Short primers

[hk940]

Mar 24, 2019 New
I have been reloading 6ppc for my self and a good friend of mine for over 25 years, with no problem.
Recently he got a rail gun and had some local guy make up some loads for him (I live over 800 miles away now).
This guy made up three different loads and told my friend to shoot them and let him know what shot the best.
After deciding on the best load the guy made up a box of 50.
14 of the fifty did not fire; it appeared the primers were low in the primer pocket.
My friend sent me the 50 rounds and when I deprimed the fired cases the primers were .122" tall, when I pulled the heads and deprimed the unfired rounds the primers were only .114" tall!
Has any one ever seen this before?
My next question is the load was 28.2 g of LT-32 with a 64g bullet (I don't know the brand) I could see some cratering on the fired primers so I think it might have been a little hot.
I did pick up a pound of LT-32 last week ($48.00 with tax).
I don't have 64 gr heads only 68gr Berger’s. Would a load of 27.2 gr of LT-32 behind a 68 gr Berger be safe?
I don't usually load for a gun I don't have in hand.
The cases are Lapua .220 Russian converted to 6ppc









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[itchyTF]

Was the edge of the anvil sitting above the primer cup?

 

[divingin]

I don't have 64 gr heads only 68gr Berger’s. Would a load of 27.2 gr of LT-32 behind a 68 gr Berger be safe?

GRT comes up with about 47K psi and a muzzle velocity of 3093fps. Sounds reasonable to me. The LT-32 data is new and experimental so take that with a grain of salt. They list max pressure as 58740 psi.

I don't shoot 6PPC, but run 6 BR with 30gn LT-32 and a 64 or 66 FBHP; gets about 3400 fps; no pressure signs.

 

[hk940]

Was the edge of the anvil sitting above the primer cup?

Wouldn't that make the primer taller? It says this post was made at 11:57AM. What is the off set for local time?

 

[itchyTF]

Wouldn't that make the primer taller? It says this post was made at 11:57AM. What is the off set for local time?

This is a Winchester LR primer that measures .130”. You can see the anvil sitting above the cup. My thought was if there was less (or no) priming compound the anvil would sit lower thereby measuring less and sitting deeper in the primer pocket.


Your measurement of .122 for a fired case, did that include any cratering around the indent?

 

[Ray123]

Seated primers will be thinner in height than unseated primers, as the anvil is pushed down toward the bottom of the cup slightly crushing the mixture arming the primer so the mixture will explode when hit with the firing pin. Like a .120" thick unseated primer, seated in the case then decapped and then remeasured will be thinner in the. 116" area. Unseated Primers tend to vary in height....Small Rifle were Rem 7.5 average .122" CCI Br4 up to .124" . Small pistol were .117" to .120" depending on brand.
Could check cup thicknesses to make sure they are not pistol primers, as they have a cup thickness less than the BR 4. Seating the primer to the bottom of the cartridge primer pocket is important as firing pin spring energy will be wasted pushing an improperly seated primer to the bottom and sometimes not enough energy to
fire the cartridge....and sometimes they will fire on the 2nd attempt.

 

[White Eagle]

he may have substituted pistol primers instead of using rifle primers
just a thought

 

[kiwijohn]

My first thought was pistol primers too.

 

[Bronsin]

The primer may have been seated hard enough to crack the pellet or break the anvil. Pistol primers are certainly a possibility too.

I shoot LT-32 in my 6PPC, and my loads aren't light. Using CCI450's, .004 jump, and .003 neck clearance, my rifle likes 28.9 to 29.3grs with a 68gr bullet.

 

[BoydAllen]

Mar 24, 2019 New
I have been reloading 6ppc for my self and a good friend of mine for over 25 years, with no problem.
Recently he got a rail gun and had some local guy make up some loads for him (I live over 800 miles away now).
This guy made up three different loads and told my friend to shoot them and let him know what shot the best.
After deciding on the best load the guy made up a box of 50.
14 of the fifty did not fire; it appeared the primers were low in the primer pocket.
My friend sent me the 50 rounds and when I deprimed the fired cases the primers were .122" tall, when I pulled the heads and deprimed the unfired rounds the primers were only .114" tall!
Has any one ever seen this before?
My next question is the load was 28.2 g of LT-32 with a 64g bullet (I don't know the brand) I could see some cratering on the fired primers so I think it might have been a little hot.
I did pick up a pound of LT-32 last week ($48.00 with tax).
I don't have 64 gr heads only 68gr Berger’s. Would a load of 27.2 gr of LT-32 behind a 68 gr Berger be safe?
I don't usually load for a gun I don't have in hand.
The cases are Lapua .220 Russian converted to 6ppc



Normal firing pin protrusion is around .055 which should be able to easily reach any primer. My conclusion is that something else was going on. As to the difference in primer height, when primers are seated by feel to bottom, which is the common method in the world of PPC, the anvil compresses the pellet and when you remove an unfired primer it is always going to measure shorter than before it was seated. On an action where you can measure down from the back of the shroud to the back of the cocking piece, take that measurement in fired position on an empty chamber and then after firing a live round or primed case, before you lift the bolt. Let us know what you find, and what you concludes stops the firing pin's forward travel when firing a live round. Some time back I spoke with a CCI technician, asking him what their recommendation for primer seating is. He told me that they recommend seating them so that the anvil is flush with the bottom of the cup, which in my experience takes a fair amount of pressure when using a hand priming tool. Recently, I took a look at a primer that had been seated with my normal solidly bottomed by feel method. I found that in order to really determine if the anvil was all the way flush required putting the primer in my dial caliper as if measuring its height, and using 20X magnification with good light. While close, My primer was minutely short of the the manufacturer's specification.






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[hk940]

I am not able to take any measurements on the gun as it is 800 miles away. These rounds were loaded by a person who's whereabouts are unknown at this time (might even be dead).
At first I thought about the pistol vs rifle primer but aren't they the same height?
My depth mike's rod will not fit the primer pocket hole, so I am stuck using my Starrett dial vernier.
I never thought about looking at the anvil before firing and checking it after firing.
Looks like I have a weekend project!

 

[Bronsin]

What depth mic do you have? My Brown and Sharpe fits fine.

 

[fkimble@charter.net]

LP primers are shorter than LR primers. Once primers are seated the anvil is preloaded, reducing the amount the anvil is proud and they will measure less. If shoulder is pushed back too much, primers will not fire. Combinations add up fast. Sounds like maybe he ran out of LR an substituted LP!

Frank