[SirLSD]

in another thread now closed i am told that velocity is a function of pressure and that it is impossible to get more velocity out of a projectile by using more powder in longer cases? how then does 22lr and 22mag both have SAAMI specs of 24000psi?
how does a 40gr 22lr running at 1450fpr with 24000psi and a 22mag 40gr running at 1800fps with 24000psi? all i can see is that the longer case allows the larger charge of powed create higher velocities without changing the 24000psi pressure. however i was shot down in another thread for suggesting this?

 

[MoKen]

Dwell or burn time.

 

[glenwolde]

in another thread now closed i am told that velocity is a function of pressure and that it is impossible to get more velocity out of a projectile by using more powder in longer cases? how then does 22lr and 22mag both have SAAMI specs of 24000psi?
how does a 40gr 22lr running at 1450fpr with 24000psi and a 22mag 40gr running at 1800fps with 24000psi? all i can see is that the longer case allows the larger charge of powed create higher velocities without changing the 24000psi pressure. however i was shot down in another thread for suggesting this?

Well since you can decrease pressure just by changing powders for a given bullet whoever said that was incorrect. I certainly did not mean to imply that. Just look at any loading table that shows pressures. You always see varying velocities for a given pressure. But I think there was a bit of confusion in that other thread regarding parameters.

If you're using the *same* powder and bullet the statement is true. If you have the ability to calculate or measure pressure, or can find the data, then you could do what you want. Your theory needs to be quantified.

 

[glenwolde]

Here's where you get into trouble: It's impossible to predict the pressure you're going to get. The pressure increase is not linear, it's a parabolic curve. So a lot of guys will look at data and try to extrapolate. It goes something like this.....

Oh. Look. Titegroup is only 12,700 CUP, some there are 14,000 CUP so I've got some room to push that a little. Wrong. For all you know, since pressure is not linear, another .01 grain might be 20,000 CUP. Yes, really. Maximum loads are usually the highest they could go before things got erratic. The erratic results are a warning that you're close to "unstable".

Your theory is only half right. Yes, for a given load and bullet a longer case will drop the pressure. But once you change anything else you can't say with any certainty where you're going to end up. This is why we have all this data that people go to a lot of expense and trouble to supply. We're dealing with chemicals that have unpredictable explosive properties. So unless you can find some sort of confirmation for the load you want to use you are on your own.

I've loaded ammo that has no data. I did find some confirmation in others than had loaded it before and I trusted the source. I was going down the performance ladder, not up. Do you really want to be the trailblazer on this? Has anybody else ever tried this?

 

[guesser]

Glen hit it hard and right. I've worked up loads for several wildcat cartridges in rifles I had built the way I wanted them. I came close to a dangerous situation a few times simply by trying a little more powder or a different primer or where I really got in deep was when I mixed in cases with different head stamps, all 30-06 cases are not the same; and I was working up into 338-06 years before the cartridge was SAAMI standardized. There is a lot of information available to be read by anybody. Sometimes it will seem to conflict; keep reading, you will come to a consensus in your mind and you will start at the bottom and work up.
The simplest lesson I learned about 60 years ago was that the 308 load that I developed and tested in March was way, way over pressure in August. I had fired over a hundred rounds in the spring at 40-50 degrees and all was fine. By August the temp was in the low 90's and I flattened primers, had to pry the bolt up to open it and then drive it open with a block of wood. I learned a lot that year, 1957, as I remember. Was a good year but kinda skeery in retrospect!!

 

[flareside_ford]

Also note that just because SAAMI pressure ratings are the same, it does not mean that all loads are loaded to the max pressure.

 

[glenwolde]

Was a good year but kinda skeery in retrospect!!

Ah, yes. Life on the edge. The Good Old Days, when we weren't smart enough to be properly terrified.

 

[texastaurusguy]

I've always thought that reloading isn't for somebody who can't follow instructions, or can't help themselves from trying to push max loads up on their own. I'm not necessarily talking about anybody on this forum, I'm just talking generally. We had a guy here until a couple of years ago that was always posting stuff about pushing limits and it was amazing that he lived to be 10 years old. If a reloader can't accept load limits provided by a variety of reliable sources, and thinks they can improve on expert input, then it's probably for the best that they buy factory ammo. Accidents of this type make reloaders look bad, and endanger people around them.

 

[SixFalls]

I've always thought that reloading isn't for somebody who can't follow instructions, or can't help themselves from trying to push max loads up on their own. I'm not necessarily talking about anybody on this forum, I'm just talking generally. We had a guy here until a couple of years ago that was always posting stuff about pushing limits and it was amazing that he lived to be 10 years old. If a reloader can't accept load limits provided by a variety of reliable sources, and thinks they can improve on expert input, then it's probably for the best that they buy factory ammo. Accidents of this type make reloaders look bad, and endanger people around them.

. very well said

 

[Driswalds]

This is what I don't understand. Take a look at these pressures.
Bullet Weight 300 GR. FA JFPPowder Grs. Vel. (ft/s) Pressure

Hodgdon H110 30.0 1,716 53,700 CUP
Hodgdon Lil'Gun 31.0 1,746 45,000 CUP

Lil'Gun burns just slightly faster on the Burn Chart. In fact it is just before H110
Why such a huge difference in Pressure?

 

[jtg452]

Unless you have access to a full ballistics lab like the ones used to test the loads in the manuals, you are just guessing when you go off the reservation with a load. External pressure signs are not a reliable means of judging a load's safety.

 

[maloy]

I think you, (OP), are looking at things being linear. I can use cases, the same volume case, the exact same powder and weight, use two different 200 grain projectiles and change the pressure. Lead vs. Jacketed as one example.

A 10 grain powder charge of say Reddot in a .45 Colt could act different in a .454 case if it is more open volume. Too little powder can cause a detonation rather than a burn. At the least, you'll get an inconsistent burn. Also using 22 LR vs. .22 Mag is two different powders. .22 Mag uses a slower burn powder. .22 LR usually has all its powder consumed between 10 and 12 inches depending on the load or brand. .22 Mag can take 12 to 16 inches to consume all the powder. The longer the burn pulse, the faster you can go and still keep the pressure down. Burn duration changes velocity by pushing longer rather than harder.

.22 LR will be at full velocity by the time it hits 20" and can loose velocity at 24" and is noticeable at 26". .22 Mag can hits full speed before 22" and depending on brand still shows an increase at 24".

So .22LR and .22 Mag is apples to orange comparison. The main reason for the longer .22 Magnum case is to keep it from being chambered older weaker guns.

Maloy

 

[NativeTexan]

I don't mess with H110, but Li'l Gun is a lot slower than 2400 or WW296 or such. It works well in carbines in .357, but is slow enough burn it has a rep for eroding forcing cones on revolvers.

 

[MadKaw]

This is what I don't understand. Take a look at these pressures.
Bullet Weight 300 GR. FA JFPPowder Grs. Vel. (ft/s) Pressure

Hodgdon H110 30.0 1,716 53,700 CUP
Hodgdon Lil'Gun 31.0 1,746 45,000 CUP

Lil'Gun burns just slightly faster on the Burn Chart. In fact it is just before H110
Why such a huge difference in Pressure?

Because.

Read what guesser said. The interactions between components are very nonlinear. Small changes in components can cause major and unpredictable changes in results.
Non-linear interactions are difficult to understand even though they are all around us. Research the Butterfly effect, it's a layman's description of these interactions.

 

[MadKaw]

Also, you are misreading the pressure specs for .22LR and .22WMR.
SAAMI has found greater variation in pressure in sampled .22WMR loads than .22WMR.

The maximum pressure for .22WMR is about 10% higher than for .22LR. Because of the higher sample variation the design specification of the .22WMR is lowered so that the maximum sample pressure observed does not exceed the maximum allowed pressure.
When you look at any SAAMI pressure specification, you have to realize that that is the mean pressure for a large number of tests, not the maximum pressure observed.

 

[glenwolde]

This is what I don't understand. Take a look at these pressures.
Bullet Weight 300 GR. FA JFPPowder Grs. Vel. (ft/s) Pressure

Hodgdon H110 30.0 1,716 53,700 CUP
Hodgdon Lil'Gun 31.0 1,746 45,000 CUP

Lil'Gun burns just slightly faster on the Burn Chart. In fact it is just before H110
Why such a huge difference in Pressure?

Exactly my point. The results are unpredictable. Take the same two powders and a different cartridge and you could get different results. Change the case volume, or change the bullet weight, and those two powders might be opposite on which pressure is higher/lower.

 

[NativeTexan]

Interior ballistics, the science of what goes on in the cartridge before the bullet leaves the barrel, is VERY complicated and, for the most part, not really predictable in small arms. Army ballistics labs still struggle with it. It's much more straight forward in cannon, I've read, don't know why, but that's what I've read on the subject. There's really no math to adequately model interior ballistics in small arms, though, so I don't try to understand it, just follow the recipes I find in manuals and accept that that's the way it is. When I experiment, it's done within the manuals and I chronograph mainly to make sure I'm not getting some wild velocity not predicted by the manual. It's a safety back up IOW. If I need something more, then I likely need a new gun perhaps in another caliber and, hey, who doesn't like a new gun???

 

[glenwolde]

Interior ballistics, the science of what goes on in the cartridge before the bullet leaves the barrel, is VERY complicated and, for the most part, not really predictable in small arms. Army ballistics labs still struggle with it. It's much more straight forward in cannon, I've read, don't know why, but that's what I've read on the subject. There's really no math to adequately model interior ballistics in small arms, though, so I don't try to understand it, just follow the recipes I find in manuals and accept that that's the way it is. When I experiment, it's done within the manuals and I chronograph mainly to make sure I'm not getting some wild velocity not predicted by the manual. It's a safety back up IOW. If I need something more, then I likely need a new gun perhaps in another caliber and, hey, who doesn't like a new gun???

A chronograph will also show you when things are getting erratic. Which is a gigantic red flag. When standard deviation blows out, watch out.

 

[Driswalds]

Exactly my point. The results are unpredictable. Take the same two powders and a different cartridge and you could get different results. Change the case volume, or change the bullet weight, and those two powders might be opposite on which pressure is higher/lower.

You are 100% correct. In 44 magnum H110 has the lower pressure of the 2.

 

[glenwolde]

You are 100% correct. In 44 magnum H110 has the lower pressure of the 2.

The defense rests....