45 caliber Air Rifle

[Butcher45]

I spoke to LI Bob about this problem a week or two ago . He said he machined the lever to except a cap allen screw and milled the lever grove to except it. . But on a gun with a really heavy spring he has removed the lever and back were the nob would normally be he has drilled and taped the hammer to take a large diameter bolt handle . But he said that it had to be exactly centered or the gun would not choch and hold . Hope this might help . I have thought about haveing something done with this as well . Marvin

I like what I see in PatMarlins sketch. I always thought off-setting the lever behind the hammer is the way to go. Seems like the simple solution.
I'm not worried about the screw coming loose anymore since I started using the teflon tape around it awhile back.....just the crazy-cheap lever material. The screw was still in tight on this last breakage.

[JIMinPHX]

It is tricky to find the boolit/fill pressure combination that will give you two identical shots for the same POI@50yards

Has anyone ever tried building a rifle with twin air tanks, so that you can get 2 true 3,000psi shots?

[Butcher45]

Has anyone ever tried building a rifle with twin air tanks, so that you can get 2 true 3,000psi shots?

You can get tights fps variances off of one air reservoir regardless of dropping psi levels....it's all about the valve, and having a large enough air capacity in the reservoir. I can get several boolit designs to shoot four shot strings within a maximum 20fps total variance (sometimes only 7fps or so in a string). The 909S has a larger valve than the 909 which makes for more power, but a smaller air reservoir so there are less shots available. Having a large air reservoir makes getting tight fps variances within a shot string much easier.

Here are some links to some comprehensive testing/shooting with my tuned 2tube 909.

http://castboolits.gunloads.com/showthread.php?t=76446

http://castboolits.gunloads.com/showthread.php?t=78281

[HollowPoint]

I've wondered about some of the fps numbers posted around the internet; even on the "Tuned" Big Bores.

I realize that we're talking about an air reservoir that reduces in psi after every shot so, it stands to reason that the fps numbers would go down in more of a linear way. What I mean is; as an example; each shot dumps 200 psi. So, this would mean that your shots would slow down incrementally because there is less air in the reservoir to draw from.

Some of the numbers I've seen will start at a certain level, (generally the highest fps in the shot string) then the next shot may be a little higher than the first, then back down, then a couple shots higher still. It's rather erratic to say the least.

I can see why this might happen with traditional firearms where there are many components such as brass, powder, primers, seating depth, runout, reloading inconsistencies etc.. In an airgun, where an air valve should open up to or near the same amount each time the trigger is pulled, such a fluctuation in fps just doesn't add up.

I'm starting to come to the conclusion that it has to do not with the function of the valve, trigger, hammer or spring but, it's the position of the projectile in the chamber at each shot.

When we load a bullet into the chamber, is it pushed all the way in to the same spot in the chamber each time? With round ball especially; it can be a good fit in the bore but, while in the chamber -which is generally a looser fit- if it moves even a little bit it's bound to effect the fps as well as accuracy.

Now, I know that there are some that will argue that they've been getting fairly good consistency and accuracy from their air guns by just loading a bullet in the chamber without fiddling with the exact position of their projectile in the chamber but, that's not the point I'm trying to make.

If they're getting good accuracy that way; good. That's better than good but, I'm talking about the up and down variance of the fps numbers. Up where you wouldn't expect them to be and down where you'd expect slightly higher numbers.

I admit there are alot of variables that I'm not taking into consideration with these observations about fps but, what do you guys think?

HollowPoint

[Butcher45]

I've wondered about some of the fps numbers posted around the internet; even on the "Tuned" Big Bores.

I realize that we're talking about an air reservoir that reduces in psi after every shot so, it stands to reason that the fps numbers would go down in more of a linear way. What I mean is; as an example; each shot dumps 200 psi. So, this would mean that your shots would slow down incrementally because there is less air in the reservoir to draw from.

Some of the numbers I've seen will start at a certain level, (generally the highest fps in the shot string) then the next shot may be a little higher than the first, then back down, then a couple shots higher still. It's rather erratic to say the least.

I can see why this might happen with traditional firearms where there are many components such as brass, powder, primers, seating depth, runout, reloading inconsistencies etc.. In an airgun, where an air valve should open up to or near the same amount each time the trigger is pulled, such a fluctuation in fps just doesn't add up.

I'm starting to come to the conclusion that it has to do not with the function of the valve, trigger, hammer or spring but, it's the position of the projectile in the chamber at each shot.

When we load a bullet into the chamber, is it pushed all the way in to the same spot in the chamber each time? With round ball especially; it can be a good fit in the bore but, while in the chamber -which is generally a looser fit- if it moves even a little bit it's bound to effect the fps as well as accuracy.

Now, I know that there are some that will argue that they've been getting fairly good consistency and accuracy from their air guns by just loading a bullet in the chamber without fiddling with the exact position of their projectile in the chamber but, that's not the point I'm trying to make.

If they're getting good accuracy that way; good. That's better than good but, I'm talking about the up and down variance of the fps numbers. Up where you wouldn't expect them to be and down where you'd expect slightly higher numbers.

I admit there are alot of variables that I'm not taking into consideration with these observations about fps but, what do you guys think?

HollowPoint

I myself seat the projectile against the rifling the exact same way with each projectile.

I'm no pneamatic expert by any stretch, but I've done enough testing to know that I can get four or five shots without a significant velocity drop, and the pressure in the reservoir drops from 3000psi to 2500 after 3 shots. It doesn't sound right, but that's just how it is. A large reservoir helps a lot.

You should see some of the strings the non-regulated smallbores get......Sometimes as little as 10fps max variances for 50-80+shots!

I'll write more later....got to get some work done. Here are some numbers from my friends stock 909 with 3000[psi fills. Check out that 245grain REAL string!

[HollowPoint]

What does the "REALS" bullet look like? I don't remember ever hearing about that particular design. It would be interesting to see what it looks like.

I'd like to know about any similarities this "REALS" bullet and the EPP/UG's have in common. It looks as though there are some bullet designs that really outshine all the others when shot from one of these Big Bores.

I'm wondering if a bore-rider style cast bullet would do well in my 909? I've been playing around with some drawings of a bullet design using the measurements I got when I slugged my barrel.

If I get enough free time I might just get brave enough to try to make me a Gun-Specific bullet mold in the bore-rider style. If not, I'll just put it in my Idea-Folder along with all the other drawings and ideas I've had in the past that most likely won't come to pass.

HollowPoint

[Butcher45]

What does the "REALS" bullet look like? I don't remember ever hearing about that particular design. It would be interesting to see what it looks like.

I'd like to know about any similarities this "REALS" bullet and the EPP/UG's have in common. It looks as though there are some bullet designs that really outshine all the others when shot from one of these Big Bores.

I'm wondering if a bore-rider style cast bullet would do well in my 909? I've been playing around with some drawings of a bullet design using the measurements I got when I slugged my barrel.

If I get enough free time I might just get brave enough to try to make me a Gun-Specific bullet mold in the bore-rider style. If not, I'll just put it in my Idea-Folder along with all the other drawings and ideas I've had in the past that most likely won't come to pass.

HollowPoint

The R.E.A.L. is a muzzle-loader design......I think it stands for "rifling engaged at loading" or something like that. The similarities to the EPP/UG are very small contact area with the barrel, bore-riding qualities, and an angled/tapering top band (I think this may be key for proper boolit alignment).

The EPP/UG has a bore-riding heel, and on the REAL boolit all the bands are smaller than the top one (not sure if they get smaller and smaller towards the base as my calipers batteries are dead). The REAL is available in approx. 200grains, and 250grains, and seems to work great in a 909 for most that try it.....wish it had a large meplat, though.

Maxi-Balls also have bands that get smaller from top to bottom (I want to say, .457/.455/.450 but I can't remember exactly...some copies have a .455 top band though), and almost always shoot very well.

[HollowPoint]

Those cast bullets look real interesting. They seem to have alot in common.

I wonder what made them decide on such a very small bullet shank diameter rather than going with a bullet shank say about .440 or .450?

If these lead slugs bump-up a little when fired -like those in traditional firearms- a diameter of .440 should still clear the bore while letting the larger diameter parts of the slug catch the rifling to get enough gas seal and impart spin.

I notice that neither one of these bullets have their tail ends hollowed out .

I finished work early to day so I looked around my stash of metal stock to see if I had anything I could use to make up a new cocking lever. I didn't have any steel that was thick enough so just for spits-N-giggles I tried making one out of solid aluminum stock.

I see now why the factory cocking lever is made as thin as it is. It's almost impossible to get it into place otherwise.

If you make one up that resembles the design that Pat Marlins drew up (or the one I drew up as well) you won't be able to tilt it back enough to get it into the slightly larger slot opening at the forward part of that cocking slot.

I had to alter the base a little to get it in. If you look at the cocking lever I made from the underside, it resembles the outline of a guitar. It's the only way I could get this particular attempt at a replacement cocking handle to go in.

This attempt gave me a little bit of a lesson. I think the next one will be a little more refined.

HollowPoint

[Butcher45]

I see now why the factory cocking lever is made as thin as it is. It's almost impossible to get it into place otherwise.

If you make one up that resembles the design that Pat Marlins drew up (or the one I drew up as well) you won't be able to tilt it back enough to get it into the slightly larger slot opening at the forward part of that cocking slot.

HollowPoint

Did you try using a phillips head screwdriver to cock the hammer back, before installing the new lever? A lot more room to work with that way.

[HollowPoint]

Did you try using a phillips head screwdriver to cock the hammer back, before installing the new lever? A lot more room to work with that way.

Yes I did cock it all the way back.

When you install the factory cocking lever (even when you cock the lever back) you still have to tilt the cocking lever backwards a little to get it to slide into position; at least on my gun anyways.

If you make your replacement cocking lever so that it extends back a little farther, (as depicted in the concept drawings) that little bit of rearward extension will not allow you tilt the new lever back far enough to insert it into its slot quite as easily.

The one I made up was kind of low profiled near its base. I suppose if I had made it stand a little farther away from the side of the receiver it may have cleared a little easier but then it would have looked out of proportion and prone to snagging brush while in the field.

Next time I'll now better. I'll have to keep my eyes open for some scrap steel I can use. I think this aluminum lever should hold pretty well but, I'd rather have a steel one instead.

HollowPoint

[BCall]

I've wondered about some of the fps numbers posted around the internet; even on the "Tuned" Big Bores.

I realize that we're talking about an air reservoir that reduces in psi after every shot so, it stands to reason that the fps numbers would go down in more of a linear way. What I mean is; as an example; each shot dumps 200 psi. So, this would mean that your shots would slow down incrementally because there is less air in the reservoir to draw from.

Some of the numbers I've seen will start at a certain level, (generally the highest fps in the shot string) then the next shot may be a little higher than the first, then back down, then a couple shots higher still. It's rather erratic to say the least.

I can see why this might happen with traditional firearms where there are many components such as brass, powder, primers, seating depth, runout, reloading inconsistencies etc.. In an airgun, where an air valve should open up to or near the same amount each time the trigger is pulled, such a fluctuation in fps just doesn't add up.

I'm starting to come to the conclusion that it has to do not with the function of the valve, trigger, hammer or spring but, it's the position of the projectile in the chamber at each shot.

When we load a bullet into the chamber, is it pushed all the way in to the same spot in the chamber each time? With round ball especially; it can be a good fit in the bore but, while in the chamber -which is generally a looser fit- if it moves even a little bit it's bound to effect the fps as well as accuracy.

Now, I know that there are some that will argue that they've been getting fairly good consistency and accuracy from their air guns by just loading a bullet in the chamber without fiddling with the exact position of their projectile in the chamber but, that's not the point I'm trying to make.

If they're getting good accuracy that way; good. That's better than good but, I'm talking about the up and down variance of the fps numbers. Up where you wouldn't expect them to be and down where you'd expect slightly higher numbers.

I admit there are alot of variables that I'm not taking into consideration with these observations about fps but, what do you guys think?

HollowPoint

The problem is you are thinking about it in a linear fashion, and it just doesn't function like that. You are not taking into consideration the pressure behind the valve.

All of these airguns operate on a simple knock open valve. The hammer hits the valve, causing it to open for a certain amount of time. When the pressure is high, the hammer has a harder time opening the valve because the pressure in the air cylinder is keeping it closed. The hammer hits it, it opens, and a certain amount of air is released. On the second shot, the pressure is lower, so the hammer has an easier time opening the valve, it stays open a little longer, so more air is released. This is why you often see the first shot lower then the second. If you simply lower the max fill pressure, you can see this disappear. On subsequent shots, more air is passed through the valve, so even though it is of lower pressure, more of it flows through, keeping the velocity higher.


Most airgun shooters will find a sweet spot on the fill pressure they use. Especially noticeable in smaller calibers. Starting at 3000 may give you 45 shots within 50 fps or so, but starting at 2900 may give you 35 shots with only a 15 fps variation. Starting lower, going up to max velocity, and falling as pressure falls below the sweet spot. They follow a curve, and by tracking velocity and pressure, you can find your "sweet spot" on the curve that gives you the most shots with the least variation. Then you know you can say- fill to 2850, and 35 shots later, refill.

This may or may not apply directly to bigger bores, but you can see that thinking about it in a linear fashion does not work. Each shot doesn't simply release 200 psi. It just doesn't work that way. Fill pressure alters the valve function, and fill pressure changes with each shot, so you cannot track it in a linear fashion. Plus there is the volume vs pressure function. You can get high velocity without high pressure. The Lewis and Clark air rifle certainly got high velocity, but I gaurantee you that it did not use 3000 psi. They made up for it with volume air flow.

If you are interested, here is a link to a fun book that can help explain some of it.
http://www.amazon.com/Practical-Guid...0545991&sr=1-3

[Butcher45]

A cocking lever that is off-set, and extends back behind the hammer is certainly do-able. Just needs to be made to fit is all.

[Butcher45]

This may or may not apply directly to bigger bores, but you can see that thinking about it in a linear fashion does not work.

Applies to bigbores, too. I'm talking airguns with non-regulated valves here.

Go above a certain fill pressure, and you can see the velocity of the first shot go down as a result of what is known as "valve lock". Take a 4-shot airgun for example. The idea with the low shot count bigbores is to fill just over this point of valve lock, to where the first shot is only 10 or so fps slower than the next. Ideally, the third shot will be about the same as the second, then the fourth shot is about what the first shot was.

With my 909, I fill to about 3000psi, and after the four shots are up I am down to about 2200-2300psi. The last shot seems to use a bit more psi than any one of the first three, so I often re-fill after only three shots if time is short, and/or I have only my HillPump to fill with (which is overwhelmingly most often the case).

[HollowPoint]

Hi BCall:

Having read your thoughts on this subject, what you're saying appears to make alot of sense. But when I look at the (sometimes erratic) numbers that are posted here and around the internet I have a hard time getting your assessment and the documented numbers I'm reading to come together to make some cohesive sense.

It may be that none of the fps, fpe or fill pressure numbers were as formally studied as we'd like but, enough guys have informally charted these numbers so you would think we would be able to draw some conclusion; even if they were weak and inconclusive conclusions.

The only conclusion I could come up with was the one about the position of the projectile in the chamber.

I checked out that book you recommended. It looks like it might be a good read. I'll have to check out the local used book store and hope I get lucky.

By the way; the 200 PSI I listed in my example was just that; an example. I don't really know how much of the total PSI is used up at each shot. I used that number in order to help me explain the point I was trying to make.

Also; anything I post regarding Big Bore Air guns has to be taken with a grain of salt. I'm a novice Big Bore Air gun owner. I haven't even taken my new Air Rifle out for the first time. Right now I'm having to scrape up some spending money to buy myself a hand pump.

I am unable to shoot it at the moment but, that's not stopping me from setting it up the way I like and finding out as much as I can about it and other Big Bore Air Guns in general. I think when my Hand Pump finally gets here I'm going to be a real happy camper.

Thanks alot for your input.
HollowPoint



Thanks for your input.

[BCall]

Projectile FIT probably has more to do with it than chamber position, but it may play a factor, just not as large of one as you think. There will always be a variation up or down in velocity due to variations in projectile size and weight. Not all of them are going to be the EXACTLY the same, so they will not all act the same when shot. There has been extensive testing done on it. I don't know what numbers you are viewing, but minor variations can alter the tests.

As far as 200 psi, the point I was trying to make was that each shot does not release the same amount of pressure unless you start with the same pressure for each shot. If you repump the rifle to the same amount of pressure for each shot then you will get a linear comparison, but when your fill pressure decreases with each shot, each valve duration is different, so each shot releases a different amount of air. It is impossible for an unregulated system to release the same volume of air for each shot. The amount of PSI used for each shot varies in relation to where it is in the shot string.

You don't have ot take my word for it, there has been extensive testing on the matter. Just like this
http://www.pyramydair.com/blog/2008/...-curve-of.html

Notice that his velocity does not go in a linear fashion, but follows a curve. There are some up and down fluctuations, but it still follows the trend. No matter how carefully you place the projectile, you are still dealing with an imperfect machine. You will not be able to stop all the variation, the variables are too great.

Pellet fit will make a difference, as will placement, just remember that unlike a firearm, each shot is different, because the starting point is always changing. If you are finding alot of instances of erratic velocities, I would like to see the links about what they are doing. Billy

[garbear]

Not much to add other then go to your region meetings if AZ has them. We have Regional area conference and the wildlife board members are there to get their butts chewed or praised for there decisions for our hunting regulations. Try get organized or join a air gun hunter organization to make your wants heard. The bow hunters in my state pretty much get what ever they want because they are loud at eh RAC meetings. We predator hunters need to be. Nice gun from what I have heard about them. Good luck
Garbear

[Butcher45]

If you are finding alot of instances of erratic velocities, I would like to see the links about what they are doing. Billy

I am interested in seeing those links as well. They won't be links to my 909 that is for sure. I get very consistent velocities out of mine, and I would venture to say that I have posted more bigbore airgun shot strings, at more fill pressures, with more boolit designs than anyone I know of. I know of others that have a 909 tuned by the same guy, and their numbers are practically identical to mine.

Remember, air capacity is required to get a few consistent shots out of a powerful bigbore. Otherwise velocity will go down, then down some more past shot #2 or so. The numbers you see will be consistent from fill to fill when filled to the same psi unless there is something wrong with the rifle. So if you hop-up your 909S, focus on getting the first two shots as close together as you can. A tuned 909S is a two shot gun with a "finishing" shot or two. That is what the air capacity of the 909S will accommodate.

[HollowPoint]

The numbers you see will be consistent from fill to fill when filled to the same psi unless there is something wrong with the rifle. So if you hop-up your 909S, focus on getting the first two shots as close together as you can. A tuned 909S is a two shot gun with a "finishing" shot or two. That is what the air capacity of the 909S will accommodate..

This sounds a little more down to earth to me. The other statements posted regarding the possible reasons for the ups and downs of velocities also came across as logical as well but, my little pea-brain has alot of trouble with the seeming contradictions the actual numbers tend to pose.

Could just be some kind of dyslexia thing on my part. When one tries too hard to figure something out that can't be figured out, after a while you begin to come across as just a babbling fool.

I'll just leave it alone for now and move on to some other lessons about these Big Bore Air Guns.

HollowPoint

[Butcher45]

This sounds a little more down to earth to me. The other statements posted regarding the possible reasons for the ups and downs of velocities also came across as logical as well but, my little pea-brain has alot of trouble with the seeming contradictions the actual numbers tend to pose.

Could just be some kind of dyslexia thing on my part. When one tries too hard to figure something out that can't be figured out, after a while you begin to come across as just a babbling fool.

I'll just leave it alone for now and move on to some other lessons about these Big Bore Air Guns.

HollowPoint

That's why I enjoy posting my tests and results with these bigbore airguns so much. It can help save people a lot of time, energy, and boolits doing research shooting.

When a regular Joe like me that doesn't have a broad understanding of pneumatics is left to his own devices, it can take a very long time to get these bigbore airguns figured out. When I got my 909 just 3 years ago, there was almost no information available on how to go about maximizing the usage and performance of the rifle (and I'm not talking about tunes here....just how to best use the dang thing).

No one was posting anything comprehensive about the testing of various boolit diameters, alloy hardness, and repeated accuracy comparisons, fill pressure/shot string optimization testing, etc.

For example, a couple of years ago, it was commonly recommended to fill to a certain pressure, then "throw away/shoot/get rid of/waste the first shot because it was to slow". It wasn't common knowledge to simply use a lower fill pressure to get rid of the slow first shot (sometimes it only takes 50psi difference).

That's why we need more boolit casters involved with these air rifles....boolit casters strike me as the sort that will figure out what works best in a particular airgun as fast, or faster than most anyone! It's an opportunity to pioneer something that is just getting off the ground so to speak, and is rapidly growing in popularity. The testing won't break the bank, because air is free and lead in a boolit trap is recyclable!

For me, understanding the principles of the valve is the toughest thing to grasp. Took a couple years for me to realize particular dynamics I was seeing, and yet I still don't have the understanding to actually explain why these dynamics are happening.

So long as I'm seeing the best results possible out of my 909, and have an understanding of how to go about getting there, I can live with simple "faith" when it comes to all the complicated technicalities as to the "why" part.

Try not to learn everything all at once.....just dial-in a good load and enjoy shooting. Remember that more psi does not always mean more power. I'm a bit burnt-out on all the testing, and ready to just plink and hunt for awhile with just a couple of proven designs that have established optimum shot strings/pressures/accuracy, instead of constantly trying new stuff. After three years, I can finally move on to the more technical explanations, and be able to somewhat relate to them due to the personal experience I have gained.

[HollowPoint]

Try not to learn everything all at once.

Well said. It's time to move on.

Yesterday I tired to tweek my newly made cocking lever on the mill. It wasn't clamped down as tightly as I though so, as soon as the edge of my end mill touched the part it jerked the part forward and proceeded to gouge the bloody-**** out of it.

Oh well; back to the drawing board. I got some good steel flat bar coming. I think that the second time around will be the charm.

Do you know where a guy can get a replacement cocking spring with a slightly stronger compression rating? Also; what is a good way for a do-it-yourselfer to measure the compression strength of the existing spring?

Thanks
HollowPoint