Deformed primers when seating SPP

[brokeasajoke]

I was loading some 9mm the other day and noticed most of my primers were deformed when seating. Got a half moon shape, flattened, and dents on a lot of them. I was using an RCBS universal seater. So, I tried seating in the rockchucker and better but still some. Tried a K&M and a Lee seater and still though not as bad. My little plastic piece inside the RCBS that hold the tray (white small, black large I think) does look rough where the seating stem comes through. I tried a small rifle primer and much better but still a small amount I could see. Before someone flies apart I decapped it so I wouldn't accidentally shoot it. Cci seems better than the Federals I was loading. Soft primer coupled with a tight pocket? Just too much hand pressure? I may test some more after I get home from work. I tried reaming with a chamfer tool and it didn't help. The nickel was worse than brass but it was still there on the brass too. I've seen this before and they all went bang, it just concerning.

 

[Chubbs]

I think you have already come up with answer. Tight pockets, which leads to you using more pressure when seating. Some will seat and you will still apply force denting the primer with the seating stem. Federals tend to be a snug fit. Plus is this new brass or primers to you. Had this with S&B 357 Magnum brass and Federal primers. Doesn’t look pretty but will fire ok.

 

[SeabeeKen]

I agree, tight pockets. You might want to swage or ream them again since some appear to be made on military machinery and may still have some level of crimp. I'd also recommend primer pocket go-no go gauges. I use them on everything now and they save me some grief.

Small and Large Primer Pocket Swage Gage ® Set

Swage Gage Small Primer Pocket Gauge

ballistictools.com

 

[K22]

It might be what others have described in previous posts.

However, those dents look like you had something foreign in the seating tool plunger. Perhaps you are shaving some the primer cup, and the shaving is getting stuck in the seating tool plunger causing dented impressions on the next primer seated.

The half-moon deformity often is the result of the primer not being centered and when seated creating differential pressure on one side of the primer.

I had both of these conditions occur with an RCBS tube feed priming system which did not align the tool plunger with the primer pocket of the case. It's one of many reasons I switched many years ago to the Sinclair tool for precise seating of primers. Also, the case not being centered in the shell holder then forcing the primer in the pocket can cause both conditions.

The reason you will see this less with CCI primer versus Federal is that the CCI cups are harder than Federal but that is not the root cause of your problem. While it could be a primer pocket issue, I strongly suspect has more to do with the tools you are using and / or operator error, at least that has been my experience with both of the conditions you described.

 

[brokeasajoke]

It might be what others have described in previous posts.

However, those dents look like you had something foreign in the seating tool plunger. Perhaps you are shaving some the primer cup, and the shaving is getting stuck in the seating tool plunger causing dented impressions on the next primer seated.

The half-moon deformity often is the result of the primer not being centered and when seated creating differential pressure on one side of the primer.

I had both of these conditions occur with an RCBS tube feed priming system which did not align the tool plunger with the primer pocket of the case. It's one of many reasons I switched many years ago to the Sinclair tool for precise seating of primers. Also, the case not being centered in the shell holder then forcing the primer in the pocket can cause both conditions.

The reason you will see this less with CCI primer versus Federal is that the CCI cups are harder than Federal but that is not the root cause of your problem. While it could be a primer pocket issue, I strongly suspect has more to do with the tools you are using and / or operator error, at least that has been my experience with both of the conditions you described.

I checked for debris and tried multiple tools. This is range pickup brass so swaging the pockets may help this issue.

 

[K22]

Forgot to all to my post (#4), that I traced the problem with the RCBS tool to the spring actuated plunger.

This design caused the seating cup to wiggle side to side and at random would create an off-center condition seating the primer. The effect worsened over time as the spring weakened and more slop was created. I would suspect the same would occur with other tools similarly designed.

 

[K22]

I checked for debris and tried multiple tools. This is range pickup brass so swaging the pockets may help this issue.

See my post # 6.

 

[brokeasajoke]

See my post # 6.

That universal RCBS tool is the worst offender. It does have that plastic tray holder that is chewed up which I have replaced several times. I'm fixing to unload all my priming tools and buy a bench mount of some sort. I never use the K&M anymore as it's really slow though I may keep it because it's super smooth just slow.

 

[nmkid]

This happened to me before. Turned out I was using the small primer stem for large primers.

 

[K22]

That universal RCBS tool is the worst offender. It does have that plastic tray holder that is chewed up which I have replaced several times. I'm fixing to unload all my priming tools and buy a bench mount of some sort. I never use the K&M anymore as it's really slow though I may keep it because it's super smooth just slow.

Since I began using the Sinclair priming tool, I have never had a deformed primer and I've primed thousands of pistols and rifle cartridges. Yes, it is slow, but I learned a long time ago that in reloading, quality over quantity should be the goal.

Another issue to check is the cleanliness of your shell holder in the priming tool. If you are tumbling cases and depending on the media you use, this stuff can accumulate in the recesses of the shell holder causing the rim of the case to seat off center with the shell holder priming hole. Periodic cleaning of the shell holder may help.

 

[Charlie-NY]

I use all Federal GMM primers. All of my primer pockets are uniformed with the Sinclair tool. Very often I need to use a stupid amount of force to seat the primers and a flattening of the primer surface is noticed. Since the pockets "probably" are in spec, I assume that the Fed primers are overly large. Not sure how to remedy this problem.

 

[SeabeeKen]

That universal RCBS tool is the worst offender. It does have that plastic tray holder that is chewed up which I have replaced several times. I'm fixing to unload all my priming tools and buy a bench mount of some sort. I never use the K&M anymore as it's really slow though I may keep it because it's super smooth just slow.

I've been using the RCBS Universal for about 15 yrs and never an issue. For tight primers I use the Lee ram prime which has excellent feel to it. I was surprised. It doesnt have auto feed though

 

[K22]

I use all Federal GMM primers. All of my primer pockets are uniformed with the Sinclair tool. Very often I need to use a stupid amount of force to seat the primers and a flattening of the primer surface is noticed. Since the pockets "probably" are in spec, I assume that the Fed primers are overly large. Not sure how to remedy this problem.

I use the same primers and I uniform pockets.

I have experience the same condition ocassionally even with the high quality Sinclair priming tool. The condition you describe is most likely due to the case being slightly off center in the shell holder. With the Sinclair tool, when you turn the tool head to lock the case in place, sometimes the case will rotate off center. By hold the case in place why rotating the head you can assure proper alignment. When you encounter resistance, stop. Reset the case and slowly apply force while keeping the case from moving in the priming tool.

Worn case rims can exacerbate the issue. But by carefully seating the case in the priming tool, you can eliminate the problem you describe.

 

[brokeasajoke]

I've been using the RCBS Universal for about 15 yrs and never an issue. For tight primers I use the Lee ram prime which has excellent feel to it. I was surprised. It doesnt have auto feed though

I do like the no shell holder required feature of the RCBS universal.

 

[CaptainMal]

Mis-alignment is a problem seating primers with some tools, both press and hand mounted. Another issue is the sharp edge around the cases' primer pocket. I have found that on some brass a minor "deburring" of the primer pocket edge helps the primer and priming tool to align and get the primer in properly.

 

[PhilC]

I was loading some 9mm the other day and noticed most of my primers were deformed when seating. Got a half moon shape, flattened, and dents on a lot of them. I was using an RCBS universal seater. So, I tried seating in the rockchucker and better but still some. Tried a K&M and a Lee seater and still though not as bad. My little plastic piece inside the RCBS that hold the tray (white small, black large I think) does look rough where the seating stem comes through. I tried a small rifle primer and much better but still a small amount I could see. Before someone flies apart I decapped it so I wouldn't accidentally shoot it. Cci seems better than the Federals I was loading. Soft primer coupled with a tight pocket? Just too much hand pressure? I may test some more after I get home from work. I tried reaming with a chamfer tool and it didn't help. The nickel was worse than brass but it was still there on the brass too. I've seen this before and they all went bang, it just concerning.

I run 9mm through a Dillon 750 pretty much trouble free except for WMA brass, they are the only ones that are apt to have primer seating problems. I prefer CCI but use what I can get, the SA (Argentian) small pistol primers tend to be a tad touchy most especially with WMA brass.

 

[Webster]

I was loading some 9mm the other day and noticed most of my primers were deformed when seating. Got a half moon shape, flattened, and dents on a lot of them. I was using an RCBS universal seater. So, I tried seating in the rockchucker and better but still some. Tried a K&M and a Lee seater and still though not as bad. My little plastic piece inside the RCBS that hold the tray (white small, black large I think) does look rough where the seating stem comes through. I tried a small rifle primer and much better but still a small amount I could see. Before someone flies apart I decapped it so I wouldn't accidentally shoot it. Cci seems better than the Federals I was loading. Soft primer coupled with a tight pocket? Just too much hand pressure? I may test some more after I get home from work. I tried reaming with a chamfer tool and it didn't help. The nickel was worse than brass but it was still there on the brass too. I've seen this before and they all went bang, it just concerning.
View attachment 1507102
View attachment 1507103

Thinking about your post. Without looking at my priming tool, I believe the rod that pushes the primer in is slightly convex and the primer cup center is flat or slightly convex. This means the primer is seated by pushing on the weakest part of the cup, the top center. Would it make more sense for the push rod to be slightly concave so it is pushed in by the strongest part of the cup, the o.d. over the side walls? I know that if I have to push hard with my priming tool the top of the cup is flattened slightly. Agree with others the o.d. diameter of the pockets is a little small.

 

[brokeasajoke]

So here's what I found. 3 raised places on the seating stem. Maybe it's supposed to be like that, I don't know. I happened to have another and it is perfectly flat. After swapping it out and lightly chamfering, they seat like butter. With a magnifying glass that is the shape of the majority of the primers. You can see those raised places are transferring to the primer. Tight pockets coupled with low contact area I believe is the problem.

 

[brokeasajoke]

Anyone else's RCBS universal seater like this one above?

 

[RegionRat]

No.

Are there also any signs of dents on the OD? I ask because it almost looks like that part was damaged by a three-jaw chuck after that end was faced off.

ETA: if you write that up and show it to RCBS, I have a hunch they will replace your bad part for the trouble.
If you have the resources and dexterity, it is trivial to correct the part you have.