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June 22nd, 2018

How to Improve Case Concentricity with Standard Seating Dies

USAMU Handloading Hump Day Seating Die Adjustment Stem TIR Concentricity Run-out

Each Wednesday, the U.S. Army Marksmanship Unit publishes a reloading “how-to” article on the USAMU Facebook page. This USAMU “Handloading Hump Day” article, the second in a series on improving concentricity, has many useful tips. If you use standard (non-micrometer) seating dies when loading some cartridge types, this article is worth reading. And visit the USAMU Facebook page next Wednesday for the next installment.

Once again, it’s time for USAMU’s “Handloading Hump-Day!” Last week, we addressed achieving very good loaded-cartridge concentricity (AKA “TIR”, or Total Indicator Runout) using standard, “hunting grade” reloading dies.

We explained how to set up the Full-Length Size die to float slightly when correctly adjusted for desired case headspace. We also cited a study in which this method loaded ammunition straighter than a set of [higher grade] match dies from the same maker. [One of the keys to reducing TIR with both sets of dies was using a rubber O-ring below the locking ring to allow the die to float slightly. READ Full-Length Sizing Die TIP HERE.]

Now, we’ll set up a standard seating die to minimize TIR — the other half of the two-die equation. As before, we’ll use a single-stage press since most new handloaders will have one. A high-quality runout gauge is essential for obtaining consistent, accurate results.

Having sized, primed and charged our brass, the next step is bullet seating. Many approaches are possible; one that works well follows. When setting up a standard seating die, insert a sized, trimmed case into the shell-holder and fully raise the press ram. Next, back the seating stem out and screw the die down until the internal crimping shoulder touches the case mouth.

Back the die out one-quarter turn from this setting to prevent cartridge crimping. Next, lower the press ram and remove the case. Place a piece of flat steel on the shellholder and carefully raise the ram. Place tension on the die bottom with the flat steel on the shellholder. This helps center the die in the press threads. Check this by gently moving the die until it is well-centered. Keeping light tension on the die via the press ram, secure the die lock ring.

USAMU Handloading Hump Day Seating Die Adjustment Stem TIR Concentricity Run-out

If one were using a micrometer-type seating die, the next step would be simple: run a charged case with bullet on top into the die and screw the seating stem down to obtain correct cartridge OAL.

However, with standard dies, an additional step can be helpful. When the die has a loosely-threaded seating stem, set the correct seating depth but don’t tighten the stem’s lock nut. Leave a loaded cartridge fully raised into the die to center the seating stem. Then, secure the stem’s lock nut. Next, load sample cartridges and check them to verify good concentricity.

One can also experiment with variations such as letting the seating stem float slightly in the die to self-center, while keeping correct OAL. The runout gauge will show any effects of changes upon concentricity. However, the first method has produced excellent, practical results as evidenced by the experiment cited previously. These results (TIR Study 2) will reproduced below for the reader’s convenience.

TIR Study 2: Standard vs. Match Seating Dies

50 rds of .308 Match Ammo loaded using carefully-adjusted standard dies, vs. 50 using expensive “Match” dies from the same maker.

Standard dies, TIR:
0.000” — 0.001” = 52%;
0.001”– 0.002” = 40%;
0.002”– 0.003” = 8%. None greater than 0.003”.

“Match” dies, TIR:
0.000”– 0.001” = 46%;
0.001” — 0.002” = 30%;
0.002” — 0.003” = 20%;
0.003” — 0.004” = 4%.

AccurateShooter Comment: This shows that, with careful adjustment, the cheaper, standard dies achieved results that were as good (or better) than the more expensive “Match” Dies.

These tips are intended to help shooters obtain the best results from inexpensive, standard loading dies. Especially when using cases previously fired in a concentric chamber, as was done above, top-quality match dies and brass can easily yield ammo with virtually *no* runout, given careful handloading.

Permalink Reloading, Tech Tip 14 Comments »
February 16th, 2011

Redding Now Offers Micrometer Heads for Standard Seating Dies

Redding MiRedding has introduced a new series of Bullet Seating Micrometers (aka Micrometer Bullet Seater Plug Replacements). These can be retro-fitted into standard Redding seater dies with 1/2-20 thousandths threads, replacing the standard dies’ seater plugs. So, for about forty bucks, you can now make your standard Redding seater die into a Micrometer Seater — and you can swap one Micrometer Seater top among a variety of dies in the same caliber class (such as .223 to 22-250). Notably, the new Bullet Seating Micrometers are offered in two different configurations — one for traditional bullet shapes, and another for VLD bullets. Redding’s new Bullet Seating Micrometers are priced at $48.90 MSRP, but expect to see an initial “street price” of about $37.00-$39.00.

VLD Version of Micrometer Fits Berger Bullets
Eric Stecker of Berger Bullets stated: “I spoke with Redding and confirmed that the new VLD-Version Micrometer plugs are specifically designed for Berger VLD bullets. We provided all of our VLD bullets to them from which they took deliberate measurements and made these new plugs. This is news that needs to be shared with anyone shooting Berger VLD bullets.”

Bad News: You Need Different Micrometer Units for VLD and Non-VLD Bullets
Unfortunately, the Micrometer Seater Plug Replacement is ALL ONE UNIT. You cannot interchange VLD and non-VLD seater stems inside a given Bullet Seating Micrometer. You have to buy one of each (one Micrometer unit for VLD bullets and another Micrometer unit for standard bullets). Likewise, you cannot swap in larger or smaller diameter seater stems to make one Bullet Seating Micrometer head work with dies for widely different bullet diameters. That means you can’t buy one Micrometer head and use it in both a .223 Rem Seater Die and a 30-06 die, for example. You have to stay within the same die class, as explained next.

Good News: Bullet Seating Micrometer — Use in Multiple Dies
As long as you stick with the same seater die class, one Bullet Seating Micrometer can be used on multiple dies. In practical terms, you can usually (but not always) use the same Micrometer assembly on multiple dies within the same caliber family. And when you move the Micrometer unit from one die to another, all you need to record is the Micrometer setting. Look at the photo — the knurled ring at the bottom of the black replacement plug is a dead-stop collar that does not move. That means the lower section of the Micrometer always maintains the same position relative to the die when installed. When moving the Micrometer plug from one die to another, simply adjust the Micrometer knob to the proper setting for that cartridge/bullet. Each hash mark represents an .001″ change in seating depth.

Redding VLD Seater Stem

There are sixteen (16) part numbers for the new Bullet Seating Micrometers. These correspond to the VLD and Standard versions for eight (8) different classes of Redding seater dies. To see which Micrometer replacement you need, look for the number on the top of your standard Redding seater, and find that in the right-most column. Then chose whether you want the standard or VLD version (shown in columns one and two on the same line).

Editor’s Comment: We like that fact that Redding is offering these retro-fit Micrometer Seater Plug Replacements. And it’s great that the buyer has a choice between VLD and non-VLD styles. However, we think the lack of interchangeability of bullet seater stems is going to be a “deal-breaker” for many shoppers. Redding obviously wants to sell as many Micrometer Seater Plugs as possible. It doesn’t want you to be able to buy one $40 Replacement plug and use that one product for a half-dozen or more calibers. That’s to be expected. However, we think that, for a given cartridge/caliber, Redding should have engineered the Micrometer Bullet Seater Plug Replacement with swappable seating stems so that one $40 Micrometer head could seat BOTH VLD and non-VLD bullets… at least for that cartridge/caliber.

Permalink Bullets, Brass, Ammo, New Product, Reloading 3 Comments »