Issues with head spacing on a Dillon?


September 2, 2009, 07:58 AM
I started to load for 308 the other night. I purchased the Dillon head space gauge (only because everyone else was out of stock on the Lyman's), set up my dies etc. on my 550B and started to adjust the decapping / sizing die (BTW - this is on another tool head as I do this operation seperately). When I load for my 223, I had no problem setting up the die. Cranked it down to the shell plate, backed it out a little, sized a case, checked in in the head space gauge and adjusted everything till it was good to go. My 308 however was a little different.

I set the sizing die into the tool head, raised the ram to the top of the stroke, screwed the die in till it touched the shell plate, backed off half a turn and tightened everything down. Put a case in and sized it. Checked it in the head space gauge and it was too high, so I cranked the die down a little more. Continued to do this till it appeared to be ok. I checked a couple of empty cases in my rifle, and it was slightly difficult to close the bolt. It closed, but not smoothly, so I continued to adjust the die downwards.

I ultimately had the case sized correctly, looked to be perfect in the head space gauge and the bolt closed very smooth. The problem, if it is one, is the die is screwed down about an eighth of a turn past where it was initially screwed down to make contact with the shell plate. I don't remember this happening with the 223's. There's no undue force being placed on the shell plate when I move the ram to the top of the stroke (I removed the case to check this in order to make sure I wasn't going to jam the die into the shell plate) and it feels fine.

I'm just curious if any of you have had to do this when using the Dillon?

thanks for the input......

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September 2, 2009, 09:22 AM
The Dillon Shell Plates can have different thickness. To FLRS a bottle neck case you must have a case gauge. My 223 plate will give 4 totally different sizings of the case if the die is turned down to touch the shell plate. I learned the hard way with my Early Dillon RL450. The shoulder was pushed back way to far, causing case seperations in the body. Back then Dillon gave no instruction that the FLRS dies was to be set different than any single stage RCBS type press, die touching the shell holder. You can measure the shell plate to see how close it comes to spec. I could have blown up my M16A1. The ammo had been in storage for year, didint know till i fired some. Depending on what slot of the shell plate the die was set up on, i got 4 different sizings of the cases.

September 2, 2009, 10:34 AM
When sizing cases consideration is never given to the cases ability to resistance sizing or the ability of the press to resist flexing, the Dillon has a large diameter ram, the shell plate is a cantilever, about 1/8 turn on 14 tpi is about .008 thousands.

In the perfect world a case that is sized when the die is adjusted down an additional 1/8 to 1/4 turn after contact (.008 to .017 thousands) with the shell holder is said to be full length sized, that would be .000 or .005 shorter from the head of the case to the shoulder than the perfect chamber length (go-gage size) which would be .005 longer from the bolt face to the shoulder of the chamber. Back to resistance to sizing and flexing: If a cases ability to resist sizing is greater than the ability of the press to resist flexing the case can not be full length sized. To measure resistance to sizing the lack of ability of the press to resist flexing MEASURE, For most this will require a trip to a tool store to purchase a feeler gage. If the press is not sizing the full length sizing the case there will be a gap between the top of the shell holder and bottom of the die, measure before lowering the ram.

There is something about a case not being full grown until it is fired 5 times, after that there is a problem with neck sizing and the case requires full length sizing, I believe the five firings increases the ability of the case to resist sizing, sizing a case is as good as it gets when it is new or once fired, after that problems are created for the press and case.

Again, I do not shoot gages, the chamber is not adjustable, that leaves the case, when sizing a case the press, die and shell holder is adjustable, this works when the process is not complicated with cases that need annealing.

Cantilever and leverage, the RCBS shell holder is designed to mount in the center of the ram.

F. Guffey

September 2, 2009, 12:12 PM
I also had trouble with my 550B when resizing bottleneck cartridges.

While the shellplate thickness and uniformity seems to be the culprit, it really isn't the entire story.

I had trouble because the shellplate was slightly loose. If the center bolt isn't screwed down almost to the point of binding, it's loose.

If the shellplate is correctly adjusted, the brass should consistently touch the shellplate platform under it. The rim should not be supported by the shellplate. (This also makes primer seating more "square" than with a loose shellplate.)

I'm using Hornady dies, and I'm getting consistent resizing with both .243 and .30-06.

I agree that the design is a problem, as you're trying to duplicate a shellholder's dimensions with two separate pieces (the shellplate and the shellplate platform.) The manual should probably explain how important it is that the shellplate is as tight as possible, as critical dimensions are involved.

I'm not sure that measuring to the bottom of the shellplate is a fair comparison. As the shellplate platform supports the case, one should measure to that surface, with the shellplate adjusted and ready for use.

September 2, 2009, 12:52 PM
I'm not sure that measuring to the bottom of the shellplate is a fair comparison. As the shellplate platform supports the case, one should measure to that surface, with the shellplate adjusted and ready for use. The die pushes the shell plate down making contact with the platform. There is no clearance if the center bolt is adjusted correctly and the die is given the needed extra 1/8 or so turn down. I ask Dillon Comments:
Hello, Problem? Case separation 5.56mm Dillon Loader RL-450 yes, old like me lol.


The Dillon shell plate used to load 5.56mm seems to be undersize. A standard RCBS shell holder measures .125". The Dillon is from .116" to .124" on the same(5.56mm) #3 shell plate taking measurements using 2 different methods. A different shell plate #1, used for 243/30-06 is undersize at .117" If you adjust your Full Length Sizing die by turning it down till it hits the shell plate as per Dillon instructions & RCBS, your shoulder could be pushed back to far resulting in excessive headspace by as much as .009" Firearm used M16A1, rifle headspace checked with field gauge, OK. Cases, Federal and LC fired 1 to 3 times. Failure rate of ammo 4 % , 2 different separation points, Federal in shoulder area, LC 2/3 way down from head. Bullet 55gr fmj. Load IMR 4198-20.5gr. Misc primers. Ammo in storage/loaded 1987. Dillon RL-450 the one before the 550B. Dies RCBS. FLRS die adjusted to just kiss the shell plate. The 2 methods used to check the shell plate are 1. A .020" feeler gauge was held under the plate and a micrometer used, then subtraction of the feeler gauge dia. for the final measurement. 2nd method was a steel plate under the shell plate, an RCBS dial caliber used to measure from the leading edge of the plate to the bottom steel plate. Both measurement were the same give or take .0005" A Shoulder Comparator or a case gauge would have been useful back in 1987. So my question is (if you have read this far lol) What do your Dillion shell plates measure?? Am i looking at this wrong? Thank You, Reply From Dillon-- On Tue, 11/18/08, Dillon <> wrote:

From: Dillon <>
Subject: RE: Web Form Contact From:
Date: Tuesday, November 18, 2008, 4:24 PM

No 450 dimensions available anymore. 550 plate dimensions should be .250? thick top to bottom, .132 +/- .005 from underside of the shellplate to top recess where the die contacts.

Thank you,

Dillon Precision Products, Inc.

September 2, 2009, 01:30 PM
When sizing cases consideration is never given to the cases ability to resistance sizing or the ability of the press to resist flexing

An excellent, often overlooked, point F. Guffey.

Dead soft new brass will need the die adjusted up further than brass that has been fired several times fired and is "work hardened" and springy.

As brass continues to work harden every time it is fired, the sizer will have to be adjusted along the way to maintain the same headspace. Not every firing, but it will need to be adjusted. Then if you anneal the brass, you will have to back the sizer back out again since the brass is soft at the shoulder again.

September 2, 2009, 09:21 PM
One other thing to have brass in all for stations when setting things up, and if you are using different brands of brass you can be off a tad too! Consistency in operations help eliminate the variations.

Ol` Joe
September 2, 2009, 09:36 PM
You simply installed the die as they are meant to be. From the RCBS web site on die set up;

Step 5: Install the Sizer Die

Thread the sizer die into the press until the die touches the shell holder when the ram is at the top of the press stroke. Raise the press handle and turn the die down another one-eigth to one-quarter of a turn and set the large lock ring. If you're using a carbide sizer die, make slight contact with the bottom of the die and the shell holder

The press has some flex to it that has to be taken in account at times. Turrets and progressives by nature are slightly more prone to play then a strong single stage. They and also don`t use shellholders made to a specific height that mesh properly with the die.
There also is a tolerance stack in both the rifle chamber and the die that needs to be addressed.
Starting with the die a 1/2 turn off the shellholder size a case and see if it chambers properly. If not add a 1/8 turn to the die then try again with a FIRED UNSIZED CASE, a case that has been already resized won`t show the true amount of resizing the die is doing. Repete if needed until the case enters the chamber smoothly or you are at about a 1/8-1/14 turn past touching.
RCBS and some other die makers suggest you start right out at the extra 1/8 turn past touching to ensure chambering. this works but can shorten your case life if the slight extra sizing is not needed.

September 2, 2009, 10:06 PM
Thanks for the additional info. The trouble I had was the shellplate was backed out too far.

The press couldn't compress the center bolt and make the shellplate lay flat on the platform, it was that far out.

I wasn't aware that the Dillon shellplate wasn't even close to standard shellholder dimensions.

When I ran into trouble with resizing, I got a cartridge headspace gauge, looked carefully at the press, and eventually figured it out.

On a positive note, with the additional resizing avaliable, 550B owners shouldn't be tempted to grind on their resizing dies! :)

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