Bushing Dies and Honed Full-Length Sizing Dies
We were recently asked: “What size neck bushing is best for Lapua 6mmBR brass in a ‘no-turn’ chamber?” The questioner planned to purchase a Redding Type ‘S’ full-length sizing die with neck bushings. The quick answer is that one should probably get 0.265, 0.266, and 0.267 bushings and see what works best.
Using current “Blue Box” Lapua brass, a loaded 6BR round with an unturned neck will typically run about 0.2680-0.2685 (depending on the bullet). A 0.266 neck bushing, after springback, will give about 0.0015 tension which can work well in a bolt gun. NOTE: With the older “Brown Box” Lapua Brass, the neckwalls are slightly thicker, so you may want to start with a .267 bushing. Remember, however, that with either older or newer Lapua brass you may want to experiment. Some bullets prefer more tension than others. And, you may find that it is useful to tweak neck tension slightly if you make major changes in seating depth during load development. In a gas gun, such as an AR15, you probably want .003 or more tension.
Alternative to Bushings — Honed Full-Length dies
Conventional, non-bushing full-length sizing dies can create ultra-accurate ammo with very low run-out. For some applications, we prefer a non-bushing FL die over a bushing die — so long as the neck tension is correct. But many FL dies have an undersized neck diameter so you end up with excess neck tension, and you work the brass excessively. Forster offers a simple, inexpensive solution — honing the neck diameter to whatever size you want.
If you purchase a Forster non-bushing, full-length sizing die, Forster will hone the neck dimension to your specs for $12.00 extra (plus shipping). This way you can have a FL die that provides the right amount of tension for your particular load. (The max amount of diameter change Forster can do is about .008″) Forster dies are relatively inexpensive so you can afford to have a couple of FL dies with necks honed to different diameters — such as 0.266″ and 0.267″ for a no-turn 6mmBR. The die itself is fairly inexpensive — currently Sinclair Int’l charges $33.99 for a Forster 6mmBR full-length sizing die (Forster Part # 018121).
Forster FL dies, necks honed to .265″, .266″, and .267″.
Steve Rasmussen of IowaHighPower.com gave this a try. In fact, he had three dies made — each with a different neck dimension. Here’s his report: “My original Forster 6BR FL die sized the necks down a lot [to about 0.260″]. I sent my die in and asked if they could supply two more FL dies (for three total) to have the necks honed to 0.265″, 0.266″, and 0.267″.” In addition to the purchase cost of two more FL-sizing dies, Steve paid $36 ($12 per die) for the three dies to be honed, plus about $12 for return shipping.
The table below shows the neck diameter range of 10 sized cases using each die. [NOTE: This is with older “Brown Box” Lapua brass!] Brass springback after sizing is running 1 to 1.3 thousandths. My loaded rounds are running 0.2697-0.2699 using Lapua I bought last year. So far the dies are working well. I sized 80 cases with the 0.266″ necked die. The shoulder is running 0.4582″ and 0.300″ up from the base is 0.4684". I spun 20 of ‘em and 16 had a runout of one thousandth (0.001) and the other 4 at 1.5 thousandths (0.0015).”
| Die Diameter | Sized Brass | Springback | Neck Tension |
| 0.267 Die | 0.2683-0.2684 | 0.0013 | 0.0014 |
| 0.266 Die | 0.2672-0.2674 | 0.0013 | 0.0025 |
| 0.265 Die | 0.2659-0.2660 | 0.0010 | 0.0039 |
Have the best of both worlds-use a Lee Collet Die w/ a Body (FL) Die.
+1 on the Lee Collet Die. I’ve found it to be much more consistent with regards to neck tension on my 6 Dasher (at least, my S.D./E.S. numbers have gone down significantly which I attribute to more consistency). It definitely needs to be polished up out of the box, but once it’s setup, it’s exceptionally consistent.
EDITOR: Jay. You got lucky. The two Lee Collet dies (.223 Rem and 6mm PPC) I’ve recently purchased and tried were downright awful. Lot of internal burrs and roughness. The mandrel was oversize so you couldn’t reduce the neck diameter enough no matter what you did. The edges of the collet fingers weren’t radiused properly so they dug into the neck. The dies could not size consistently AT ALL and the Collet fingers had bad burrs. But the worst thing was when your brass came out of the die the necks were rectangular, not round. Single worst piece of reloading equipment I’ve ever tried. In fairness I had a .30-06 Lee Collet die (older production) that worked OK on very hard Lake City brass, but the .223 Rem and 6mm PPC dies were absolute junk.
I must be lucky too, the last collet die I bought was a year ago, and it was good. IMHO the Lee collet dies (w/ a little work)are excellent dies for consistent ids and concentricity. I have lapped out fl dies from Forster and RCBS that are very good, but there is nothing like squeezing the neck over a mandrel for good ids. If the collet die was made by another manufacturer, slicked-up and $150 they would be more popular. I think the patent runs out next year, maybe we will see.
Squeezing the neck over a mandrel for good ids, that’s ok if the mandrel is the right OD.
Editor: That’s correct. If the mandrel is over-size, as was my Lee .223 Rem die, you get no sizing at all. The collet die can work, and work well — but it’s all about quality control. Good QC, good die. Bad QC, worthless die that can actually ruin your necks.
Quality is everything but almost everyone that likes collet dies usually indicate that they slicked them up. I know I send Lee a couple of cases to make one for the 6.5/284 (neckturned and sized (w/ bushing dies), and fired right out of the chamber, and the die is great, then I ordered 4 extra mandrels and turned them down for different purposes and they all work great. You have to turn them the od you want for about 3/8″ and the rest of the mandrel down to the decapping pin can be smaller if you don’t use this part to expand anything.
Maybe I’m wrong and if anybody disagrees they can disregard this, but it seems to me that in this accuracy game you have to modify or have modified most of the stuff (reloading tools) to achieve the accuracy we want. Dies lapped out, dies cut off the bottom, shellholders ground down, Powder Measures converted (not as much anymore), balance beam scales tuned,neck turners modified (esp mandrels), custom mandrels made for expanders, measuring devices, chambering blank dies for custom chambers, lapping bushings out for bushing dies to get that 1/2 thousandths. Quality tools improved by their own manufacturers esp ergonomics now w/ aging shooters. Adapting a dial indicator or micrometer to just about everything we use. However quality is still king because if it’s off center you can’t modify that w/o replacing or rebuilding.Someone once said “to an accuracy nut the most expensive rifle is a factory rifle because when he’s done w/ it the cost will exceed a custom”. I hope this makes sense.
I guess what I’m trying to say if a person believes in the system of the Lee collet die and thinks it’s worthwhile then they could have custom mandrel(s) made up by a gunsmith or modify it themselves and polish up the collet and other parts like we do w/ other reloading tools to make them work right. It’s the only die of its kind that I know of at this time. If machining is bad then send it back to Lee for fix or replacement.
EDITOR: When you buy dies from Forster, Redding, John Whidden, Wilson etc., they don’t need polishing and band-aid fixes to work right…
Basically you’re right (imho RCBS is also in the no band-aid fix list) but the Lee collet die is the only one of a kind, and if a person believes in that system, then they will fix it or change their procedure. Not too many years ago I had a Redding fl standard sizer modified to use Wilson bushings to size the neck because Redding didn’t make bushing dies yet. Before that we used to turn down and polish exp balls for different ids and send sizing dies back to the manufacturer to be lapped out in neck area which some still do. I love Wilson seaters but there again some shooters want a custom seater made w/ the reamer that cut the chamber. But what the heck at least we have all these options today. My collet dies work great but I haven’t bought one for over a year now.