strange possibly over pressure sign

georgehwbush · March 17, 2024, 08:21 PM

yes i hand load. this is the first time i have ever seen pierced primers.

was trying a new powder in the 243 "hoping for a little more speed".
loaded well within safe starting charge, and first shot; pierced primer.
there were no other visable signs the primer cup is not flattened the case head has no marks... easy eject... i'm stumped.

second shot pierced primer. same thing....

third shot no fire. take the gun apart and remove the primer peaces from the firing pin hole...

could it be the primer cup is brittle ? they were imported from the cheepest sourse in the world...
thoughts ?

NH15-45 · March 18, 2024, 04:53 AM

Had you used these primers before with good results or are they part of the "new powder" recipe?

mehavey · March 18, 2024, 05:38 AM

and please give us the load...
- Actual bullet, it's weight,
- Powder, it's weight
- Overall length when loaded
- The primer manufacturer

HiBC · March 18, 2024, 06:38 AM

Check your bench trash can for your primer package.
I don't know for sure that you used pistol primers, but I'll just about guarantee
if you load pistol primers a .243 you will get the same results.

FWIW , the hot, high pressure gas will very quickly erode the firing pin tip and firing pin hole in the bolt face.

I suggest pulling the bullets rather than shooting them up.

tangolima · March 18, 2024, 11:21 AM

Recheck brass sizing to make sure there is no excessive head clearance.

Inspect firing pin head profile. It should be smooth hemisphere without any sharp points/edges.

Check firing pin fit in the hole. It should be good slip fit. Any slop there allows room for the brass to flow. My cheap ar-10 had that problem. The bolt has over sized hole. Bought another bolt from a friend and problem solved.

-TL

Sent from my SM-N960U using Tapatalk

georgehwbush · March 18, 2024, 08:01 PM

NH15-45 i had used one box of them before but these were the first out of this box.

HiBC: the outer container (box of 1000) says large rifle but the inner sleeves (100 count) are just plain white sleeve no writing.

tangolima: yes this is that cheap ar-10, that could be something to check indeed.

as per mehavey: ladder testing, hodgdon hybrid 100V, with SMK-107's,
winchester cases, and these cheap china white box large rifle primers.

charge weights: 38.7 40.1 40.5 40.9 41.1 41.3 41.5

only fired the first batch because the primers were being a pain.

georgehwbush · March 18, 2024, 08:03 PM

also of note. the velocities were only in the 2700-2730 range.

georgehwbush · March 18, 2024, 08:04 PM

i had a few cci-200 primers left i'll test them at about 40gr powder and see what they do.

mehavey · March 18, 2024, 08:10 PM

Betcha: Bad primers.

FrankenMauser · March 19, 2024, 12:14 AM

I had, and unfortunately still have the majority of, a batch of Winchester primers that had brittle cups.
But it sounds like you have questionable primers in a questionable rifle.

Assess the rifle and try different primers first.
(If those primers are Chinese, they're probably corrosive, btw. Clean your gun as you would for corrosive ammo.)

stagpanther · March 19, 2024, 07:07 AM

Inertia/weight of the firing pin strike is enough by itself to cause pierced primers. I think you mentioned before you had issues with the carrier set-up on this particular rifle. I recommend you take a look at JP Enterprises enhanced and enhanced high pressure bolts.

tangolima · March 19, 2024, 02:46 PM

I have been dealing with this issue on AR-15/ar-10 platform, mostly related to budget parts. The bolt hole is machined oversized, and the bolt is expensive. Have been trying to find firing pins that have thicker tip. But they are stubbornly elusive. Please let me know if there are sources for such firing pins.

I have thought about retipping the firing pin. I have done that many times for old guns with worn firing pin hole. But I need more desperation to kick start the action.

Actually such issue doesn't seem that uncommon. A lot of once fired brass I have picked up have cratered primers.

-TL

Sent from my SM-N960U using Tapatalk

FrankenMauser · March 19, 2024, 03:26 PM

tangolima,
Why not bush the bolt, instead of searching for a mythical fat firing pin?

tangolima · March 19, 2024, 04:28 PM

Bushing is certainly an option. But I tend not to put it to the front. Bolt is expensive. It hurts if I screw up. The steel is hardened. It could be difficult to machine. Annealing is not preferable as it requires proper rehardening.

-TL

Sent from my SM-N960U using Tapatalk

gwpercle · March 19, 2024, 05:14 PM

Before you do anything ... if the load is not excessive ...
Try some new and better primers ... could be a batch of primers with thin cups or that maker just uses thin metal cups to save money .

Way back in the stone age Alcan sold primers and powder branded S&W ... most of the primers were OK ... but one lot of small pistol primers were bad about piercing primers on firing ... I'm talking a 38 special - 148 gr. WC - 2.7 grs. Bullseye load ... not excessive in the least but the primers would pierce 3 out of 5 ... they were just poor primers with thin cup metal ... they all fired but it just didn't look right !
Changed to CCI and never any problems ... check the primers first !
Gary

stagpanther · March 20, 2024, 04:01 AM

Quote:

NH15-45

Made by whom?

tangolima · March 20, 2024, 11:53 AM

I took a quick stock of what I have. Here are a few figures to illustrate the point.

AR-15
Bolt A, hole diameter 0.063"
Firing pin 1, tip diameter 0.058"
Firing pin 2, 0.060"

Bolt A + pin 1: shallow crater at mid range loads.

Bolt A + pin 2: ok

I believe the hole is supposed to be 0.060". Bolt A + pin 2 came with a budget complete upper. I managed to find pin 2 to make it work.

AR-10
Bolt B, 0.084"
Bolt C, 0.080"
Pin 3, 0.075"
Pin 4, 0.077"

Bolt B + pin 3 came with a budget complete upper. It craters primer event at minimum loads. Pierced primers when close to max load.

Bolt B + pin 4 is better but still not kosher.

Bolt C is the one I bought from friend. It work well with pin 4.

The hole is probably spec'd to 0.080".

The pin / hole fit must be <0.005", better <0.003", best 0.

-TL

PS. I just keep buying cheap steel firing pins of different brands whenever I order parts. Sometimes I get lucky and get one with thicker tip.

Sent from my SM-N960U using Tapatalk

**44 AMP** · March 20, 2024, 12:55 PM

Do you have a firing pin protrusion gauge? If you have one, do you use it??

I don't know if there is one for the AR 10, but there ought to be, as there is one for the AR 15 and it was part of the small arms repairman's kit. Min/max firing pin protrusion for the M16 rifle series.

Too much firing pin sticking out can cause pierced primers. Not saying this is the cause of you problem, only that it could be, and if you don't measure it, you don't know if it can be ruled out.

tangolima · March 20, 2024, 01:22 PM

I just measure the protrusion with the tail of caliper.

-TL

Sent from my SM-N960U using Tapatalk

georgehwbush · March 20, 2024, 03:35 PM

while we are measuring things anyone know where a full set o specs for the ar-10/15 are posted? i would like to know what i'm looking for on things like firing pen protrusion or diameters ...

tangolima · March 20, 2024, 04:04 PM

Or even better, the complete drawings of all the parts.

I have been using the "universal equation" for protrusion.

P=0.5*D+0.01"

where D is the pin diameter.

The actual spec may deviate slightly. 0.04" for AR-15, and 0.05" for AR-10.

-TL

Sent from my SM-N960U using Tapatalk

mehavey · March 20, 2024, 05:10 PM

See:
https://www.ar15.com/forums/AR-15/Fi...2311/#i8248119

Bottom Line: 0.055" - 0.060"

georgehwbush · March 21, 2024, 06:40 PM

well i got around to taking the ar-10 apart and measuring pin protrusion, and checking for slack in the pin / hole fit. nothing out of the normal, and all within specs.

i think the powder was hot, (110F) that would raise the pressure a bit, but still a safe load. and the primer cups are thin. that's what i think it is. when i can find some cci-200's for sale i'll continue with that load development. thanks to one and all, for the input.

March 17, 2024, 08:21 PM	#1
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	strange possibly over pressure sign yes i hand load. this is the first time i have ever seen pierced primers. was trying a new powder in the 243 "hoping for a little more speed". loaded well within safe starting charge, and first shot; pierced primer. there were no other visable signs the primer cup is not flattened the case head has no marks... easy eject... i'm stumped. second shot pierced primer. same thing.... third shot no fire. take the gun apart and remove the primer peaces from the firing pin hole... could it be the primer cup is brittle ? they were imported from the cheepest sourse in the world... thoughts ?

March 19, 2024, 12:14 AM	#10
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,427	I had, and unfortunately still have the majority of, a batch of Winchester primers that had brittle cups. But it sounds like you have questionable primers in a questionable rifle. Assess the rifle and try different primers first. (If those primers are Chinese, they're probably corrosive, btw. Clean your gun as you would for corrosive ammo.) __________________ Don't even try it. It's even worse than the internet would lead you to believe.

March 19, 2024, 07:07 AM	#11
stagpanther Senior Member Join Date: March 2, 2014 Posts: 11,813	Inertia/weight of the firing pin strike is enough by itself to cause pierced primers. I think you mentioned before you had issues with the carrier set-up on this particular rifle. I recommend you take a look at JP Enterprises enhanced and enhanced high pressure bolts. __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!*

March 19, 2024, 03:26 PM	#13
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,427	tangolima, Why not bush the bolt, instead of searching for a mythical fat firing pin? __________________ Don't even try it. It's even worse than the internet would lead you to believe.

March 20, 2024, 12:55 PM	#18
44 AMP Staff Join Date: March 11, 2006 Location: Upper US Posts: 28,871	Do you have a firing pin protrusion gauge? If you have one, do you use it?? I don't know if there is one for the AR 10, but there ought to be, as there is one for the AR 15 and it was part of the small arms repairman's kit. Min/max firing pin protrusion for the M16 rifle series. Too much firing pin sticking out can cause pierced primers. Not saying this is the cause of you problem, only that it could be, and if you don't measure it, you don't know if it can be ruled out. __________________ All else being equal (and it almost never is) bigger bullets tend to work better.

March 18, 2024, 04:53 AM	#2
NH15-45 Member Join Date: April 15, 2018 Posts: 15	Had you used these primers before with good results or are they part of the "new powder" recipe?

March 18, 2024, 05:38 AM	#3
mehavey Senior Member Join Date: June 17, 2010 Location: Virginia Posts: 6,903	and please give us the load... - Actual bullet, it's weight, - Powder, it's weight - Overall length when loaded - The primer manufacturer

March 18, 2024, 06:38 AM	#4
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,289	Check your bench trash can for your primer package. I don't know for sure that you used pistol primers, but I'll just about guarantee if you load pistol primers a .243 you will get the same results. FWIW , the hot, high pressure gas will very quickly erode the firing pin tip and firing pin hole in the bolt face. I suggest pulling the bullets rather than shooting them up.

March 18, 2024, 11:21 AM	#5
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,839	Recheck brass sizing to make sure there is no excessive head clearance. Inspect firing pin head profile. It should be smooth hemisphere without any sharp points/edges. Check firing pin fit in the hole. It should be good slip fit. Any slop there allows room for the brass to flow. My cheap ar-10 had that problem. The bolt has over sized hole. Bought another bolt from a friend and problem solved. -TL Sent from my SM-N960U using Tapatalk

March 18, 2024, 08:01 PM	#6
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	NH15-45 i had used one box of them before but these were the first out of this box. HiBC: the outer container (box of 1000) says large rifle but the inner sleeves (100 count) are just plain white sleeve no writing. tangolima: yes this is that cheap ar-10, that could be something to check indeed. as per mehavey: ladder testing, hodgdon hybrid 100V, with SMK-107's, winchester cases, and these cheap china white box large rifle primers. charge weights: 38.7 40.1 40.5 40.9 41.1 41.3 41.5 only fired the first batch because the primers were being a pain.

March 18, 2024, 08:03 PM	#7
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	also of note. the velocities were only in the 2700-2730 range.

March 18, 2024, 08:04 PM	#8
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	i had a few cci-200 primers left i'll test them at about 40gr powder and see what they do.

March 18, 2024, 08:10 PM	#9
mehavey Senior Member Join Date: June 17, 2010 Location: Virginia Posts: 6,903	Betcha: Bad primers.

March 19, 2024, 02:46 PM	#12
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,839	I have been dealing with this issue on AR-15/ar-10 platform, mostly related to budget parts. The bolt hole is machined oversized, and the bolt is expensive. Have been trying to find firing pins that have thicker tip. But they are stubbornly elusive. Please let me know if there are sources for such firing pins. I have thought about retipping the firing pin. I have done that many times for old guns with worn firing pin hole. But I need more desperation to kick start the action. Actually such issue doesn't seem that uncommon. A lot of once fired brass I have picked up have cratered primers. -TL Sent from my SM-N960U using Tapatalk

March 19, 2024, 04:28 PM	#14
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,839	Bushing is certainly an option. But I tend not to put it to the front. Bolt is expensive. It hurts if I screw up. The steel is hardened. It could be difficult to machine. Annealing is not preferable as it requires proper rehardening. -TL Sent from my SM-N960U using Tapatalk

March 19, 2024, 05:14 PM	#15
gwpercle Senior Member Join Date: November 30, 2012 Location: Baton Rouge, Louisiana Posts: 1,752	Before you do anything ... if the load is not excessive ... Try some new and better primers ... could be a batch of primers with thin cups or that maker just uses thin metal cups to save money . Way back in the stone age Alcan sold primers and powder branded S&W ... most of the primers were OK ... but one lot of small pistol primers were bad about piercing primers on firing ... I'm talking a 38 special - 148 gr. WC - 2.7 grs. Bullseye load ... not excessive in the least but the primers would pierce 3 out of 5 ... they were just poor primers with thin cup metal ... they all fired but it just didn't look right ! Changed to CCI and never any problems ... check the primers first ! Gary

March 20, 2024, 11:53 AM	#17
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,839	I took a quick stock of what I have. Here are a few figures to illustrate the point. AR-15 Bolt A, hole diameter 0.063" Firing pin 1, tip diameter 0.058" Firing pin 2, 0.060" Bolt A + pin 1: shallow crater at mid range loads. Bolt A + pin 2: ok I believe the hole is supposed to be 0.060". Bolt A + pin 2 came with a budget complete upper. I managed to find pin 2 to make it work. AR-10 Bolt B, 0.084" Bolt C, 0.080" Pin 3, 0.075" Pin 4, 0.077" Bolt B + pin 3 came with a budget complete upper. It craters primer event at minimum loads. Pierced primers when close to max load. Bolt B + pin 4 is better but still not kosher. Bolt C is the one I bought from friend. It work well with pin 4. The hole is probably spec'd to 0.080". The pin / hole fit must be <0.005", better <0.003", best 0. -TL PS. I just keep buying cheap steel firing pins of different brands whenever I order parts. Sometimes I get lucky and get one with thicker tip. Sent from my SM-N960U using Tapatalk

March 20, 2024, 01:22 PM	#19
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,839	I just measure the protrusion with the tail of caliper. -TL Sent from my SM-N960U using Tapatalk

March 20, 2024, 03:35 PM	#20
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	while we are measuring things anyone know where a full set o specs for the ar-10/15 are posted? i would like to know what i'm looking for on things like firing pen protrusion or diameters ...

March 20, 2024, 04:04 PM	#21
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,839	Or even better, the complete drawings of all the parts. I have been using the "universal equation" for protrusion. P=0.5D+0.01" where D is the pin diameter. The actual spec may deviate slightly. 0.04" for AR-15, and 0.05" for AR-10. -TL Sent from my SM-N960U using Tapatalk Last edited by tangolima; March 20, 2024 at 04:14 PM.*

March 20, 2024, 05:10 PM	#22
mehavey Senior Member Join Date: June 17, 2010 Location: Virginia Posts: 6,903	See: https://www.ar15.com/forums/AR-15/Fi...2311/#i8248119 Bottom Line: 0.055" - 0.060"

March 21, 2024, 06:40 PM	#23
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	well i got around to taking the ar-10 apart and measuring pin protrusion, and checking for slack in the pin / hole fit. nothing out of the normal, and all within specs. i think the powder was hot, (110F) that would raise the pressure a bit, but still a safe load. and the primer cups are thin. that's what i think it is. when i can find some cci-200's for sale i'll continue with that load development. thanks to one and all, for the input.