Debugging the Lock-n-Load EzJect

After years of flawless operation and thousands of rounds, my one press started malfunctioning on the eject.

The problem began with the odd round not ejecting, which I just ignored, then progressed over time to every other round not ejecting, which was extremenly frustrating. At no time did I consider that the press was faulty, I just assumed I was not doing something right, and in too much of a hurry to try figure out what.

Initially, it also seemed that the problem was more pronounced with smaller rimless cases, and the larger rimless cases were not affected. Over time, the problem was occuring irrespective of caliber, and also began to affect rimmed cases.

The rim of the case seemed to be binding on the ejector, and it got to the point where I needed to manually remove every loaded round from the shellplate. On examining the ejector, I noticed that the vertical edge facing the case rim had worn down to convex. The cases were riding over the ejector instead of being deflected off the shellplate. I disassembled the press, removed the sub-plate, spot welded the ejector to build it up again, and filed it down to size and shape with a dremel.

Hornady would have shipped me a new sub-plate, but it takes weeks to get to this part of the world, and I needed it fixed right away.

A few months later, my second press started doing the same thing [ video link below ]. This video illustrates the problem :

 

 

 

I was curious as the to cause of the problem, this being my second press with the same symptoms at more or less the same age and similar overall loaded round count.

I wanted to see if the problem could be solved without spot-welding the ejector and reshaping it.

During the discovery process, I attempted to recreate the old wire ejector, and while doing that I observed that if the base of the round was pressed down on the sub-plate, ejection was always flawless.

I then checked the clearance between the shellplate and the sub-plate, and found that there was enough extra space for the case rim to ride up over the ejector, binding the shellplate and causing the ejection failure.

In my case, the ejector was 0.7mm high at the unworn part, and the groove on the underside of the shellplate that it travels in is 1.2 mm.

After verifiying that the shellplate hex screw was in fact tight, I removed the shellplates from both presses and compared the position of the drive hub relative to the sub-plate on both presses. I saw that on the press with the problem, the drive hub was permanently and prominently raised above the sub-plate, and very importantly, there was no slack on it, it was fixed in place as if it was press-fit to the drive shaft.

This is now two problems, a drive hub too far above the sub-plate, and a worn ejector.

The drive hub does need to be a fraction higher than the sub-plate, and I will explain why in the following pages.

Repairing a Worn Ejector

 

This is how the ejector in the video looks up close. You can see that the leading edge of the ejector is mostly fine, there is just a small section near the middle that seems to be wearing, and that is where the case rim is riding up the ejector instead of being pushed along the face to eject.

 

Once the ejector starts to wear, there is no adjustment you can make to any other part to get it working, you have to either re-create it or get a new sub-plate.

The fix is dramatic, but effective. A weld bead deposited on the ejector, then it is ground back to shape with a dremel.

I have fixed both my presses this way, and they now cycle flawlessly.

Hornady Customer Service would have shipped me a new sub-plate free of charge, but time was a factor for me to get the press working again.

The ejector on the Hornady Lock-n-Load is a weak point in the design of the press, and can easily be improved by Hornady.

The ejector needs to be made as a removable part held in place with a tapered head screw. The ejector can be 1mm thick [ not 0.7mm ] and of a harder steel than the sub-plate. As a replaceable part, Hornady could save a lot of money by not having to replace the entire sub-plate whenever the ejector gives problems under warranty.

Note that if the shellplate is not tight on the drive hub, the clearance between the shellplate and the ejector allows the case rim to slip between the shellplate and the ejector, causing a bind.

It takes very little apparent wear on the ejector to render it faulty.

I will show how a cumulative variation in parts tolerance can contribute to the ejector becoming worn initially.

Comparing Sub-Plates

I have 2 presses, one was pre-Ezject and got the Ez-ject upgrade, the other was purchased with the Ez-ject system.

The underside of each sub-plate appears different, but the difference is cosmetic as the critical dimensions are almost identical.

.image 2_sub_plates.png

On the right sub-plate, there is a more prominent groove worn into it where the lip of the drive hub rotates against the bottom of the sub-plate. This further increases the part tolerance difference.

There is a difference of 0.66 mm in critical dimension between the sub-plates.

23.74 mm

24.40 mm

This means that if the drive hubs were identical, one sub-plate would allow the drive hub [ and hence the attached shellplate ] 0.66mm higher over the sub-plate [ and the ejector ] than the other. The ejector is only 0.7mm high, and gives a 0.5mm clearence between the shellplate and the ejector. With this 0.66mm dimension variation, the possible gap becomes 1.16mm, so increasing the probability of the case rim riding over the ejector, causing the initial wear, and over time rendering the ejector ineffective.

Note the wear on the bottom of the sub-plate by the lip of the drive hub. This potentially adds to the critical dimension variation. Both drive hubs show degrees of wear at that contact point, and is expected where metal parts move in contact with each other.

If the ejector was replaceable, and made to 1.0mm, this wear would not be a factor in shellplate clearance of the sub-plate.

Comparing Drive Hubs

The variation of the critical dimension on these drive hubs is 0.18 mm. This 0.18 added to the possible 1.16mm brings the overall to 1.34mm, which is nearly double the 0.7mm height of the original ejector. Because the shellplate is flush against the drive hub, it cannot be tightened further, and the gap between the shellplate and the ejector can not be reduced.

This is how a drive hub fits normally to a drive shaft. There is a degree of movement in the vertical.

Tightening the hex bolt with a shellplate fitted moves the drive hub slightly above the level of the sub-plate. That small difference is the clearence available to the shellplate when rotating over the sub-plate.

The drive hub must be able to move vertically freely on the drive shaft, because if it is stuck to the drive shaft and remains below the shellplate, like the picture below, when you fit the shellplate and tighten the hex bolt, the shellplate binds to the sub-plate and does not rotate.

Initially, I thought that the drive hub had shifted up off the drive shaft causing the problem. After looking at the problem more carefully, I realised that the vertical position of the drive hub on the drive shaft had nothing to do with the problem, as the lip of the drive hub could not pass the bottom of the sub-plate, so it is not possible for the drive hub to move above the shellplate any variable amount.

Instead, the difference in height between the top of the drive hub and the sub-plate is the sum of the dimensional tolerances of the critical dimensions.

The Primer Punch and the Frame

At a point, I noticed that my primers were not seating as well as when the press was new.

The problem was tracked to the bottom of the primer punch creating an indent where it contacts the frame. This in turn reduces the travel of the primer punch, increasing the number of primers not being seated properly.

A quick fix is a steel washer epoxied to the frame under the primer punch.

A proper fix from manufacturing is to have a high carbon steel button insert at the point where the bottom of the primer punch contacts the frame. To simplify manufacturing, it need not be screw-in, just a drop-in would be fine.

Notes to Hornady

You can increase the product quality and durability very easily and at minimal cost by making two small changes to the press design.

Make the ejector thicker and replaceable, from a material harder than the sub-plate.
Add a high-carbon steel button insert to the frame below the primer punch.

These small changes will greatly extend the period of smooth and trouble-free operation of the press, and should result in overall cost saving to Hornady by reducing the need to ship out large parts under guarantee that are expensive to manufacture.

Both enhancements will be invaluable to the high-volume reloader, and worth paying for as an existing press upgrade.