Gun Thread: Load Development Edition! [Weasel]

Earlier in the week I noticed a comment and question from our pal Xipe Totec in another thread about reloading and load development, and it's a subject I've been meaning to write about for some time. One of the fun aspects of reloading is experimenting with new powder and bullet combinations to find an accurate load. With common sense and by following some basic rules, this can be a rewarding aspect of the reloading hobby. Also, we haven't had a long and bigly boring Gun Thread topic in a while which is reason enough. Let's find out more below, shall we?

Here is Xipe's (can I call you Xipe?) comment, observations and question.

Question for reloaders; Ever notice some serious discrepancies in various reloading manuals? Case in point: I am working up loads for my 7.62 X 54R. In my oldest Sierra manual a max load of IMR 3031 is 44.4 grains with 150 grain bullet. 2700 fps. I have another manual that lists the max load at 50 grains with this bullet with a MV of 3000 fps. The Sierra load seems quite mild. I doubt the 2700 fps. I want a MV of 2700 with a 20" barrel. I suppose I will start using my chronograph and the max Sierra load and start loading up and checking for signs of excessive pressure until I get the 2700 fps.

Any thoughts?

Posted by: Xipe Totec-Death to AntiFa!

So there is a lot to unpack here. First, yes, there can be significant variances between different reloading manuals for what seems to be the exact same load and bullet, generally with some overlap, and there are a few reasons for this. In no particular order they are; differences in ballistic testing equipment, powder profiles which change over time, and lawyers. There are probably some more, but these will get us started.

Different testing labs use different equipment which can and do result in different observations. These are generally listed in a manual's load section and at a minimum contain information on the weapon or test barrel used. Even if everything is the same, differences in published information will be noted. Powder manufacturers tweak powder profiles from time to time, so it's best to only use current manuals. Although it's fun to collect and read older manuals, the information they contain should always be cross-checked against other, more recent, information. Finally, although the reloading manuals are written by reloaders, they are reviewed by company attorneys who are typically risk-adverse. Depending on how risk-adverse plays a big part in what makes it into the final manual edition.

Xipe goes on to observe two different manuals showing different recommended powder charge weights for the same bullet. All reloaders have heard the advice to start low and work up, which simply means to begin testing at the low end of a given range and work up incrementally looking for pressure signs indicating the maximum load has been achieved. This is very good advice.

Practical Application
Well that's all fine and dandy, but how does a reloader determine the very best load? In Xipe's example above, he's looking for a velocity around 2,700 fps. For most applications when researching loads for a particular cartridge you'll get some sense of the conventional wisdom for optimum velocities whether it's from reloading manuals or other sources. NOTE: Always confirm "other sources" against published data! It's then a simple matter to start at a lighter charge and work up until the desired velocity is achieved. If you get to 2,700 fps and you like the results at 2,700 fps, then you're good to go. But how do we know the optimum velocity for that particular rifle isn't 2,750 fps, or 2,775 fps? In other words, how do you determine the right load for your particular firearm?

From here on out we'll be discussing rifle loads, although many of the same concepts apply to handgun loads. At the greater distances where rifles are employed, load development becomes much more mportant, while not so much at 25 yards with a handgun. You're just going to have to trust me when I say that every single rifle barrel is different. I have my match barrels cut from consecutive sections of bar stock and chambered with my own reamer, and they still shoot differently and each requires a different load for maximum performance. The reasons are complicated and involve a science known as interior ballistics and a large part of that involves the harmonics of the barrel when a shot is fired. Barrel harmonics is simply a term used to describe how a barrel flexes and torques as a bullet passes through it.

For every single rifle where I want to maximize potential, I develop a custom load. As you have seen in some of the videos, I still shoot commercial or surplus ammunition for funsies, but when it really counts, I'm shooting handloads. So what is the process? How do you develop the best custom load for your rifle?

Load Development and the Audette Ladder Test - The Weasel Way
So you have a new rifle and you want to get the best possible performance. You're not necessarily going to compete, but you are curious just how accurate your rifle can be. You have researched various published reloading data, and talked to some of your shooting buddies using the same caliber, and have determined the popular powder BOOM! and bullet X works well at a velocity of around 2,900 fps. There are two steps to the process; determining powder charge weight and the bullet jump. Powder charge weight is self explanatory, and bullet jump is simply the distance the bullet travels in the throat of the chamber before engaging the rifling. First you determine the most stable charge weight and next you determine the best bullet jump at that powder weight. Easy peasy.

Let's say your initial research has shown a charge weight of around 48.0gr of BOOM! should result in a muzzle velocity around 2,900 fps. I would bracket that target charge weight, and begin loading at 47.0 gr and work up to maybe 50.0gr in 3/10ths of a grain increments. When shooting the series at a horizontal line on a target at 100yds, you would expect each consecutively higher charge weight, with each step theoretically traveling at a higher velocity, to result in a higher impact point on target. So if you start on the left side and work to the right, you should see a relatively straight line of impacts moving higher as you go to the right with heavier loads. With me so far?

Instead, what you get is this:

Interpreting the Results
Well that's not a straight line at all. In fact the bullet impact points seemingly move up and down randomly, without a correlation to the powder charge weight. What gives? Shenanigans! What you're seeing is that some charge weights do not perform well with the harmonics of your particular barrel. What you're looking for is an "accuracy node" or the place in the series which shows the least vertical dispersion, or a flat spot, in consecutive shots. This is where you want to be. It can be very subtle, and there are often multiple nodes in a given range of powder, but look at the impacts between 48.3 and 48.9 gr, where there is very little change in the vertical separation. It means that in this range the powder charge is the most stable and offers the greatest consistency. It also means that changes in atmospheric conditions, or imprecise techniques at the reloading bench, will have the least effect on vertical dispersion on the target. I generally choose a load in the lower third of this range. I always shoot two series of this test, considering and comparing both to rule out any variables caused by my marksmanship, and it is imperitive this test be conducted from a bench with as stable a firing platform as possible. You will also notice I haven't mentioned measuring velocities at all. Velocities are fine to target a desired load range, but what is important is what happens on the target.

Bullet Jump
So with that, let's say you have decided on 48.5 gr as the powder charge in the node showing the greatest stability. Next you need to tune the load to your particular barrel. For this, you will need three tools that aren't terribly expensive, although I will tell you they require a bit of practice to use correctly. They are the Stoney Point or Length Gauge , a caliber specific modified case, and a bullet comparator. You'll also need a good set of calipers.

I'm not going to go into a long explanation on using the Stoney Point tool because it's difficult to describe, it would take about two thousand words, and it would still suck. Instead, here is a decent video on its use:

I like the bullet comparator I linked above, but any one that measures the ogive of the bullet, or the point where bearing surface changes into a curve, will work. You're looking for the point on the bullet that first touches the rifling. Measuring the overall length, or OAL, is imprecise and not recommended due to tolerance differences found in the hollowpoint bullet manufacturing process. I also don't care for bullet ogive comarators which attach to calipers because they can create inconsistent measurements.

Once you have practiced using the tools and can generate consistent measurement results with zero jump, or with the bullet ogive just touching the rifling, you load a series of live cartridges with increasing jump (deeper seating) in .003" steps. You can use any increment you like, but I find .003" steps work well for me. Again, I load two sets bracketing what I think is going to be the right jump based on research or my experience, and fire them on separate targets in 3 round groups. The result looks like this:

As you can see, I tested a jump range of .006" to .021" using exactly the same powder charge. These are all three round groups fired at 100 yards. Which one would you choose? Call me crazy, but I went with a bullet jump of .015" and all three bullets going into a single hole. This is not a particularly difficult process, and look at the difference in results. Simply by tuning the bullet jump, I improved the performance of the rifle from close to 1 MOA to something under 1/3rd MOA. Imagine if I'd just used .006" jump and called it good. Only after these tests do I chronograph the load to establish a baseline for future performance. If you notice a degredation in performance, likely due to barrel wear and throat erosion over time, you can simply perform the test again and adjust accordingly.

These pics are actual load development tests from one of my match rifles. If you're interested in improving your rifle accuracy, give the methodology a try! Questions? Just drop me a line.

OK, it doesn't get much better than this. Here's a picture from our pal Nevada Dave of his daughter (Little Nevada Dave'ette?) after hitting her first target at 1,000 yards.

Long time lurker but was looking at the thread today and saw the spotting scope setup, it looks similar to mine. Here’s a picture of my daughter after her first 1000 yard hit on steel. Since then she has gone out to one mile with same the gas gun. The gun is a 6.5 creedmoor, proof barrel, JP bolt, Gisele trigger, American precision brake, Smoke Composits furniture, Accutac bipod and Leupold Mark 8 3.5-25. Spotting scope in the background Leupold with Badger Ordinance SLICK chassis, Kestral, Eotech..

Seriously, look at that smile! Fun, ain't it? And did you all notice how he casually mentions she's gone on to working targets at one mile? Did you not notice that little particular casual detail?

For those of you wondering, that is not easy to do. Very not easy. Welcome to the Gun Thread and congratulations to you both!

The shooting eyewear topic has generated a lot of great suggestions. Our pal Mazzman sends us a recommendation for SSP Eyewear.

Like anything else optical, these take a little getting used to, but they are designed so that you don't need to move your head from a proper firing position to see your front sight better. I'm right eye dominant and have the clear lens, no magnification on the left side, as I shoot with both eyes open. I only use them for pistol, as I have other ways of dealing with rifle iron sights and they're not needed with optics.

Thanks Mazzman!

Our pal TBone sends in the following pictures of something I referred to in the M1917 video, and that's the Remington Model 30.

Here is a pic of my grandfather's deer rifle. Evidently Remington had a lot of receivers left over after the war, so they came out with their own factory sporter, called the Model 30. These were built from 1920 to 1940, the "Express" model being introduced in 1926. This particular rifle probably dates from the late 20's as it cocks on closing. After 1932 they cocked on opening.

Thanks, TBone! What a great rifle and story to go with it! You are very lucky to have it!

Sad people who cannot make the new NoVaMoMe date of August 29th

Due the Chinese Cooties hysteria in Virginia, the NoVaMoMe 2020 has been postponed until Saturday, August 29th. The time and location remain the same. If you haven't already, please check your email and let the Central Planning Committee know if you are able to make the new date. If not, your registration fee will be refunded and we will open your spot to those on the wait list. Questions? Just email us at NoVaMoMe2020 at gee mail dot com. Thank you!

Link-O-Rama

I'm really very seriously not kidding around anymore. Buy Ammo
AmmoSeek - online ammo search tool
GunBot - online ammo search tool
SG Ammo
Palmetto State Armory
Georgia Arms
AmmoMan
Target Sports USA

In response to last week's video of a reloading and gun bench, our pal WTM sends us a picture of his own setup, which I suspect is much closer to the norm. Thanks WTM!

So what does your bench look like?

Please note the new and improved gmail account morongunthread at gmail dot com. An informal Gun Thread archive can be found HERE. If you have a question you would like to ask Gun Thread Staff offline, just send us a note and we'll do our best to answer. If you care to share the story of your favorite firearm, send a picture with your nic and tell us what you sadly lost in the tragic canoe accident. If you would like to remain completely anonymous, just say so. Lurkers are always welcome!

That's it for this week - have you been to the range?

posted by Open Blogger at 07:00 PM

| Access Comments