alucard0822
For great Justice
If it has a cannelure, I crimp it, it may be fine without the crimp, but many lighter weight bullets have a fairly small ammount of bullet for the case neck to hold onto, and especially in military pattern semi's they basically get smashed into the chamber, and can easily set back if there is not enough neck tension. It can also happen if a lot of carbon fouling is in the neck when you go to size the case, and later seat the bullet. Crimping solves the first issue, using a bronze bore brush to clean the inside of the neck every couple loadings solves the second. For crimping, I like the Lee factory crimp dies, they work well, and have loaded accurate ammo, that also can take a beating without set back(bullet bumped deeper into the case). OTOH, match bullets get every neck cleaned every time, the bullets also tend to be longer, and seat all the way into the neck, therefore there is more tension on them, I also feed them individually most of the time, although not always, and they do not setback.
To check for setback, bring your caliper with you to the range, measure the OAL of 5 rounds, keep them in order, and load the ma with them. Vigorously rack the bolt and let it slm the round into the chamber, then eject it, write down the OAL, and do this with each round while keeping them in order. Finally load them in the same order, fire 1, eject and check 2, fire 3, eject 4, then fire 5. If the 2 rounds that were fed by normal gas cycling and every oter chec of every round shows none got more than .002" shorter, then you can be reasonably sure your method of loading is not causing setback. I also store FMJ and match ammo differently, the loaded match ammo is stored in plastic boxes with individual spots for each round as opposed to my FMJ plinking ammo that gets put on 10rd stripper clips and thrown in a couple ammo cans, and basically dropped and thrown around until it is fired. I have never had a problem with either, although I have found a moderate crimp on the FMJ ammo seems to produce the most consistent velocities and accuracy, like I said in my previous post, it allows the case to build pressure and ignite before the bullet leaves and changes the volume the burning powder has to fill.
Too tight probably just mashes the necks and deforms the bullets, both hurts accuracy, too little or no crimp may setback although it is unlikely, but it does lead to erratic building of pressure and a wider range of velocities and larger group. This does not seem to affect match bullets as much if they are loaded to short OAL, and te cases are prepped well, however loading math bullets out to within a few thousandths of the rifling(the ideal distance to the rifling to produce the most accuracy varies rifle to rifle) is the most consistent way to load, instead of a crimp that may or may not be uniform across every round, the leade and rifling dimentions will stay constant, and produce greater consistency, downside is that a round loaded to this length won't fit in the mag.
As far as full length vs neck sizing weakening the case, the neck will get sized every time reguardless of the die you are using, it has to hold the bullet, and simply won't if it is not resized. The shoulders and body are somewhat optional, but basically you have to balance 2 sets of dimentions, the standard dimentions of the case vs the dimentions of your particular chamber. When a round is fired, the firing pin pushes the round to the front of the chamber, it stops as the shoulders push aggainst the front of the chamber as it strikes and the primer lights. Next the case begins to swell in the thinnest part, the neck as the pressure causes the neck to expand to grab the throat and release the bullet into the leade, or tapered portion of rifling directly in front of the chamber. As the bullet begins to travel down the bore, the case expands from the neck and shoulders first and the swelling progresses to the case web (base of the case right in front of the solid case head where the walls of the body begin), it streaches to contact the face of the bolt, and swells to fill the chamber and fits very tightly aggainst the walls. Once the bullet leaves the barrel, temperature and pressure drop quickly, and the case shrinks slightly away from the walls, and is extracted. Tis fired case is fireformed to a thousandth or two from the exact dimentions of the chamber, and will fit tightly in all respects, minimizing both the streaching going on as it is fired, and erratic movements that are detrimetal to accuracy. It is so exact that you can actually measure headspacing or find annomalies in the chamber by looking at these fired casings.
As far as accuracy is concerned you want to change as little as possible from this perfectly formed case custom to that rifles chamber, basically sizing the neck only, being it has to hold a bullet is the minimum ammount of work needed, but being the fit is as tight as it is, any slight buildup of fouling will cause the case to jam, or feeding and extraction to be very tight. If you also bump the shoulders back, the case body is held concentric to a tight fit in the chamber, and will only have to streach part of the distance it normally would to contact the case head, this preserves most of the benefits of neck sizing, but is a little more forgiving of minor fouling, or being fed from a magazine, where the round as to be fed into the chamber from an angle, and is not placed straight into it. Occasionally neck sized brass can streach enough that even after it is fired it maintains pressure on the bolt head, it doesn't shrink away from the walls as much as it did when it was a factory spec case, and it can make the bolt hard to turn to either feed it into the chamber, or extract once it has been fired, bumping the shoulders back a little helps alleviate this, and makes the round feed reliably and able to be neck sized for a few more times before the shoulders get tight and have to be bumped back again. Full length sizing simply returns the case to it's original factory dimentions, made to fit every rifle in that caliber, and instead of pushing into and binding aggainst fouling, it expands to grab it, and sweeps some of the fouling out keeping the chamber clean. This is the most reliably feeding resizing method, and neccesary if you are loading brass for a gun other than the one the fired casing came from, or with use in semi-autos, or even some manual action levers and pump guns prone to jamming with the very tight fitting fireformed cases. There is not that much accuracy lost, perhaps only 1/2" larger group at 100 yards, and probably less, hard to tell with a garden variety AR, but could mean the difference between first and fiftieth place in a 1,000 yard benchrest match.
Some manufacturers claim neck sizing makes the brass last longer than full length sized cases, in my experience that has not held true. Being the neck is the thinnest part of the case, it is expanded and resized with every load reguardless of what other portions of the case have been sized, it is also the portion that will crack before any other part. Basically 99% of the cases I scrap are due to cracked necks due to work hardening of the brass, and it doesn't really matter how they were sized to begin with, that neck is getting sized every time.
As far as crimping or not crimpig handgun rounds, they are loaded slightly differently, instead of easy to seat boat tailed bullets, or trimmed and chamfered cases tat easily take flat base bullets, the case mouths are relatively square on pistol calibers, and normally do not need to be trimmed due to the much lower pressures, some magnum loads being an exception. The case mouths have to be belled slightly to allow a bullet to squeeze into the case through the now slightly funnel shaped mouth. For autoloader rounds, you use what is called a taper crimp. This crimp is more a straightener than a crimp, meaning the belling is ironed flat, and the case mouth is straight aggainst the bullet, sometimes slightly angled inward into the cannelure of a hunting bullet. Most of these cartridges headspace on the case mouth in the chamber, so there has to be some case mouth around the bullet to hit the front of the chamber and headspace the round. For reliability, at bare minimum the belling has to be taken out by a crimp die, if left, it can jam easily by hanging up on the feed ramp. For revolver rounds that headspace on the case rim, the case mouth does not need to contact the front of the chamber, but due to heavier recoil, the bullets need to be crimped in securely, for these a roll crimp is used, the case mouth is rolled into the cannelure, or soft lead bullet forming a light radius to the crimp, and locking the bullet in tight.
Same deal as with rifle calibers, you can get a better crimp with a separate crimp die than with a seat/crimp combo die. There is also post sizing. This produces the most reliable ammo that is all but guaranteed to feed in any gun. Simply it is a sizing die meant to work on a loaded round, it sizes the loaded case to exact factory specs, and will iron out slight bulges from seating a bullet or belling the case mouth. I love the Lee factory crimp dies for pistols, unlike the collet style factory crimp dies for riles, the pistol dies crimp and post size with a carbide insert, however the crimp has to be adjusted carefully as it can crush a case, and jam the die up as the carbide sizing ring tries to iron it out. This step will produce ammo that will feed every bit as good as factory ammo in even the most finnicky guns.
As far as trimming goes, I covered it in the last post mostly, but it depends on how exact you want the rounds to be. If you are checking every case, and trimming anything that won't pass through calipers set to the max length, and the trimmer cuts to about .005 shorter, then every case you load will be within this .005" spec, and is plenty consistent to get a good crimp with a collet crimp die, and get consitent loading and feeding, while none of the cases are long enough to jam up the leade and produce overpressure from having too long a neck. This is how I load most every round I plan on crimping, and use for hunting, plinking, and some target shooting. For match loads that won't get crimped, I am going for top accuracy, so every little bit helps, accuray comes from ding a lot of small things the same way every time, not from spending a lot of time on a couple big things, it is the attention to detail that produces the tightest groups. For this, I run every case through the trimmer so while they may all be .005" short of max length, they are all the same .005" short, and therfore consistent to within a thousandth or two. Also it stands to reason because they are not crimped, and thefore the neck tension is affected by the length of the neck, and the surface area that is in contact with the bullet, this also makes the bullets release from the neck more cosnitently. Along with uniforming the flash holes, turning the necks, trickling the powder charges to an exact measurement, and taking my time to load every case the same it takes a whole lot more time to load them, but the groups speak for themselves.
And wit that, my slow day at work is over, yay, time for beer
