I am ready to start Reloading!!!

[prof_fate]

Less volume = higher pressure. It's how your car engine works - piston compresses the intake charge (air and fuel) and when compresses the spark plug ignites, the explosion pushes the piston down creating the power to move the car.
The more compression the more power, the more efficient the engine - to a point. Typical gas car engines run compression ratios of 8.5 to 10 or so. Diesel engines run 22 to 1 - they compress the fuel so much it spontaneously combusts and no spark plug is needed.

Diesel engines are about 50% heavier than gas engines and cost a lot more to build because of all this extra pressure they must contain.

If you have a 9mm shell and put a .53 long bullet in with an OAL of 1.125 you have about .430 space under teh bullet in the case. If your powder takes up .3" of that, you have .13 open space. Change to an OAL of 1.10 and you have NO space left in the case. You're not reducing space by 10% or 30% but by 100%. This WILL raise pressures - potentially a dangerous amount. You may even be compressing your powder and there are numerous warnings on doing that.

[UnspokenVendetta]

Originally Posted by prof_fate

If you have a 9mm shell and put a .53 long bullet in with an OAL of 1.125 you have about .430 space under teh bullet in the case. If your powder takes up .3" of that, you have .13 open space. Change to an OAL of 1.10 and you have NO space left in the case. You're not reducing space by 10% or 30% but by 100%. This WILL raise pressures - potentially a dangerous amount. You may even be compressing your powder and there are numerous warnings on doing that.

Am I missing something, or is your math wrong?

1.125" to 1.100" is a change of .025". If you previously had .130" of clearance, you now have .105" of clearance.

I could be wrong on that.

As an aside, no one is arguing that decreasing OAL increases pressure. I'm not sure why you're arguing that point, because no one is claiming that. Fred's point was that the OAL is not min, as you mentioned. There are two different OALs to be aware of in your manual. The first is located on the bullet diagram at the beginning of the caliber section that you are looking at, which shows all kinds of critical dimensions. As I understand it, those are MAX measurements. The second OAL to consider is the one listed alongside the load data for each bullet type. It may be the same as the MAX OAL listed at the beginning of the section, but it may be shorter as well. However, whatever it is, it's neither a min or a max, it is what it is. You can go shorter, but as you are mentioning, it's prudent to understand that if you do go lower, you need to adjust your charge to compensate for the higher pressure, just as fred is mentioning. I think you're point is that it's safer to use that load OAL as the min for safety sake, and that's true, but you also need to make sure it will chamber properly in your barrel.

[prof_fate]

If you take the available internal space in the case with the powder and bullet seated and it all sitting vertically you have some empty space. If you seat the bullet deeper it is this space that goes away. It is a very small space so this is why min OAL can be critical , pressure wise.

I too thought that OAL in recipes was not a cast in stone min - then I did some reading and asked some questions and found out it is a pretty important MIN figure, not an ideal or max. Max is 1.169 SAAMI for 9mm, or whatever your gun will chamber/feed.

I started loading Berry's 124 flat nose plated bullets. CZs and XDs have very small leade spaces compared to most other 9mm pistols. The berry's bullet holds it's diam farther out on the bullet that a RN does - if I want the case to properly headspace the absolute max OAL is 1.080. You don't want the bullet hard up against the rifling as that can cause a pressure spike too (it's best if the bullet can get moving some before it hits the rifling). Seems .005 is sufficient. Now most presses don't make perfect OAL - be that from variations in operator stroke length, case length or bullet variation or whatever, but .005 seems a normal variance. So now I need to be .010 under the 1.08, or at 1.070.

No formula I had allowed for that short of a cartridge. Some googling and asking around turned up one in an older book - 1.06 and I've since found another at 1.05 for a different bullet (same powder at least). Upon asking I did get a LOT of folks telling me (again) the the figure in books is a MIN figure for OAL and going shorter is dangerous.

Granted, if you're not maxing out loads there is some leeway - but powders do not act in a linear fashion, so there's little reason to think reducing the avail space will not have an affect.

[UnspokenVendetta]

Originally Posted by prof_fate

If you take the available internal space in the case with the powder and bullet seated and it all sitting vertically you have some empty space. If you seat the bullet deeper it is this space that goes away. It is a very small space so this is why min OAL can be critical , pressure wise.

I too thought that OAL in recipes was not a cast in stone min - then I did some reading and asked some questions and found out it is a pretty important MIN figure, not an ideal or max. Max is 1.169 SAAMI for 9mm, or whatever your gun will chamber/feed.

I started loading Berry's 124 flat nose plated bullets. CZs and XDs have very small leade spaces compared to most other 9mm pistols. The berry's bullet holds it's diam farther out on the bullet that a RN does - if I want the case to properly headspace the absolute max OAL is 1.080. You don't want the bullet hard up against the rifling as that can cause a pressure spike too (it's best if the bullet can get moving some before it hits the rifling). Seems .005 is sufficient. Now most presses don't make perfect OAL - be that from variations in operator stroke length, case length or bullet variation or whatever, but .005 seems a normal variance. So now I need to be .010 under the 1.08, or at 1.070.

No formula I had allowed for that short of a cartridge. Some googling and asking around turned up one in an older book - 1.06 and I've since found another at 1.05 for a different bullet (same powder at least). Upon asking I did get a LOT of folks telling me (again) the the figure in books is a MIN figure for OAL and going shorter is dangerous.

Granted, if you're not maxing out loads there is some leeway - but powders do not act in a linear fashion, so there's little reason to think reducing the avail space will not have an affect.

I don't understand the point of this point. Seems like you just said a whole lot of nothing. Also, you didn't address my post at all on your flawed math.

You're trying to establish that reducing the OAL causes an increase in pressure, which everyone already knows. In order to compensate, you reduce the charge load. Start low and work your way up. Not sure what I'm missing.

The listed load OAL is not min, it's just what they used for testing purposes. You can go shorter, but you need to adjust your charge load accordingly.

Loading for .45, both my reloading manuals listed 1.270" for OAL, but I found an overwhelming amount of people on another forum that said they've been loading the same powder and bullet at 1.250" for years. In fact, I didn't find a single person that loaded at (what you would describe as MIN) OAL of 1.270". I loaded up a few rounds at 1.270", 1.260", and 1.250" and shot them in that order. All had about the same recoil, but 1.250" seemed more accurate. Granted, I'm on the very low end of the charge weight.

[garryb]

Ha prof what was the auto bullet seater for 40 s@w did you get, as there is two sizes.

[fredj338]

Originally Posted by prof_fate

Less volume = higher pressure. It's how your car engine works - piston compresses the intake charge (air and fuel) and when compresses the spark plug ignites, the explosion pushes the piston down creating the power to move the car.
The more compression the more power, the more efficient the engine - to a point. Typical gas car engines run compression ratios of 8.5 to 10 or so. Diesel engines run 22 to 1 - they compress the fuel so much it spontaneously combusts and no spark plug is needed.

Diesel engines are about 50% heavier than gas engines and cost a lot more to build because of all this extra pressure they must contain.

If you have a 9mm shell and put a .53 long bullet in with an OAL of 1.125 you have about .430 space under teh bullet in the case. If your powder takes up .3" of that, you have .13 open space. Change to an OAL of 1.10 and you have NO space left in the case. You're not reducing space by 10% or 30% but by 100%. This WILL raise pressures - potentially a dangerous amount. You may even be compressing your powder and there are numerous warnings on doing that.

Again, you are correct, but not. It is NOT unsafe to compress powder, it just depends on the powder. It is NOT unsafe to load to 110% density, it just depends on the powder. Look thru any reloading manual. lots of loads show C or + = compressed loadings. You are getting all theoretical w/o understanding the physics of combustion. Anything is possible if you start low & work up the load. Even loading completely off the book w/ no data. I've done it many times, in fact, it is the only way to develope loads for wildcat rounds. I appreciate safety & always recommend staying with book loads, but the sky isn't falling if you load diff than the book. They are guides, not bibles. You ignored the specific example of BlueDot in the 9mm. It will always be compressed w/ any bullet wt. I am not even sure you can get enough into a casse to exceed max pressures.

[prof_fate]

You are not reading the manuals- you seem to think the info in them is a guideline that you can do what you want with.

Can you compress powder, some powders? Sure. Should you do it when you don't have a tested recipe for it? Hell no.

Shorten the cartridge and reduce the powder load. Makes sense except all recipes have a min and a max. The max is kinda obvious of course. But the min is there for a reason or there'd be no need to have a min powder load ever! You need enough powder to get it to explode. How it fills the case can affect this - so going below the min may cause it to not fire, or fire erratically, or fire inconsistently depending on how the powder is sitting in the case as it's fired.

Perhaps blue dot will be compressed - but someone has tested that and measured the pressures and knows what's what. Powder does not explode in a linear manner - 10% more gives you 10% more power/pressure (or vice versa). This is why there are recipes and why they list pressures with them.

[prof_fate]

Originally Posted by garryb

Ha prof what was the auto bullet seater for 40 s@w did you get, as there is two sizes.

I load 9mm not 40, sorry can't help you.

[fredj338]

Originally Posted by prof_fate

You are not reading the manuals- you seem to think the info in them is a guideline that you can do what you want with. Actually I can & most of us have for some 100yrs.

Can you compress powder, some powders? Sure. Should you do it when you don't have a tested recipe for it? Hell no. Every day, all day, depending on the powder. Example, you could pack so much 2400 under a 9mm bullet, tht it barely seats & pressurs woudl be very low. A load of TG tht is only 10% over max could take your gun apart. So it jut depends.

Shorten the cartridge and reduce the powder load. Makes sense except all recipes have a min and a max. The max is kinda obvious of course. But the min is there for a reason or there'd be no need to have a min powder load ever! You need enough powder to get it to explode. How it fills the case can affect this - so going below the min may cause it to not fire, or fire erratically, or fire inconsistently depending on how the powder is sitting in the case as it's fired. Again, you just don't understand burn rates & combustion. The slower the powder the more need for good complete combustion, one reasom to use mnag primers. Uberfast powders will completely combust well below min charge wts. The trick is getting enough vel to overcome bullet mass. A primer will get the bullet out of the case & into the bbl, so you don't need a qhole lot more.

Perhaps blue dot will be compressed - but someone has tested that and measured the pressures and knows what's what. Powder does not explode in a linear manner - 10% more gives you 10% more power/pressure (or vice versa). This is why there are recipes and why they list pressures with them. You can reload any powder into any cartridge & make it go bang. It doesn't have tp be tested in a lab, although that is good, it can be done by an exp reloader.

I'm sorry, you just have no idea what you are talking about. You have some facts, then make a bunch of assumptions. SOme facts for you. BTW, I will have bet I have read more manuals than yo uhave, for what ever that is worth.
Until recently, you never found pressure data in manauls, some still don't show it. Until recently, you never had OAL in manuals, some only show SAAMI max today. SOme data sources only show max loads, you have to develope your own min loads. So loading from scratch is how everyone used to do it.
Smokeless powder does NOT explode, not in the least, it burns in a controlled rate. You are correct, pressures do NOT build in a linear fashion, but, every powder builds pressures diff & in diff calibers. SO again, you know a little bit & are being cautious, that's good. Telling other they should or should do or attempt soemthing w/o actual knowledge of the results is just chicken little stuff. You are telling guys they can't copmpress powders period, just not true. Many powders in the 9mm will be compressed, some more than 100% density.
I am NOT advocating noob reloaders go off the books, but you need to understand, the books are guides. Much of the reloading done is NOT done w/ book componenents, so for all intents, most are doing some reloading off the books. Keep in mind, the guys that write the books are just like me, expereinced reloaders. The only diff, they have pressure equip to verify their actual shooting results.

[UnspokenVendetta]

Originally Posted by prof_fate

You are not reading the manuals- you seem to think the info in them is a guideline that you can do what you want with.

Shorten the cartridge and reduce the powder load. Makes sense except all recipes have a min and a max. The max is kinda obvious of course. But the min is there for a reason or there'd be no need to have a min powder load ever! You need enough powder to get it to explode. How it fills the case can affect this - so going below the min may cause it to not fire, or fire erratically, or fire inconsistently depending on how the powder is sitting in the case as it's fired.

They are a guideline, not a bible.

You say it makes sense, but clearly you don't understand. As fred is saying, it's important for noobs to follow the mins and max listed in their manuals, but for people that know what they're doing, the information is just a guideline. Otherwise, how do you explain the fact that different manuals will list different min and max for the same powder and bullet weight/type? By your logic, you should not go below min every, so when my Speer manual lists 5.6gr W231 min I shouldn't go below this, right? But wait, my Lyman manual lists 5.2gr min and 5.6gr max. Oh no, what should I do? I can't possible go below the 5.6gr min that Speer states, so I guess I'll just load at or above what Lyman consider max. Oh wait, is that not allowed either? Ah crap, I give up...