45 caliber Air Rifle

[HollowPoint]

I took the male Foster fitting back off the Big Bore and broke out my digital calipers. I wanted to see what kind of differences there were in the dimensions; if any.

Sure enough, there was a big difference.

I had to screw the aftermarket Foster Fitting in as far as it would go to keep it from leaking air. Unfortunately, having it screwed in so deeply caused the effect that Butcher eluded to; it was somehow keeping the Air-Reservoir plug for completely sealing.

As a result, the Foster Quick disconnect fittings had full constant PSI pushing against them. That's why I couldn't disconnect them once I'd pumped the PSI up to about 300PSI and above.

The Ace Hardware store down the street had a full selection of rubber O-Rings so I was able to find a slightly larger replacement O-Ring (as well as a few larger sized just-in-case replacement O-Rings) for the face of that Male Foster Fitting.

All is right with the world again.

I cast a few of the Lyman Devastator bullet from the mold that I had opened up. I was anxious to see if they would work in this air rifle. The bullets looked good out of the mold but, when I put my calipers to them I noticed that the tail end that I had opened up to .457 was slightly out of round.

I couldn't wait; I closed all the doors and window of the house and shot a couple of these lyman devastators and a couple of the bullets that JIMinPHX gave me into a box of old tax papers that I've been getting ready to shred. I wanted to see if the rifling was printing onto the tail ends of these cast bullets.

It worked! I could see that the tail ends of my Devastator bullets were engaging the rifling. And just ahead of the lube groove there was just a hint of contact with the rifling. It was the type of rifling imprint you would get from a good "Bore-Rider" bullet setup. The smallest of the bullets that Jim gave me showed a slight trace of rifling imprint but not to much. The others, none at all.

The only down side to this particular bullet is what I stated earlier. When I opened it up to .457 I didn't get a true-round .457. It is presently an oblong-round. It goes from .455 to .457.

I have a couple of Boring-Bars coming in a couple of days. I'll be able to true-up the tail end of my Devastator mold at that time.

With any luck I'll be taking this new toy out next weekend for its maiden rabbit hunt.

HollowPoint

[Butcher45]

!!!That battle station is fully operational!!!

[HollowPoint]

I hope you Big Bore Air Gun Shooters and other interested parties will bare with me while I show off a little bit.

After what seems to me like a real long time, I finally got my new Sam Yang ready to hunt. I hope to take it out next weekend to see what it will really do.

I know a place where there's alot of cottontail targets. I know this new toy is more than enough gun; wether I can hit them or not is another story.

I broke out the camera and took a couple of pics of my finished Big-Bore Air Rifle. Nothing to outlandish; I just wanted to show you the peep sights and the Lyman Devastator slugs I'll be shooting.

[Butcher45]

I hope you Big Bore Air Gun Shooters and other interested parties will bare with me while I show off a little bit.

After what seems to me like a real long time, I finally got my new Sam Yang ready to hunt. I hope to take it out next weekend to see what it will really do.

I know a place where there's alot of cottontail targets. I know this new toy is more than enough gun; wether I can hit them or not is another story.

I broke out the camera and too a couple of pics of my finished Big-Bore Air Rifle. Nothing to outlandish; I just wanted to show you the peep sights and the Lyman Devastator slugs I'll be shooting.

Nice peep sights!

Penetration is not what the HP's do. Especially with a 909 that has not been tuned (tuning makes a HUGE difference). Use a 220-250 grain solid, or roundball if you want to see penetration. Roundball works great on small game.

I'm sure the Devastators will work more than OK on a rabbit.

Do you have a chronograph?

[HollowPoint]

In all fairness these Devastator slugs were cast from straight Stick-On wheel weights. Around 6-7 BHN.

I'm not surprised that I didn't get deep penetration, just not impressed with what I got as far as penetration.

A while back I made an adjustable hollow-point pin for this very mold. By using it I can adjust the depth of the hollow point from just a dimple on the tip of the bullet, to about 5/16" deep hollow point cavity.

If I need more penetration I can just decrease the depth of my hollow point and increase the hardness of my alloy a bit.

I do have a chronograph. It's brand new. I've only had it out of the box once; and that was just to look at it. I've had it for about three years now. I've never used it.

I guess I'll have to blow the dust off of the box it came in and check the velocity of these Devastator bullets.

HollowPoint

[Butcher45]

Remember to have the chrony about 10 feet away from the muzzle to avoid false readings from the airblast. Just be sure to aim level, and a bit high over the sensors. I've shot more than one chrony in my time.

[Bob.]

Nice lookin rifle HP
Really like those peep sights.



Bob

[HollowPoint]

Thanks for the compliments gentlemen.

I went back and forth about putting a scope on this air gun but, in the end I decided to try to keep it as simple as possible.

The peep sights seemed like a good compromise. They basically give me the sighting effect of a zero-powered scope and still allow me to make sufficient adjustments for the close up shooting this gun was made for.

I mentioned before, without these peep sights I would just be wasting my time because I wouldn't be able to see the sights clearly enough to shoot straight.

I plan on posting a couple of bullet ideas I've had just to see what you guys think. I want to know if they look like they might have some merit. They are dimensionally based on my Air Rifle's bore dimensions.

I want to try to make a bullet mold that puts out cast bullets specifically made for this rifle.

HollowPoint

[Butcher45]

I plan on posting a couple of bullet ideas I've had just to see what you guys think. I want to know if they look like they might have some merit. They are dimensionally based on my Air Rifle's bore dimensions.

I want to try to make a bullet mold that puts out cast bullets specifically made for this rifle.

HollowPoint

Now we're getting to the good stuff!

Here's what I would like to see: a combination of the EPP/UG, and "JR" WFN designs, with the common factors mentioned earlier in the thread (very small contact area with the barrel, bore-riding qualities, and an angled/tapering top band). About 215-220grains, with a meplat around .33 or so. It'll happen some day.

[HollowPoint]

As far as bullet designs go, I really don't have the experience to say one way or the other.

I'm looking for a lighter weight design with some of the same characteristics that were mentioned. I don't want to copy anyone else's design but, it seems that there are certain similarities that all good designs have to incorporate in order to get them to fly right.

The heavies are OK but, at this point I have no use for them. Since I'll be shooting real-small game a 200-plus grain slug is more than I really need.

I'll try to post what I had in mind a little later.

HollowPoint

[Butcher45]

The .45Slim is super-accurate in my 909.....about 170grains in pure lead.

[HollowPoint]

That last picture looks similar to a bullet and bullet mold that I drew up a couple of weeks ago. On my drawing the front grease groove looks similar to the rear grease groove. I figured the deep grease grooves would go a long way toward reducing my weight. I also made mine a hollow point for the same reason.

I was hoping for something about in the 150-155 grain range. Never having designed bullets before, I'm not sure how to calculate the weight of a given design so, I just have to guess.

I use my Lyman Devastator mold as my comparison. At that given length and shape, it weighs close to 200 grains. I figured if I design a bullet of the same length and general thickness and include some deep grease-grooves and a hollow point, that might get me to the 150 grain mark I was hoping for.

Here's one of the other bullet drawings I've been working on. I think it's stubby enough to get me into the weight range I'm looking for.

HollowPoint

[Butcher45]

That last picture looks similar to a bullet and bullet mold that I drew up a couple of weeks ago. On my drawing the front grease groove looks similar to the rear grease groove. I figured the deep grease grooves would go a long way toward reducing my weight. I also made mine a hollow point for the same reason.

I was hoping for something about in the 150-155 grain range. Never having designed bullets before, I'm not sure how to calculate the weight of a given design so, I just have to guess.

I use my Lyman Devastator mold as my comparison. At that given length and shape, it weighs close to 200 grains. I figured if I design a bullet of the same length and general thickness and include some deep grease-grooves and a hollow point, that might get me to the 150 grain mark I was hoping for.

Here's one of the other bullet drawings I've been working on. I think it's stubby enough to get me into the weight range I'm looking for.

HollowPoint

That's a very interesting/cool looking boolit design. Looks like a double-ended target/hunting boolit. Wonder how that would fly with the HP in the back?

Another thing to consider, is the affect the extra surface area at the face of the boolit (more surface area for the air to push). Very interesting.

Again, neat looking boolit!

[PatMarlin]

Fine looking rifle HollowPoint.

Nice cocking lever ...

[PatMarlin]

http://www.youtube.com/watch?v=GEacr...eature=related

[Butcher45]

http://www.youtube.com/watch?v=GEacr...eature=related

That corsican ram was shot in the spine. The guy that shot that video said so.

Hit'em in the spine with just about ANY boolit, and that's what happens.

[HollowPoint]

Thanks for the compliment Pat.

After I mounted it on the gun it kind of looked out of proportion with the rest of the receiver. I left it on because it really does cock more easily in that configuration.

I have since removed it and whittled it down a little more; just so it doesn't look quite as chuncky. I have one more piece of metal left so I can make one last cocking lever later on if I'm feeling energetic. Next time I'll make it to set a little closer to the side of the receiver.

Bucher45: "(more surface area for the air to push)"

I'm not really sure what to make of this statement. I did a little bit of informal research into the optimal shape of slow moving bullets and I was able to google up a study that was done by Lapua. If I paraphrase what that study conveyed it's some thing like this:

Optimum bullet design for slow moving pistol bullets include a truncated cone-like nose and a Rebated Boat Tail.

The down side to a feature like a rebated boat tail is the fact that it may have the effect of directing the hot gasses to edges of the bullet's tail and there by inducing gas-cutting. (this is in a conventional firearm.)

I don't know if this applies to air guns with such a low PSI behind the bullet as it gets pushed forward. In the bullet I drew up, I thought a good way to mitigate the "gas-cutting" would be to modify my rebated boat tail by setting it into the tail end of the bullet's semi-hollow-base.

In my minds eye I pictured the gasses that my have been directed to the outer edges of my bullet's tail, as being re-directed by the curvature of the semi-hollow-base back into the oncoming gasses.

This would create a sort of donut-shaped vortex of pressure/gasses which would expand and seal the rear-most driving band up until the bullet exited the barrel; at which time the benefits of the rebated boat tail would add to the aerodynamics of the bullet in flight.

Of course, things don't always work the way we hope they will but, that was the idea behind the design.

The truncated cone just seemed a whole lot more aerodynamic than just about any of the air-gun-bullet designs I've seen so far. That's why I wasn't sure what to make of the, "(more surface area for the air to push)" comment.

By drawing it the way I did I was hoping to get this bullet to slice through the air rather than "push" it through the air. If there's something I'm missing here please let me know so I can incorporate it into the next idea.

HollowPoint

[Butcher45]

The truncated cone just seemed a whole lot more aerodynamic than just about any of the air-gun-bullet designs I've seen so far. That's why I wasn't sure what to make of the, "(more surface area for the air to push)" comment.

By drawing it the way I did I was hoping to get this bullet to slice through the air rather than "push" it through the air. If there's something I'm missing here please let me know so I can incorporate it into the next idea.

HollowPoint

I wasn't referring to the nose when I said "more surface area for the air to push". I was referring to the base of your boolit design, and the reservoirs air pushing for power. This is speaking in turns of air-specific efficiency, rather than accuracy, or terminal ballistics.

From what I have gathered thus far, any airgun calibers appear to have a power-ceiling, with the larger calibers having more fpe potential. Meaning the greater the area for the air to operate in AND ON, the greater the power potential.

The rebated boat tail's very minute increase in barrel volume (the "area in" part) is not what I'm getting at here, but the "area on". That boat tail base provides more area for the force of the air to be applied. A substantial increase in area over a plain base. I'm thinking this additional area just might provide some of the benefit a larger caliber also brings.

Another way of explaining it.....think of the boolit base as the tip of your pool cue, with the air being you operating the cue. If for some reason you are wanting to hit that Q-Ball as hard as you can, which applies more force; a pencil, or a pool cue?

I could be wrong about any or all that, but that's been my personal impression.

The 174 or so grain (BHN6) Truncated Cone is unbeaten in accuracy from my 909. Another super-accurate boolit is the old #45266 BullsEye boolit, which many describe as reminiscent of a boat-tail. My 909 loves that 226grain boolit (brained a small Oklahoma boar hog with a #45266).

Lyman#45266 third from the left

[Butcher45]

The truncated cone just seemed a whole lot more aerodynamic than just about any of the air-gun-bullet designs I've seen so far.

HollowPoint

Finding a "good" target design that shoots .5 to .9inch c-to-c at 50 yards is fairly easy....the ones with "great" accuracy do appear to have somewhere between a medium/modest meplat, to no meplat to speak of. So you seem to be on the right track for a small game/acuracy boolit. With the few airgun boolit designs that are out there, (off the top of my head) supreme accuracy was never the goal.

The objective with the large meplat airgun boolit designs you refer to has been to create the best hunting slug intended for creating larger wound channels/quicker kills when taking heart-lung shots on larger game animals. A proper Keith nose, LFN, and better yet WFN is PLENTY accurate for big game and plinking at 50 yards.


Forgot to mention, that aside from Barnes (he has a few designs for different calibers), you can count the airgun-specific designs on one hand.

[HollowPoint]

("From what I have gathered thus far, any airgun calibers appear to have a power-ceiling, with the larger calibers having more fpe potential. Meaning the greater the area for the air to operate in AND ON, the greater the power potential.

The rebated boat tail's very minute increase in barrel volume (the "area in" part) is not what I'm getting at here, but the "area on". That boat tail base provides more area for the force of the air to be applied. A substantial increase in area over a plain base. I'm thinking this additional area just might provide some of the benefit a larger caliber also brings.")

Hey Butcher:

Do know of any links you can refer me to so I can read up on exactly what you're trying to explain in the quoted sentences above?

I believe you know what you're talking about but, I'm having trouble understanding it. I thought perhaps if I read the same things you've read concerning air guns and power ceilings and surface areas and such, I could better understand what you're getting at.

The bullet study that I googled up the other day that lead me to design the bullet in the drawing I provided seemed to indicate something slightly different. Of course this study I'm referring to applied to conventional firearms; not air guns of any kind. I just assumed that this same study might have some relevance to air guns as well.

Following is the link to that study. http://www.swage.com/ftp/rbt.pdf

It's true I'm looking to make an accurate air gun bullet but not to the exclusion of terminal ballistics. Thats where a shallow hollow point comes in. With air gun slugs cast as soft as they are, even a shallowest hollow point should induce expansion even at the slow speeds that these big bore air guns function under.

Even a slight expansion should compensate for the generally low terminal ballistics of an otherwise pointy nose bullet, while hopefully still retaining its aerodynamics and accuracy .

HollowPoint