New Case Preparations for BPCR Competition

By Wayne McLerran

5/2021

I follow the process detailed below when preparing new brass for black powder cartridge rifle (BPCR) competition.  The key words here are “for competition”.  If you’re reloading for hunting or general target shooting than many of the steps detailed below are not required.  It may seem like a lot of work and can be depending on if all the steps discussed are followed.  But I’d rather put in the effort up front and feel confident that all reasonable variables have been addressed.  There are several steps some shooters include that are not part of my process and will be discussed in more detail at the end of this article.

The following procedures assume the cases are new or have been newly reformed.  For example it’s somewhat common to reform .40-65 from .45-70 brass.  And the following steps assume you know the distance from the breechblock face to the chamber-to-throat transition step (maximum case overall length) and neck diameter of your rifle chamber.  If you don’t I strongly suggest making a chamber cast or impact impression to determine the dimensions.  To make a cast or impression see my article titled, Chamber Casts and Impact Impression.  With the possible exception of resizing and neck expanding to match the bullet diameter there should be no need to repeat the following modifications when reloading after firing the cartridge for the 1st time.

1. Clean the case - Cleaning may or may not be necessary.  If there are any concerns that new cases may contain grit, clean them or risk damaging the loading dies.  There are various methods and equipment to clean cartridge brass.  The Thumlers Tumbler Model B (Figure 1) is, in my estimation, the best case cleaner on the market for BPCR cases.  For more details on two types of cleaning techniques see my article titled, Case Cleaning - Ultrasonic vs Tumbler with Ceramic Media and Stainless-Steel Pins.

2. Anneal the case neck - Annealing is not required but is a good idea for all brass prior to the following steps.  It’s especially important when reforming and/or lengthening cases.  Several methods can be used to properly anneal cartridge brass necks.  Since I tend to anneal after each match I use a Bench Source brand annealer (Figure 2).  For more details on annealing methods and equipment options see my article titled, Annealing BPCR Case Necks.

Note: Starline brass should be annealed regardless, as it’s harder than other brands.

3. Full-length or neck-only resize – It’s common for the necks of new brass to be out of shape due to being banged around during the manufacturing process and later packaging and shipping.

4. Lengthen the case if necessary – Although many competitive shooters routinely reload with brass that may be as much as 0.020” shorter than the chamber length, the ideal fireformed case length should match the chamber length to within 0.010” for best accuracy.  0.005” is even better but definitely not longer than the distance from the face of the breechblock to the chamber-to-throat transition step.  With this goal in mind, if possible, a brand new unfired case that has been full-length resized should be approximately 0.015” longer than the final case length.  The reason for the extended length should become obvious in the following steps which will result in case shortening.  If the cases are shorter, which is typical with new brass, there are methods to lengthen the case but they can be very labor intensive.  See my article titled, Lengthening Short Brass to Fit Your BPCR Chamber.  Another option is to purchase brass for a longer chamber and trim to the required length.  One example is trimming .45-90 cases to fit a .45-70 chamber.

5. Expand the case neck - Use a neck expander to increase the internal diameter (ID) of the case neck sufficiently to accept a bullet. The full-length or neck-only resized case will shorten approximately 0.005” or a bit more when the neck is expanded.

6. Trim the case – Assuming the case is longer than the ideal length; trim the expanded unfired case to the ideal length plus 0.010”.  I use a Hornady trimmer (Figure 3).  When initially fired (fireformed) expect the case to shorten approximately 0.008” to 0.010” as it expands to the chamber diameter.

7. Deburr the case lip - Using a chamfering or deburring tool, gently remove only metal burrs or whiskers from inside and outside of the case lip created by the trimming step.  Don’t get aggressive with this step as it can shorten the case and is most likely the reason some shooters have reported that cleaning cases in a tumbler with ceramic media will shorten them.  If the case lip is very thin the impact of cases full of media banging against each other during the tumbling can easily roll over, burnish or wear down the edge.  The result is a wider space between the case lip and the chamber transition step, potentially resulting in lead building up in the gap and reducing accuracy.  Several reloading equipment suppliers make manual or powered deburring tools.  Figure 4 is one example and is the one I use.

8. Deburr the flash-hole – Flash-holes are typically punched through the primer pocket from the outside to the inside of the case resulting in irregular or rough edges on the inside.  See my short article titled, Comparison of Remington, Winchester and Starline Brass.  Many shooters will skip this step assuming it does not affect accuracy.  Believing that it’s better to be safe than sorry, I always include this step in my initial case preparation process.

Note: It’s important that this step follows neck expanding, case length trimming and case lip deburring to ensure the flash-hole deburring tool (Figure 5) removes the burrs and tapers the inside edge of the flash hole to the same depth in all cases.

9. Turn the case neck - This step applies to any rifle chamber with a constant diameter neck, which is another reason for making a chamber cast.  Without a cast it’s impossible to determine the chamber neck dimensions.  The Browning .40-65 BPCR is one example.  It has a well-defined constant diameter 0.5” long neck.  To ensure consistent bullet tension, bullet alignment and uniform obturation throughout the length of the neck, case necks should have no taper for this rifle.  Therefore the inside of the neck can be reamed or the outsides “turned” to remove any taper.  If an outside neck turner is used (Figure 6), when the case is fireformed the lack of taper will be transferred to the inside of the case neck resulting in a constant inside diameter (ID).  If the case neck taper is not removed the increasing thicker walls will increase the tension on the bullet base as it’s seated into the case and when fired.

A “trial and error” process will be necessary to determine the minimum amount of material to remove.  Using the thin-edge jaws of a caliper will provide a rough measure of case wall thickness, but will most likely induce a positive error of 0.002” or so.  The better tool to use is a ball-tip-anvil tube micrometer (Figure 7).  After determining the maximum seating depth of the bullet, case necks are turned to a uniform wall thickness to just below the base of the bullet.

Note: Turning case necks is not recommended for rifles with chambers that taper all the way to the case lip (no well-defined neck).  The case wall taper compensates for the chamber ID taper, essentially resulting in a uniform case neck ID, constant tension along the seated length of the bullet and uniform bullet expansion (obturation).

After the above steps are completed, the brass should be ready for loading many times without repeating the steps.  But be sure to check and monitor the case length to determine how closely it matches the desired length, and only trim if necessary.  If the chosen bullet diameter closely matches the fired case-neck ID than, once a fired case is cleaned, primed and charged, the bullet can be finger seated without use of loading dies, only requiring a powder compression plug to compress the powder and wad to the required depth.  But there are some rifles with chamber necks that I refer to as being “generous”.  One such rifle is the Browning .40-65 BPCR.  The correct bullet diameter for the bore is 0.409” or 0.410”.  But due to the fireformed neck ID the brass will require neck resizing and expanding with the correct expander die to hold the bullet.

I mentioned earlier there are several steps some shooters incorporate in their brass preparation process which I do not include in mine.  It’s my opinion the benefits, if any, are not worth the additional effort and time, but you may feel differently.  If it increases your confidence in your loads then by all means for go for it.  Following is an overview of the steps:

• Measure and sort each case by water volume – Fill each case with water to the same level and sort/mark the case by the weight of the water it holds.  The intent is to determine the differences in the case volume which is thought to have a direct correlation to chamber pressure and bullet velocities.  I.e., the same amount of powder in a smaller volume will result in increased pressure and higher bullet velocity and vice versa.

• Measure and sort each case by weight – This is another method to determine differences in case volume assuming a heavier case will have thicker walls, hold less volume and, if filled with the same amount of powder, will result in increased pressures and higher bullet velocity when fired.  This is an easy test and, for no other reason, may be worth doing at least once to determine if the weight spread of your cases is an issue.

• Case indexing for wall thickness – Measure the case wall thickness using a tube micrometer and mark (notch) the rim of the side with the thick or thin wall to ensure the same orientation is used when chambering a cartridge.  Assuming the necks are not turned, the premise is the difference in wall thickness can contribute to bullet deformation.  I.e., if the thickness of the case neck walls varies, when the bullet obturates (expands or bumps up) prior to leaving the neck, the thicker wall area will displace some of the lead resulting in a weight shift to the opposite side.  Any instability effects on accuracy are minimized by orienting all the cartridges the same.

• Case indexing for run-out – Measure the case run-out using a concentricity gauge and mark (notch) the rim at the high or low orientation of the case body to ensure the same orientation is used when chambering a cartridge.  The premise is similar to the reason cases are index for wall thickness.  I.e., a case that is not concentric will not release a bullet that is concentric with the throat and bore.  Any instability effects on accuracy are minimized by orienting all cartridges the same.

• Indexing the bullet to the case – Mark and insert the bullet into the case with the same orientation.  The bullet orientation can be determined by paying attention to the mark left by the sprue plate when the bullet was removed from the casting mould.  Another technique is to use a punch to put a small shallow “dent” in the inside of the mould close to the nose which transfers to the bullet.  When the bullet is inserted into the case the mark on the bullet is always aligned with an identifying mark on the case rim.  As with case indexing this is thought to minimize instability effects and may arguably be a benefit if a mould is out-of-round a significant amount.

The above comments should provide some insights into the process I use and hopefully will help you with your reloading.  With the possible exception of neck turning, all the steps are applicable to loading ammo for BPC rifles of any brand and caliber.  Although several of the steps are not mandatory, such as case lengthening, flash-hole deburring and neck turning, I feel they are worth the additional effort to maximize the accuracy potential of my rifles.

Wishing you great shooting,

Wayne