why I need to get another one to my wife... (again) wasn't a factor I have been really temped to take my .45 Texan and .308 Texan and my .357 Bulldog set up the chron at 100 yards and see if I can get some hard data on fps at 100 yards. computer sims are good and well but nothing can replace true hard data. 

I shoot black powder so may I advise attempting to use sabot rounds as this will allow a .50 caliber barrel to shoot down to a .45 caliber round ( I have even seen 50 caliber down to .357) You can use the same concept for smaller chamber rounds. This will give you the chamber volume you may need to reach the kind of speeds your looking for. Since sabot rounds has less friction and weight to size ratio. Look for Nylon sabot they offer much less friction than plastic or poly and stand up to the rifling my better.
 
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I made a steel plate backstop with a wooden shelf screwed to the back of it. The shelf sits low enough for my chrony to sit on and still be protected. It has held up to my big bores and muzzle loader. It would have to be a thicker plate for a rifle. We use to cut 55 gallon barrels in half and set a cement block in the bottom. Just the right height for a chrony to sit on and be protected. Works good for the smaller air rifles. Put a couple bales of straw in front and you can shoot a bow over it. Cheep and simple. 
 
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