Thursday, December 12, 2013

Reloading basics: Brass, bullets, powder, and primers.




Cartridge cases…

Handloaders typically have two types of cases to work with, commercial and military.  The differences between the two are distinct, but in most cases minor.  Military casings will usually have their primers crimped into place, as a primer falling out can seriously disable a weapon in the heat of battle.  They’ll also typically look a bit different, having the brass discolored from the annealing process, skipping a final polish that commercial buyers demand. In most cases, the bullets will be crimped into the case, to prevent bullets setting back or falling out with harsh treatment.  Most military ammunition will have both primer and bullet sealed to prevent moisture intrusion.  The sealing compound will often show as a red or green stain.

There has long been the belief that military casings were thicker, and that powder charges had to be dropped a grain or two to take into account the smaller interior space within the case.  The reason being that two identical charges fired in two pressure vessels, one smaller than the other, will show substantial pressure differences.  The charge in the smaller area will usually show a higher pressure.  Translated into firearms terms, a case with thicker walls, and thus a smaller interior, will show higher pressure given identical charge weights of the same powder.

While the pressure difference is certainly real, and must be taken into account, the idea that military cases are universally thicker than commercial is not so certain.  Testing done by this author has found the weight and thickness variations between commercial and military brass are all within the same general range, with no particular leanings in either direction.  A particular lot of Lake City 7.62x51mm brass may show the same weight as any particular lot of Federal brass, and it’s a coin toss which will be heavier in comparison of two other lots.

The lesson to be carried away is that weight and interior dimensions need to be accounted for in any batch of brass, and sorting a large batch by weight, as well as brand, makes sense whether dealing with commercial or military brass.

If the handloader is dealing with military brass, no matter the country of origin, odds are the primers are staked in.  Some early military brass had the case peened over the primer in a neat circle, but most have three or four dimples punched into the case head, forcing a bit of brass to clamp the primer in place.  While this usually causes no issue in firing, sizing, or punching out the spent primer (sometimes it takes extra force to remove the staked primer), it causes a serious issue when it comes time to insert a new primer.  With the primer pocket crimp in place, it’s nearly impossible to seat a new primer cleanly.

The answer comes in one of two different solutions.  The brass disturbed in the crimping process is ‘swaged’ or ironed back into place using special dies in the press, or the crimp is cut away from the primer pocket using a special reamer.  For those salvaging large amounts of military brass on a regular basis, RCBS makes a bench mounted primer pocket swager that works a treat, although it’s a somewhat more expensive answer.

Swaging is the more desirable of the two processes, even though it’s slower and more costly in the form of tooling.  The advantage is that it removes no brass, instead pressing the case back to pre-crimped status by simple precision brute force. 

Primer pocket crimp removal with a reamer is not to be confusing with primer pocket reaming and truing for reasons of more precise primer seating.  The two reaming operations are generally not the same.

Reaming (cutting) to remove a primer crimp usually only impacts the shoulder area of the primer pocket where it meets the base of the case.  A reamer, typically a hand tool, is inserted and given a few firm but gentle twists.  The crimp marking are cut away, and often a slight bevel is cut into the shoulder to make seating new primers easier.  It’s quick, easy, cheap, and it’s how most handloaders deal with crimped primer military brass.

Whether commercial or military brass, a little needs to be understood about the metallurgy of working with brass. There are some factors that will impact even the most novice or small volume handloader.

Foremost is the fact that brass ‘work hardens’.  This means the more it’s hammered, pressed, bent, or shoved around the harder and more brittle it becomes.  Each event in its firing cycle can have this effect, adding up over time to a brass case that cracks, splits, or even separates in two.
The answer comes in understanding that very same metallurgy.  Brass does indeed work harden, but careful heating to fairly exacting temperatures can ‘anneal’ the brass.  This breaks up the crystalline structure of the metal and it becomes softer, lessening the likelihood it will crack… and extending its working life.  All bottleneck rifle cartridges are annealed at the factory when they are made, as the drawing process of manufacturing the cartridge would otherwise leave it likely to crack or fail when used.

Can handloaders anneal their own cases to extend their life?  Certainly.... but it must be done with care and knowledge.  Making the case too soft in the wrong place will result in disaster and possible injury.

There is also the factor of chamber sealing when the weapon is fired.  This is accomplished when the pressure of firing forces the case against the chamber walls so tightly that gas pressure can’t or at least shouldn’t, leak past into the action.  It almost always works splendidly, yet the time it doesn’t is one reason we always wear eye protection while shooting.

Work hardened brass is less likely to seal the chamber as well as brass that is somewhat softer. This is just another thing the handloader must be aware of, and watching for.   Gas leakage from a too-hard case neck may show up as heavy carbon fouling creeping down outside of the case neck after firing, or a number of split necks within that batch.
It’s possible for a handloader to anneal their brass cases, and extend their life.  That said, it’s a process beyond the ability of most beginning reloaders, and perhaps they should simply be careful in how many times they reload a batch of brass, discarding the batch when it becomes clear the brass has grown too hard.  For most rifle calibers, this will be between four and six loadings depending on the cartridge and its operating pressure.  

Speaking of batches…. Yes, any rifle brass loaded for accuracy should be sorted into batches by make and weight, and then worked together from then on.  Careful records should be kept regarding how many loadings each batch has had, and the load data involved.  Pistol brass does not seem so picky, excepting for those involved in competitive shooting who cannot accept an ammunition problem during a match.  They typically follow the same brass use guidelines as precision rifle shooters, keeping cases in batches and working them together.

It’s not uncommon for both precision rifle shooters and competitive pistol shooters to have numerous ‘grades’ to their case batches, with some reserved for practice and others for when the pressure is on and everything has to be perfect.

This seems a perfect time to discuss the magic which is ‘range found brass’, or used brass.

This is an area where handloaders can stumble upon gold, or upon a heachache. ‘Free’ or range found brass can be a real money saver, since brass is a large part of a handloaders expense.  The danger is in knowing the provenance of the brass.  If you see a shooter unboxing new ammunition, and end up taking their spent cases home, you know it’s once fired and that’s a really good thing.  On the other hand, finding a bunch of brass on the ground takes away that assurance and you might be looking at some handloaders throw away brass at the end of its life span.  Pistol brass is generally a safer bet when reloading range scrounged cases, but rifle cases need to be approached with some caution and care.  At the very least, they need to be carefully examined for case stretching, cracks, splits, and damage.

Case stretching can be difficult to spot, but it will typically show up as a discoloration or bulging of the case just ahead of the base, where the case web reduces in thickness to become the case wall.  Sometimes a thin sharp pick can be inserted in the case neck, and dragged up the inside of the case to feel for anything unusual.

There is a condition in a firearm that can cause the cases to appear to be overly stretched, and that’s a chamber towards the large side of acceptable dimensions.  It’s something more often found in older military rifles, where a larger chamber meant less ammunition fit issues, and reloading was not on the radar.  WWII rifles show this feature more the any other, with the BritishLee-Enfield leading the pack.
What happens is the slightly wide chamber allows the case to expand more, all except the very thick base of the case, which stays at original size. The fired case shows the expansion just in front of the case web.  Here, the issue is in resizing working the brass excessively, leading to premature cracks.  The answer is, if possible, to only neck size the brass.  We’ll be discussing various forms of case sizing later, as we get into the reloading process.

·        Oooo… Shiny!   What about nickel plated brass?
Can nickel plated brass be reloaded?  Yes, of course it can, but there are a few slight differences in what handloaders must be aware of.

Since such cases have two dissimilar metals bonded together, they will expand and contract at different rates.  This means nickel plated cases are more likely to crack or split if reloaded a number of times.  It’s not a serious issue, but is certainly one to watch for.  The reloader should be especially vigilant in checking the necks and case mouths for such flaws, more so as the cases are recycled again and again.

Also worth paying attention to is the case mouth, where the hardness of the nickel plating can result in quite a sharp edge.  This can shave a bullet during seating, resulting in some loss of accuracy.  A little attention to chamfering in rifle cases, or case mouth expansion in pistol cases, will solve the problem.

Why do we even have nickel plated cases to start with?  Well….. For the most part…. Because they are shiny, and shiny sells better.  There is some truth to the notion that nickel plated cases resist corrosion better, and are perhaps just a little slicker in feeding, but these are minor factors for the most part.  Mostly it’s the Shiny.

·        Corroded brass….. What is acceptable?
It’s a fact of life, brass can corrode.  When kept dry and cool, as in a sealed container properly stored, ammunition loaded forty years ago is probably perfectly viable.  However, just one summer under humid conditions in unsealed containers, and brass can develop corrosion.   

Some slight surface discoloring is hardly an issue, and will not affect the brass to any degree.  Once the corrosion is allowed to develop into pitting, the case is useless and should be discarded.

In extreme cases, ammunition which has been poorly stored may have corrosion that’s eaten all the way through the case, weakening it dangerously and allowing the propellant inside to be contaminated.  In these cases, not only is case failure possible, but a dangerous condition known as a ‘hang fire’ may occur.  This is when the weapon is fired, ignition occurs, but the actual ‘explosion’ takes some time to happen.  It can be a heartbeat, or even 60 seconds; Plenty of time for the shooter to point the weapon in an unsafe direction, or open the action to eject the round.

A rule of thumb for handloaders, especially those using a lot of range pick (found) brass, is to discard any brass with corrosion that can’t be wiped away with a few swipes of steel wool.  If it requires actually scrubbing, it may be better safe than sorry… and let that case go.

·        Bullets…….
Well, we have to install something for the gun to spit out… don’t we?

Experienced shooters are probably already flipping to another article, but some things just need to be discussed, most importantly for the new folks joining us on the path.

Some time ago, a friend sent yours truly a package with .30 caliber bullets pulled from military M2 30-06 ammunition.   These were for an accuracy related project, and the bullets needed to be sorted by weight and style.  At the end of the sorting, there were no less than seven piles, separated by construction of the bullet and weight.  Remember…. All these bullets were pulled from one caliber of military cartridge, supposedly highly standardized ammunition.  The point is, there are a LOT of differences in bullets, even in any given caliber.  The range of choices is huge!

To begin with, lead bullets and jacketed….

In the beginning, there was lead.  At a time when firearms used black powder and the projectile got shoved in from the business end of the gun, the bullet had to be soft enough to make that work.  Lead, being relatively cheap and very easy to cast into pleasingly round balls, was the obvious choice.

As smoothbore muskets, long arms, and even cannons advanced into the age of rifling and breech loading, the shape of the bullet moved away from round, to something more like a cylinder with a pointy end.  Being more aerodynamic, heavier, and better able to take advantage of the spin rifling imparted, such conical bullets became the norm.

As cartridge arms took the place of front stuffers, the lead bullet remained the standard, as did black powder. The modest velocity achieved from the charcoal based propellant lent itself nicely to large soft lead bullets. 

Late in the 19’th century, with the development of ‘smokeless’ powders based on far more powerful chemicals, the lead bullet simply wasn’t up to the task anymore.  Military arms engineers, as usual, drove the new technology, and quickly discovered the power of the new propellants allowed for a smaller bullet at higher velocity.  To prevent lead fouling the barrel at the new high speeds, the bullets had to be jacketed with something stronger, like copper.  

Suddenly we are in the modern era, with small jacketed bullets at high velocity performing far better than the big lead slugs of the black powder days.  As the United States military found to their chagrin when they first confronted the modern (at the time) Mauser rifle with its tiny 7mm bullet at unheard of speeds… black powder propelled lead bullets were now ancient history.

Jacketed bullets progressed from fairly crude affairs to some incredibly complex designs available today.  The engineering that goes into modern projectiles is impressive, with a wide range of possibilities open to most handloaders.

For pistol shooters, most calibers offer several choices.  Solid lead, lead hollow points, half jacketed lead, plated lead, full jacketed, jacketed hollow points, and even highly complex self-defense bullets designed for maximum effect in one particular caliber at one particular velocity.

Rifle shooters have most of those choices, plus quite a few more. Bullets comprised of multiple components, some with polymer points and some with weight retaining partitions.  Bullets of solid copper and bullets coated with molybdenum disulfide to smooth their way down the bore.

The handloader is faced with making the choice, balancing cost against desired outcomes.  Target loads at moderate velocity usually means lead bullets in a pistol load, while hunting or self-defense usually demands something more modern.  Competition rifle shooters will typically be loading hollow pointed, boat tailed bullets designed for extreme accuracy…. With a suitable reflection in the price.

What every handloader must keep in mind, and you new people listen up close, is that each bullet type and design works at certain speeds and pressures.  A lead bullet at 900fps is a joy to shoot… while one at 2800fps will make an unholy mess of the bore.  A jacketed varmint bullet at 2800fps may perform with astounding results, but at 1000fps it’s just going to punch a little hole.

The key is to pick your end result, choose the bullet to match, and then load to support that bullet in that firearm.
That’s not to say envelopes can’t be pushed, and experiments made, but for the vast majority of reloading the way is clear.  Match the bullet to the target, and load for that bullet in that gun.  

·        Powders……

Even back in the black powder days, there were variations in the powder available.  So much so that military armorers came equipped with strange little devices to test the ‘strength’ of powder lots.  It was all part of their job.
Modern handloaders don’t have such worries, typically being able to rely on the powder manufacturers to provide stable, reliable, and consistent lots of specific powders.    For most reloaders, simply following the recipes in a quality load data book will result in acceptable results.   For some… and I’m looking at you long range rifle shooters… even the minor variations in modern powder lots will make a difference.

To the new handloaders, a few points that must be understood:
·   
   Smokeless powders come in myriad forms from many makers, but the key to using it properly is understanding burn rates and working pressures.  Some powders burn faster than others, and some need higher pressures to burn well.  The reverse is true, with some powders designed for long barrel big bores burning slower, and some powders specifically designed to work well at the lower pressures generated by older cartridges.

·   Different calibers in different firearms will respond differently to different powders. One .243 with a 20” barrel may shoot well with IMR 4895, and another ‘identical’ rifle may shoot better using Winchester 760.  It’s in areas like this (load development) that handloaders can take advantage of matching a load to their firearm.  Within accepted parameters, experimentation is not a bad thing, and can be fascinating.

·   There is a very real danger in choosing the wrong powder, or the wrong charge weight.  Too much of almost anything can result in an overpressure situation, and an unfortunate kaboom.  Strangely, too little of some powders can cause the exact same fate.  The reason for this is complicated, but very well documented and real. Handloaders, and especially new handloaders, need to stay within the strictures imposed by factory load data.  As a rule of thumb, the faster the powder burn rate, the more one needs to careful of overcharging, and the slower the burn rate, the more one needs to take care not to undercharge.

Sticking to load ranges published in the manufacturer’s data guides is usually a safe bet. Handloaders are strongly advised to do so.  That said, even some of the load data guides published by the industry can’t seem to agree in some areas, which points out the value of having several load guides on hand to compare and contrast.

·        Primers……

One would think simple things like primers would be an area we can ignore the subtleties and just get to loading.   Nothing can be further from the truth.

Aside from their ability to withstand firing pressure…. Meaning ‘large rifle’ is not the same as ‘large pistol’, we need to be mindful of the ‘power’ of the primers we choose, and their consistency.  Magnum primers generate a larger, hotter, and more powerful flame front than standard primers.  This is necessary when trying to ignite large masses of slow powders in big bore magnums rifles, and the same holds true in magnum pistols as well. 

One might think this a good thing, but not all powders or cartridges need this boost.  In fact, some faster burning powders do not react well to magnum primers, giving inconsistent pressures and accuracy issues.  On the other hand, taking a load developed for standard primers, and simply substituting magnum primers in the recipe, can cause pressure spikes and an unsafe condition.

The handloaders rule of thumb:  Save magnum primers for cartridges that require them, when loaded with heavy charges of slow powders that need the extra ignition power of the magnum primer.

Once we make sure we have the right size primer, and the right strength, there are other factors to consider.  Each manufacturer has their own design of primer cup, with some being harder than others. Shooters burning ammo through their M1 Garands need to be aware; those rifles have been known to slam fire when soft primers are used.  Folks feeding particular situations like that generally do a little research, find one that works, and stay with it.

Precision shooters have the options of buying ‘Bench Rest’ quality primers, or ‘Match Grade’.  These cost more, with the idea they are built with more care, and will provide a higher degree of consistency during ignition. To someone trying to shrink group size at long range, even this tiny detail matters.

When a certain primer is specified in load data, it’s best to stay with that if possible.  If not, and another primer is used for whatever reason, the powder charge needs to be backed off a little and load development begins again. Most handloaders quickly develop preferences, and buy their primers by the thousands once they settle on a load.


Your humble author is hoping these words are of value somewhere down the line, be it to experienced handloader or the new acolyte just beginning the journey.  Always remember and never forget:  Safety first, follow the manual, and focus on what you are doing!

 



2 comments:

drjim said...

Thanks for posting this.

As a beginning reloader, I take all advice and recommendations seriously!

Carteach said...

DrJim,

My pleasure. I began reloading as a kid... with a book. No help at all.

I figure if I can help others get started a bit easier, it's a good thing to do.