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Discussion Starter · #1 ·
I splerrshed for a labradar chrono and I have some questions. I notice on some powders the longer I go the velocity increases. For example titegroup, book value is 1.100 3.2 grains of titegroup gives 902 fps, I move it out to 1.130 and I increase velocity to 917 fps decrease extreme spread by 22 fps and decrease standard deviation by 8 fps. And I also noticed that with vv N320, 1.142 is perfect... either side of this, shorter or longer, velocity decreases. How do I, or can I, fine tune the OAL to my barrel for best results and accuracy? Or am I just driving myself crazy? BTW I am using a stock Glock 34 barrel.
 

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I splerrshed for a labradar chrono and I have some questions. I notice on some powders the longer I go the velocity increases. For example titegroup, book value is 1.100 3.2 grains of titegroup gives 902 fps, I move it out to 1.130 and I increase velocity to 917 fps decrease extreme spread by 22 fps and decrease standard deviation by 8 fps. And I also noticed that with vv N320, 1.142 is perfect... either side of this, shorter or longer, velocity decreases. How do I, or can I, fine tune the OAL to my barrel for best results and accuracy? Or am I just driving myself crazy? BTW I am using a stock Glock 34 barrel.
In my experience, as far as velocity is concerned, deeper seating of the bullet increases pressure (velocity) and tends to decrease the ES and SD numbers as most powders burn more consistently as pressures increase.

When it comes to accuracy, in semi pistols, I have always found seating as long as the chamber/throat/feed will allow seems to give best accuracy.

PS - There are a lot of things that affect velocity, SD and ES. When you are running tests, take your time before coming to hard answers as things like different head stamps (with varying case wall thickness) can greatly affect results and lead you astray in your conclusion.
 

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I am with willy here, in a pistol, never gotten higher vel seating longer UNLESS you get close enough to touch rifling. Could be some weird anomaly with TG, never liked that powder much anyway.
There is no magic oal. Oal is always bullet & gun specific. So make a long dummy round & drop it in your bbl. it should fit like dudel shows. Then try it in the mag, all the way down. That is your max oal. Then work your powder charge up or down until you get the vel you want. Change bullet design or even manuf, start over.
Btw, did you test your ammo on the same day? Everything affects vel; powder charge, primers, cases, bullets, temp, elev, humidity. So unless all tests are done the same day, results will be skewed.
 

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I can't say that I've worried about it with handgun. Even though I've been at it a long time, I'm probably not able to shoot well enough to determine a max oal or a bit less. With rifle, absolutely it makes a difference.
 
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I can't say that I've worried about it with handgun. Even though I've been at it a long time, I'm probably not able to shoot well enough to determine a max oal or a bit less. With rifle, absolutely it makes a difference.
The only real issue with handgun is getting a round too long that jambs the bullet in the barrel or wont feed all the way down the mag. As long as you work the powder charge up, it doesn't even affect pressures, until you start moving the OAL.
 
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In my experience, as far as velocity is concerned, deeper seating of the bullet increases pressure (velocity) and tends to decrease the ES and SD numbers as most powders burn more consistently as pressures increase.
Yep. One time I loaded up a bunch of 147 gr. 9mm for a match and when I tested some they were just short of the IDPA power factor. I took them back to the press and crunched them all down just a little shorter and the velocity got up to what I needed to make the power factor.
 

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Yes, you are mostly just driving yourself crazy. For an OE G34 barrel and production ammo, my go-to is 1.140 for RN bullets. Conventional wisdom seems to be that longer is better, within reason. For Glock, the limitation is probably feeding in the mag, and my max number for that is 1.150.

So I shoot for 1.140 and case for 1.150 max. And when I'm casing match ammo and come to a 1.152, I put it in the box - just to prove to myself that I am not governed by neuroses.

In a non-OE barrel, you'd want to check feeding up the ramp pretty carefully, especially if using FP bullets.
 

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Discussion Starter · #9 ·
I am with willy here, in a pistol, never gotten higher vel seating longer UNLESS you get close enough to touch rifling. Could be some weird anomaly with TG, never liked that powder much anyway.
There is no magic oal. Oal is always bullet & gun specific. So make a long dummy round & drop it in your bbl. it should fit like dudel shows. Then try it in the mag, all the way down. That is your max oal. Then work your powder charge up or down until you get the vel you want. Change bullet design or even manuf, start over.
Btw, did you test your ammo on the same day? Everything affects vel; powder charge, primers, cases, bullets, temp, elev, humidity. So unless all tests are done the same day, results will be skewed.
Fred, I tested on different days. Like sciolist said, 1.150 works for my barrel and magazine and yes a little neurotic figuring out the chrono data.

Clays for example, book states 1.100. if I go out to 1.140 I will use more powder to make PF which should increase recoil correct?
 

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Fred, I tested on different days. Like sciolist said, 1.150 works for my barrel and magazine and yes a little neurotic figuring out the chrono data.

Clays for example, book states 1.100. if I go out to 1.140 I will use more powder to make PF which should increase recoil correct?
You might add 1/10gr of clays to account for 0.050" longer oal, you wont feel any diff in recoil.
 

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Clays is so low pressure should I even go that long?
Clays is NOT a low pressure powder by quite a bit. Fact, its very fast & gets pressure spikey at the top end. Why i would only use it for minor loads.
 
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Clays is NOT a low pressure powder by quite a bit. Fact, its very fast & gets pressure spikey at the top end. Why i would only use it for minor loads.
Definitely only minor. Definitely only book loads, that is, if the book says X gr at 1.100" and you want to load to 1.150" and by doing that you fall below a safe margin with your PF, find another powder. Clays is very fast.
 

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Discussion Starter · #14 ·
Book states 27,000 psi for a 130gr plated that's why I called it low pressure, I miss spoke, cause these cases can take 35,-38,000 psi. So yes Willie, I have 132 PF with a P Delta 147gr FMJ over 3.0gr @ 1.130 should be fine, recoil is good. Just trying to find the floor for PF then will check all for accuracy on a bench. The heaviest bullet Hodgdon has data on is the 125 FMJ 3.5-3.7 with max pressure of 32,500 @ 1.090. what I am doing should be fine where I am. The cases and primers are showing absolutely no pressure signs.
 

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i copied this from a forum member at brian enos loading forum... this really cleared up loading 9mm for me atleast, hope this helps... iDescribe says:


EVERY bullet has a maximum OAL in a particular pistol, where by maximum I mean the maximum OAL you can load to without the bullet engaging the lands when in battery. That maximum OAL is different for every bullet. And it's different for a particular bullet when you switch pistols. Inside the chamber, there is a step against which the case mouth headspaces. And there is a place forward of that where the rifling begins. The space in between the headspacing step and the rifling is called the Free Bore (or throat). Different manufacturers will have free bores of different lengths, and that is what causes bullets have different maximum OALs in different pistols. The angle or curve of a bullet's ogive is what causes different bullets to have different maximum OALs in the same pistol.

I made a couple changes to an image I already had to help you see what's going on. The image below does NOT represent particular bullets or weights. It's just meant to help you conceptualize what is happening.

Note that in the first two, the Round Nose and the JHP, the space between the ogive and the rifling (inside the gold circle) is identical IN SPITE OF the two cartridges having significant OAL differences. ALSO, if you compare that same space between the JHP and the truncated cone, you'll see that the space is significantly different, despite their having identical OALs. This shows that when it comes to OAL, what happens with one bullet is not the same as what happens with another. This is why what's happening with the other bullets is irrelevant to what's happening with this one.







Now to your problem. YOUR bullet is loaded TOO long for that chamber. It's not that the bullet doesn't work in your pistol (at least it's too early at this point to say). It's not that the chamber needs to be reamed. All you can say at this point is that it is loaded too long for the chamber. And that is entirely predictable because you didn't see how that bullet worked in your chamber when you starting to develop the load. That should be literally your first step in load development. The box arrives in the mail. Your wife gives you the evil eye because you bought more shooting stuff. Then you open the box, pull out a bullet, and skip over to your reloading space, where you immediately determine your max OAL for that bullet in whatever pistol you plan on shooting it in. That's what you should do with every new bullet.

There are a couple of ways to do that. The first is to find a case that you fired in that pistol, AND that will hold the new bullet snugly, but not so snugly that it won't slide in and out in the case with a little force. THEN you pull the barrel from the pistol, hold the barrel parallel to the floor, and slide the case and bullet into the chamber, all the way, until it stops. THEN slowly pull it back out, and the case should should hold the bullet where the rifling pushed it back into the case. THAT should be very close to the max OAL for that bullet in that chamber. Some people will do that several times until they can see a number around which the several OALs are clustering, and consider THAT the true max OAL. THEN they knock off .010-.015 for a working max, because you and your gear will inevitably create some variation, and you don't want that variation to put some bullets back into the lands, so knocking off a cushion of .010-.015 from the true max is a good practice.

The second method, which is what I use, is to do the above method just once, then make a dummy round about .020 LONGER. I resize, bell, seat to the too long OAL, and crimp. From there I check it in the chamber too see if it will chamber all the way AND spin freely. Because of the extra .020 that I added, it should not spin freely on the first test. Then I seat it .003 deeper. Then test it again. Then seat deeper. Then test it again. And so on and so on until it chambers all the way AND spins freely. You will hit a point, where it chambers all the way and spins with a little drag. That means it's still touching the rifling. Keep lowering OAL until it spins freely. That is my true max for that bullet with that pistol. Then, I will usually knock of .010 as a starting point for load development.

That's how to determine the max so that you don't have the problem you're having. There is, however, another problem. It is possible to load too short, especially with 147gr bullets. If you follow the case walls from the case mouth to the head, there is point where the case walls start to get thicker. In 9mm Luger, this spot is typically at .300 from the case mouth. You should consider .300 the hard deck or "mechanical limit" for seating depth. If the bullet base is beveled, you can get a little deeper than that, but once the shank of the bullet hits .300, if you go deeper, it will either swage the bullet base, which is not good for accuracy, or it was bow out the case walls, which isn't good for feeding and function, or it will do both. It's just easiest to consider .300 the maximum seating depth unless you absolutely need to go deeper, and even then, you're not going to get too much deeper without running into problems. The hard deck/mechanical limit is represented in that image by the vertical green line. It is not to scale. I just threw one in. But you can see what you want to avoid in that fifth image, labeled "too short".

Easy seating depth formula -- CASE LENGTH + BULLET LENGTH - OAL = SEATING DEPTH Do NOT measure case lengths individually. For 9mm just, use .750.

Here's the bad news. When I look at that Precision 147gr FP, that profile looks like it's going to lead to especially deep seating. YOU might find that your MAX OAL with this bullet based on rifling engagement is shorter than your minimum OAL based on not seating the base deeper than than the hard deck. If that happens, THEN you have two options -- ream the barrel to make the throat a little longer so that you can seat longer, OR don't use that bullet.

Reaming the barrel is popular here in the Benos forums, where the majority will tell you it's easy to do and causes ZERO problems. If you head over to CZFirearms.us, you'll get the opposite, where people will recommend against it and warn you that it may or may not cause problems, and that if it does, accuracy will be the problem. I really don't know the probability either way, but I can tell you that if I bought a pair of shoes that were too small for my feet, I damned sure wouldn't cut a quarter inch off the fronts of my toes to make theshoes fit, and if I spent $1300 on a pistol, I damned sure wouldn't cut the pistol so that I could try out a bullet. Finding a bullet that won't work at all is a rarity, but the exact bullet you bought is one that I have wanted to buy but chose not to precisely because it looks like an OAL problem for a CZ. And at the other end of the spectrum, finding a bullet that works well is easy. There are lots and lots.

If you must use a 147gr bullet, I'd recommend ACME or SNS, or, better yet, the ACME 145 RN.

 

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Discussion Starter · #17 ·
i copied this from a forum member at brian enos loading forum... this really cleared up loading 9mm for me atleast, hope this helps... iDescribe says:


EVERY bullet has a maximum OAL in a particular pistol, where by maximum I mean the maximum OAL you can load to without the bullet engaging the lands when in battery. That maximum OAL is different for every bullet. And it's different for a particular bullet when you switch pistols. Inside the chamber, there is a step against which the case mouth headspaces. And there is a place forward of that where the rifling begins. The space in between the headspacing step and the rifling is called the Free Bore (or throat). Different manufacturers will have free bores of different lengths, and that is what causes bullets have different maximum OALs in different pistols. The angle or curve of a bullet's ogive is what causes different bullets to have different maximum OALs in the same pistol.

I made a couple changes to an image I already had to help you see what's going on. The image below does NOT represent particular bullets or weights. It's just meant to help you conceptualize what is happening.

Note that in the first two, the Round Nose and the JHP, the space between the ogive and the rifling (inside the gold circle) is identical IN SPITE OF the two cartridges having significant OAL differences. ALSO, if you compare that same space between the JHP and the truncated cone, you'll see that the space is significantly different, despite their having identical OALs. This shows that when it comes to OAL, what happens with one bullet is not the same as what happens with another. This is why what's happening with the other bullets is irrelevant to what's happening with this one.







Now to your problem. YOUR bullet is loaded TOO long for that chamber. It's not that the bullet doesn't work in your pistol (at least it's too early at this point to say). It's not that the chamber needs to be reamed. All you can say at this point is that it is loaded too long for the chamber. And that is entirely predictable because you didn't see how that bullet worked in your chamber when you starting to develop the load. That should be literally your first step in load development. The box arrives in the mail. Your wife gives you the evil eye because you bought more shooting stuff. Then you open the box, pull out a bullet, and skip over to your reloading space, where you immediately determine your max OAL for that bullet in whatever pistol you plan on shooting it in. That's what you should do with every new bullet.

There are a couple of ways to do that. The first is to find a case that you fired in that pistol, AND that will hold the new bullet snugly, but not so snugly that it won't slide in and out in the case with a little force. THEN you pull the barrel from the pistol, hold the barrel parallel to the floor, and slide the case and bullet into the chamber, all the way, until it stops. THEN slowly pull it back out, and the case should should hold the bullet where the rifling pushed it back into the case. THAT should be very close to the max OAL for that bullet in that chamber. Some people will do that several times until they can see a number around which the several OALs are clustering, and consider THAT the true max OAL. THEN they knock off .010-.015 for a working max, because you and your gear will inevitably create some variation, and you don't want that variation to put some bullets back into the lands, so knocking off a cushion of .010-.015 from the true max is a good practice.

The second method, which is what I use, is to do the above method just once, then make a dummy round about .020 LONGER. I resize, bell, seat to the too long OAL, and crimp. From there I check it in the chamber too see if it will chamber all the way AND spin freely. Because of the extra .020 that I added, it should not spin freely on the first test. Then I seat it .003 deeper. Then test it again. Then seat deeper. Then test it again. And so on and so on until it chambers all the way AND spins freely. You will hit a point, where it chambers all the way and spins with a little drag. That means it's still touching the rifling. Keep lowering OAL until it spins freely. That is my true max for that bullet with that pistol. Then, I will usually knock of .010 as a starting point for load development.

That's how to determine the max so that you don't have the problem you're having. There is, however, another problem. It is possible to load too short, especially with 147gr bullets. If you follow the case walls from the case mouth to the head, there is point where the case walls start to get thicker. In 9mm Luger, this spot is typically at .300 from the case mouth. You should consider .300 the hard deck or "mechanical limit" for seating depth. If the bullet base is beveled, you can get a little deeper than that, but once the shank of the bullet hits .300, if you go deeper, it will either swage the bullet base, which is not good for accuracy, or it was bow out the case walls, which isn't good for feeding and function, or it will do both. It's just easiest to consider .300 the maximum seating depth unless you absolutely need to go deeper, and even then, you're not going to get too much deeper without running into problems. The hard deck/mechanical limit is represented in that image by the vertical green line. It is not to scale. I just threw one in. But you can see what you want to avoid in that fifth image, labeled "too short".

Easy seating depth formula -- CASE LENGTH + BULLET LENGTH - OAL = SEATING DEPTH Do NOT measure case lengths individually. For 9mm just, use .750.

Here's the bad news. When I look at that Precision 147gr FP, that profile looks like it's going to lead to especially deep seating. YOU might find that your MAX OAL with this bullet based on rifling engagement is shorter than your minimum OAL based on not seating the base deeper than than the hard deck. If that happens, THEN you have two options -- ream the barrel to make the throat a little longer so that you can seat longer, OR don't use that bullet.

Reaming the barrel is popular here in the Benos forums, where the majority will tell you it's easy to do and causes ZERO problems. If you head over to CZFirearms.us, you'll get the opposite, where people will recommend against it and warn you that it may or may not cause problems, and that if it does, accuracy will be the problem. I really don't know the probability either way, but I can tell you that if I bought a pair of shoes that were too small for my feet, I damned sure wouldn't cut a quarter inch off the fronts of my toes to make theshoes fit, and if I spent $1300 on a pistol, I damned sure wouldn't cut the pistol so that I could try out a bullet. Finding a bullet that won't work at all is a rarity, but the exact bullet you bought is one that I have wanted to buy but chose not to precisely because it looks like an OAL problem for a CZ. And at the other end of the spectrum, finding a bullet that works well is easy. There are lots and lots.

If you must use a 147gr bullet, I'd recommend ACME or SNS, or, better yet, the ACME 145 RN.

Thanks beezil for the info. Good information. The pictures didn't copy over. Can you post the link here. Much appreciated.
 

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I'm in the process of looking up the thread now... it was very informative.
a lot of good performance shooters on that forum!!
I have been reloading for over 25 years... and learned something new from iDescribe, specifically for 9mm. its very easy to over pressure that cartridge.... especially using fast burning powders. I use WST which is a faster burning powder... searching for that "Bunny Fart" load. I use ACME 147grn TC bullet, with 3.2 grn WST at oal 1.14. thats in my STI. my sig needs to be shorter. which i haven't worked up yet. My glocks can go longer. Remember each barrel will be different.
 

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Book states 27,000 psi for a 130gr plated that's why I called it low pressure, I miss spoke, cause these cases can take 35,-38,000 psi. So yes Willie, I have 132 PF with a P Delta 147gr FMJ over 3.0gr @ 1.130 should be fine, recoil is good. Just trying to find the floor for PF then will check all for accuracy on a bench. The heaviest bullet Hodgdon has data on is the 125 FMJ 3.5-3.7 with max pressure of 32,500 @ 1.090. what I am doing should be fine where I am. The cases and primers are showing absolutely no pressure signs.
Understand, I just think probably when Fred and I read the "low pressure powder" alarm bells went off. Clays (and most fast powders) is very sensitive given its speed. Making up for "lost pressure" when seating longer than what is in the book as minimum by adding powder is fraught with problems. The difference between 27K PSI and 35K or even 40K (+P kind of pressures) with a powder like Clays isn't a lot when playing with heavy for caliber bullets.

BTW, you probably need to get over 45K PSI before you start breaking things even in the weakest guns, a Glock higher than that, the bad news is it is really easy to do with a powder like Clays. :)
 
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