This is Part 3 of the Load Development Article, if you were bored before, it is not about to get more exciting, except now it's time to load test cartridges.
Loading Test Cartridges
To most people this is what they've been waiting for, a chance to load up some cartridges and head to the range. Depending on your circumstances and how serious you are about your craft, you could go one better than most people, and take a portable reloading bench with you to the range, working out of the back of your pickup making custom cartridges one by one and testing them out. I don't care if you do this, for me at least I think this approach is actually easier on the mind than many others because if a problem comes up you can deal with it right then and there, rather than having to make another trip.
Now it's time to pick some candidate loads. For statistical purposes I typically shoot 3 rounds to establish velocity, and I shoot 10 rounds to establish an average velocity and calculate a standard deviation. 10 rounds allows me to exclude anything that looks like it may be erroneous data, like a bird flying over one of the sky screens, or round not being measured correctly because the chronograph saw the gas and measured it's velocity.
Refining Specifications and Choosing Test Data
Looking back at the last post, here is the spec I decided I was going to load up:
Caliber: .223 Remington
Powder: Varget, H335
Charge Wt. 24-26, 22-24
OAL: 2.235-2.250"
Velocity: 2850-3000FPS
Looking at the load data from the last post, it seems a minimum load will likely not meet the minimum velocity specifications. The book velocities given for Varget were 2784-3010FPS at 24 and 26 grains respectively, doing some basic math that's roughly 113FPS for each grain of powder, so 25gr should be somewhere about 2897, which is perhaps faster that needed for our minimum loading, so lets split that in half again... 24.5gr is somewhere about 2840FPS, which is just a hair slow, so lets use 24.6gr as our first load. For most charges of this size, I will typically do the next several loadings in .3gr increments, typically .1gr does not offer enough change to really be measurable except in large lots, and .3 is a good baseline. Also, I always subtract .1gr from any max loading to account for variations in powder drop when I'm loading progressively.
For the H335 load, it looks like H335 will not achieve the higher velocity Varget will, using the same process, a starting load of 22.7gr was selected. Follow the same procedure to select the rest of the loadings.
Selecting an OAL
OAL is an important variable in loading ammunition, but for auto-loading rifles is much less critical than most might think. However, I out of habit tend to load long, so lets go with a 2.245" OAL, this will make sure none of the ogive is inside the case mouth, allowing us maximum neck tension on the bullet. Under certain conditions, this can be a very major factor (such as with the very long 75gr AMAX which cannot be loaded to a length which satisfies magazine constraints) maximizing neck tension is a necessity for loading good ammo for an autoloader. Too little can cause bullet setback.
Loading Procedure
If you have been reading my blog for any length of time, you probably know what the best practices for loading procedures are, but lets constrain things a little further since it's serious this time:
Process your brass (small base size, trim, wash and tumble)
Seat your selected primers, for AR-15 loads I use CCI-400, #41 Arsenal, or Winchester WSR primers exclusively. Seat these using a bench or hand priming tool being sure primers are minimum of .003" inside the case, and no more than .010" below the base of the cartridge.
Assuming this will be a single stage operation, put your shell holder into the ram, insert a case, and raise the ram. Back the seating plug all the way out of the die, now screw in the seating die until you feel the resistance of the die starting to crimp the case, back off at least 1/2 turn but no more than 1-1/2 turns. Lower ram, now put a charged primed case in the shell holder and place a bullet on top of the case. Raise the ram with one hand while guiding the bullet with the other hand, before the ram is at Top Dead Center, insert the seating punch and begin screwing down. Slowly adjust the seating punch by lowering the ram a little, turn the seating screw, and then seating the bullet slightly farther periodically taking measurements until the seating depth is adjusted to that outlined in our specifications.
Now go ahead and charge and load the rest of the cases.
Next Installment... Getting Data at the range!
Tuesday, March 27, 2012
Monday, March 26, 2012
Load Development (Part 2)
This is the second post in a multi-part series on Load Development. Here is Part 2 Setting Standards.
Setting Standards
If you are asking why set a standard? Well, if you don't set a standard, or a goal, then there isn't much point in going through this whole process of developing a load. No matter what your goal, you should set a standard, and make sure you conform to it. This will make reloading easier and more fun, it will also make shooting more fun and hopefully reduce stress at matches when you could be worried about how your ammo is going to perform.
So what goes into a standard? Well, the first thing you should do is decide what you want the ammunition to do. At the same time you should remember that every decision is a trade off, and the number of decisions you get to make every time you make one shrinks exponentially. If your goal is creating a round that uses the cheapest bullet, cheapest powder, has the lowest charge volume, gives phenomenal accuracy, insanely high muzzle velocity, and has zero recoil that's great. Send me a message when you've achieved this, I've been trying for nearly 20 years and have never even come close.
The first thing you should decide is what the basic requirements are for your cartridge. Let me illustrate this with an example, .223 Remington. A good goal: "I want it to cycle my AR-15 without issue" Sounds easy right? Well this immediately limits you to medium burning powders such as H332, Varget, AA2230, TAC, and eschews fast burning powders like IMR4198, IMR4227 and the like. The next goal should be either your accuracy or muzzle velocity. Most frequently the most accurate loads are not the ones pushing maximum velocity, in fact quite far from it. So this is a fork in the road. Since you clearly want to fire this cartridge out of a semi-automatic rifle, you are bound by a certain max over-all length of the cartridge, in this case 2.260" but it works best when loaded to 2.250" or less.
So lets pick an accuracy load, in my opinion, life is too short to miss, and missing is much more affordable when shooting a .22LR than a high powered rifle.
I also want to shoot at medium to long ranges, so I want a bullet that's heavier and more streamlined than the short FMJ-BT bullets that are so cheap, the Sierra 69gr Match-King is a great bullet, but the 60gr SMK, and 55gr SMKs are also great choices for certain applications, like if I was shooting with a carbine length barrel instead of a rifle length barrel.
So lets browse through the available loads, here are a few from data.hodgdon.com:
69 GR. CFE 223 2.235" 23.5 2788 25.8 3029 54,600 PSI
69 GR. Varget 2.235" 24.0 2784 26.0C 3010 50,200 CUP
69 GR. IMR 4320 2.235" 23.0 2673 24.8 2873 53,100 PSI
69 GR. IMR 4064 2.235" 22.5 2690 24.0C 2872 50,900 PSI
So it seems I can expect a muzzle velocity out of my 20" gun up to around 3000FPS. Now like I said earlier, the fastest load will not always be the most accurate, so 3000FPS is going to be the upper limit of how fast I'm expecting this bullet to go. The next consideration is the minimum velocity I'm willing to tolerate. After doing a little bit of checking, the 69gr SMK has a BC that averages about .305, so using an online ballistic calculator, if I load to a minimum velocity of around 2700FPS, I can expect the bullet to be transonic as the bullet approaches 800 yards, however if I can keep the muzzle velocity to around 2850FPS the bullet will still be marginally supersonic at 800 yards, giving this round an accurate range out to this distance. So now I have an upper and lower bound.
In a home situation, now would be a good time to pick out a powder, usually the starting point for this, is "what do I have?" otherwise it is now time to make a shopping run and go buy some powders. If you have experience and certain favorites for this, by all means use that. One of my personal favorite powders is Varget, which conveniently is shown above. However, for completeness, I like to choose at least one other powder I think may work well, this may be because a different powder is more available, it meters better, or any number of other reasons. A common powder for .223 Rem is H335, I have a lot of it around, so I will add that to the spec.
So now I have created a rough specification for my cartridge:
Caliber: .223 Remington
Powder: Varget, H335
Charge Wt. 24-26, 22-24
OAL: 2.235-2.250"
Velocity: 2850-3000FPS
Now it's time to load some test cartridges, which will be the next installment.
Setting Standards
If you are asking why set a standard? Well, if you don't set a standard, or a goal, then there isn't much point in going through this whole process of developing a load. No matter what your goal, you should set a standard, and make sure you conform to it. This will make reloading easier and more fun, it will also make shooting more fun and hopefully reduce stress at matches when you could be worried about how your ammo is going to perform.
So what goes into a standard? Well, the first thing you should do is decide what you want the ammunition to do. At the same time you should remember that every decision is a trade off, and the number of decisions you get to make every time you make one shrinks exponentially. If your goal is creating a round that uses the cheapest bullet, cheapest powder, has the lowest charge volume, gives phenomenal accuracy, insanely high muzzle velocity, and has zero recoil that's great. Send me a message when you've achieved this, I've been trying for nearly 20 years and have never even come close.
The first thing you should decide is what the basic requirements are for your cartridge. Let me illustrate this with an example, .223 Remington. A good goal: "I want it to cycle my AR-15 without issue" Sounds easy right? Well this immediately limits you to medium burning powders such as H332, Varget, AA2230, TAC, and eschews fast burning powders like IMR4198, IMR4227 and the like. The next goal should be either your accuracy or muzzle velocity. Most frequently the most accurate loads are not the ones pushing maximum velocity, in fact quite far from it. So this is a fork in the road. Since you clearly want to fire this cartridge out of a semi-automatic rifle, you are bound by a certain max over-all length of the cartridge, in this case 2.260" but it works best when loaded to 2.250" or less.
So lets pick an accuracy load, in my opinion, life is too short to miss, and missing is much more affordable when shooting a .22LR than a high powered rifle.
I also want to shoot at medium to long ranges, so I want a bullet that's heavier and more streamlined than the short FMJ-BT bullets that are so cheap, the Sierra 69gr Match-King is a great bullet, but the 60gr SMK, and 55gr SMKs are also great choices for certain applications, like if I was shooting with a carbine length barrel instead of a rifle length barrel.
So lets browse through the available loads, here are a few from data.hodgdon.com:
69 GR. CFE 223 2.235" 23.5 2788 25.8 3029 54,600 PSI
69 GR. Varget 2.235" 24.0 2784 26.0C 3010 50,200 CUP
69 GR. IMR 4320 2.235" 23.0 2673 24.8 2873 53,100 PSI
69 GR. IMR 4064 2.235" 22.5 2690 24.0C 2872 50,900 PSI
So it seems I can expect a muzzle velocity out of my 20" gun up to around 3000FPS. Now like I said earlier, the fastest load will not always be the most accurate, so 3000FPS is going to be the upper limit of how fast I'm expecting this bullet to go. The next consideration is the minimum velocity I'm willing to tolerate. After doing a little bit of checking, the 69gr SMK has a BC that averages about .305, so using an online ballistic calculator, if I load to a minimum velocity of around 2700FPS, I can expect the bullet to be transonic as the bullet approaches 800 yards, however if I can keep the muzzle velocity to around 2850FPS the bullet will still be marginally supersonic at 800 yards, giving this round an accurate range out to this distance. So now I have an upper and lower bound.
In a home situation, now would be a good time to pick out a powder, usually the starting point for this, is "what do I have?" otherwise it is now time to make a shopping run and go buy some powders. If you have experience and certain favorites for this, by all means use that. One of my personal favorite powders is Varget, which conveniently is shown above. However, for completeness, I like to choose at least one other powder I think may work well, this may be because a different powder is more available, it meters better, or any number of other reasons. A common powder for .223 Rem is H335, I have a lot of it around, so I will add that to the spec.
So now I have created a rough specification for my cartridge:
Caliber: .223 Remington
Powder: Varget, H335
Charge Wt. 24-26, 22-24
OAL: 2.235-2.250"
Velocity: 2850-3000FPS
Now it's time to load some test cartridges, which will be the next installment.
Saturday, March 24, 2012
Load Development
Load Dev is probably one of the biggest "black arts" of making ammunition, but once it can be understood as a process, much of the art fades to science. While some of the initial data that goes into load creation is largely due to experience and intuition there are great many ways you can back up a gut feeling with science. I will do my best to tear away the shrouds in this post.
Since this is a very complex topic I'm going to be breaking it up into multiple posts. Here is Part 1: Tools
Tools
When everyone first gets into reloading, they spend a lot of time buying tools, constantly finding they need this gizmo, or that whiz-bang, and in general they will make more than a few runs to the sporting goods store to pick up the next thing they never knew they needed. Having the right tools to understand what ammunition is doing when you fire it is an essential part of load development. So what are the tools?
The primary tools needed for load development are those that measure, whether you're trying to squeeze the most accuracy, the highest muzzle velocity, (or lowest in some cases) having the right tools is an essential part. If you are reading this post, you probably already have one of those essential tools: A computer. Computers are very handy for their ability to quickly and easily make complex calculations on large amounts of data. I highly recommend having a spreadsheet type program, like Microsoft Excel, or OpenOffice's Calc application, both have a similar look and feel.
The next necessary tool is a good chronograph, there are many different ones on the market with all kinds of options, under most circumstances, if you have a pen and paper, you don't need the type with the memory and built in calculators and the like, you just need one of the basic ones that when a shot goes over it, it gives you the velocity in your favorite units (I recommend Feet per Second, as it's a little more granular than M/s but it's all a matter of tolerance in the long run).
You will also need some targets, any kind of targets will do, most people use a calibrated target that will have 1" grid squares on it, or something similar. For certain purposes I have a set of transparencies which have group size circles on them, so I can determine if a particular group is 1 MOA, 2 MOA, etc.
Clearly, you will need a firearm that chambers and fires the particular round you are conducting the experiment for, preferably one with repeatable sights, and reasonable accuracy. (Most modern firearms have excellent accuracy)
Some other measuring tools are usually handy to have too, a set of calipers for measuring OAL and group size. A magnifying glass, a tablet and a pen for writing down numbers, sometimes a scientific calculator is handy too.
Since this is a very complex topic I'm going to be breaking it up into multiple posts. Here is Part 1: Tools
Tools
When everyone first gets into reloading, they spend a lot of time buying tools, constantly finding they need this gizmo, or that whiz-bang, and in general they will make more than a few runs to the sporting goods store to pick up the next thing they never knew they needed. Having the right tools to understand what ammunition is doing when you fire it is an essential part of load development. So what are the tools?
The primary tools needed for load development are those that measure, whether you're trying to squeeze the most accuracy, the highest muzzle velocity, (or lowest in some cases) having the right tools is an essential part. If you are reading this post, you probably already have one of those essential tools: A computer. Computers are very handy for their ability to quickly and easily make complex calculations on large amounts of data. I highly recommend having a spreadsheet type program, like Microsoft Excel, or OpenOffice's Calc application, both have a similar look and feel.
The next necessary tool is a good chronograph, there are many different ones on the market with all kinds of options, under most circumstances, if you have a pen and paper, you don't need the type with the memory and built in calculators and the like, you just need one of the basic ones that when a shot goes over it, it gives you the velocity in your favorite units (I recommend Feet per Second, as it's a little more granular than M/s but it's all a matter of tolerance in the long run).
You will also need some targets, any kind of targets will do, most people use a calibrated target that will have 1" grid squares on it, or something similar. For certain purposes I have a set of transparencies which have group size circles on them, so I can determine if a particular group is 1 MOA, 2 MOA, etc.
Clearly, you will need a firearm that chambers and fires the particular round you are conducting the experiment for, preferably one with repeatable sights, and reasonable accuracy. (Most modern firearms have excellent accuracy)
Some other measuring tools are usually handy to have too, a set of calipers for measuring OAL and group size. A magnifying glass, a tablet and a pen for writing down numbers, sometimes a scientific calculator is handy too.
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