How do I predict velocity?

[billmc2]

Using the cartridge I am currently working on as an example, the 45 Colt. I'm looking at the 4th Ed of the Lyman Cast Bullet Handbook, on page 285. For a 230 gr bullet (RCBS 452-230-CM) using Accurate No 5, they show a starting charge of 9.2 gr with a velocity of 845 ft/sec. They show a max load of 11.6 gr with a velocity of 1038 ft/sec. They state a barrel length of 7.5 inches.

I'm working with a 4 inch barrel.

If I assume the pressures will be the same as what Lyman had, how do I know what velocity I should see out of my gun with the shorter barrel?

I tried using a ratio of barrel lengths, with my barrel being 52% of their test barrel, but that didn't work. If I have an already know velocity for my gun with the same powder and bullet, I can work out what I should expect to see. The problem I have is not having a know starting velocity for my gun.

How do I go from the unknown to the known?

[Recycled bullet]

You need a chronograph.

[billmc2]

I have a chronograph. The question is, with a shorter barrel, what should I expect the chronograph to read?

[justindad]

ballisticsbytheinch.com

[Winger Ed.]

I have a chronograph. The question is, with a shorter barrel, what should I expect the chronograph to read?

You just have to shoot across it and see.
There's no real formula for what you're doing, but a good guess would be about 15% less than the longer barrel.
Then there is the variable of cylinder gap bleeding off pressure. Is yours more or less than the test gun?

[Larry Gibson]

If the chronograph [which make/model?] is set up correctly (at least 10' from the muzzle) it will give a correct reading. Trying to out guess a chronograph is tantamount to trying to outguess a compass. With the first you will be wrong, with the second, not only wrong but....lost.....

[billmc2]

The chronograph that I have is a Competition Electronics ProChrono DLX. I usually set this up 12 feet from the muzzle.

In this instance I'm using a newly acquired S&W 625-7 Mountain Gun.

I consider myself to still be relatively new to hand loading.

It is my understanding that the chronograph is used to measure the results. All the loading books I have state a given velocity for a given barrel length. If I don't have the same length barrel that they have used, I have no way of knowing if I'm in the ballpark for the powder and charge I'm using. Ballistics by the inch doesn't help me because they do not tell me which powder was used nor how much powder was used. I can and do measure the velocities I am getting, but I have no way of knowing if the velocity I am measuring is the velocity I'm supposed to be getting for the powder and charge I've used.

This might not be an issue with a starting powder charge but what happens when I get to the max charge? Because I have a shorter barrel (along with the other variances mentioned, not to mention the weather conditions) the velocity I measure will be less than what is stated in the book. Another variable to add to the mix is the primer, more than likely I'm using a different primer (in this case I'm using CCI while the book calls for WLP). But how much less? How will I know if I'm at, above, or below the pressure I am supposed to have?

[justindad]

If you are concerned that loading to max book loads could over-pressure, given your lot of components, then stay at min-mid level charges. If you need max power in your ammo, buy from Underwood or Buffalo Bore. In handloading, you have to accept that you will typically not get the power levels that factory ammo can provide.
*
But what is your real goal here? Are you just trying to be safe, or are you pursuing max power for your gun?

[Larry Gibson]

While I've not tested the 230 gr bullet over No 5 powder I have tested the Lee 230 TC bullet over Unique, Bullseye and 700X in the 45 Colt chronographing the loads in a 10" Contender and a 4 3/4" barreled Uberti revolver. On average the velocity loss runs 140 - 190 fps (variation depends on powder/charge used) given the same load in the revolver compared to the Contender.

Thus, I would guestimate when you are close to 120 fps of the Lyman max velocity with a No5 load in your 4" barreled revolver and are also at the max listed load you are probably close to, if not at, that max.

[billmc2]

If you are concerned that loading to max book loads could over-pressure, given your lot of components, then stay at min-mid level charges. If you need max power in your ammo, buy from Underwood or Buffalo Bore. In handloading, you have to accept that you will typically not get the power levels that factory ammo can provide.
*
But what is your real goal here? Are you just trying to be safe, or are you pursuing max power for your gun?

My real goal is to learn how to adjust the numbers I read in manuals to the gun I'm loading. I'm not real concerned about what I end up with. I don't usually load to max and the guns I'm loading for are able to withstand the pressures. I want to learn how to do this task. I know somebody has had to figure this out by now. Cartridges have been loaded for a long time now.

To take things a little further afield, I'd like to know how to figure a charge for a powder which could be used but don't have data for.

Not knowing for sure, so I'll go out on a limb and say it has to boil down to math. I'd like to learn the math that is involved.

[rockshooter]

It probably does boil down to the math, but you have an unknown number of unknown variables. Since you have the chronograph, let it guide you. No need to go down the path that a lot of guys named "Lefty" have trod.
Loren

[Winger Ed.]

How will I know if I'm at, above, or below the pressure I am supposed to have?

Stay within the parameters of published and trusted data.
Sure, you could develop a over max. load that would do OK in the short barrel.
However; if one of those rounds finds its way into something else with a longer barrel, and weaker frame-- it might get real exciting.

As far as going up to and possibly over max loads is concerned:
If the .45Colt isn't powerful enough, and you feel the need to get up into .454 level performance-- just buy one.

Here's a $1500.oo Colt Anaconda .44Mag someone felt needed some improvements in its ballistics.

[dtknowles]

..... I'd like to know how to figure a charge for a powder which could be used but don't have data for.

Not knowing for sure, so I'll go out on a limb and say it has to boil down to math. I'd like to learn the math that is involved.

It is not math or even algebra or calculus. Too many indeterminate variables. No precise calculations will be satisfying.

You could use a theory of limits and excursions. If your gun with your components exceeds the manual's predicted velocity when your gun has a shorter barrel you probably produced a higher pressure than the loads tested for the manual. If you load seriously underperformed, then possibly you are seeing lower pressures, possibly. Even fancy math computer programs for calculating loads are only gross approximations.

Tim

[billmc2]

It is not math or even algebra or calculus. Too many indeterminate variables. No precise calculations will be satisfying.

Tim

As I'm sure you already knew but this answer is also not very satisfying.

My background is failing me again. I'm used to measuring things, using very expensive equipment, down to the millionths or smaller. This past year I developed type 1 diabetes. My baby sister, who came down with it at age 13, has been coaching me (I'm retired now). She keeps telling me that I can't be as exacting as I want to; that it doesn't work that way. That's not very satisfying either.

How do the professionals do it? I'm not looking for an exact number in this case, just a ballpark figure. I would like to apply it in more than one instance but I think you guys are telling me it can't be done. That first I must have a reference from my equipment before I can make other predictions for that equipment. I have begun building my own database for my own guns, but as of yet, it is not very extensive. Once I have it all documented, then I'll have my answer. On the other side of that coin, once I have it all documented I won't need to ask the question.

[35 Rem]

Using the cartridge I am currently working on as an example, the 45 Colt. I'm looking at the 4th Ed of the Lyman Cast Bullet Handbook, on page 285. For a 230 gr bullet (RCBS 452-230-CM) using Accurate No 5, they show a starting charge of 9.2 gr with a velocity of 845 ft/sec. They show a max load of 11.6 gr with a velocity of 1038 ft/sec. They state a barrel length of 7.5 inches.

I'm working with a 4 inch barrel.

If I assume the pressures will be the same as what Lyman had, how do I know what velocity I should see out of my gun with the shorter barrel?

I tried using a ratio of barrel lengths, with my barrel being 52% of their test barrel, but that didn't work. If I have an already know velocity for my gun with the same powder and bullet, I can work out what I should expect to see. The problem I have is not having a know starting velocity for my gun.

How do I go from the unknown to the known?

I'm not sure I understand your question. The loading manual gives a STARTING and MAX powder charge with respective velocities of 845 ft/sec and 1,038 ft/sec and this is in a 7.5 inch barrel. You should accept that those powder charges are the boundaries you have to work within regardless of barrel length. Also very important is that if you were to buy 5 different 7.5 inch barrel revolvers, they would absolutely NOT yield the same results NOR would any of them likely match those loading manual numbers. So trying to mathematically predict with financial logbook accuracy what the velocity is going to be in your gun can't be done.

[414gates]

I tried using a ratio of barrel lengths, with my barrel being 52% of their test barrel, ...

The velocity in a shorter barrel will be closer to the published load for longer barrels if the powders are relatively fast. It's not a direct ratio, and you can only know what it is if you measure it.


My real goal is to learn how to adjust the numbers I read in manuals to the gun I'm loading. .

We don't adjust the numbers in the manual, we use them as they are.

The charge data is not for barrel length, it's for chamber pressure. Chamber pressure in a 2" is the same as a 10".

There is a point below which if the charge density in the case is reduced, it causes the chamber to explode like a hand-grenade. That point is caliber and powder dependent. Some people say that is a myth. Some people have the blown up guns to prove it.

If you think, for example, that because you have 52% barrel length you can reduce the charge to 52%, you're right on track to eventually blowing up your revolver from a SEE.

Changing the numbers is the same as reloading blind.

Load development for an uncommon bullet weight or uncommon powder is a different subject, and has nothing to do with picking numbers in the book and changing them.

[dverna]

I am not a fan or user of it, but Quick Load is used by a number of people.

BTW, I am not a fan or user because I am an engineer. By that, I mean I take a practical approach to most endeavors. In reloading, I do not fuss over one load being 50 fps different than another. That deer at 300 yards will not know the difference. I load for accuracy for loads that matter.

Quick Load will satisfy your desire to crunch numbers. There are quite a few users on this forum who will likely chime in.

IMO you are going down a rabbit hole but if that is what interests you...go for it. BTW, using a chronograph to determine a safe load can get you into trouble. I ignore folks who think like that. My little "engineer voice" calls our "Danger Will Robinson".

You sound like you are new to this. Stay with published loads and ignore loads others post on forums like this. There is no practical need to stray from published loads that have been proven and tested to be safe.

[JonB_in_Glencoe]

Using the cartridge I am currently working on as an example, the 45 Colt. I'm looking at the 4th Ed of the Lyman Cast Bullet Handbook, on page 285. For a 230 gr bullet (RCBS 452-230-CM) using Accurate No 5, they show a starting charge of 9.2 gr with a velocity of 845 ft/sec. They show a max load of 11.6 gr with a velocity of 1038 ft/sec. They state a barrel length of 7.5 inches.

I'm working with a 4 inch barrel.

If I assume the pressures will be the same as what Lyman had, how do I know what velocity I should see out of my gun with the shorter barrel?

I tried using a ratio of barrel lengths, with my barrel being 52% of their test barrel, but that didn't work. If I have an already know velocity for my gun with the same powder and bullet, I can work out what I should expect to see. The problem I have is not having a know starting velocity for my gun.

How do I go from the unknown to the known?


You just have to shoot across it and see.
There's no real formula for what you're doing, but a good guess would be about 15% less than the longer barrel.
Then there is the variable of cylinder gap bleeding off pressure. Is yours more or less than the test gun?
Add to that, the test gun may not be a revolver.

to the OP, I'd suggest to do as we all do, Start with the starting load and work up to desired load using all the tools you have available to you. Published 45 colt loads are pretty tame, due to the antique guns out there, so if you are loading for a modern US made gun, you can't really go wrong...unless you make a mistake, like a double charge.
Good Luck.

[JonB_in_Glencoe]

My real goal is to learn how to adjust the numbers I read in manuals to the gun I'm loading. I'm not real concerned about what I end up with. I don't usually load to max and the guns I'm loading for are able to withstand the pressures. I want to learn how to do this task. I know somebody has had to figure this out by now. Cartridges have been loaded for a long time now.
To take things a little further afield, I'd like to know how to figure a charge for a powder which could be used but don't have data for.

This isn't really something a beginner should be thinking about. This type of knowledge is gained with experience. I could explain how I interpolated a 41 mag cast boolit load using obsolete powder, like Alcan AL-7, which I did and believed at the time that no data existed, but later did find a load in a Ken Waters book. The "how" will be different for every different situation.

So keep on loading by the book, starting with Starting charges and working up, gaining experience...especially how certain powders react differently than others, and collect as many different reloading manuals as you can find and afford...because, that is one of the tricks to interpolating or extrapolating Data...is the finding of Data in similar calibers and working with that to find a Starting load.

[JonB_in_Glencoe]

Not knowing for sure, so I'll go out on a limb and say it has to boil down to math. I'd like to learn the math that is involved.
The Main reason a simple Math formula doesn't work, is because different powders react differently. Every burn rate pressure curve is different and overall non linear. Now most powders do have a pressure range where the pressure curve does increase in a fairly linear fashion...somewhat. That is what published load data gives you, from Starting load to Max load is typically the fairly linear part of the curve, of course the Caliber (think case capacity) plays a big part of that, along with gun type and barrel length play a "little bit" in it also.

[Winger Ed.]

Add to that, the test gun may not be a revolver.
.

At a glance, most test data is done with a similar gun to what we'd be loading for.
.45ACP data is usually done with a 1911.
Revolver cartridges are usually developed with a fairly common revolver.
However; I've seen some cartridges listed as having been developed in a vented test barrel, with a vent line to simulate cylinder gap.
But I don't remember seeing how big the simulated gap was.

[billmc2]

The velocity in a shorter barrel will be closer to the published load for longer barrels if the powders are relatively fast. It's not a direct ratio, and you can only know what it is if you measure it.



We don't adjust the numbers in the manual, we use them as they are.

The charge data is not for barrel length, it's for chamber pressure. Chamber pressure in a 2" is the same as a 10".

There is a point below which if the charge density in the case is reduced, it causes the chamber to explode like a hand-grenade. That point is caliber and powder dependent. Some people say that is a myth. Some people have the blown up guns to prove it.

If you think, for example, that because you have 52% barrel length you can reduce the charge to 52%, you're right on track to eventually blowing up your revolver from a SEE.

Changing the numbers is the same as reloading blind.

Load development for an uncommon bullet weight or uncommon powder is a different subject, and has nothing to do with picking numbers in the book and changing them.

I guess I stated that wrong. When I said adjusting the numbers in the manual, what I meant was the velocity numbers; not the charges. I realize that the charge data is based upon pressure and that pressure shouldn't change. Because I don't have a means to measure pressure, the only way I know of to tell if I've done things correctly is to measure velocity. To do this, however, I need to have some idea as to what velocity should be.

I'm not wrong in thinking that a barrel which is much shorter than the barrel that was used to develop the load will produce much less velocity; am I? The problem is "how much less".

Way back when I was being taught to divide numbers, they taught me to multiple my answer back to see if I got the same number I started with, as a means of checking my work. In this case, not having a starting point I have no way of checking that I'm getting the correct answer.

If I'm still not being clear, please let me know. As I stated and someone else pointed out, I do consider myself to be relatively new to all this. I've heard it said that if I learn to shoot the correct way to begin with, I don't need to go back and unlearn bad habits later.

[35 Rem]

There are rough "Rules of thumb" for guestimating velocity loss as barrel length gets shorter. The problem with them is that there are so many variables that the accuracy of such guestimates makes them sort of a waste of time. For instance, the burn rate of the powder will change how much velocity is lost due to barrel length variations. A slow burning powder will give greater loss as barrel length reduces compared to a fast powder such as Bullseye or Red Dot. There is no precise table anywhere with a set of factors you can multiply to convert from loading manual velocity to what your gun will produce.

I take dverna's view of the situation. I also being an engineer like to calculate and do things properly when warranted but at the same time recognize there are factors that aren't practical to worry about. This is in the latter category. Another is the tedious control some try to have over their alloy content. They must believe they are a manufacturing engineer in a large production line. Most of us are working with scrap lead alloys here. We have no real control over the makeup of the alloy. Control it to the point of practicality, in other words flux to get rid of dirt and do a finger nail hardness test then start pouring bullets! Shoot a few and see if they do what you want and if not THEN you can adjust.

[justindad]

Crimp strength will affect the pressures you see. How will you quantify crimp strength? If you can do that, how will you develop a precise relationship to the pressure?
*
Neck tension affects the pressure required to release the bullet from the case mouth (here I refer to neck tension outside of the crimp). What side of manufacturing tolerance is your sizing die? Expander die size? The burn rate and and burn efficiency are dependent upon instantaneous pressure. How will you quantify all of these and then write a formula to determine the effect on pressure developed?
*
Lube groove design affects pressure developed. How will you relate torsional bullet stiffness to frictional drag in a barrel?
*
I’ve read that PC coating gives higher velocities for the same charge. Does this mean the bullet has less drag in the barrel, so you have higher velocity and lower pressure when coating your bullets? How can you quantify this?
*
We know that bullet obturation can explain why a softer alloy sometimes cures leading of the barrel. If these bullets are being smashed deeper into the rifling, would the pressure developed be different? How can this be quantified?
*
What happens when a full wadcutter hits an 11 degree forcing cone? How is this different from a round nose hitting a 5 degree forcing cone?
*
Sometimes we have to rely on empirical models because precise numerical models are impossible to develop.

[billmc2]

I do like learning new things. When it comes to hand loading or reloading, whichever you prefer, I have no one to ask questions of. So instead, I come here to ask the questions. Many times asking a question can lead to more questions or even better, more information that I knew nothing about. You guys are offering up so much information, that if left on my own, I would have never known to ask about.

I fall into that category of I don't know what I don't know. Keep the info coming.

[Recycled bullet]

Stay within the parameters of published and trusted data.
Sure, you could develop a over max. load that would do OK in the short barrel.
However; if one of those rounds finds its way into something else with a longer barrel, and weaker frame-- it might get real exciting.

As far as going up to and possibly over max loads is concerned:
If the .45Colt isn't powerful enough, and you feel the need to get up into .454 level performance-- just buy one.

Here's a $1500.oo Colt Anaconda .44Mag someone felt needed some improvements in its ballistics.That hurts my hand just to look at it.

[Winger Ed.]

That hurts my hand just to look at it.

Oh yeah....... It just starts there.
Years ago a buddy was at a public range when a revolver let go way down at the end of the firing line.
The guy at the bench next to the gun that blew up had a decent size chunk of his scalp blown off.

[P Flados]

The "math" associated with how fast a given round will accelerate a bullet is beyond what I would call "hand calcs" and is best handled by software. And it is not all pure math. I am pretty sure that built into the process are "fudge factors" based on empirical testing. I use Quickload a good bit. It does have limitations, and requires a good bit of knowledge to get good results. However, overall I find it to be a useful tool.

If the only thing affecting velocity was a reduction in barrel length, software like Quickload would probably be pretty accurate.

However, there is much more to the story. The following are just a few items that may cause velocities to be different than expected:

Powder burn rates vary from batch to batch
Chamber designs and tolerances
Bullet resistance to start of motion
Component substitutions (different brands for bullet, case, primer)
Component variations (even when an exact brand component is used, components can vary from batch to batch)
Loading to a different seating depth

The above affect all guns. However, even bigger variations are expected as soon as you start talking revolvers. This is caused by cylinder gaps and throat dimensions. I typically estimate the losses for the cylinder gap to be 50 to 100 fps. However, when I compare Quickload velocity projections to chrony data, some revolvers seem to lose a lot more than I expected.

Using a chrony to "double check" that you are not getting more velocity than expected probably makes more sense in something like a rifle with a tight chamber and a load where all of the components are good matches to the load that was tested.

Having said all of the above, I will provide an estimate. For your example I am going to assume the load data was taken using a 7.5" revolver. Quickload uses breech to muzzle for barrel length, so I estimate the Lyman gun at 7.5 + 1.7 = 9.2". Your gun would be input with with something like 4 + 1.7 = 5.7". I did not find a 230 RCBS bullet, so I used a 250. I adjusted the AA #5 charge to get close to the test velocity, 1039 fps. The difference in the predicted result with a 5.7" barrel came to 1039 - 906 = 133 fps.

[billmc2]

Thanks for all that.

[dtknowles]

As I'm sure you already knew but this answer is also not very satisfying.

My background is failing me again. I'm used to measuring things, using very expensive equipment, down to the millionths or smaller. This past year I developed type 1 diabetes. My baby sister, who came down with it at age 13, has been coaching me (I'm retired now). She keeps telling me that I can't be as exacting as I want to; that it doesn't work that way. That's not very satisfying either.

How do the professionals do it? I'm not looking for an exact number in this case, just a ballpark figure. I would like to apply it in more than one instance but I think you guys are telling me it can't be done. That first I must have a reference from my equipment before I can make other predictions for that equipment. I have begun building my own database for my own guns, but as of yet, it is not very extensive. Once I have it all documented, then I'll have my answer. On the other side of that coin, once I have it all documented I won't need to ask the question.

Well you don't have to weight powder charges to millionth or velocity to fractions of a fps. Yes, baselining your guns is helpful but you have to have some sort of standard ammo. Are your guns hot or cold and by how much. What are you going to use as the standard of comparison.

If all you wanted to know is how much velocity loss you will see with your shorter barrel someone already pointed you to a resource and you can find more elsewhere online. From what I have seen, going from 7.5 inch barrel to a 4 inch barrel you might see almost no reduction to a couple hundred fps as the gun to gun variation is in that range even with the same barrel length but I doubt you will see a velocity increase.

I have Dan Wesson Revolvers and I have 4, 6 and 8 inch barrels (more than one of each) and I can control the cylinder gap. I can measure velocity but not pressure. Personally, I am not interested in testing all that. I don't chronograph all my loads. I am more interested in accuracy than velocity.

I am the Chief Engineer at an Aerospace company that employs a number of highly talented analysts. I have to constantly remind them that their sophisticated analysis tools still only produce approximations.
Our rule is that a design that has not been tested and relies on analysis only must have a factor of safety of 2.0.
Our most sophisticated designs that have been tested to failure still require a factor of safety of 1.1 to yield and 1.5 on ultimate.

A firearm is like a human rated aircraft. If you get it wrong someone could get badly hurt or die.

If you want to do hand calc's to predict velocity, I expect your will be off by hundreds of FPS. On a good day the most sophisticated computer models will be lucky to be within a hundred psi. Add to that the likely occurrence that variably of a given load will be many tens of FPS. I am having a hard time understanding what you are trying to accomplish. If you tell me a load and the firearm you are shooting it in, I think I can approximate the velocity as closely as you can calculate. I have seen many calculations or computer analysis results that were clearly erroneous.
The variables are numerous and some of them are not defined, like primer brilliance. You got numbers for that and for how it affects pressure rise.

Variable to consider.

Primer brilliance
Powder type and charge weigh (with lot to lot variations)
powder position
Case capacity
Bullet diameter, weight, hardness, bearing area, lubrication.
Bullet seating depth
neck tension/crimp type.
bore diameter.
barrel length
cylinder to barrel gap
throat diameter
jump to rifling.
ammo temperature

Tim

[justindad]

I have used Gordon’s Reloding Tool to predict pressures and velocity - both were often low by 50%. I took a .45 Colt load from Lyman’s 49th Manual, entered the max load data into GRT, and the output was around 7,000 psi.
*
I suspect Quickload is better than GRT, but I have no concrete reason to believe that. If they are similar, blindly trusting software could cost you your fingers.

[414gates]

I guess I stated that wrong. When I said adjusting the numbers in the manual, what I meant was the velocity numbers; not the charges... I need to have some idea as to what velocity should be. .

Most of that work has been done by the powder manufacturers.

There are some manuals that list velocity for shorter barrels, especially when using the faster powders.

There are some you won't find the data for. The 45LC is not commonly loaded in a snubbie, for example.

There is a way to get the precise velocity, without guesswork or math. A chronograph. If you must know what the velocity is, get yourself one.

Prochrono Digital is a cheaper, reliable option. Stay away from that useless Canadian folds-in-a-box piece of rubbish, deceivingly named a 'Shooting Chrony'.

Keep your reloads as safe as possible by following exactly what the books tell you. Never load what someone tells you to load if it's not in one of the manuals.

[waksupi]

If you have a known load and velocity, divide the grains of powder by the velocity to get the approximate FPS per grain.

[Willie T]

You are over complicating things. As a hand loader the parameters you work around are pressure. Published data is generated with a strain gauge. Every firearm is a rule unto itself. Some have tight chambers. Some have loose chambers. Some have fast barrels while others have slow barrels. In your instance you can use published data to work up to the charge that falls within the published data that shoots best in your firearm. Your chronograph will tell you what the velocity is but that will be what it is. There is no hard and fast rule to tell you how much velocity per inch you will lose compared to the longer barrel. Experimenting with different powders will give you data points to decide which powder performance suits you best in your firearm. Faster burning powders will be more efficient in shorter barrels. The velocity lost per inch of barrel will vary by powder. It will also vary by firearm. You are trying to make a concrete prediction using an equation that has a variable answer.
Willie

Edit to add:
Shooting a starting load over the chronograph will give you an idea of what your velocity loss may look like however, velocity gains will most likely not be linear enough with powder charge to predict your velocity at a maximum charge. As pressure builds, burn often is more complete and pressure the curve is altered.

[billmc2]

OK guys you've convinced me. As several different people have stated there are to many variables involved to come up with a prediction of what velocity I should expect to see when I shoot over the chronograph.

In answer to the question I asked about how to predict velocity, a couple of responses told me to use a chronograph, so that's what I did. The published charges for the Accurate No 5 powder for a 230 gr cast lead bullet range from 9.2 - 11.6 gr. Because I did not have enough prepped cases to step through each 0.1 gr increment, I loaded every other increment beginning at 9.2 gr. The temperature at the start of this was 76 F and the barometer was 30.1 inches of mercury.

In the manual the starting charge was 9.2 gr with a velocity of 845 ft/sec.
The max charge was 11.6 gr with a velocity of 1038 ft/sec.
The manual states that a Universal Receiver & Ruger Blackhawk was used. The barrel length was 7.5 inches.

Using a tape measure, the chronograph was 12 feet from the muzzle.

Brass - Starline
Primer - CCI 300
Case trimmed to 1.275"
OAL 1.605"

Arsenal Mold 454424 230 gr LSWC.
Powder Coat bullet sized 0.452”. S&W 625-7 Mountain Gun, 4 inch barrel.
Accurate No 5
9.2 gr, 10 rounds used; all others 5 rounds used.

9.2 gr Average 771 ft/sec
9.4 gr Average 790 ft/sec
9.6 gr Average 795 ft/sec
9.8 gr Average 807 ft/sec
10.0 gr Average 849 ft/sec
10.2 gr Average 862 ft/sec
10.4 gr Average 881 ft/sec
10.6 gr Average 909 ft/sec
10.8 gr Average 908 ft/sec
11.0 gr Average 940 ft/sec
11.2 gr Average 948 ft/sec
11.4 gr Average 965 ft/sec
11.6 gr Average 982 ft/sec


Last week I did something similar but using Win244 powder. If someone is interested I can post those results as well.

Thanks for all the good information and the help.

[justindad]

I wonder what our more experienced folks would consider a good max charge here?

[JonB_in_Glencoe]

I wonder what our more experienced folks would consider a good max charge here?

The short answer is 11.6gr

If you had a Ruger, you could look up "Ruger only" loads, and work up to a MAX published "Ruger Only" load.

[dverna]

I wonder what our more experienced folks would consider a good max charge here?

One thing about not enjoying recoil is I never ask that question. Book maximum is as far as I go.

[Winger Ed.]

I wonder what our more experienced folks would consider a good max charge here?

I'd stay at or a little under 11.6.
Then I don't think I'd ever shoot my eye out.:bigsmyl2:

It's one of those deals where if I didn't think staying under a max. charge in the .45Colt would get me where I wanted to go--
I'd save up and buy a .454 Casull or a S&W 500.

[justindad]

The reason I asked about a safe max here is because I am wondering if the book max is only good for the book bullet. If he ought to see 100 - 150 fps velocity loss due to the shorter barrel, should his max charge be reduced to somewhere around 10.6-11.2 grains? Maybe closer to 11.2 given the PC?

[Larry Gibson]

The reason I asked about a safe max here is because I am wondering if the book max is only good for the book bullet. If he ought to see 100 - 150 fps velocity loss due to the shorter barrel, should his max charge be reduced to somewhere around 10.6-11.2 grains? Maybe closer to 11.2 given the PC?

That is a possibility as seating depth differences between different bullets of the same weight can have a great effect on pressure.

[billmc2]

The reason I asked about a safe max here is because I am wondering if the book max is only good for the book bullet. If he ought to see 100 - 150 fps velocity loss due to the shorter barrel, should his max charge be reduced to somewhere around 10.6-11.2 grains? Maybe closer to 11.2 given the PC?


That is a possibility as seating depth differences between different bullets of the same weight can have a great effect on pressure.

This is the drawing of the bullet from Arsenal Molds.
313155

When I seat to the crimp groove, the OAL of the cartridge is longer than what is usually published. In this case the data from Lyman's book shows the RCBS mold having an OAL of 1.575" and using the Arsenal bullet I have an OAL of 1.605". What I have been doing is to try to find other bullets that use the published data and check to see how deep into the case those bullets are seated, then seat this bullet so it has the same amount of remaining space inside the case. I did trim all my cases to 1.275". For this time, I was not able to get info on the RCBS bullet, but I did seat the Arsenal bullet 0.290" into the case.

I did pick up a copy of the QuickLoad program. Right now, the program is way over my head but I did get some useful, to me, information from it. Using the figure of my seating depth it does show me the available remaining case capacity, so I can compare that to other bullets. Something else I noticed was that it has a standard for 45 Colt (SAMMI) and 45 Colt (CIP). Using the SAMMI spec QuickLoad shows the 10.6 gr charge to be close to maximum. while using the CIP spec it shows 11.6 gr to be close to maximum. My velocities are not lining up with QuickLoad, but I'm thinking that's more do to pilot error (me being the pilot) than the program itself.

[justindad]

CIP can be used if your gun was made & proof tested in Europe. Otherwise, you use SAAMI.

[dondiego]

I predict velocity by referring to 3 or more established loading manuals.

[lar45]

Quickload can give an estimation of pressures and velocities. You can change powders, seating depth, barrel lengths or just about anything you can think of...

[P Flados]

The measured velocities were a little higher than I expected. I am guessing that this is likely from seating deeper than the reference load and/or just a "fast gun".

I ran each one of his test results though Quickload. Measured velocities were 50 - 100 fps below predicted with his bullet and AOL. Given expected cylinder gap losses, this is a good match. With a good velocity match, this tends to make the Quickload pressure predictions likely to be reasonably close also.

The predictions indicate that to stay under the SAAMI 14,000 psi applicable to 45 Colt, do not exceed 10.58 gr of AA#5 with this bullet and AOL.

I poked around at his gun. Based on various postings, people note that the same basic gun is chambered in the 20,000 psi rated 45 ACP. As such, his loads (including the 16,759 psi predicted for the 11.6 gr load) seem safe in his gun.

[billmc2]

The measured velocities were a little higher than I expected. I am guessing that this is likely from seating deeper than the reference load and/or just a "fast gun".

I ran each one of his test results though Quickload. Measured velocities were 50 - 100 fps below predicted with his bullet and AOL. Given expected cylinder gap losses, this is a good match. With a good velocity match, this tends to make the Quickload pressure predictions likely to be reasonably close also.

The predictions indicate that to stay under the SAAMI 14,000 psi applicable to 45 Colt, do not exceed 10.58 gr of AA#5 with this bullet and AOL.

I poked around at his gun. Based on various postings, people note that the same basic gun is chambered in the 20,000 psi rated 45 ACP. As such, his loads (including the 16,759 psi predicted for the 11.6 gr load) seem safe in his gun.

I've also read John Linbaugh's (who recently died) thoughts on the gun. Everything is the same as the 629 which is the 44 Magnum. Linbaugh said, with the thinner cylinder walls, it is at least 80% as strong as the 629, which places the pressure at the upper end of the 45 Colt. around 32,000 psi. What John did point out was the design of the gun. He said it wouldn't blow up but the numerous smaller parts will wear much faster. If you wanted to keep it around for a while, don't shoot the higher pressures.

Brian Pearce, in his article in Handloader (April-May 2022) magazine includes this gun in his Category II guns able to withstand 23,000 PSI.

At the moment I can't seem to find the reference to something I read before, that the 625 chambered in 45 ACP was capable of the 45 ACP +P loads, which I believe are 23,000 PSI.

[Larry Gibson]

"Brian Pearce, in his article in Handloader (April-May 2022) magazine includes this gun in his Category II guns able to withstand 23,000 PSI.

At the moment I can't seem to find the reference to something I read before, that the 625 chambered in 45 ACP was capable of the 45 ACP +P loads, which I believe are 23,000 PSI."

Your information is correct.

FYI; in the 45 Colt a classic load is the 250 gr Lyman 454190 loaded over 8.5 gr Unique. It is indeed a very good load and it shoots very well in my Uberti 5 1/2" Artillery and 4 3/4" Evil Roy SAs. Pressure testing that load at the recommended OAL of 1.600" reveals it runs at 17,500 psi +/-, a bit over the SAAMI MAP of 14,000 psi. Seating to 1.589" OAL and the psi bumps up to 18,000 +/- psi. Seating the bullet out to a max OAL for the Uberti's of 1.664' drops the psi to 15,700 psi.