Failure to Fire / Light Strikes when reloading .223 on a Dillon 550

[swhiteh3]

I've been attempting to load .223 precision ammo for a ARC Nucleus-based rifle on my Dillon 550, but I'm getting a ton of light strikes. Nearly every round does not fire the first time.

I'm loading brand new virgin LC brass and CCI primers. The primers are as close to flush as I can measure them. I've tried BR-4s and 450s.

I've seen lightstrikes from this ammo in other rifles, and I when I switch to factory ammo, this rifle shoots 100% with absolutely no issues. So I'm confident in narrowing it down to the ammo as the primary cause.

I've been reloading precision ammo in single-stage presses for over a decade, but I'm pretty new to using a Dillon for this.

Any ideas on what to investigate? Are certain primers in the S/R family easier to set off than others?

 

[Modoc]

Have you checked the depth that the primers are seating to? You may have to adjust the stem height.

 

[swhiteh3]

Have you checked the depth that the primers are seating to? You may have to adjust the stem height.

Thanks for the reply. I will try to measure more installed primers, but they were all measuring almost exactly flush. The Dillon 550 really does not have a way to adjust depth. With that said, I have tried grinding a few thousandths off the bottom of the primer installation cup (several people discuss this ‘mod’ but for me it made no difference I could measure).

Also, I had considered trying to use another primer tool to see if the primers would seat any further, but I have not done that yet.

 

[CK1.0]

Read this, it might help:

Finally: How to adjust 550b primer depth

I have loaded a few thousand rounds on my 550b, and I have always had a problem with getting the primers to seat flush. Well skimming the forum last night, I found a post from the Dillon rep on here saying how to do it. There is no purpose built 'adjustment' but you can use the shell plate bolt t...

forums.brianenos.com

 

[kriller134]

Sounds like you’re not seating the primers deep enough. First strike is seating it and second is firing.

 

[AllenOne1]

I agree with kriller you are likely not getting the primer all the way to the bottom of the primer pocket. Measure the depth of the primer pocket and compare that to the thickness of the primer that should tell you how deep they need to be seated to be seated firmly against the bottom of the primer pocket.

 

[Marine52]

Sounds like you’re not seating the primers deep enough. First strike is seating it and second is firing.

Yes. measure your primer height including the protruding anvil (a) and measure the primer pocket depth (b) of your cases. Subtract a from b. This tells you the distance below the casehead to seat the primer for no crush. You can experiment with the level of crush that work best for your loads. I usually use about 0.004“ crush. Excessive crush or an excessive gap between the anvil and the bottom of case primer pocket may give erratic ignition.

 

[RegionRat]

If you have had previous success with those same components, then by all means try and adjust your primer seating depth to match the depth you used when you had reliability and go run a test. That test tends to exonerate the rifle.

Have a look at the protrusion of the pin from the bolt face just to make sure your bolt group isn't polluted.

Also, the advice to inspect the brass prep is important. Shoulder Datum lengths need to be close to ammo specs for a spec chamber.

If you think about how that ammo may sit versus the bolt face, when the firing pin strikes we don't want the extractor to be the basis of where the cartridge case head is controlled. It is better if the shoulder datum is correct. So, you don't want short (over sized) shoulders.

Primers should not sit exactly flush, especially for an AR. The primer pocket depth and primer height advice above is good. Check the dimensions and determine how far below flush the dimensions would stack, then press in a few thousandths more, then inspect.

You will get the Dillon figured out and this will all be behind you soon enough. Good Luck.

 

[swhiteh3]

Read this, it might help:

Finally: How to adjust 550b primer depth

I have loaded a few thousand rounds on my 550b, and I have always had a problem with getting the primers to seat flush. Well skimming the forum last night, I found a post from the Dillon rep on here saying how to do it. There is no purpose built 'adjustment' but you can use the shell plate bolt t...

forums.brianenos.com

Thanks for this reply! This is what I did (and tried to explain in my original post, but I did so poorly), and I saw no difference in primer depth, but I will look into this again. Did you do this? Did it work? I went about 0.004” but was afraid to go too far without spare parts.

 

[swhiteh3]

Sounds like you’re not seating the primers deep enough. First strike is seating it and second is firing.

Yes, it makes me wish I brought calipers to the range and measured a few after the failure to see if they did seat deeper! I will manually try to seat some deeper and see how much they move.

 

[swhiteh3]

I agree with kriller you are likely not getting the primer all the way to the bottom of the primer pocket. Measure the depth of the primer pocket and compare that to the thickness of the primer that should tell you how deep they need to be seated to be seated firmly against the bottom of the primer pocket.

Thanks! That measurement is simple! Not sure why I didnt think of that! Will do!!

 

[swhiteh3]

Thank you @Marine52 and @RegionRat . Great info! I will look into this and reply back.

 

[Sheldon N]

Are certain primers in the S/R family easier to set off than others?

450's have a harder primer cup and are more prone to light strikes, I believe BR4's are similar. Try standard CCI400's or Federal primers and see if that helps. My 223 trainer bolt gun has never really liked 450's, I've had light strikes also.

Regardless, agree with getting primer seated a bit deeper. My Dillon 550 seats them around 0.004 below flush. One thing to check is the tightness of your shell plate. If it's loose it sits higher and moves the case farther away from the priming rod. You want it as tight as possible while still allowing the shell plate holder to rotate smoothly without binding.

 

[whatsupdoc]

ARC Nucleus has an adjustment for firing pin protrusion, you should confirm that measurement and
confirm the headspace is correct before you go any further.

 

[Haney]

Have yo tried a seating them deeper after going through the Dillon ? Something sensitive enough to feel them bottom out if they moved ?

 

[Mike_in_FL]

ARC Nucleus-based rifle, but I'm getting a ton of light strikes. Nearly every round does not fire the first time.

I don't want to muddy the water too much but what generation is your Nucleus? There were a few people saying that the Gen. 1 wouldn't light off rounds consistently with the 16lb. spring in the bolt. I've never had any trouble myself although I bought the 19 and 21 (?) lb. springs in case.

 

[swhiteh3]

Yes. measure your primer height including the protruding anvil (a) and measure the primer pocket depth (b) of your cases. Subtract a from b. This tells you the distance below the casehead to seat the primer for no crush. You can experiment with the level of crush that work best for your loads. I usually use about 0.004“ crush. Excessive crush or an excessive gap between the anvil and the bottom of case primer pocket may give erratic ignition.

So many good replies. I'll start with this one.....
I measured 10pcs of new virgin brass from this lot, and they averaged a pocket depth of 0.1189". My CCI 450s measure an average thickness of 0.1195". So flush is about half-a-thousandth of crush.

I measured 10 pieces of brass that I had loaded, and they averaged less than 0.0005" (half-a-thou) below the surface. So basically flush. I then tried to reseat them all on my RCBS bench-top seater, which has a lot of leverage. I honestly probably used a bit too much force. And I was able to get them to average over 0.004" below the surface, but I really felt like all I did was crush the primers - that they were already fully seated. The primers now appear to have a LOT more crush (flatness to the top surface). And the measurements of the primer and primer pocket depth seem to concur with that. The proof will be in shooting them (hopefully this weekend).

Have yo tried a seating them deeper after going through the Dillon ? Something sensitive enough to feel them bottom out if they moved ?

See above. I didn't feel any of them move, but they did average about 0.004" farther below the surface. I honestly think that was just more crush....

 

[swhiteh3]

ARC Nucleus has an adjustment for firing pin protrusion, you should confirm that measurement and
confirm the headspace is correct before you go any further.

I tried to measure the firing pin protrusion, but it's hard without a real protrusion gauge. It's tough to tell if the calipers are completely and 100% straight. I was getting measurements from 0.052" to 0.057". What should that number be? What adjustment is there?

Headspace wise, the cases were all virgin when I started, and measured 1.4465" to a 23° datum insert. I tried to size them as little as possible, but it looks like I averaged about 1.4455" when it was sized. Fired cases are averaging about 1.4530", so they're growing a decent amount, but I think that's expected with new brass.

Any thoughts based on those measurements?

 

[swhiteh3]

450's have a harder primer cup and are more prone to light strikes, I believe BR4's are similar. Try standard CCI400's or Federal primers and see if that helps. My 223 trainer bolt gun has never really liked 450's, I've had light strikes also.

Regardless, agree with getting primer seated a bit deeper. My Dillon 550 seats them around 0.004 below flush. One thing to check is the tightness of your shell plate. If it's loose it sits higher and moves the case farther away from the priming rod. You want it as tight as possible while still allowing the shell plate holder to rotate smoothly without binding.

I actually just set the shellplate before I loaded the last time. It was crazy how sensitive it was. Just a few degrees was the difference between feeling a wobble and the shellplate being completely locked up solid. But I think I had it as tight as I could get away with. I've considered one of the bearing kits....

When I first noticed the Dillon loading the primers flush, I did some reading, and found a good article which included a discussion on primer seating. In an effort to get the primers deeper, I tried the modification he suggests - about 0.004", but it didn't seem to make a difference. He also mentions grinding the bottom the shellplate a bit, something I did not do.

I may need to try some other primers....

 

[swhiteh3]

If you have had previous success with those same components, then by all means try and adjust your primer seating depth to match the depth you used when you had reliability and go run a test. That test tends to exonerate the rifle.
<snip>

Take a look at the measurements above regarding primer height and pocket depth, as well as shoulder datum measurements.

You will get the Dillon figured out and this will all be behind you soon enough. Good Luck.

I hope you're right!!

 

[swhiteh3]

I don't want to muddy the water too much but what generation is your Nucleus? There were a few people saying that the Gen. 1 wouldn't light off rounds consistently with the 16lb. spring in the bolt. I've never had any trouble myself although I bought the 19 and 21 (?) lb. springs in case.

Pretty recent. Bought it Black Friday, 2022. I assume that makes it Gen II?

The rifle sets off factory ammo (American Eagle 55gr) 100%. It was about 40/40 on that ammo, and my ammo is probably 10-20% on the first trigger pull. So I don't *THINK* the action is at fault, but I have not totally ruled it out as a contributing factor.

 

[TheOfficeT-Rex]

I tried to size them as little as possible, but it looks like I averaged about 1.4455" when it was sized. Fired cases are averaging about 1.4530",

If you're bumping 8k that may be part of your problem. That means that case is moving 8k forward before the pin starts doing work on the primer, in conjunction with the primer maybe needing a little deeper seating.

Try bumping the shoulder a bit less and tightening the shell plate down snug. I like to go all the way snug, then back off until it rotates, but not full weeble-wobbly. That should seat your primers 2-3k under flush. If they aren't, we need to fix that first.

ETA: 50-60k is good for firing pin protrusion, so that sounds ok.

 

[CK1.0]

^^^ I'd look hard at this.

If all your primers seem seated well and your firing-pin-protrusion looks good, then bumping them too much is really all that's left...

 

[swhiteh3]

If you're bumping 8k that may be part of your problem. That means that case is moving 8k forward before the pin starts doing work on the primer, in conjunction with the primer maybe needing a little deeper seating.

Try bumping the shoulder a bit less and tightening the shell plate down snug. I like to go all the way snug, then back off until it rotates, but not full weeble-wobbly. That should seat your primers 2-3k under flush. If they aren't, we need to fix that first.

ETA: 50-60k is good for firing pin protrusion, so that sounds ok.

^^^ I'd look hard at this.

If all your primers seem seated well and your firing-pin-protrusion looks good, then bumping them too much is really all that's left...

Thank you @CK1.0 and @TheOfficeT-Rex for the replies. I agree with both of you that this might be an issue. I could see how moving the cartridge forward in the brass could rob momentum from the firing pin, and that would certainly also explain why they often (usually) fire on the 2nd firing, but this is virgin brass. I'm not bumping it .008", it's starting out that short from the factory. (Okay, I'm bumping 0.0005"-0.0010").

On a hunch, I just measured 10pcs of the American Eagle 55gr that this rifle shot 100%, and it's shoulder measurement was 1.447x", or about 0.001" longer than what I'm loading. I can't imagine that 0.001" is the different between nearly 0% first shot bang, and 100%.

I've spent the last few hours working on seating depth on the press. Several people, including the paper I linked above (and here) talked about taking material off the primer cup. If you assume that is what stops the downward motion of the shell holder when you're pushing the handle forward, then that sorta makes sense, but I didn't see a correlation - I ground about 0.006" off and didn't see more than (maybe) 0.001" deeper primers. Then I realized that it was not the cup that stops the shellholder, but the spring underneath it which goes into coil-bind. Looking in the side while pushing the handle forward, I can see a very small gap between the bottom of the spring cup and the top of the primer slide. So I polished off a few thou off that spring, and now I'm seating consistently 0.002"-0.003" below flush, which is a definite improvement.

It amazes me that these presses don't have an adjustment for this.

 

[Doom]

Primer crush is not crushing the primer. It is setting the anvil into the priming compound. It sounds like this is not happening. You are probably seeing the light strike because the firing pin is driving the cup down to seat the anvil. It you have a light strike and rechamber and fire again and it goes BANG then this is the issue and headspace is not the issue.

 

[swhiteh3]

Primer crush is not crushing the primer. It is setting the anvil into the priming compound. It sounds like this is not happening. You are probably seeing the light strike because the firing pin is driving the cup down to seat the anvil. It you have a light strike and rechamber and fire again and it goes BANG then this is the issue and headspace is not the issue.

Thank you! Some good logic here.

So if I got a light strike in the past, I have just lifted the bolt handle and dropped it - resetting the firing pin without disturbing the round from the chamber.

If I understand correctly, you’re saying eject the round and then rechamber it, because if its a headspace issue it will FTF again, but if the primer is being seated / crushed then it will fire the second time.

Thanks! Great idea! I will try that again when I go to the range.

 

[Haney]

So many good replies. I'll start with this one.....
I measured 10pcs of new virgin brass from this lot, and they averaged a pocket depth of 0.1189". My CCI 450s measure an average thickness of 0.1195". So flush is about half-a-thousandth of crush.

I measured 10 pieces of brass that I had loaded, and they averaged less than 0.0005" (half-a-thou) below the surface. So basically flush. I then tried to reseat them all on my RCBS bench-top seater, which has a lot of leverage. I honestly probably used a bit too much force. And I was able to get them to average over 0.004" below the surface, but I really felt like all I did was crush the primers - that they were already fully seated. The primers now appear to have a LOT more crush (flatness to the top surface). And the measurements of the primer and primer pocket depth seem to concur with that. The proof will be in shooting them (hopefully this weekend).

See above. I didn't feel any of them move, but they did average about 0.004" farther below the surface. I honestly think that was just more crush....

Bottoming out and beginning crush most likely, not more crush . Simple test is check one that failed to fire and see if it was set deeper by first strike.

 

[TheOfficeT-Rex]

If I understand correctly, you’re saying eject the round and then rechamber it, because if its a headspace issue it will FTF again, but if the primer is being seated / crushed then it will fire the second time.

Not quite - If a second trigger pull sets it off, the first pull only set the anvil/primer into the proper position, and the second trigger pull set it off, as the primer was now properly seated (aka not a headspace issue).

You need to get your primers seated properly coming off the press - If they're now coming off 3k below flush, you might be there. Go test em!

 

[swhiteh3]

So first I modified the Dillon slightly more to seat the primers deeper. That required a bit of polishing on both the primer seating cup and the spring. Now I’m averaging about 0.002” deep with a bit of crush.

Then I loaded 60 rounds from the Dillon, and half of them went across my RCBS primer seater for another squeeze. The RCBS may have seated them 0.001” deeper on average, and showed a but more crush.

The Dillon only ammo averaged about 60% FTF rate.

The Dillon + RCBS ammo averaged about 30% FTF rate.

Then I loaded with other lot #s of SRPs I had:
CCI 450s
CCI BRs
CCI 400s
And all three exhibited 30-40% or more FTF.

I continued to use 223 factory ammo as a baseline during each shooting session, and over about 100 rounds of American Eagle and Fiochi 223, I had zero FTFs, so I doubted the rifle itself was the root cause.

Then I found a 20 year old box of FGMM SRP primers. What the hell, its worth a try! And every single one fired.

So I loaded 50 more, Dillon only, and yesterday every single one fired.

As a side note, when I was getting the FTFs, i was getting SDs around 25. Clearly there was combustion issues. Now I’m getting under 10 SD.

Morale of the story: I think CCI primers are great when they are properly being ignited, but are harder to ignite (thicker cup maybe?), and in systems that might be closer to marginal, an easier to ignite primer like a FGMM might be worth testing both for FTF% and for S/D.

 

[spife7980]

I've been attempting to load .223 precision ammo for a ARC Nucleus-based rifle

Know what firing pin spring weight you have installed?

They had some teething issues earlier with the 16lb spring and that may be why you are getting low energy strikes. Also, take the bolt apart and run a paper towel through the bolt body to make sure its clean and clear of any obstructions and energy robbing heavy greases.

That said, my gen2 with a 16lb has shot every 450 ive thrown at it without a hitch.

 

[swhiteh3]

Its a recent Nucleus and per Ted, has a 16# spring. Given that it sets off factory ammo of multiple different brands with zero issues I’m inclined not to look too hard at the rifle. Also, I’ve taken this Dillon/CCI ammo to another rifle and also had issues. Not saying that maybe the rifle being “marginal” is not contributing to the issue…..

 

[Dead Eye Dick]

Without going through every word here, I have this to add. The seating assembly on the 550 is quite hard to fully set. That leaves the primer seating punch not deep enough into the cup that holds the primer. When this is too high, typically, a lot of the primers fall out of the cup in the process. This is all due to the spring which is quite heavy as it rebounds the entire assembly after the primer is seated.

What I do, is leave the Allen wrench in the screw that holds the primer punch in place. I lower the faceplate to its lowest point and then tighten the Allen screw. Its a pain, but get it right and it works.

 

[swhiteh3]

So after very systematically testing all aspects of the rifle / ammunition system, and collecting a lot of data, I think the root cause was drag on the sear. I was using a Bix'N'Andy with a MEDIUM sear. When I measured the offset per Bix'N'Andy instructions, the measurement indicated that even the low sear would not work well - I need something even lower. Having access to some VERY precise machining equipment and some amazing professional machinists making aircraft and space parts, I found someone to very carefully take a few more thousandths off it, and Whoila! NO MORE FTFs! Several things seemed to move the needle just a bit, like a softer primer and more firm seating, but I was still stuck with 30-50% FTFs until I changed the trigger. Since then I have had no issues with any ammo.