Primer piercing causes

[Hengehold]

I would like to know what can be the root cause of pierced primers.

I pierced two primers today and two more had primer flow back into the firing pin hole. I can feel it raised up over the rest of the primer. I was doing load development in a new-to-me cartridge.
Day 1: I shot about 40 rds with this load, the temp was 70 degrees outside. No primer or pressure signs on any of the cases.
Day 2: I shot 25 more rds of the same load when it was 40 degrees. I pierced two primers (see pic) and two additional cases had primer metal flowing into the firing pin hole (see second pic). No additional signs of pressure were experienced (no sticky bolt lift, no ejector swipe on the brass, primer pockets are still tight after day 1, etc)

Cartridge specs:
-223 Rem,
-Starline 5.56 brass,
-Fed 205M,
-25.0gr of N150,
-90gr Sierra SMK (naked).
-Loaded rd NK has .004” clearance on either side.
-Brass times fired: 2, 3, & 4 times fired, segregated into separate lots.
-OAL without comparator: 2.620”
-Muzzle velocity: 2790

I believe the primer issues are from something other than excessive pressure. Although, I acknowledge that I am toeing the line for max pressure. Maybe someone can check my chamber pressure with quick load?

2. The only other cause of pierced primers that I am aware of is excessive space in firing pin hole.

Action specs: (Pierce, Rem700 clone). I have only fired 150 rds through the action so can’t say if this a trend associated with the action yet.
Barrel: 32”

I am thinking the root cause of the primer piercing is due to excessive space in the firing pin hole and not pressure. Am I wrong? Is there another causal factor that I am not aware of?

-Trevor

 

[kyotekiller25]

Need the bolt/firing pin bushed.

Unless the Pierce already comes with the smaller firing pin? Usually it's around .060" I believe.

It's a super common issue with R700s. I had the same issue with my R700 223 Wylde build. After I had the bolt bushed, it completely went away.

 

[ELR LVR]

Only time I had it happen was when I used a Rem 6-1/2 primer instead of a Rem 7-1/2
6-1/2 cups are too thin for anything over 222
1. Thin primer cups
2. Excess charge - high pressure
I am seeing primer flow / primer cratering on your primers
Pressures are too high , bump the load down AT LEAST 1 grain
Notice the edge of the primer indentation from the firing pin
The rim has a crater like a meteor hit
Bump your charge down until it not longer shows a crater at the rim
SMK 90 is a Big bullet for 223
That charge weight (25.0) may be good for lighter bullets , maybe not good for 90 SMK
3. Too much clearance between firing pin hole and firing pin
A bushing wont cure excess pressures,

Here's a pic showing no Cratering
I just looked at a 7mm Rem Mag Brass that the indent looked like this one, smooth round dimple
No Crater Rim
Make Sense?

 

[jelenko]

GRT says the pressure is 57.5K. But, that's without actual data from your rifle.

 

[big5ifty]

I would like to know what can be the root cause of pierced primers.

The root cause of pierced primers is pressure.

Pin clearance and pin protrusion may aggravate the situation. Primer type is only a factor if you're using the completely wrong primer.

In your case, to eliminate pressure as the cause, measure.

Take virgin brass, measure the diameter of the base just ahead of the extractor groove. Then do the same with the same case, fired. There will be a difference, measuring with a 1/10,000 micrometer.

You already have fired brass, and hopefully you still have virgin brass from the same batch. Measure, you will see a trend.

If the difference is 1 or 2/10,000 or less, there is no pressure issue. The cause is something else.

 

[Straightshooter1]

I would like to know what can be the root cause of pierced primers.

I pierced two primers today and two more had primer flow back into the firing pin hole. I can feel it raised up over the rest of the primer. I was doing load development in a new-to-me cartridge.
Day 1: I shot about 40 rds with this load, the temp was 70 degrees outside. No primer or pressure signs on any of the cases.
Day 2: I shot 25 more rds of the same load when it was 40 degrees. I pierced two primers (see pic) and two additional cases had primer metal flowing into the firing pin hole (see second pic). No additional signs of pressure were experienced (no sticky bolt lift, no ejector swipe on the brass, primer pockets are still tight after day 1, etc)

Cartridge specs:
-223 Rem,
-Starline 5.56 brass,
-Fed 205M,
-25.0gr of N150,
-90gr Sierra SMK (naked).
-Loaded rd NK has .004” clearance on either side.
-Brass times fired: 2, 3, & 4 times fired, segregated into separate lots.
-OAL without comparator: 2.620”
-Muzzle velocity: 2790

I believe the primer issues are from something other than excessive pressure. Maybe someone can check my chamber pressure with quick load?

2. The only other cause of pierced primers that I am aware of is excessive space in firing pin hole.

Action specs: (Pierce, Rem700 clone). I have only fired 150 rds through the action so can’t say if this a trend associated with the action yet.
Barrel: 32”

I am thinking the root cause of the primer piercing is due to excessive space in the firing pin hole and not pressure. Am I wrong? Is there another causal factor that I am not aware of?

-Trevor

My QuickLoad is showing you're under max pressure by ~ 3,500 psi, though the case fill appears to be over 100%.

In addition to having excess space in the firing pin hole and the 205M primers that aren't quite as robust as some others, you might want to try other primers like the Rem 7 1/2's or the CCI BR4's, or the CCi 450's before having your bolt bushed to see if that helps.

 

[ELR LVR]

The root cause of pierced primers is pressure.

Pin clearance and pin protrusion may aggravate the situation. Primer type is only a factor if you're using the completely wrong primer.

In your case, to eliminate pressure as the cause, measure.

Take virgin brass, measure the diameter of the base just ahead of the extractor groove. Then do the same with the same case, fired. There will be a difference, measuring with a 1/10,000 micrometer.

You already have fired brass, and hopefully you still have virgin brass from the same batch. Measure, you will see a trend.

If the difference is 1 or 2/10,000 or less, there is no pressure issue. The cause is something else.

Def measure your case at the .200" line to gauge for case head swelling
this is part of reading pressure signs
as well as primer condition after firing
----------------------------------------------
Some computer program can SAY you are within pressure limits but cannot take into account all real world factors such as barrel condition, barrel length, suppressor etc etc etc
Read pressure signs of your case also to be more certain

measuring the base diameter tells you the strength and elastic limits of the brand of case you are using and how much pressure it can take.
Primer cratering is the first sign of over pressure
As well as Ejector marks on the rim of the case head - Look for the round mark from the ejector pin being printed on the brass.
Swelling coupled with primer cratering = Def. over pressure
----------------------------------------------

 

[Hengehold]

The root cause of pierced primers is pressure.

Pin clearance and pin protrusion may aggravate the situation. Primer type is only a factor if you're using the completely wrong primer.

In your case, to eliminate pressure as the cause, measure.

Take virgin brass, measure the diameter of the base just ahead of the extractor groove. Then do the same with the same case, fired. There will be a difference, measuring with a 1/10,000 micrometer.

You already have fired brass, and hopefully you still have virgin brass from the same batch. Measure, you will see a trend.

If the difference is 1 or 2/10,000 or less, there is no pressure issue. The cause is something else.

I did measure the base of the case immediately above the rim groove on the first firing when conducting a pressure test ladder and there was an increase of 0.001” on all cases at all charges.

I did not have any reference to tell me how much growth is too much. Consequently, I continued with loading and paying attention to primer seating force needed after each firing.
Where is the threshold between safe pressure and over-pressure?

You provide a value of .0001-.0002 of movement is max increase in diameter before reaching excess pressure. Where did you get that number from?

 

[NorCalMikie]

How bout an easy fix like the case is "too short" for the chamber?? (brass headspace issue, NOT a chamber problem)
Round goes BANG and being too short, gets slammed back against the bolt face and the primer gets pierced.
Go ahead and spend $$$$ having the firing pin bushed and when that's done and you STILL have the piercing problem, you might consider an easy fix. But it's YOUR $$$ so, do whatever makes YOU happy.

 

[Hengehold]

How bout an easy fix like the case is "too short" for the chamber?? (brass headspace issue, NOT a chamber problem)
Round goes BANG and being too short, gets slammed back against the bolt face and the primer gets pierced.
Go ahead and spend $$$$ having the firing pin bushed and when that's done and you STILL have the piercing problem, you might consider an easy fix. But it's YOUR $$$ so, do whatever makes YOU happy.

Brass is being bumped .002”.

 

[Webster]

I would like to know what can be the root cause of pierced primers.

I pierced two primers today and two more had primer flow back into the firing pin hole. I can feel it raised up over the rest of the primer. I was doing load development in a new-to-me cartridge.
Day 1: I shot about 40 rds with this load, the temp was 70 degrees outside. No primer or pressure signs on any of the cases.
Day 2: I shot 25 more rds of the same load when it was 40 degrees. I pierced two primers (see pic) and two additional cases had primer metal flowing into the firing pin hole (see second pic). No additional signs of pressure were experienced (no sticky bolt lift, no ejector swipe on the brass, primer pockets are still tight after day 1, etc)

Cartridge specs:
-223 Rem,
-Starline 5.56 brass,
-Fed 205M,
-25.0gr of N150,
-90gr Sierra SMK (naked).
-Loaded rd NK has .004” clearance on either side.
-Brass times fired: 2, 3, & 4 times fired, segregated into separate lots.
-OAL without comparator: 2.620”
-Muzzle velocity: 2790

I believe the primer issues are from something other than excessive pressure. Maybe someone can check my chamber pressure with quick load?

2. The only other cause of pierced primers that I am aware of is excessive space in firing pin hole.

Action specs: (Pierce, Rem700 clone). I have only fired 150 rds through the action so can’t say if this a trend associated with the action yet.
Barrel: 32”

I am thinking the root cause of the primer piercing is due to excessive space in the firing pin hole and not pressure. Am I wrong? Is there another causal factor that I am not aware of?

-Trevor

Where did you get your reloading data from? Without seeing published loading data for your bullet and powder I would guess your way to hot. You never did the obvious, back off on the powder charge.

 

[Laurie]

@Hengehold You don't say what chamber your rifle has (and hence the allowable COAL) or what the barrel length is (to put the 2,790 fps MV into context).

My QuickLoad is showing you're under max pressure by ~ 3,500 psi, though the case fill appears to be over 100%.

QL using N150's default powder values produces garbage results on the GIGO principle. Both powder burn charts and QL list this grade as slower burning than turns out in actual applications. (Hence its widespread use as an alternative to VarGet in 308 Win.)

Have a look at my review of four Viht powders in the 223 with the 77gn SMK seated out in a chamber whose freebore is a little shorter than that from PT&G's '223 ISSF'.

https://www.targetshooter.co.uk/?p=3856

QL calculated 2,962 fps (30-inch barrel) from 26.0gn N150 at 54,442 psi PMax. Actual MV was 3,083 fps which the program says needs 63,959 psi with my components and set-up. Actuals vs prediction ran as:

23.4 gn N150 ................ + 140 fps

24.2 gn N150 ................ + 115 fps

25.0 gn N150 ................. + 126 fps

25.4 gn N150 ................ + 121 fps

25.7 gn N150 ................ + 122 fps

IME, N150 is rather too bulky for even the heaviest / longest bullets in 223. Years back when my 223 for set up for long-distance FTR using the 90gn Berger VLD and with an appropriate throat length (ca. quarter-inch freebore) I had a short-range Berger 90gn LRBT N150 load which gave superb precision, but low MVs. Even in the original Lapua 'Match 223' case which is higher-capacity than current lots (and probably more than Starline cases), this was a full-case charge.

 

[Hengehold]

Where did you get your reloading data from? Without seeing published loading data for your bullet and powder I would guess your way to hot. You never did the obvious, back off on the powder charge.

The throat is cut really long to accommodate for the 90gr bullets.

I am using load data from successful competitive shooters that I know that have similar chamber specs.

 

[William Vogel]

The throat is cut really long to accommodate for the 90gr bullets.

I am using load data from successful competitive shooters that I know that have similar chamber specs.

It’s unfortunate but you’ll have to bush the bolt face and reduce the firing pin diameter to 0.0625 once the primer piercing has begun. The erosion of the firing pin hole and firing pin progresses very quickly as each piercing event occurs. I don’t understand why the erosion is so aggressive here vs in the barrel throat but maybe it’s the velocity of the hot gasses through an orifice. I’ve had to bush my bolt faces. You’ll never be satisfied with the performance of the rifle again until you have it fixed because you never know when it’s going to happen again until it does and it creates an uneasy feeling every trigger squeeze. Once it’s fixed, the fired primers look beautiful and you can use regular primers again if you choose. Just my experience.

 

[Coyotefurharvester]

Why are you bumping 0.002? Or should ask why are you bumping?

 

[Hengehold]

@Hengehold You don't say what chamber your rifle has (and hence the allowable COAL) or what the barrel length is (to put the 2,790 fps MV into context).



QL using N150's default powder values produces garbage results on the GIGO principle. Both powder burn charts and QL list this grade as slower burning than turns out in actual applications. (Hence its widespread use as an alternative to VarGet in 308 Win.)

Have a look at my review of four Viht powders in the 223 with the 77gn SMK seated out in a chamber whose freebore is a little shorter than that from PT&G's '223 ISSF'.

https://www.targetshooter.co.uk/?p=3856

QL calculated 2,962 fps (30-inch barrel) from 26.0gn N150 at 54,442 psi PMax. Actual MV was 3,083 fps which the program says needs 63,959 psi with my components and set-up. Actuals vs prediction ran as:

23.4 gn N150 ................ + 140 fps

24.2 gn N150 ................ + 115 fps

25.0 gn N150 ................. + 126 fps

25.4 gn N150 ................ + 121 fps

25.7 gn N150 ................ + 122 fps

IME, N150 is rather too bulky for even the heaviest / longest bullets in 223. Years back when my 223 for set up for long-distance FTR using the 90gn Berger VLD and with an appropriate throat length (ca. quarter-inch freebore) I had a short-range Berger 90gn LRBT N150 load which gave superb precision, but low MVs. Even in the original Lapua 'Match 223' case which is higher-capacity than current lots (and probably more than Starline cases), this was a full-case charge.

Laurie,
Thank you for the detailed response.

Chamber reamer used is the Manson 223 Rem Fullbore T15. Throat length is advertised to be .195 inches.

Barrel length is 32 inches.

 

[charlie b]

FWIW, I've had two rifles that made craters even on lighter loads with magnum primers (Rem 7 1/2 and CCI). Yes, bushing the FP hole would probably prevent it. One of those rifles has over 6000 rounds through it with no mishaps, and it has cratered primers since the first shots (with factory loads). I usually load one node below book max.

I have pierced primers with it, due to inadvertently using small pistol primers instead of small rifle.

Have had the same issue with a couple 9mm pistols.

 

[Hengehold]

View attachment 1705941View attachment 1705942

Thanks for the published data. I appreciate you sharing it. There is something that stands out to me.

My COL is 2.620.
VV COL is 2.354.
Sierra COL is 2.430

Since my throat is .200-.300” longer than the load manual, I can presume than my chamber pressure is lower.

How much lower? I have no idea. This is why I am using some guidance from others with similar throat dimensions.

I am hoping that someone can assist with the chamber pressure estimation through the use of a ballistic software such as quickload or something else.

 

[mgunderson]

Question. Does the starline 556 brass have the larger diameter hole in the primer pocket like the starline 223 brass. Just curious. A larger hole might suggest a brass change to a small hole might help.

A second thought. Take a really good look at the tip of the firing pin. And look for wear. The pin indent looks a little irregular in the pictures. Had that issue with a few firing pins along the way. The irregular shape and can initiate local stretching of the primer cup.

 

[Laurie]

Chamber reamer used is the Manson 223 Rem Fullbore T15. Throat length is advertised to be .195 inches.

Barrel length is 32 inches.

With that chamber and 32-inches, your pressures should be fine at 2,790 fps. Top US FTR competitors run their 90s at 2,800 - 2,850 fps from 30-inch barrels, mostly with VarGet for the lower value and H4895 for the higher (at a cost in case-life though!). The one remaining question mark is Starline 223 case capacity. (I bought some recently to give them a try, but have yet to load and fire any, so don't have the fireformed-case 'water overflow capacity' yet to compare to Norma or Lapua 223. Their case weights are however relatively low which usually results in greater internal capacity.)

So, it looks like it may be a primer cup toughness allied to firing pin diameter and its clearance in the bolt face issue. Although Federal says its 205/205M 22.5 thou' thick cups are NATO standard, every other maker uses heavier 25 thou' cups for higher pressure applications. My own limited experience of the F205M is that is much more robust than thin Rem 6 1/2 / CCI-400 models, but not as tough as CCI-450/BR4s and (maybe) the Rem 7 1/2BR. So, before exploring firing pin turning / bolt bushing, I'd at least try one of them with your existing load.

There is a great deal of information about long-range 223 / 90gn FTR loads on the forum. Do a search of '223 90gn FTR' and also of @Ned Ludd who is a prolific source of good information on this combination on the forum.

Since my throat is .200-.300” longer than the load manual, I can presume than my chamber pressure is lower.

How much lower?

A huge amount! That's why Dave Kiff at PT&G and Manson produce the 223 ISSF and T15 respectively to accommodate 90s seated right out.

As an example of the difference between loads for the 90gn SMK provided by Vihtavuori and Sierra at their short COALs based on CIP and SAAMI standard 223 Rem chambers (25 thou' throat in the latter case) and your throat giving a 2.620-inch COAL, I ran QuickLOAD for Sierra 6th Ed manual's 2.43-inch COAL and H. VarGet in a 30.5 gn water capacity case (what Lapua comes out at with my minimum-SAAMI match chamber) in a 32-inch barrel. And then again at 2.620-inch. (Unlike N150, QuickLOAD's default powder values are pretty good for 223 and heavy bullets, and this is probably the favourite powder for the application anyway on your side of the Atlantic.)

2.43-inch COAL ....................... 23.3gn: 55,243 psi / 2,785 fps

Run that combination in your T15 chamber at 2.620-inch COAL, and the 23.3gn charge is calculated to produce 46,892 psi / 2,703 fps.

Using the pressure reduction produced by the long throat (not to forget the extra room in the case for powder below the bullet, and the charge increases to:

2.62-inch COAL ....................... 24.6gn: 54,770 psi / 2,827 fps

This is of course just a computer model and the usual caveats apply, but I'd reckon the PMax / MV differences won't be far out. @Ned Ludd may care to comment as he has considerable experience with actual loads and MVs for this powder and 90s in long throated chambers.