June 17, 2024

My Dillon 550

I bought one of these over 10 years ago and have loaded a lot of ammunition with it. Ever since the day I bought it, it has had troubles with the primer feed. I called Dillon and they sent me an entire new primer bar, but that didn't fix the problem and I just lived with it. Until July 16, 2024 (see the end of this page) when I made a modification that fixed the problem.

Primer feed issues - Round 1

Ever since the first, it has been plagued by issues with the primer feed. People say this is the biggest source of trouble with the 550.

It is all about the primer bar. Sometimes it won't come back far enough to pick up a primer. If I notice, I grab it and pull it back and all is well. Maybe.

Sometimes the primer bar sticks in the back position. So I wiggle and push on it as I lower the ram and all is well. Maybe.

Sometimes it gets going all of a sudden when I am wiggling it and then tosses the primer off someplace.

The worst of this is the distraction while loading ammunition. If I am really lucky (and in the worst of cases) I may raise the ram a second time while fighting with the primer system and get a double load of powder. This would be a disaster later with pistol ammunition if I didn't catch it. With rifle ammunition, the case is already nearly full, so I just end up dumping powder all over the press.

Because of this and the added confusion involved, I have given up progressive loading for rifle ammunition. I just run one case around by itself through all the stations. If I was trying to load progressive with all the primer system confusion, I would be led to drastic measures.

I have tried all the recommended fixes, cleaning all the relevant parts with alcohol, scrubbing the bar with a scotch-brite, and most recently polishing the bar with 600 grit wet/dry paper. I checked the bar with a machinist parallel to decide whether it might be warped or bent.

Apparently I am not the only one to suffer in this way. An outfit in Texas is making an extended primer plate with a ball bearing to guide the primer slide. I have one on order. I see they are getting plenty of other orders and it has only come out recently.

308 reviews on Amazon, almost all 5 star.

Primer feed issues - Round 2

I installed the new slide with ball bearing. It seems nicer, but does not solve my problem. I call Dillon. They tell me about filing possible bumps and swelling, and point me to their online videos. I watch most of those. They also ship me (for free) a new primer slide bearing plate, with the comment that they doubt it will fix my problem. Indeed it does not.

I try the business of filing down the side of the primer feed where people had had trouble with the metal swelling due to overtightening of the two cap screws that come in from the bottom. Before I began filing, I painted the surface with red Dykem so I could see where metal was being removed. I did not see the telltale pattern of metal being removed on bulges above the tapped holes for those cap screws.

Primer feed issues - Round 3

I decided to work from basic principles. I installed the new bearing plate from Dillon. I cleaned everything up. I even bought some pipe cleaners so I could clean the hole the white plastic piece runs through. Without any springs or the control rod, I move the primer slide by hand and feel for where it hangs up. Indeed, it does hang up when the rod is all the way out and in position to pick up a new primer.

What is happening is that the primer cup is rubbing the right side (viewed from the operator position) of the gap in the primer dispenser. Aha! I use a slip of paper and indeed, there is clearance on the left side, but not on the right. I measure the diameter of the primer cup as 0.431 inches and the gap it must pass through as 0.445. That gives 0.014 of clearance, so .007 on each side -- but all 14 thousandths are being used on the left side. I now remeber that I discovered this many years back -- and Dillon sent me a new primer slide at the time, which fixed absolutely nothing. But I have 3 slides not and all of them rub on the right side. So a reasonable person would conclude it is not the slides, but the piece they should pass through.

I contemplated making a mandrel for my lathe and turning down the primer cups, but this is not the right way to fix this problem. I study the "primer dispenser" and realize that it is not out of the question like I thought it was to put it on my mill and open up the passage.

Here is the primer dispenser in my mill. I made a gentle attempt to remove the primer tube, but is seems to be cemented in place -- and the job can be done without removing it. I am cutting metal from the surface behind the cutter.

Here is is after I have finished. Metal was removed from what is the left side in this view. You canot tell anything has been done from this direction. The red Dykem on the lower right is left over from when I filed that surface.

Here is a view that shows the cut I made. I only removed .008 inches of metal (and didn't really intend to remove more than .004). It looks like more because the cutter cut more deeply into the curve at the back of the slot.

The width of the slot before I began work was 0.445, and is 0.453 after I finished. So I opened it up by .008. Now the primer cup does not rub on either side and the mechanism seems to work as it should.

Note: the piece I worked on is called the "RL550 primer housing and shield". part 20263.

Here is a post where someone describes what sounds like exactly the issue I had/have:

So, my machine has had an out of spec "primer housing" since the day I bought it and I lived with the erratic behavior until now. I am sure that if I had pestered Dillon they would have fixed it (I could have driven up to Phoenix with the machine -- and I considered it). It certainly is pleasant to have a working, reliable primer feed.

Even though my machine may have been flawed from the start -- I would buy another to replace it if that was for some reason necessary.

Feedback? Questions? Drop me a line!

Tom's Computer Info / [email protected]