Mike's Reloading Bench
The Armory Clubhouse
Now that Ron and I have been working at squeezing all the accuracy out of our rifles that we can for a while now, we have started to see how a bunch of little tweeks here and there can add up to a big improvement overall. To begin our search for accuracy we chose the easy things to deal with like bullet types and weights, different powders, various charge weights, primers and bullet seating depths. We tried really hard to make sure we followed good simple case prep by cleaning our brass well and then sizing it and trimming it as needed along with primer pocket and flash hole uniforming. For the most part it has been a good trip so far and we have certainly learned a bunch. Earlier, on another page of this website I talked about whether or not one could apply the same reloading practices to an off-the-shelf rifle that one would use with a custom built target rifle. The answer I have come up with is pretty much what I figured it would be, yes and no. The biggest no being the ability to load your rounds very close to, or touching the lands. This is because we have chambers designed to work for the masses unlike the chambers in custom built rifles that are purpose built, many times even for a specific bullet.
Obviously all the standard reloading practices that have been handed down over the years from one generation to the next apply, be it a target gun or a field gun. The difference between the two comes into play when you go from being able to place a round on a game animal to putting a few rounds into the same hole on a target. Now all of the little fine detail things that don't matter much one way or the other when shooting at a game animal at a reasonable distance suddenly become very important. Things like minimal head space, neck tension, case volume, case neck wall thickness, flash hole diameter, primer pocket depth, case concentricity, loaded round concentricity, bullet seating depth, ballistic coefficients of various bullets, muzzle velocity, extreme velocity spread, standard deviation and above all, consistency.
OK, this topic (case prep) is a big one so I am going to work on it a little at a time by breaking it down into its basic elements and then deal with each of them one at a time. I am only going to talk about the extra steps which are over and above the normal case prep required to bring the brass to its highest level of usefulness. Among these steps would be precision neck sizing, precision shoulder bumping, primer and flash hole uniforming and neck turning. You could also add case volume sorting if you just really don't have anything else to do with your time. I don't think at my skill level I can definitively measure the benefit of it so I don't do it. I'm not saying it doesn't help. I'm just saying I don't do it..............yet.
Mike's Reloading Bench is not afilliated with Lee Precision.
More coming so stop back often.
Case Prep Learning Curve
Neck Sizing vs Full Length Sizing
Normally when you run your cases through the full length sizing die the neck is reduced in diameter as the case gets fully inserted into the die. When the case is retracted the neck sizing ball in the die is pulled through the case neck and expands the neck to the diameter of the ball. This is fine for 90% of us, but not for the 10% who are looking for ultimate accuracy. This is where bushing style neck sizing dies come into play. These dies handle the neck sizing operation differently in that they use a changeable bushing to reduce the case neck diameter from the outside rather than a ball being pulled through the neck to set the diameter. The two main advantages of the bushing style die is its ability to maintain perfect outside case concentricity and the ability to vary the neck diameter in .001" increments by changing bushing diameters. A third advantage of the bushing die is that you can adjust it so that only a portion of the neck gets resized. To reap the highest level of precision from these dies the case necks must be turned to insure uniform neck wall thickness. If you do not turn the neck of the case the internal diameter of the neck will not be concentric with the external diameter due to the variances in the neck wall thickness.
Many bench rest shooters routinely neck size only and full length resize only when they start to feel some bolt lift resistance in an effort to reduce work hardening the brass by continually resizing the entire case. Obviously a case that has not been full length resized will fit the chamber of the rifle it was fired in very closely and therefore remove or greatly reduce another variable that could cause a reduction in accuracy or round-to-round consistency. Personally I full length resize every time. I don't like surprises and by full length resizing I never get any.
The general rule of thumb in regard to selecting the proper bushing for your die is to measure the outside diameter of a loaded round in several locations, average the reading and then select a bushing .002" smaller. This method should provide acceptable neck tension in most cases. This is where the fun begins as now you can change bushings up or down and see how your file responds to the changes. You can get away with very light neck tension if you are single loading a bolt gun but not if you are feeding with a magazine as recoil will definately set your bullets back if you run them too loose. I also would never attempt to run low neck tension rounds in any semi-auto even if single feeding as the bolt closing is too violent and will cause the seated bullet to move.
I think neck sizing only is a choice you would have to make based on your results. If you do not see any improvement in your group size by doing it I would say just full length resize and be done with it.
When you put a round in your rifle how do you know whether or not it fits the chamber as it should? Good question and with just a little patience and a couple of tools, one of which you should already have if you reload, you can find out. The greatest majority of us shoot off-the-shelf guns and therefore have no idea what the chamber measurements are. We just assume that the factory got it right and so it should all be good and for the most part you would be correct. After all don't they make these guns to a dedicated spec for each caliber? Short answer is yes, they do but like most things in life there is a little wiggle room. The problem is what is generally called "production tolerance". It is pretty much a necessary evil. From a manufacturing standpoint, as the tolerances decrease the manufacturing times increase and the price of the finished part goes up. It is much more desireable for a shop foreman to hand a job to one of his employees and tell him or her to make the part within +/- .005" than to say make me this within +/- .0005". The chances of success are much higher with the first senario for many reasons. Engineers take these things into consideration when they design things. I know this to be true because I have spent my life doing it.
So, now you have your gun which was made within the production tolerance for its given caliber and as luck would have it the chamber turned out to be on the high side of the allowable tolerance. Now you go to your local gun store and grab a box of ammo which was made with the same standards but unfortunately it is on the low side of the tolerance. So what is the problem with that you ask? They are both within tolerance and should work just fine. You're right, it will. However, when you pull the trigger and that round goes off the cartridge case will expand in all directions to fill the chamber and because the gun and the case are at the oposite ends of the tolerances for each, the case will get streached the maximum amount. Fear not! This is a good place to bring up the topic of shoulder bumping.
OK, so now you have a case that has been fired in your rifle and except for a slight amount of spring-back, fits your chamber perfectly. Now is the time to get out your calipers and your case length measuring tool. (See photo below) Measure the fired case from its bolt face to the datum point on the shoulder of the neck and record this measurement. The idea now is to adjust your sizing die or shoulder bump die to bump the shoulder back only enough to allow the bolt to close without resistance. Many target guys set the shoulder back so that when a sized case is inserted in the chamber there is an ever so slight amount of resistance felt while closing the bolt. This is done with the firing pin assembly removed. If you don't want to do this or you are loading for a semi-auto then .001"-.002" set back by measurement is good. Running the minimum amount of headspace will reduce the amount of case growth reducing the number of trimmings needed and help prevent incipient case head separation due to case wall thinning at the base of the case right above the web area.
Shown below is the Forster bushing bump die. It is unique in that it allows you to size only the case neck and set the shoulder back at the same time. Turning your case necks along with using this die will insure the best possible results for your prepped brass.
Hornady Headspace Case Gauge
Forster Bushing Bump Die
Neck turning is one of those things you read about and wonder if it really is worth the effort. I thought that for a long time until I started measuring the necks on some brass I was getting ready to load for the third time. I have been using a Lee collet neck die to size my case necks and was happy with the results. However, when I measured the neck diameter of the sized cases I found that they were tapered! The ID of the neck is straight but the OD is not and that's not a good thing. This is not the fault of the Lee die. It is because the brass has migrated forward and become thicker close to the shoulder. When the round is fired with the neck wall in that condition, there is no way it can evenly expand in the throat of the barrel and cleanly release the bullet. Duh!
I had been thinking about buying the tools to neck turn for some time but I would always talk myself out of it because I figured how much good will it do if I'm shooting a run of the mill Remington 700. As luck would have it I stumbled across a few videos of a top notch bench rest shooter holding a class and talking about how he processes his brass. I listened intently to what he had to say and between what he said and what I have discovered measuring my brass, I knew I was leaving a lot laying on the table by not turning my necks. It can't hurt anything and for sure it might make a real noticeable difference in my group sizes, factory rifle or not. What this man did that I had not heard before was explain why he does what he does and then exactly what the result was and it was an eye opener. His first hand account of his experience and my own measurements was enough to cause me to order the required tools to turn my necks.
Round-to-round consistency is the holy grail of accuracy. Anything you can do to get each round to release the bullet from the case exactly like the round before it has got to help group size. Making sure that the case neck is centered in the chamber and that there is adequate and equal space all around the case neck for expansion is the reason for turning case necks. Anything you can do to get that bullet started straighter into the lands and grooves of the barrel is a step in the right direction. I think it might even be more critical on a stock gun with a long throat like mine. I am not able to seat my bullets so they contact the lands because the throat in my barrel is so long. For that reason I have found that the closer to the SAMMI length I load my rounds the better they shoot. That tells me that the neck of my case is actually acting sort of like a barrel during the time the bullet is jumping the extended chamber length before it hits the leade. It follows that if I try to make the neck of the case as true as possible it should guide the bullet in a straighter path. I believe this is why my rifle groups better when I seat my bullets deeper in the case instead of trying to load them closer to the lands.
As I said earlier, turning the necks lets you take full advantage of the bushing neck sizing dies available from several die makers and when you begin to link all these different operations together it becomes clear why hand loaded ammo can be far superior to anything you buy off the shelf.
Primer Pocket Uniforming
Making the primer pockets identical on all your brass is just one more little step toward getting all the accuracy you can out of your rifle. Consistant ignition is critical to holding tight groups. Taking the time to uniform your primer pockets insures that each primer will have the best chance of being fully seated squarely and completely. There has been some extensive research done that clearly shows the benefit and results of making sure that the primers are properly seated. Also the deburing and uniforming of the flash hole aides in round-to-round consistency. After all, the primer is shooting a flame through the flash hole so wouldn't it follow that if all the holes were identical from case-to-case the round-to-round consistency would improve? How could it not. A little thing to be sure but as I have said before, every little thing helps. If you don't have a primer pocket uniformer get one and use it. What have you got to loose?