Basics: New Brass Preparation

Rob's questions about new brass are some that I commonly hear, so this might be a good topic to cover in our Basics series. - GAS -

New Brass Preparation
by Germán A. Salazar

Hello German,

I've been reading through much of your info on reloading and find it incredibly valuable.

I'm now loading .308 again with 175 gr. and 185 gr. Berger long-range bullets, Lapua cases that I had sitting around, and CCI BR2 primers. I'm going to try RL17 based on your findings, hopefully working up to 2,750 fps. New brass has next to perfect run-out +/- 0.001" but in reading your info on TRJ, you indicated FL size even new brass first and then turn.

I have K&M tools as you've displayed in TRJ, still need a digital neck micrometer and a good bump gauge to keep the shoulder set-back to .001" on resizing.

Other tools I have: Wilson dies, Haydon's Press (although not that fond of it) Forster's Coaxial press, bushing/bump dies, and bench rest seater; Redding's Competition loading dies too and an RCBS Charge Master. With the Coaxial compared to the Wilson tools, I've found little to no difference in run-out so I use the Coax most often.

Anyhow, my main question was on the new Lapua brass prep. In the past, (years back) I over-worked the brass too much, (neck turned) and ended up with loose chamber, fouled necks & no accuracy. If you have couple minutes to reply I'd greatly appreciate your input on new brass as I'm a little confused on exactly what to do. Normally, I just load, fire form, neck size and reload with minimal brass rework.

I'm using factory 700 40XB-Tactical (1:12" twist) with an AAC suppressor which seems to tune nicely and creates far less noise than unsuppressed. Most of the rounds though this gun have been with Sierra 155 Palmas, Varget and BR-2 primers. Tuned loads shoot nearly one hole 3 shot groups shot after shot at 100yds. Almost boring, it's so accurate for a factory rifle.

What got me searching the forums again was looking for the heavier loads after I found a partial box of Black Hills match 175 gr. BTHP sitting around left over from my AR-10 shooting. I decided to put five rounds down range through the 40X for the heck of it and ended up with what looks like a three shot group all holes touching. Mind you, this was at 100 yards which really doesn't do this gun justice, but it's what I have at the house.

Thanks for all the great info and time you put into TRJ.

Rob

 
Hi Rob,
 
You bring up a few interesting points, lets take a look. You haven't said what specific purpose you have for the rifle, but it sounds to me as though general, informal, accuracy shooting is the main objective. The 40XB Tactical has a 27 1/4" barrel which I'll assume has been left at that length despite the addition of the suppressor.

Brass Inspection
The first thing I do with new brass is a detailed inspection. I try to buy a small quantity and then, if it looks good, follow-up with a purchase of more of the same lot. Even with a single purchase, inspection is fundamental to determining whether to keep the brass or sell it off and try another lot.

The first, simple check is case weight - I want to make sure that the new lot isn't materially different from previous lots.  For instance, I expect Winchester .308 cases to weigh about 156 grains.  If a new lot suddenly was in the 166 grain range (as some older lots of Winchester are) I would not continue with it.  There's nothing wrong with heavier brass, but my loads are tailored to the lighter cases and I'd rather not have to rework them to suit the brass.  I don't, however, weigh every case or segregate them in any manner as I have not found this to have an impact on the rifle's scoring ability.  The Lapua brass you have is of excellent quality and I'm not suggesting that you change it, your loads will be developed with that case capacity and will work perfectly well.

The most important part of my inspection is performed with the NECO/Audette tool. This inspection is to make sure that most of the cases have no more than 0.003" case wall thickness variance at a point approximately 0.200" up from the interior base. Most current Winchester and Lapua brass easily meets this standard. All cases are then checked and indexed as long as the lot itself appears to be acceptable.

Finally, each case is examined visually for any defects or damage, areas of attention are the case mouth (damage), the shoulder (wrinkles or other damage), the primer pocket (damage) and the flash hole (significantly off-center).  Take a look inside each case too, recently I found a fairly large coil of brass inside a new case, can't figure where it originated.
 
Neck Turning and Concentricity
You stated that the new Lapua brass you have has nearly perfect runout, in the range of 0.001", presumably this is measured at the neck prior to loading. That is a good reading, no doubt, but not necessarily indicative of perfection in the neck. Neck thickness variance on unfired and unloaded brass is seen on the inside diameter more than on the outside diameter. In essence, the opening is not concentric to the case body, although the outside of the neck is concentric to the case body.  Imagine, if you will, a case neck with one side twice as thick as the other. If that case was run through a die with no expander ball, the outside of the neck would be concentric to the case body, but the hole itself would be offset.  To a certain degree, that happens with all new brass as it comes from the factory.

You'll eventually need a good ball anvil micrometer to measure case neck thickness.  Whether it's a digital like the Mitutoyo shown in the picture or a vernier scale model like the Sinclair, doesn't make much difference except in ease of reading the results.  Get one and learn to use it properly, it'll teach you a great deal about preparing case necks properly.
 
Most unfired brass doesn't need to be full-length sized prior to neck turning. As I mentioned in the neck turning article, you can full-length size it in a standard, non-bushing die, or you can simply run it over the expander. In some instances, you may find that the new cases slide over the expander with minimal effort - this is an indication that they should be full-length sized. The quality of your neck turning depends to a large degree on a very close fit between the case neck and the turner mandrel and that fit is established by the expander; if the case slides over the expander effortlessly, it is already too large and needs sizing to get the relationships in line. Cases should always be trimmed for length before neck turning as the end of the neck is the stop point for the turner, therefore, unequal case (neck) lengths will lead to variance in the depth of the cut into the shoulder just at the base of the neck.
 
Turning the necks will, of course, reduce neck wall thickness variance, but it won't put the hole back in the middle, you'll have to fire the case for that to happen. After the case necks are turned and the cases fired, you'll have a reliable measure of neck to body concentricity. Assuming that there's nothing wrong with the chamber, most fired cases will show excellent runout numbers - and well they should, the body and neck have both expanded to meet the chamber walls which were cut with a one-piece reamer and therefore must be concentric.  That doesn't mean you have perfect brass.

Just as with unfired brass, it's the location of the hole in relation to the case body that matters.  Unfortunately, reading concentricity on the outside of the case neck is far more common than on the inside of the neck where it really matters.  The simple way to get a useful reading of the concentriciy of the inside of the neck is to seat a bullet and read from the bullet's ogive (mark it with a Sinclair hex nut comparator or similar tool). I take my readings on the ogive, not the tip or anywhere else because that's the part that will contact the rifling first and will, to a large extent, determine how straight the bullet starts into the rifling (more on checking concentricity in this article).

Case Sizing
Now we're moving away from new brass preparation, but you brought up resizing, shoulder set-back and it sounds like you're considering neck sizing. The most useful advice I can give you is to full-length size all cases every time you load them with shoulder set-back in the range of 0.001" to 0.002". Neither accuracy nor case life will be reduced and rifle operation will be materially improved. In fact, I would say that accuracy will probably be improved with full-length sizing as the rifle will be easier and smoother to operate. Take some time to read this article on case dimension changes during resizing and this one on the misuse of full-length dies

Bullet Seating and Concentricity
You mentioned that the concentricity of rounds loaded with the Wilson dies was no better than with the Redding Competition dies.  That's not a surprising result, and is in line with my test results.  Although Wilson dies are of very high quality, their principal purpose is as a convenient way to reload at the range; concentricity results are no better or worse high quality press-mounted dies such as your Redding dies. As much as I work at improving concentricity, it should be borne in mind that it is the sprinkles on the frosting on the cake.  The bullet itself is the biggest determinant of accuracy, followed by the powder type and charge, and then all of the miscellaneous items such as brass, primers, neck tension, concentricity, seating depth, etc.  In other words, don't get too caught up in the small stuff at the expense of the truly important items.

Heavier Bullets
Your 40X will handle the 175 grain bullets with no problem at all.  With the right powders, such as H4895, you'll find excellent accuracy at useful velocities. Although the allure of high velocity with powders such as Reloder 17 or VihtaVuori N550 is understandable, I strongly recommend developing a load with standard powders first. This will really let you see the accuracy potential of a given bullet before you interject one of the more exotic powders into the mix of factors. If you're principally shooting at 300 yards and less, don't overlook the 168 grain Sierra - it is probably the single most accurate mid-weight .30 caliber bullet ever made within that distance limitation.

We've wandered a bit past brass preparation, but I think these are all useful topics for many reloaders and if you follow the various links, there's more detailed information on all of those topics.  Enjoy the rifle!

 

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