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Discussion Starter #1 (Edited)
I'm working up a load for a 223 Remington bolt gun and experienced a pierced primer. I prepared 10 rounds each using 25.1, 25.2, 25.3 25.4 and 25.5 grains of Varget under a Hornady 68 HBPT. I had previously worked up to 25 with very little pressure signs. I shot 5 shot groups - going across the different loads rather than shooting all of each load together.

I paid close attention for pressure signs the first several times I worked up the ladder. The only signs I noticed were some increased primer flattening and some slight cratering. The 25.2 loads seemed to have the most pronounced crater. ??

I finished the 25 shots for the groups - in no particular hurry (1-2 shots/min) but then decided I had time to shoot a set 3 of shot groups and began running the ladder again but shooting 3-4 shots per minute. I didn't notice the pierced primer until after I completed a ladder - but it was it was at 25.2 grains not my max load. In all, I shot 36 rounds before the primer pierce. My suspicion is that the load was near max (for the primer at least) and I didn't have a problem until I heated up the barrel by shooting faster. I was using CCI 400 primers and others have posted about problems with that primer piercing in a 223. Since I didn't see pressure signs other than the primer - I'm wondering if I could run this ladder again with a CCI BR4?

Why do you think the 25.2 gr load had the most pressure signs and was the load that pierced? Also - the rifle has never pierced a primer and I was able to get some clear pictures of the effect on the firing pin. Not only was there erosion at the point of the pierce - but there was some circular erosion around the pin where it went through the primer and there was a flame pattern further up the pin where the gas jet hit the flare on the pin. I think you can see where the vaporized primer cup deposited some brass.


 

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The Hog Whisperer (Administrator)
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I think you had a defective primer. Firing pin looks nice and rounded (nice pics by the way) and there just isn't a lot of other explanation for it, especially if it was below published max and none of the other rounds did it.

At least that is all I can tell from the pictures and your photos.
 

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I had a similar situation in my Bolt action 223 recently, blanking primers at lower charge weights. I had two things going on, an excessive amount of clearance between firing pin and bolt head leading to excessive cratering and blanking.

And my ability to measure to the lands was suspect, eventually discovering I was actually ON or into the lands with that load. Add all these up and add a hot day, hot barrel and POP goes the primer.

If you've got a good micrometer, measure the pin diameter, and using a pin gage or drill bit, get a close idea of how much clearance you have. Two or three thousandths, is fine. Seven or eight is way too much.
 

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Discussion Starter #4 (Edited)
I can measure the pin - but the hole is going to take some thought.

Here's the pin, in the bolt:


And here's the worst crater of the bunch - 25.2 gr Varget. When running a finger across the cases - this primer feels like it has a bur sticking up:


And check out the extrusion - whatever is going on - it isn't good.


The one above is the most flattened of any of the primers. However, the 25.1 round just before the one that pierced looks ready to pop.



This is the only one that looked like a sombrero and why I am thinking that the hot barrel took me over max load. Otherwise, bolt lift was fine and the cases look ok so I'm wondering if the thicker BR-4 would allow me to retry this ladder. I got some nice groups at an earlier outing at 24.8 but things seemed to be getting a little better towards 25.5.

For these bullets I measured the COAL at the lands to be 2.276 and these are all at 2.26 - so I'm pretty sure I'm not up against the lands.
 

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Several possible things could be going on here.

You might have too much tolerance in the firing pin channel which could allow the primer to flow back into the FP channel. This will cause the primer to rip or get cut as it gets forced back into the channel. Excessive cratering even with low to mid table charges is characteristic of this. I have a 700 that had an over sixed channel, it would pop primers with mid table charges. I had someone make me an over sized FP, but I think are a couple of other options to correct it. I think you can have an insert installed or possibly have a smith add some welded material to it then drill it to proper specification, if this turns out to be the cause.

And it could be high pressures were generated by the bullet at or into the lands. This is something I have a great deal of experience with and have seen happen even with low to mid table charges. Depending on the powder being used and the charge being used, a landed or jammed bullet can experience just enough delay to spike pressures extremely high. This is just as characteristic with low table charges of slow burning powders, as it is with too high of charge. To light a charge and pressures don't build quick enough to get the bullet engraved and moving down the barrel which results in pressures going red line. To high of charge and the delay created will also spike pressures enough to pop primers.

The other possible is a bad primer, but that's something I've not come across in 40+ yrs. of reloading, and I use CCI's almost exclusively.

If you didn't experience stiff bolt lift it's likely not a typical high pressure occurrence such as that experienced when exceeding max charges. OTOH a high pressure spike wouldn't necessarily exhibit typical high pressure signs, stiff bolt lift, difficult extraction, excessive primer flow that fills the primer pocket, but it could and often will pop a primer.

SMOA
 

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Discussion Starter #6 (Edited)
I'm having too much fun adding more micrographs... this is really cool.

The extrusion picture says to me that the pressure is too high for the primer and it is lifting the firing pin and extruding the primer into the bolt. Some folks have said elsewhere that CCI 400's are a bit light and will pierce short of max load in a 223.

So - I'm going to pull these bullets and wondering if this load is too hot period or if it might be ok with a thicker BR4.
 

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¨I paid close attention for pressure signs the first several times I worked up the ladder. The only signs I noticed were some increased primer flattening and some slight cratering. The 25.2 loads seemed to have the most pronounced crater.¨

That is when I stop any further shooting immediately, pull the bullets and back down one grain.
 

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I would be trying different primers.
Thats pretty amazing that it can mold that much without giving way.
Do you clean your flash holes.
On edit: what i dont get is how it can mold that much yet the primer has not flattened.
Is the firing pin full strength.
 

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A while back I bought a Remington SPS varmint rifle in .223. It had primer puncture problems with a mild load of H335. Thought it might have been some aspect or combination of components that was causing it. Tried Remington factory ammo and the first round down the tube was a catastrophic primer pierce. Not just some leakage but complete burn through.

Sent the rifle back to Remington and they returned it stating everything was "in spec". A friend who previously worked at H-S Precision took a look. According to him the firing pin channel in the bolt was oversized with too much chamfer on the bolt face.

Wonder if that couldn't be something similar to what you are experiencing?
 

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Elk Whisperer (Super Moderator)
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I'm thinking what Monty is thinking. I also have an SPS in .223 and it does the same thing, but I've never had it puncture a primer, just the odd reverse dimple thing.

RJ
 

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Discussion Starter #12
¨I paid close attention for pressure signs the first several times I worked up the ladder. The only signs I noticed were some increased primer flattening and some slight cratering. The 25.2 loads seemed to have the most pronounced crater.¨

That is when I stop any further shooting immediately, pull the bullets and back down one grain.
I agree that they need to pulled and I would have quit sooner if I had noticed that extrusion. The question I have is that backing down a grain takes me near minimum load so I'm wondering if this is the wrong primer for my application.
 

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The Hog Whisperer (Administrator)
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Whoa, that is serious extrusion of the primer back into the firing pin channel. "Flattening" of the primer (usually) refers to the rounded outer edge getting flattened into the chamfer on the primer pocket.

You can get a reasonably decent idea of the size of the hole if you can find someone with a "letter/number" drill bit set; usually 115 pieces. Even the inexpensive sets that are too soft to drill steel will make a useful gage of sorts. The solid shank of the bits will be the gage. Find the biggest one that will slide into the hole and the smallest one that won't and you will have some idea of the hole size.

Too much headspace - maybe - could contribute to this but I do think the guys hit the nail on the head when advising you to check the firing pin hole size. Any machine shop should have even better gages and be able to give you an answer down to the nearest 0.001".

Great photos by the way and far better information that we usually get when trying to guess a problem. What kind of primers? Sorry if I missed that.
 

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The Shadow
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I think the boys have you squared away on the clearance / primer differences, now lets look at the loads themselves.

Don't focus on the charge weight as though it was set in stone, they are not.
Powders have a much larger nominal burning rate variance than gets measured/discussed. No one lists what lot of powder was tested, so don't assume that you have the same animal; only the same name.
What you need to focus on is the velocity, per the charge.

So as an example for you, current Hodgy data says:

Start - 24.0 gr - 2,780 fps
Max - 26.0 - 3,010 fps

So if you tested 24gr and got the same, or MORE velocity than the data shows; that tells you that your powder is burning faster than what was tested. Meaning YOUR load of 24gr is developing more pressure than what was tested. So your lot of powder, doesn't have 24gr as a "starting load", in your setup.
 
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That much flow back into the FP channel and the lack of high pressure flow into the pocket tells the whole story IMO. No doubt about it, that bolt face need a bushing.


SMOA
 

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Discussion Starter #16
Great photos by the way and far better information that we usually get when trying to guess a problem. What kind of primers? Sorry if I missed that.
They are CCI 400's. I'll try to get a read on the firing pin hole/clearance.

My current plan is to pull these loads and create a new ladder from 24.5 to 25.5 using the CCI BR4. Now that I know what I am looking for I can stop before I pierce another.

The thing that still puzzles me is that of the 8 rounds I fired at 25.5 gr, none of them have significant extrusion.

The only thing I've found with the rifle is that when I decock the firing pin by turning the bolt carrier by hand the firing pin doesn't drop all the way to the dry-fire stop but stops a hair short. If I push it it will fall to the point that the pin is fully extending into the bolt.

Is it possible that there is a problem/dirt/whatever in the bolt carrier that is stopping the firing pin short?

BTW - I love this forum. I'm sure I'm screwing up but folks are too nice to come right out and say so.
 

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Since you obviously have some camera skills and nice equipment, maybe you could carefully remove that primer, take it apart and clean, and post a pic of the inside.

I found it very interesting when I did that. Gives you a good idea of what is going on.

To measure the pin hole in the bolt head, a pin gage works best, I had a friend who works in a machine shop measure mine. Or you could make a cast of it with some epoxy, and measure that. But I'm pretty sure you have a fit issue.

I was getting the same kind of cratering at low pressures until I changed the pin out with a tighter fitting one.
 

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They are CCI 400's. I'll try to get a read on the firing pin hole/clearance.

My current plan is to pull these loads and create a new ladder from 24.5 to 25.5 using the CCI BR4. Now that I know what I am looking for I can stop before I pierce another.

The thing that still puzzles me is that of the 8 rounds I fired at 25.5 gr, none of them have significant extrusion.

The only thing I've found with the rifle is that when I decock the firing pin by turning the bolt carrier by hand the firing pin doesn't drop all the way to the dry-fire stop but stops a hair short. If I push it it will fall to the point that the pin is fully extending into the bolt.

Is it possible that there is a problem/dirt/whatever in the bolt carrier that is stopping the firing pin short?

BTW - I love this forum. I'm sure I'm screwing up but folks are too nice to come right out and say so.
You are not screwing up , the opposite in fact .
You are learning how to fix the problem with your gun which sounds like it is some one elses screw up.
This forum is full of great people.
 

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Discussion Starter #20 (Edited)
I've managed to measure the hole in the bolt. It was easy once I realized that the extrusion on the primer was a perfect sample of the hole.

The firing pin measures 2.02 mm and the hole measures 2.05 mm. (It's a Vanguard/Howa so metric seems in order.)

I also measured the firing spring force at 70.3 Newtons (15.8 lbs.) and protrusion at 1.46mm (0.0575 in)

The hole in the firing pin isn't perfectly symmetric - eroded? So the gap isn't uniform.

 
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