Finding the maximum charge by velocity

W

Wheeljack

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CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

SAAMI lists the 9mm round with a 147gr bullet. The old standards (1993) listed a Jacketed 9mm but the new 2015 standards do not mention bullets type. Lead, plated, jacketed or what ever. What they do list is a velocity and pressure. Actually 3 pressures, but I'll stick to the MAP or maximum average pressure. For a 147gr bullet they list a velocity of 985fps and a pressure of 35,000psi. Now it seems from that, I would work up a load for my 147gr bullet, whatever kind, to a maximum of 985fps and 35,000psi. Hodgdon data list a 147gr XTP, loaded with 4.1gr of 572, with a velocity of 954 and a pressure of 32,200psi and calls this a maximum load.
Wouldn't you think that you could up the powder charge a little to get to the 985fps level for a maximum load? There are obviously other factors to consider, but what are they and is there any place to find that information.
Oh, and as I increase the load, I check the velocity with my chronograph. If I go over 985fps, I will reduce my load. Even though I could load for a +P level.
 
I'm not even sure I understand the question.I will take a wild guess at why SAAMI might give both a velocity and a pressure for max with a 9 mm 147 gr bullet.
Most all 9mm handguns are recoil operated locked breech. So,recoil impulse matters.
If there was a miracle powder that could deliver 1200 fps in a 9mm using 147 gr bullets at safe pressure,the recoil characteristics might outside the range of what 9 MM pistols are designed to run with.

Once again,its just a guess.
 
If I read the OP correctly, it asserts (or assumes) that the SAAMI document states that: if you achieve the stated velocity, you will be experiencing that stated MAP. I don't believe that to be a correct interpretation of the SAAMI document.
 
Most reloading manuals don't push cartridges to the limit of the SAAMI pressure maximums. I'm guessing this is because it leaves a safety margin for the average reloader. Not everyone is using the exact same brass as the reloading manual. Not everyone has a powder dispenser that will drop charges to the exact weight every time. Not everyone uses the exact same length as the reloading manual. Changing any of these variables has an effect on the pressure.

Additionally each powder has different burn rates and pressure curves. You can't expect to be able to get 985 FPS from every powder out there. There are some powder, bullet, brass combinations where 985 FPS is possible while staying under 35,000 psi but that doesn't mean every powder, bullet, brass combination can reach 985 FPS.
 
My way to interpret the saami spec.

35k psi max pressure. Not to exceed.
984fps. Expected muzzle velocity at 35k psi chamber pressure. My actual speed may be over or under.

Will I up the charge to get to the velocity? I generally won't, as I do have a reason to. Say I needed to have the speed for the bullet to work. I would probably find another powder. This one is too close to feel kosher.

-TL
 
SAAMI does not mention the effects of different barrel diameters (in .0001") that vary in manufacture. They don't list different powders. They list MAP as a good place in the range of pressures to provide reasonable functioning and reasonable life of the cartridge and barrel.
Pressure has very little to do with velocity. That is why you can't load a 50000psi load of Bullseye in a 3006 and expect the same velocity of a 50000 psi load of H4895.
The powder manufacturers select a range of powders that are suitable for a single cartridge and a single (or a few) bullets and then test them to produce reloading data for the reloader. They stop increasing the load when adding more powder no longer is beneficial or it becomes erratic.
If you are using the same cartridge and bullet and the same lot of powder in a gun with the same bore size (down to the nearest .000001") and the same finish in the barrel then you can, theoretically, load the same amount of powder and get the same velocity with the same bullet seated to the same length in an identical chamber. None of that is going to happen.
Lot to lot variations in the powders, bullets, primers are going to produce different velocities and pressures in your gun.
The worst use of a chronograph is an attempt to match the velocity of a listed load by increasing the charge while measuring the velocity. Aside from all the variations in the guns and components you have the variables in your chronograph. Temperature, humidity, and ambient light can make your chronograph read very different velocities with the same ammunition. Under the best of circumstances the only information you can get from a chronograph is an accurate velocity of the bullet. It can't show you pressure trends or let you know when you exceed the MAP for a given round.
No two loads or guns are the same. Reloading manuals used to list their maximum loads as "never exceed" loads. If you do exceed the maximum listed loads you are placing yourself and those beside you on the firing line at risk. You have no accurate way to determine the pressures you are working with and the pressure/time curve your load is following.
Please be careful.
 
As mentioned, in the real world examples, things usually just don't work out like you have it listed. In some examples using say a slower powder and loading for a rifle you might actually find what your looking for, but that doesn't mean you will the next time.

Problem with a 9mm, or really most semi-auto pistols is that they operate best within a specific time/pressure curve and you need to sort of stick within a bracket for things to run well. Most of these also aren't very forgiving with regard to seating depths​ and a little bit can change things a whole lot.

All this is simply to say that the folks who put out the data and components have far more money tied up in this than we do. I've been loading my own since back in the 70's and have found out from experience that they DO actually know a bit about it. I've also found that pushing the envelope just because it seems like you can, will sometimes hurt. Whether that is physically or financially depends on just what let's go and where. Thankfully for me the couple of times when I found that limit it was simply a primer or a cracked slide. Beyond that I'd rather not find out how it could be.
 
I think you're overthinking this. Or maybe, you're underthinking this. I'm not sure :D And it would seem you're trying to drive at the same thing - whatever that may be - with two separate posts.

Wouldn't you think that you could up the powder charge a little to get to the 985fps level for a maximum load?
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Well, I wouldn't think that. Which is kind of my point. Overthinking. Yes, it would seem that they could increase the charge (to 4.2?) and get closer to the 35K standard (not sure if it would get to the 985 f/s or not). But maybe 4.2 exceeded 35K so they published 4.1 as max? I don't know. But what I do know is that there's no point in activating a lot of brain cells over the matter.

Handloading is not an exact science. Not by any means. And variables abound.

I will tell you this for sure: Do NOT attempt to find the maximum charge by velocity. This is usually called "chasing velocities" and is a good way to destruct a firearm - or hand - or worse.

It's back to basics time. I suggest thinking less about Hodgdon's findings, and more about what you want to accomplish with your 147's. Start with reputable load data (Hodgdon's in this case), start low, and work up until you get the desired result - or until you run into pressure signs (flattened primers, bulged brass, far flung brass, sharp recoil, just doesn't feel right, common sense, etc.) - at which point, you back down.

How we seasoned loaders can be most helpful is if you let us know what you're trying to accomplish (the purpose of your load work-up), and how/whether you can get there with your components (147/572). We can only speculate what Hodgdon did with their work up and why they stopped short of max pressure. Hodgdon has a much better than average load data website and I myself have at times put my trust in it - I can tell you that. Which . . . brings us back around to: How may we help you with your load work up?
 
Just curious about the max. That being the max within the average SAAMI definition and not the +P range. I found someone that did some higher loads that gave me more information. He went up to 1240fps, which is more than I am looking for. I have a shorter barrel for one thing. But he said he found the powder reacted in a linear fashion with no spikes. That said, I was just curious enough to try to get to 985 or close enough that I can judge what the load will do. I will not try for 985 because of my shorter barrel. The velocity in a 3.5" barrel may be 28fps slower, but a Polygonal barrel may be 22fps faster than a 4" barrel. My Glock barrel is about a half inch shorter than that used for the Hodgdon data, so I estimate the maximum fps may be about 979fps for a Glock 26. So if I load 3.6g and 3.8 gr and 4.0 gr I will get a feel for how fast an even larger charge will be without having to load it. If 4.0 gr gives me 962fps then I can figure 4.1 will give me 979. I won't have to load to 4.1 if I don't want to, but just say I'm close enough. Looking at the Lyman manual, it seems there has not been a maximum charge that was ever the most accurate. So, I will start with the 4.0gr load and go lighter with more loads until I find one I think is the most accurate. All this may not be practical, it's just that I want to know.
Yes, I'm over thinking. If Hodgdon found that 4.2gr is over 35,000psi, I'm sure it's not by much and certainly not a +P load which in my Glock is still safe. So, I believe I am not loading to hot and definitely don't want to load until my primers flatten out. Some don't feel there is a relationship between velocity and pressure. It may not be linear, but if I load higher, the bullet goes faster and I'm pretty sure the pressure goes up not down.
Thanks all for the input. It is helpful and informative. I'll have load some rounds and get to the range. I will reply with my results. But, yes, loading is not perfectly accurate. If I publish some velocity's, if will be an average. Yes, I will have to wait for an overcast day to get better readings from my chrono. If anyone is shooting 147gr +P ammo, I'd love to know what their velocity is. Thanks again.
 
With my 147gr Xtreme plated bullets, in my Glock 26 with a 3.42" barrel, an OAL of 1.150....
Win 572 at 3.8gr gave me an average fps of 843; 4.0gr 858 and 4.2gr 872fps. The maximum fps with 4.2gr was 894.
 
Now we're getting somewhere.

I actually don't load a lot of 9mm. For me, the cartridge is purely for conceal carry self-defense. And factory range ammo is somewhat cheap (sitting on about 2k rounds). Bottom line: I shoot 500 rounds a year (tops) to keep in practice with my CCW piece; and the occasional trip to the range with my safe queen Beretta 92fs.

Point is, I have almost no experience loading 147's. Ironically enough, I rather fancy heavy bullets in many applications. That said, it is my opinion that the 147 makes for a much better bullet in a 357 Sig than 9x19. In terms of terminal ballistics for self-defense, 147's in a 9mm are marginal. My carry ammo is Speer's 124 GDHP +P's, so what little 9mm I do load is usually 124's.

Enough about me. I just wanted you to know my perspective.

Your numbers sound about right to me; but then, I've never heard of 572 until about two weeks ago :p, so much is just speculation. Since it seems 572 has a burn rate somewhere in the AA#7/Blue Dot/800X neighborhood, and if you don't see any signs of pressure, it may be safe to inch the charge up some more. That's not a recommendation, just a guess. These decisions are purely yours.

I would like to know the sample size of your chrono data.

I would like to know your purpose. Since you're using a plated bullet, I'm assuming not SD. Most likely, your purpose is to make range ammo that has a full-throttle feel. But I'm just guessing. I still wanna know the end game here.

And of course, I would also like to know your next step.

Load safe,
Nick.
 
Wheeljack , I'm not sure the 147's and a short barrel is your best combo . To pump up velocity you need a slow for caliber powder burn , which appears you have . The issue you may run into is large flash in low light as the powder burns off outside the barrel . You will also likely get a louder then average report ( bang ) then other faster powders .

I'm with nick as far as liking the 124/125gr bullets for short barrel CCW applications .
 
Like Metal god, I was going to mention muzzle flash, all that stuff he did, etc.

But since I (we) still don't know the purpose of this ammo, I chose to leave it be for the time being. Speaking for myself, muzzle blast is a non-issue because I always shoot at the range in daylight. Besides, a little light show now and then can be kinda fun :p. But yeah, if you're crafting balanced ammo for self-defense, it would be time for a re-approach - for a couple reasons.

Crafting ammo specific to your needs and your gun is the single biggest advantage of loading your own (no, lower cost is not the biggest advantage of handloading, because you will invariably shoot more - thus saving nothing ;)).

And one of the most important aspects of crafting ammo for your gun is its barrel length. Short barrels are restrictive, in terms of creating truly "balanced" high-performance ammo. Loading for long barrels is easy. Loading for short barrels takes more thought. Compromise becomes key.
 
I was figuring the OP was using this load for hunting or SD/HD do to the premium bullets being used . This is why I mentioned the flash and bang factors of using a slow powder in a short barrel . It very well may be irrelevant to the OP but thought I'd mention it .
 
I will have to wait for an overcast day to get better readings from my chrono.
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Reading through, I just noticed this. I get the most consistent readings from my chronograph when the diffusers are being bathed in direct sunlight. A light overcast (hazy) does have the advantage of not being time of day sensitive - the high-thin clouds are the diffusers - and they are already being bathed in sun ;). Since your diffusers are at 30,000 feet, you need not worry about them being covered in shade from the range rooftop.

With my 147gr Xtreme plated bullets.
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X-treme makes great range shooter plated ammo. I've got a dozen boxes of the stuff right now (38; 44; 45 ACP; & 10mm). But I don't consider them . . .
premium bullets being used
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.;) Our OP was referencing data that used XTP's, but his actual bullet is an X-treme plated. Unless, I missed something - which is possible indeed.
 
Wheeljack,

If two different powders produce the same velocity from the same bullet in the same barrel, that means the AVERAGE pressure during the bullet's travel down the whole length of the barrel was the same for both loads. It does NOT mean the PEAK pressure was the same. You can have a powder that produces a quick, high peak that drops pressure fast as the bullet moves forward, or a powder that produces a lower peak but sustains pressure better as the bullet goes down the tube, and both give the same average pressure. This is typically what is seen comparing a smaller charge of fast powder to a larger charge of slow powder. Peak pressure is the only thing that matters to safety for the shooter. Average pressure is all that matters to how much energy the bullet picks up.

Commercial loaders use pressure test barrels. A chronograph does not measure peak pressure. If a factory load test reaches maximum allowed peak pressure without achieving the desired velocity, the ballistic technician knows they have to switch to a larger charge of slower powder to get that desired velocity without exceeding the peak limit. So, he really needs both the pressure barrel and the chronograph to tell him when he needs to make a powder switch. That's the part that's missing when you only use a chronograph: knowing when you have to switch powders.

You might ask, well, then, why don't they always use the slowest powder they have? Well, there is such a thing as too slow, also. Too slow may fill the case and still not reach the desired velocity. Not to mention the heaviest charge typically costs the most to use and a slow powder burning at too low a peak pressure tends to burn very dirty. So for any given bullet in any given cartridge loaded to any given possible velocity, there will be a band of powder burn rates and energy content levels that will work best. But, again, you need both pressure and velocity instruments to learn what they are.

Incidentally, you will note the SAAMI specs include standard velocity barrel lengths. If your barrel is a different length, none of the SAAMI velocity numbers apply. This is also one source of confusion among shooters who see a certain velocity stated on a box of ammunition and then discover their gun doesn't match it. They are unaware of the standard pressure and velocity barrel length used, and that their barrel is not that length. Dimensional and machining variation also is involved in this, but the length is a simple factor that is often missed.
 
CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

I use commercial ammo for SD. I reload as a hobby. My goal keeps changing as I read and learn from others. It would be easier to learn if everyone would agree. It's OK, it would not be interesting if everyone did agree. I worked up a load I liked with HP-38, so I was finished with HP-38.
I read about 572, it was slower than HP-38 so maybe better with a heavy bullet. But then with a 3.5" barrel, maybe too slow. Manufactures give just so much data, but never enough. Anyway, I bought the 572 and will work with it until it's all gone and then I will consider an other powder, maybe something between the HP-38 and the 572. But for now the 572 data...

Latest info. Now only 10 shots per load. My Glock barrel is pitted so I switched to a L&G barrel, so speed may be slower, if you believe that. I shot groups of 10.
Win 572 4.2gr 877pfs (it was 891 with Glock barrel) Max speed was 901fps.
4.4gr 897fps Max 934
4.6gr 952fps Max 982
That 982fps was a surprise and the jump from 897 with 4.4gr to 952 with 4.6gr too. Out of the 10 rounds that max of 982 is quite a jump too.
To confound things, 4.6gr gave me the best group. My max will be 4.5gr and I'll work down from that 0.1grs at a time to check out where the most accurate charge is. I hope I find it next time out. Working with the Chrono is a pain. I use plated bullets, round nose, 1.150 COL.

The slower 572 powder does seem to be louder than the HP-38. I like the way it pours. Burns pretty clean.

On top of this I would like the charge to work in a revolver and carbine too.
 
I use commercial ammo for SD.
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Me too. Probably a good idea - for legal reasons, if nothing else. Please folks, let's not hijack this tread into a legal discussion regarding ammo for SD.

It would be easier to learn if everyone would agree.
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Heh :D Indeed it would. Don't hold your breath ;)

I read about 572, it was slower than HP-38
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It would seem so. Its burn rate appears to be in the neighborhood of AA#7, Blue Dot, 800X, N-350, and the like.

so maybe (572 is) better with a heavy bullet.
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Yes. I agree. On balance, slower propellants run more consistent and clean when pushing the heavies.

But then with a 3.5" barrel, maybe too slow.
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Mmm, maybe. But then, it may work well enough because of the heavy bullet. If you were using 115's, for instance, I'd completely agree.

That 982fps was a surprise and the jump from 897 with 4.4gr to 952 with 4.6gr.
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It raised my eybrows (literally).

To confound things, 4.6gr gave me the best group.
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You might have found its sweet spot. If you're not seeing pressure signs, you might have simply found where it likes to run.

The slower 572 powder does seem to be louder than the HP-38.
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That's to be expected. Even when running in its sweet spot, a slower propellant is generally going to have more "residual burn" as the bullet exits the barrel; and thus, more muzzle report.

(572) Burns pretty clean.
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Another sign you're running it where it like to run.

Barring any pressure signs, it sounds like you're making some good ammo there.
 
CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.


Wheeljack,

I think you are operating on a number of incorrect assumptions about the relationships between pressure and velocity. Here are some things you need to know:

  • The SAAMI standard pressure test barrel for 9 mm Luger is 4.000 ±0.010 inches long. It has a chamber that is the minimum size (produces maximum pressure with a given load) within 0.0005 inches in the pressure critical values (headspace and diameters). All velocities reported by Hodgdon and by ammunition manufacturers adhering to SAAMI standards (the big ammunition makers) are reported for barrels that length as measured by a chronograph for which the half-way point between the start and stop screens is fifteen feet from the muzzle. All other barrel lengths and dimensions and distances from the chronograph will produce different results. The measurements are all for a ten shot average and do not tell you the highest and lowest values.
  • Velocity will go up close to linearly with powder charge in the normal operating pressure range. That is, if you divide the highest and lowest velocity difference that the published minimum and maximum charges produce and divide it by the difference in the powder charges that produced them, you will get some number of fps per grain of powder charge change. If you are working up a load and the velocity is suddenly anything different than that fps/grain number predicts, be it either higher or lower, that is a pressure sign and you need to back the load off.
  • Any time you put loads on the forum that are outside published loads, you are required to add in the warning I put at the top of this and your posts. See the sticky on this topic at the top of this forum. Once I realized where your loads were going and checked the published data, I added them in, but please observe this rule in the future.
  • Average pressure on the bullet multiplied by the distance it travels down the bore is the amount of work put into the bullet. Work has the same units as kinetic energy. Work converts to energy and you can deplete energy by using it to do work. Some look at energy as stored work, and some at work as creating energy. Either way, average barrel pressure is thus proportional to bullet energy, not bullet velocity. Since energy increases as the square of velocity, velocity increases as the square root of average pressure. In other words, if you double average pressure, the velocity goes up by 1.414 (the square root of two). If you double velocity you have quadrupled average pressure. So if you think velocity indicates average pressure, you are off by a power of two. Pressure goes up faster.
  • Peak pressure goes up even faster than average pressure does when you increase powder charge.
  • You have noticed that Hodgdon maximum loads, for which they report the average peak pressure (not the overall average pressure in the barrel) are not as high as SAAMI allows. This is because, according to Hodgdon's printed manual, they limit that average peak pressure based on shot-to-shot pressure variation they've see in the load. They set it so the variation they see does not exceed the SAAMI pressure. So, when the 572 maximum pressure was set to 32,200 psi, it was because some individual rounds in the average could get to 35,000 with that load. That's ±8% possible pressure swing for this powder. Interestingly, this Hodgdon system means you can tell which of their powders produced the most consistent pressure: its the one whose maximum load pressure is highest.

I have an Excel worksheet that estimates pressures and velocities based on the logarithmic relationships between pressure and velocity in the start and maximum loads given by Hodgdon load data. This shows that if Hodgdon gets 32,200 psi from 4.1 grains, they would get an average of 38,045 psi from 4.6 grains. This is with their bullet, their primer, and their COL. In their 4" test gun, the velocity should go from 957 fps (about 937 fps in your shorter barrel) to 1039 fps.

Here's the concern: since you have a load that would average 38,045 psi in their test gun, with 8% swing, some shots could be at 41,353 psi. The fact you are seeing velocity jumps in excess of those predicted by the number of fps per grain of powder in the Hodgdon data (about 18 fps for each tenth of a grain), it is a pressure sign. Powder burn rates increase with pressure, and that's the cause of the exponential rise of pressure with charge weight.

You have a different bullet, a different COL and maybe a different primer. You almost certainly have a different lot of powder, for which the standard condition burn rate can vary about ±3% from lot-to-lot. So there is no way to know what pressure you are actually getting in your gun. But the fact a small charge change makes velocity change so much tells me it is almost certainly too high.
 
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