Newbie question

[Sammichman]

I,ve noticed when re-loading different weight bullets of the same caliber a using the same powder that lightweight bullet ask for more powder,, and the amount of powder specified reduces as the bullet gets heavier,,I would think that the reverse would be true,,for instance
125gr=51 gr
150gr=47.7
170gr=40gr
i can see the difference in FPS and Muzzle velocity change but why would,nt you want the heavier bullet to get to target just as fast as a lighter bullet ?

[Countryfried Frank]

Several reasons. One of the biggies is that with a larger bullet it sits deeper in the case effectively reducing your case volume and consequently raising pressures. A lower charge is then necessary to keep pressure safe. I'm sure you'll get more in depth info but this is the one that sticks in my head most easily.

[Molasses]

It's more of a pressure issue, than a desired velocity matter.

A heavier bullet generally has to be seated deeper in the case to meet OAL requirements or not extend up past the chamber throat. That results in a decreased case capacity. Also the heavier bullet gives more resistance, both from inertia and due to likely having a longer bearing surface against the bore. Both are going to have an effect...

Editted to add: I am entirely too slow at typing.

[Countryfried Frank]

Editted to add: I am entirely too slow at typing.

You're good. I went the KISS route and skipped bearing surface and mass. You filled in those blanks. Either that or you were channeling your namesake.

[rugersol]

Several reasons. One of the biggies is that with a larger bullet it sits deeper in the case effectively reducing your case volume and consequently raising pressures. A lower charge is then necessary to keep pressure safe. I'm sure you'll get more in depth info but this is the one that sticks in my head most easily.

Yep!

... the ways I think of 'em is ...

1. dia. of the bullet, can't be changed ... and, fer the most part, OAL of the cartridge, can't be extended ... at which, with a heavier bullet, there's only way fer that extra mass to go ... into the case!

2. at some point, ya simply can't squeeze more than a certain amount of powder into a case ... as well as, a bullet ... seated to proper OAL ... moreover, with some quicker powders, ya don't even wan't 'em touching!

3. "power-factor" and ft/lbs are two measurements of "power" ... fer the most part, as ya increase bullet weight, ya must decrease velocity (powder charge) to decrease ft/lbs ... and, as ya do, ya'll most likely see "power-factor" increase ... if ya do not, yer truly making a "less powerful" load ... at which, in a semi-auto, at some point, it won't cycle the slide (w/o a lighter recoil spring, anyhow)

4. relative to #3, as ya decrease bullet weight, ya gotta increase velocity (powder charge), to maintain "power" to cycle the slide

5. if ya are truly making less powerful loads ... IOW, ya don't increase powder charge relative to decreasing bullet weight, with some slower powders, ya 'sposedly run the risk of a "detonation"!

If ya go thru all them a few times, ya realize there's somewhat of a "balance" of bullet-weight, powder-charge, and powder burn-rate, that must be maintained!

To the extent ya don't, ya risk bad things!

There are some instances where, as ya increase bullet-weight, powder-charge is either the same, or even goes up a skosh! This is not typical! When ya see such a published load, cross-check it with AT LEAST two other sources! ... not a bad way to go for ANY load ya find!

Put 'nother way, if ya don't have a published load fer a lighter bullet, don't simply guess as to how much powder ya should add ... ya may not need to add any!

Fer the most part, if ya want a heavier bullet to reach the target as quickly, ya'll need a larger case!

[sgruenhagen44]

Several reasons. One of the biggies is that with a larger bullet it sits deeper in the case effectively reducing your case volume and consequently raising pressures. A lower charge is then necessary to keep pressure safe. I'm sure you'll get more in depth info but this is the one that sticks in my head most easily.

Yep!

... the ways I think of 'em is ...

1. dia. of the bullet, can't be changed ... and, fer the most part, OAL of the cartridge, can't be extended ... at which, with a heavier bullet, there's only way fer that extra mass to go ... into the case!

2. at some point, ya simply can't squeeze more than a certain amount of powder into a case ... as well as, a bullet ... seated to proper OAL ... moreover, with some quicker powders, ya don't even wan't 'em touching!

3. "power-factor" and ft/lbs are two measurements of "power" ... fer the most part, as ya increase bullet weight, ya must decrease velocity (powder charge) to decrease ft/lbs ... and, as ya do, ya'll most likely see "power-factor" increase ... if ya do not, yer truly making a "less powerful" load ... at which, in a semi-auto, at some point, it won't cycle the slide (w/o a lighter recoil spring, anyhow)

4. relative to #3, as ya decrease bullet weight, ya gotta increase velocity (powder charge), to maintain "power" to cycle the slide

5. if ya are truly making less powerful loads ... IOW, ya don't increase powder charge relative to decreasing bullet weight, with some slower powders, ya 'sposedly run the risk of a "detonation"!

If ya go thru all them a few times, ya realize there's somewhat of a "balance" of bullet-weight, powder-charge, and powder burn-rate, that must be maintained!

To the extent ya don't, ya risk bad things!

There are some instances where, as ya increase bullet-weight, powder-charge is either the same, or even goes up a skosh! This is not typical! When ya see such a published load, cross-check it with AT LEAST two other sources! ... not a bad way to go for ANY load ya find!

Put 'nother way, if ya don't have a published load fer a lighter bullet, don't simply guess as to how much powder ya should add ... ya may not need to add any!

Fer the most part, if ya want a heavier bullet to reach the target as quickly, ya'll need a larger case!

If OAL can't be extended then should you always shoot for the minimum? Because I forget how long my cartridges are but they are not the minimum either.

[rugersol]

fer the most part, OAL of the cartridge, can't be extended

If OAL can't be extended then should you always shoot for the minimum? Because I forget how long my cartridges are but they are not the minimum either.

There's obviously a min/max. ... if not a magazine, the "throat" will dictate max. OAL ... regardless, whatever that might be ... it can't be extended!

[sgruenhagen44]

fer the most part, OAL of the cartridge, can't be extended

If OAL can't be extended then should you always shoot for the minimum? Because I forget how long my cartridges are but they are not the minimum either.

There's obviously a min/max. ... if not a magazine, the "throat" will dictate max. OAL ... regardless, whatever that might be ... it can't be extended!

true true. I must not have reached the max then yet lol

[Seismic Sam]

Well, the best thing to do is to get rid of that idea, and whatever logic that produced it, to stay a safe handloader. What you may "want" in terms of velocity has nothing to do with the realities of handloading, and yes, there is an inverse relationship between bullet weight and velocity for any given caliber. Any cartridge has a maximum safe pressure as defined by SAAMI, and if you exceed that pressure you can blow the case and/or the gun. So visualize a 9mm case with 37,500 PSI of compressed gas in it, and then put either a 115 grain or 147 grain bullet on top of it and let it go inside a gun. In both cases you have the same amount of pressure, which will be transferred to moving the bullet, and in the case of the 147 grain bullet the pressure has to be "spread over" more mass than the 115 bullet, so the 115 bullet winds up going faster. Put 1 gallon of gas in a Volkswagen Beetle and a Ford half-ton, and then compare how far each vehicle goes. (So we're talking distance here rather than velocity, but the concept is still the same.) The Beetle can probably go twice as far as the Ford, which weighs twice as much as the Beetle. In both cases, you have a fixed amount of energy (37,500 PSI or 1 gallon of gas), and you can spread that energy over a small mass or a large mass to produce motion.

Now, with handloading, there is a double whammy lurking inside this concept, because with a light bullet, you have more space and less mass, so while it might seem that you need less powder for less mass, the fact that you have more volume in the case really means that you have to ADD powder to get to the same PRESSURE. With a heavy bullet, you have more mass and less space, so you have to reduce powder because of the smaller space and the heavier bullet, because the bullet isn't going to move as fast and thus relieve the pressure as fast as the lighter bullet. The heavy bullet situation is the one which may get you hurt because of a Kaboom, and just for the record the 9mm was never designed to use a 147 grain bullet, but somebody managed to get it to work (sort of... ), and there have been a disproportionate number of pressure problems with 9mm 147 grain loads.

So: There is an INVERSE relationship between bullet weight and velocity with any caliber, because your pressure is fixed and has to be spread over smaller or larger bullet weights. This also means that there is an inverse relationship between powder loads and bullet weight, and the powder has to reduced because of the increased mass AND because of the reduced volume in the case.

[Sammichman]

I think i understand,,the powder charge has to have a certain amount of room to expand and create energy,,to much room and the energy is to spread out and doesn,t burn effeciently ,,,interesting stuff seems like engine Compression

[Seismic Sam]

I think i understand,,the powder charge has to have a certain amount of room to expand and create energy,,to much room and the energy is to spread out and doesn,t burn effeciently ,,,interesting stuff seems like engine Compression

You're getting closer, but it's not necessarily true that the powder needs ANY extra room to burn and produce pressure, because there are safe loads of slower burning powder where the case is 100% full of powder, and even compressed loads where the powder gets squashed down by the bullet being seated. The amount of space (if any) has to be combined with a powder of the right burn rate, and if you go from that to the same load of a faster burning powder, the pressure will probably go through the roof along with parts of you and your gun. The relationship I already described is all for ONE kind of powder, and it may be the case for a light enough 9mm bullet that you can fill up the entire cartridge with powder and have it be a good load. Also keep in mind that a heavier bullet in a caliber is also a longer bullet, so there will be more friction between the bullet and the barrel. You need to compensate for this with less powder, to keep the pressure from building too rapidly.

I would stay away from trying to understand this as an engine compression analogy, because there are several things that do not carry over from one situation to another. While cases 100% full of powder do exist, there is no internal combustion engine where a cylinder 100% full of gasoline is possible.

[Sammichman]

Thanks Sam ,,I,ll just take it slow and ask a lot of questions,,Great thing about you guys lots of Help without being talked down to

[Pinnacle]

Thanks Sam ,,I,ll just take it slow and ask a lot of questions,,Great thing about you guys lots of Help without being talked down to

There are a few of us out in the world that had the benefit of a reloading mentor. Mine took me under wing at the age of 10 (a long time ago)

Ask away - knowledge is worth nothing if it cannot be passed along.. You will find that most of us are here to help...

[Seismic Sam]

Thanks Sam ,,I,ll just take it slow and ask a lot of questions,,Great thing about you guys lots of Help without being talked down to

The best thing to do is to buy a Hornady #8, Speer #14, or Lyman #49 manual and read the WHOLE reloading section carefully. I am the official 800 pound reloading troll for the board, and only climb out from under my bridge with a 2x4, and whack n00bs upside the head when they ask questions that are covered in any good reloading manual. Yours was sufficiently complex that a reloading manual wouldn't have the answer to that specific question.

[Sammichman]

I have Both a Lyman 46th edition and the Lyman 49th ,,bought both before I got my re-loading gear,,,just to try and start to understand what type of equipment I would need,,, Don T. helped me with a barrel install last year and gave me a tutorial as to what I would need somwhere down the line,and when I got some equipment a short time ago he helped me with the 223 and the 308 base on his knowledge and experience,,the 8MM is my first go it alone where I,m not copying the test from the Smart kid sitting next to me ,,Robert