Hi All. I've been loading for about a year now and offer my thanks and respect to all that contribute. My latest question that has been bangin around in my head is I see load data containing powder Load, Trim, OAL, etc. OAL would depend on the style and length of a bullet which, of course, manuals can't really cover all the types and manufacturers but, isn't the space between bullet and settled powder more critical than going by a max. OAL? I've read a volume of powder and depth of bullet set leaving about 10% of empty volume between is just about right. Why don't manuals list a depth of bullet set(per powder) as being more noteworthy than just an overal max. dimension?
bobcantputt
Thanks for the reply. Yeah, I understand and have altered for 30.06 rounds to fit my Garand better. I guess I'm just hung up on how important is the volume in a load. I've read about methods of taking volume checks to insure the right amount of load and bullet set. How important is it? If minor, then I'm just reading more into it than I need to(which is a common problem with me). If is quite impotant in creating the right amount of pressure before it pushes out the bullet then why isn't there more data about it in load manuals?
The available volume for a given cartridge inside the brass case can vary quite a lot - depending on the manufacturer of the case and the particular lot. Don't assume a given OAL for brand 'A' will have the exact same case volume available as that same OAL for brand 'B.'
That's just kind of how it is. You have to work up with your components, and variations in case volume is just one of many reasons. Some cartridges seem to be far worse in this regard than others.
And then the actual 'working volume' is not really what the volume is inside the case, but how much does the case swell up to fit the chamber? That creates more 'room' for the powder. How much freebore is there till the bullet hits the lands? That (potentially) can create still more 'room' for the powder.
So you have not just the particular lot of cartridge brass you are using to consider, but the actual chamber dimensions and throat.
That's just kind of how it is. You have to work up with your components, and variations in case volume is just one of many reasons. Some cartridges seem to be far worse in this regard than others.
And then the actual 'working volume' is not really what the volume is inside the case, but how much does the case swell up to fit the chamber? That creates more 'room' for the powder. How much freebore is there till the bullet hits the lands? That (potentially) can create still more 'room' for the powder.
So you have not just the particular lot of cartridge brass you are using to consider, but the actual chamber dimensions and throat.
I shoot a lot of single shots, so OAL is not much of a concern. I usually try to get the projectile out as far as I can, getting it as close to the Lands as possible. For bolt guns with magazines, I want the OAL length to be as long as it will fit in the mag. After finding a good load, you can play with length and see if there are any differences.
Ceteris Paribus, (All other things being equal), shorter C.O.A.L.s tend to reduce the internal volume of the round, which will tend to elevate chamber pressures. This CAN be either a good thing or a bad thing. Match-grade rounds for .38 Spl., used in the famous PPC and bullseye matches were full wadcutters ("flying soda cans"), seated deep until the forward edge is seated flush with the case. THIS reduces the space available in which the powder will combust (initially), which means less propellant necessary to launch the bullet, which means less recoil.
I've loaded "middlin" handloads for .357, .44 Spl., and .45 Colt which gave perfectly acceptable performance, but sometimes were smoky when fired. With several loads, I've "cleaned up" the burning characteristics by seating the bullet a bit more deeply (0.005" - 0.020"), and/or increasing the crimp. The new rounds loaded thus, probably developed just enough extra chamber pressure that propellant(s) used burned more thoroughly. I didn't exhaustively measure velocities, but I got the impression that there was a definite, though negligible bump in in M.V.
While I am perfectly willing to do this in larger-volume (.38 Super or larger) cases, there is potential for hazard if both these adjustments are tried in small capacity cases. I do not recall which edition of Speer's reloading manual had this illustrative tale in it, but they spoke of a 9x19mm load that developed ~29,000 p.s.i. at a certain overall length. When the overall length of the same load was shortened by seating the projectile 0.020" deeper, chamber pressures went into the 60,000 p.s.i. range. Someone with old Speer Manuals can probably relate this incident with better detail, but I think I got the important parts right.
In pistol rounds, USUALLY, greater overall length enables the use of more propellant, without jacking up the pressures out of the "safe" spectrum. In rifle rounds, this is largely true, until some other factor comes along. In single shots with extra free bore, it can often be difficult to load the round too long. Additional powder, worked up judiciously, can and often does give rise to higher velocities.
Limiting factors on C.O.A.L. also come in the form of magazine length, and barrel throats with less-generous free-bore. Even if the rifle's magazine allows greater cartridge length, a tight chamber can mean that the bullet ogive contacts the throat of the chamber, not leaving a small space in which the bullet may "jump" from the case mouth into barrel throat, and down the barrel. This drives up chamber pressures, often to an unsafe level, and generally reduces accuracy, so if it's not one thing, it's something else.
ONCE in a while, a large case loaded with medium-burning rate propellant on which a projectile is seated deep enough that the powder charge is compressed, will result in a load that develops higher velocity at pressures equal to or lower pressures than loads with "UNcompressed" charges. Putative mechanisms range from powder position with respect to the primer flash hole, to the notion that a charge having no freedom of motion inside the case also has less freedom to combust in a random manner, which would tend to spike pressures.
So the "take away" is that, USUALLY, longer C.O.A.L.s mean lower pressures and/or higher velocities, until other factors intervene. And SOMETHING else ALWAYS intervenes.
I've loaded "middlin" handloads for .357, .44 Spl., and .45 Colt which gave perfectly acceptable performance, but sometimes were smoky when fired. With several loads, I've "cleaned up" the burning characteristics by seating the bullet a bit more deeply (0.005" - 0.020"), and/or increasing the crimp. The new rounds loaded thus, probably developed just enough extra chamber pressure that propellant(s) used burned more thoroughly. I didn't exhaustively measure velocities, but I got the impression that there was a definite, though negligible bump in in M.V.
While I am perfectly willing to do this in larger-volume (.38 Super or larger) cases, there is potential for hazard if both these adjustments are tried in small capacity cases. I do not recall which edition of Speer's reloading manual had this illustrative tale in it, but they spoke of a 9x19mm load that developed ~29,000 p.s.i. at a certain overall length. When the overall length of the same load was shortened by seating the projectile 0.020" deeper, chamber pressures went into the 60,000 p.s.i. range. Someone with old Speer Manuals can probably relate this incident with better detail, but I think I got the important parts right.
In pistol rounds, USUALLY, greater overall length enables the use of more propellant, without jacking up the pressures out of the "safe" spectrum. In rifle rounds, this is largely true, until some other factor comes along. In single shots with extra free bore, it can often be difficult to load the round too long. Additional powder, worked up judiciously, can and often does give rise to higher velocities.
Limiting factors on C.O.A.L. also come in the form of magazine length, and barrel throats with less-generous free-bore. Even if the rifle's magazine allows greater cartridge length, a tight chamber can mean that the bullet ogive contacts the throat of the chamber, not leaving a small space in which the bullet may "jump" from the case mouth into barrel throat, and down the barrel. This drives up chamber pressures, often to an unsafe level, and generally reduces accuracy, so if it's not one thing, it's something else.
ONCE in a while, a large case loaded with medium-burning rate propellant on which a projectile is seated deep enough that the powder charge is compressed, will result in a load that develops higher velocity at pressures equal to or lower pressures than loads with "UNcompressed" charges. Putative mechanisms range from powder position with respect to the primer flash hole, to the notion that a charge having no freedom of motion inside the case also has less freedom to combust in a random manner, which would tend to spike pressures.
So the "take away" is that, USUALLY, longer C.O.A.L.s mean lower pressures and/or higher velocities, until other factors intervene. And SOMETHING else ALWAYS intervenes.
You have several ambiguous definitions that need clarified, and some missing information about what you're asking. Here's some things to think about.
1) OAL. Most people mean base of the case, to tip of the bullet. This ignores the variability of the actual ogive and tips, which affects actual case volume.
2) 10% case volume. This is a generality, about not reducing cases MORE than that amount; it is not a commandment about only loading up to that amount. Both compressed loads, and significantly reduced case fill loads(relative to the powder and case specifics) can have very nasty and "unexpected" pressure swings. But again, it's a generality, unless you can measure pressure.
3) Powder. Gunpowder isn't a singular constant thing. It's a blend of various different actual powders, with various different actual ages; which fit an unstated range of pressures in the standard cartridge test mule. Once you change the cartridge, the results change also. So it's frankly impossible for anyone to tell you that Powder-XYZ always needs XX amount of volume in any cartridge.
4) Gun variables. Mass produced, name brand rifles are all somewhat different. For example: I've owned a 308 which passed headspace measurements, but had a chamber so wallered out in diameter. That without casting, the classic superstitions of "signs" reported headspace problems. I've owned rifles which had(compared to SAAMI cartridge drawings) dangerously short throats, and currently a 204 which has a throat so long; I've never been able to touch the lands with any bullet.
Just load your rifle, to an OAL(preferably based off the ogive) that will reliably and safely function in your rifle and magazine. Begin your loading, with current data for the Garand; using the START loads.
Always record the velocity, and watch how it differs from the claims in the book as you progress.
Cheers
Sorry. Had I not taken "things" so seriously, perhaps I would have figured that out. Anyway, welcome to the "funny words" game!
Illigitimi non carborundum.
A lot of the LC 30-06 match loads had rather a lot of empty space in them. I experimented with some LC 64 M72 and got 80 fps difference in velocity, depending on whether the powder was forward in the case and away from the flash hole at firing (the lowest velocity and rounded primer edges) or was back over the flash hole at firing (the highest velocity and flat-looking primer). But that year, the powder charge was just 46.0 grains of a fast-ish lot of bulk grade IMR 4895, so there was about 20% empty volume in the cases. It still shot well.
I would note that Federal GM308M, which is a very popular match load for up to 600 yards, has powder that not only fills the case but has been very slightly compressed in the samples I've pulled. So I don't think 10% is optimal in any way. Indeed, leaving space in the case can mean you need to use a magnum primer to minimize velocity variation (you have to try it to see). Homer Powley set up his slide rule load computer for 85-100% load density, so I think he had concluded that was the most useful range if that gives you anything to work with.
COL (Cartridge Overall Length) is now used by most loading manuals rather than COAL. The latter stands for Cartridge Over-All Length, over-all being a hyphenated spelling of overall that became obsolete between 1948 and 1961, the years the copies I have of Webster's unabridged 2nd and 3rd Editions were printed. It is in the former as meaning total length to distinguish it from Chaucer's meaning of overall (all things considered), but which separate spelling is absent from the 3rd edition.
What happens in a rifle is that the lands being in contact with the throat raises peak pressure around 20% typically. As you seat deeper, an annular gap between the ogive and throat is created that allows gas to bypass the bullet while it is starting to move toward the throat. This depresses pressure, and the deeper you seat the bullet, the bigger that gap gets and the lower the peak pressure gets up to a point. When the gap gets larger than the gas path between the expanded neck and the bullet, this gas bypass pressure mitigating effect diminishes in influence, and soon after that, going still deeper has more influence on pressure by reducing the space the powder starts burning in, and starts raising pressure again. So there is a point at which the dominant term influencing pressure is handed off from the bullet jump and gas bypass to bullet seating depth and powder space subtraction.
What will shoot best for you is uncertain because all that adjusting is changing pressure and velocity and the amount of gas producing your final velocity, which is, in turn, changing your bullet barrel time. The latter is important to the timing of the bullet's exit in relation to recoil and pressure-induced barrel bending and muzzle displacement (so-called barrel harmonics), so where your groups will be tightest is not simply determined by locating the bullet near the lands nor to the pressure minimus (a velocity flat spot). But you can influence the pressure hand-off point with load density as well as seating depth, which is why they affect group size, AFAIK.
A lot of the LC 30-06 match loads had rather a lot of empty space in them. I experimented with some LC 64 M72 and got 80 fps difference in velocity, depending on whether the powder was forward in the case and away from the flash hole at firing (the lowest velocity and rounded primer edges) or was back over the flash hole at firing (the highest velocity and flat-looking primer). But that year, the powder charge was just 46.0 grains of a fast-ish lot of bulk grade IMR 4895, so there was about 20% empty volume in the cases. It still shot well.
I would note that Federal GM308M, which is a very popular match load for up to 600 yards, has powder that not only fills the case but has been very slightly compressed in the samples I've pulled. So I don't think 10% is optimal in any way. Indeed, leaving space in the case can mean you need to use a magnum primer to minimize velocity variation (you have to try it to see). Homer Powley set up his slide rule load computer for 85-100% load density, so I think he had concluded that was the most useful range if that gives you anything to work with.
COL (Cartridge Overall Length) is now used by most loading manuals rather than COAL. The latter stands for Cartridge Over-All Length, over-all being a hyphenated spelling of overall that became obsolete between 1948 and 1961, the years the copies I have of Webster's unabridged 2nd and 3rd Editions were printed. It is in the former as meaning total length to distinguish it from Chaucer's meaning of overall (all things considered), but which separate spelling is absent from the 3rd edition.
What happens in a rifle is that the lands being in contact with the throat raises peak pressure around 20% typically. As you seat deeper, an annular gap between the ogive and throat is created that allows gas to bypass the bullet while it is starting to move toward the throat. This depresses pressure, and the deeper you seat the bullet, the bigger that gap gets and the lower the peak pressure gets up to a point. When the gap gets larger than the gas path between the expanded neck and the bullet, this gas bypass pressure mitigating effect diminishes in influence, and soon after that, going still deeper has more influence on pressure by reducing the space the powder starts burning in, and starts raising pressure again. So there is a point at which the dominant term influencing pressure is handed off from the bullet jump and gas bypass to bullet seating depth and powder space subtraction.
What will shoot best for you is uncertain because all that adjusting is changing pressure and velocity and the amount of gas producing your final velocity, which is, in turn, changing your bullet barrel time. The latter is important to the timing of the bullet's exit in relation to recoil and pressure-induced barrel bending and muzzle displacement (so-called barrel harmonics), so where your groups will be tightest is not simply determined by locating the bullet near the lands nor to the pressure minimus (a velocity flat spot). But you can influence the pressure hand-off point with load density as well as seating depth, which is why they affect group size, AFAIK.
Seating Depth = Case Length + Bullet Length - COL
So if you have the length of the bullet somewhere (this is one free resource, as is Gordon's Reloading Tool (GRT) or buy QuickLOAD (QL)). If you want to determine the volume under the bullet, you have to measure your fired case's Case Water Overflow Capacity (the weight of water the expanded case will hold when the water is level with the case mouth and with no meniscus) and substitute that into GRT or QL and tweak the COL to match the load you are reading about and see what capacity it would involve in your chamber.
So if you have the length of the bullet somewhere (this is one free resource, as is Gordon's Reloading Tool (GRT) or buy QuickLOAD (QL)). If you want to determine the volume under the bullet, you have to measure your fired case's Case Water Overflow Capacity (the weight of water the expanded case will hold when the water is level with the case mouth and with no meniscus) and substitute that into GRT or QL and tweak the COL to match the load you are reading about and see what capacity it would involve in your chamber.
Wow. Latin, English and Math lessons all in one place. I love this forum. You guys are masters of the art. You've given me much to think about next time I press in a bullet. I shall take all in and take a step back to look at what I'm doing with a little 'what-if' thrown in. Much appreciated. I've taken a few factory loads apart to reverse see but, that doesn't mean much since they have their own blends of powder that changes things. My first consideration is safety. I think I should invest in a chronograph. I've been using feel, sound and accuracy as a meter as well as comparing 3 different manual loads. So far I still have all 9.5 digits.
You reading to much in here I think.OAL will not necessarily depend on the bullet stlye and length. What it will depend on is the distace from your bolt face to the lands in the barrel.
The space between the loaded bullet and the powder will change depending on the powder you are using. Faster powder generally leaves more room and slower powder less. Leaving 10% space sounds about right. What my understanding is is the best powder will fill up to 90% of the case. To me that means somewhere just under the base of the neck! I haven't a clue how to measure that! I guess!
Manufacturer's listing a depth of seating depth is what they do. Read the manual, it's call overall loaded length. That is going to seat that bullet so that it is well off the lands, kind of a lawyer's measurement! Seating that deep will keep the pressure safe with that load. How deep is that? Not a clue! Seat from there to about deep enough the hold the bullet, one caliber length but don't touch the lands with the bullet.
Something important to keep in mind, the measurement's and direction's in a loading manual are carefully figured to keep the hoby of reloading safe for everyone. We often defy those directions and when we do we do so at our own risk! I often go over max listed loads and if I blow up something, my fault and no one else to blame. As a resalt I spent a long time learning to read different pressure signs and my first venture over max loads was not vey high. I could tell you that most max loads can be exceded but that only works with the rifle I did it in and you may have the same exact thing and not be able to do it. Thing about chambers. I have two 243's. Both have their own set of dies and the dies are locked in after my final adjustment with the sizing die and the seating die, I do not change them. In both rifles the rounds are created to fit the chamber as best I can and put the bullet to the same depth every time. The ammo from one rifle fits in both but the ammo from the other does not. In fact the ammo from the other won't allow the first rifle to close the bolt. partial FL sizing is what I do in every rifle I have with bullet's seated just off the lands. I don't really care for loading for my handguns but I do. Light loads in every one. Reason being handgun and shotgun powders are very fast burning and a little bit goes a long way!
Concerning style and length of bullet, that shouldn't matter much. the seating die push's in the bullet with a plug the size of the ogive which in turn is supposed to be the diameter of the lands. Shouldn't be much problem there but before you start fooling with that make sure you have exactly what the manual says. You cannot change that without understanding it pretty well. Where the problem will come in in seating the bullet is seating it into the lands, that will raise pressure depending on how bad you do it, don't fool with that! If the case fits the chamber and the bullet is off the lands the thing that will raise pressure is a bullet heavier than what the directions calls for. I use data from any manual I have when looking for different powder data. Little secret though, Start low and work your way up looking for pressure signs first. and of course the data should be for the same weight of bullet or pressure will change. The best advice I think I can give anyone getting into reloading is to stick with one brand bullet and definatelly before you start experimenting, learn to make really good ammo before experimenting! Doing that will at times keep you from losing finger's! But also it is good to ask question's before experimenting.
Something I learned years ago, quite by accident is that seating depth can raise pressure. Had a 7mm mag and wasn't getting accuracy with 160gr bullet that I was with 140 gr bullet. Noticed that 140gr bullets were seated to the base of the neck so I figured if I had the lands cut out to where I could seat the 160gr bullet like that, accuracy would improve, bad thinking actually. Did it and accuracy did improve a good deal but notice something else. before that my load was max with N205 powder. I think it was 67 grs. After that the max load went up to 69grs! Today I believe the difference was in the extra case capacity I got moving the bullet farther out of the body of the case I don't know, I would assume that always happens but what I'm sure of it if I could do that with other cartridges I'd start over with load developement just to be on the safe side. Don think that space between the base of the bullet and the powder means a lot and then again it does depending on the burn rate of the powder your using. Experiment with caution!
The space between the loaded bullet and the powder will change depending on the powder you are using. Faster powder generally leaves more room and slower powder less. Leaving 10% space sounds about right. What my understanding is is the best powder will fill up to 90% of the case. To me that means somewhere just under the base of the neck! I haven't a clue how to measure that! I guess!
Manufacturer's listing a depth of seating depth is what they do. Read the manual, it's call overall loaded length. That is going to seat that bullet so that it is well off the lands, kind of a lawyer's measurement! Seating that deep will keep the pressure safe with that load. How deep is that? Not a clue! Seat from there to about deep enough the hold the bullet, one caliber length but don't touch the lands with the bullet.
Something important to keep in mind, the measurement's and direction's in a loading manual are carefully figured to keep the hoby of reloading safe for everyone. We often defy those directions and when we do we do so at our own risk! I often go over max listed loads and if I blow up something, my fault and no one else to blame. As a resalt I spent a long time learning to read different pressure signs and my first venture over max loads was not vey high. I could tell you that most max loads can be exceded but that only works with the rifle I did it in and you may have the same exact thing and not be able to do it. Thing about chambers. I have two 243's. Both have their own set of dies and the dies are locked in after my final adjustment with the sizing die and the seating die, I do not change them. In both rifles the rounds are created to fit the chamber as best I can and put the bullet to the same depth every time. The ammo from one rifle fits in both but the ammo from the other does not. In fact the ammo from the other won't allow the first rifle to close the bolt. partial FL sizing is what I do in every rifle I have with bullet's seated just off the lands. I don't really care for loading for my handguns but I do. Light loads in every one. Reason being handgun and shotgun powders are very fast burning and a little bit goes a long way!
Concerning style and length of bullet, that shouldn't matter much. the seating die push's in the bullet with a plug the size of the ogive which in turn is supposed to be the diameter of the lands. Shouldn't be much problem there but before you start fooling with that make sure you have exactly what the manual says. You cannot change that without understanding it pretty well. Where the problem will come in in seating the bullet is seating it into the lands, that will raise pressure depending on how bad you do it, don't fool with that! If the case fits the chamber and the bullet is off the lands the thing that will raise pressure is a bullet heavier than what the directions calls for. I use data from any manual I have when looking for different powder data. Little secret though, Start low and work your way up looking for pressure signs first. and of course the data should be for the same weight of bullet or pressure will change. The best advice I think I can give anyone getting into reloading is to stick with one brand bullet and definatelly before you start experimenting, learn to make really good ammo before experimenting! Doing that will at times keep you from losing finger's! But also it is good to ask question's before experimenting.
Something I learned years ago, quite by accident is that seating depth can raise pressure. Had a 7mm mag and wasn't getting accuracy with 160gr bullet that I was with 140 gr bullet. Noticed that 140gr bullets were seated to the base of the neck so I figured if I had the lands cut out to where I could seat the 160gr bullet like that, accuracy would improve, bad thinking actually. Did it and accuracy did improve a good deal but notice something else. before that my load was max with N205 powder. I think it was 67 grs. After that the max load went up to 69grs! Today I believe the difference was in the extra case capacity I got moving the bullet farther out of the body of the case I don't know, I would assume that always happens but what I'm sure of it if I could do that with other cartridges I'd start over with load developement just to be on the safe side. Don think that space between the base of the bullet and the powder means a lot and then again it does depending on the burn rate of the powder your using. Experiment with caution!
I think the answer to your question "isn't the space between bullet and settled powder more critical than going by a max. OAL?" is it depends.... on 1) caliber, 2) specific cartridge, 3) powder and lot, 4) bullet, 5) primer and lot, 6) barrel -age, quality, number of round through barrel, 6) the quality of the chamber reamer, its age meaning how many times it has been used, 7) the exact length of the lease, 8) how true the chamber and leade are to the bore, 9) brass and specifically volume and internal variation cartridge to cartridge, 10) flash hole uniformity, 11) variation throw-to-throw on powder measurement. That is all that comes to mind as I brain storm. Certain there are more. You need to spend a lot of time doing load development and become OC on your reloading. Once you find a load that works to your needs you will find it will change over time -- barrels wear, chambers wear, variation lot to lot in primers, powder, bullets, brass become unservicable. Determine what you want with regard to your ammo. Is it group size? Low SD? Consistant velocity? Then start the load development. Once you find your golden egg of a load, then comes the problem of finding it again whenever something changes and the error in performance exceeds what you want/need. Cannot stress enough you have to document everything. Record keeping is huge, and you cannot rely on memory..
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