Light strikes on primers, why?

[jski]

I’ve been reloading for my L-frame
.357 for quite some time. Recently I’ve encountered a problem I’m having trouble diagnosing. The cases are all nickel plated Starline brass. The primers are all CCI small magnum rifle primers.

The primers are seated into the case primer pocket so as to be flush with the case head.

When I try to shoot these cartridges, about 2/3s of the rounds fail to fire. When I examine one of these failed-to-fire cartridges, I notice an light strike on the primer. The rounds that did fire have a much deeper strike. None of which is surprising.

BUT, both rounds have their primers set equally deep into the case pocket. I can’t see anything that would explain why one cartridge primer has a deep strike and the other a shallow, light strike?

Any ideas?

 

[stringnut]

Have you changed any components? Does it happen with other brass? Rifle primers may have a harder cup than pistol primers as they have to withstand much higher pressure. Not sure on that one.

Most likely cause not seating the primers deep enough. Seating flush does not guarantee that the the cup is bottomed and the anvil is supported properly. If anything is not held tightly a primer will not go. It often shows as a light strike as the force of the firing pin is used to drive the primer deeper. Thus there is not enough impact to ignite the priming compound.

 

[forty_caliber]

Have you tried the ammunition in a different weapon of the same caliber? It could be a mechanical problem with the firearm rather than a problem with the ammo. Worn springs, transfer bar out of time, etc.

.40

 

[buck460XVR]

I’ve been reloading for my L-frame
.357 for quite some time. Recently I’ve encountered a problem I’m having trouble diagnosing. The cases are all nickel plated Starline brass. The primers are all CCI small magnum rifle primers.

The primers are seated into the case primer pocket so as to be flush with the case head.

SR primers have a thicker cup than SP primers, so the chance of light strikes will be more prominent. I always seat my primers below flush. Seeing as this is happening so much, there must be a issue. Have you tried to shoot the ammo again? If so, do they fire the second time? Have you checked the strain screw on your 686 to make sure it hasn't loosened up? Is this the first time to use the new brass?

 

[BCR#1]

I would think you're using the wrong primers as other posters have said. Try some Winchester SPP or regular CCI SPP and make sure they're fully seated in the primer pocket.

Bill

 

[Englishmn]

I have had a similar issue with s&w .460 and had to seat primers below flush to get reliable ignition.

 

[drband]

This:

Most likely cause not seating the primers deep enough. Seating flush does not guarantee that the the cup is bottomed and the anvil is supported properly. If anything is not held tightly a primer will not go. It often shows as a light strike as the force of the firing pin is used to drive the primer deeper. Thus there is not enough impact to ignite the priming compound.

Try seating the primers till they totally bottom out.

 

[Walkalong]

I did an informal primer test to look at velocity differences, which were small, with various ones in 9MM, and the pistol(s) failed to set off some of the small rifle primers because of the harder and/or thicker cups.

That said, make sure they are seated to the bottom of the primer pocket.

 

[Blue68f100]

Primers need to be bottomed out in the pocket no matter what the depth is. This is to be done to preload the anvil so they will fire. Unless your cutting the pockets to a specific depth, then you can set them to a distance below flush. And only then will they work consistently.

 

[reddog81]

The deep primer indents on the ones that fired aren’t an accurate representation of the strength in which the firing pin hit the primer. The deep strike on the primer pocket is a result from the cartridge igniting and the case being slammed back against the recoil shield/firing pin.

The same amount of pressure pushing the bullet down the barrel is pushing the brass case back against the recoil shield / exposed firing pin. When this happens the primer is slammed against the firing pin an imparts the deeper impression than the firing pin ever could alone from the force of the mainspring.

Have you verified that the mainspring screw is tightened all the way down?

 

[jski]

I’m using the RCBS primer-er, a.k.a., the RCBS priming tool. The piston the moves up to seat the primer is fully extended. So I’m not sure how I’d place it further into to case pocket?

The is a new 686 but is there a mechanical problem that could account for this?

BTW, From what I gather the CCI small magnum rifle primers and CCI small magnum pistol primers come off the same production line. They are identical.

 

[peels]

BTW, From what I gather the CCI small magnum rifle primers and CCI small magnum pistol primers come off the same production line. They are identical.

This statement sparked my curiosity, so I did a quick Google search on this topic. Based on the first result from the search, that statent may not be true.

Someone posted on a different forum back in 2015, recalling from his notes about a conversation that he had with a cci tech back in 2009, that the cci small pistol magnum primer is in fact the same as the small rifle primer (not magnum), down to the cup thickness, cup hardness, and the amount of primer compound used.

But the notes did not indicate that the small rifle magnum primer is the same as the small pistol magnum primer...if you have a source of information that can shed more info on this topic, can you please share?

 

[243winxb]

Are there any drag marks on the sides of tthe hammer, Where* its rubbing the frame? Their are shims for that. https://www.midwayusa.com/product/1004131353?pid=598967

Try a pistol primer first. Seat with an RCBS Ram Prime Unit.

 

[Texas10mm]

Will they go off if you try a second time?

 

[Herman B]

..reloading for my L-frame .357 ... The primers are all CCI small magnum rifle primers.

Interesting - small magnum rifle primers in a small magnum pistol load.

From what I gather the CCI small magnum rifle primers and CCI small magnum pistol primers come off the same production line. They are identical.

Dimensionally, yes. Chemically/volumetrically? Doubtful. But to your point...

The primers are seated into the case primer pocket so as to be flush with the case head.

No such thing as seating a primer too deep. If a pin can't reach a bottomed primer, pitch the brass with out-of-spec cup.

For safety (slamfire!) and function, seating primers between 0.003" and 0.005" is a good rule of thumb. CCI primers are commonly known to require a harder strike.

I'm not familiar with your priming device but suspect the primers are left high, especially in light of 2/3's failure in a new 686. I bet they go BANG on the second strike...yes?

 

[murf]

The primers are seated into the case primer pocket so as to be flush with the case head

this is the reason for the "hit and miss" primer ignition. primers should always be seated to the bottom of the primer pocket regardless the firearm. even starline cases have variations in primer pocket depth. the reason the fired cases show a "normal" firing pin strike is because the ignition pressure forms the primer cup around the firing pin (the misfires don't do this).

so, try and press those primers all the way to the bottom of the pocket.

luck,

murf

 

[mdi]

That said, make sure they are seated to the bottom of the primer pocket.

As others already mentioned, rifle primers may be your problem. But 90%+ of failures to fire for a newer reloader are from improperly seated primers. Seat all primers all the way to the bottom of the pocket and disregard "below flush measurement". When I started reloading ('69) I took a a primer apart to see how it works. The anvil needs a solid base, no movement allowed, so I seat the primers all the way down so the anvil provided a solid, immovable "anvil". I have had no FTFs from high seated primers since...

 

[jski]

Guys, riddle me this: why would seating the primer some small distance further into the primer pocket result in a deeper strike (from the firing pin) on the aforementioned primer?

 

[ReloaderFred]

Guys, riddle me this: why would seating the primer some small distance further into the primer pocket result in a deeper strike (from the firing pin) on the aforementioned primer?

Because an object that is tight against an immovable object (the bottom of the primer pocket) can't move away from the striking object (the firing pin). A movable object (an improperly seated primer that isn't bottomed out against the bottom of the primer pocket) can move away from the striking object, thus cushioning the blow. That's just part of it.

The other part is what happens when a primer explodes, and yes, it is an explosion when it goes off. The firing pin indents the primer cup, which smashes the primer pellet between the indentation and the properly seated anvil, which can't move, since it's seated against the bottom of the primer pocket. When the priming compound explodes, it pushes the primer back out of the primer pocket, and it's stopped by the back plate/bolt, and pushed onto the firing pin, since this happens in nano-seconds, before the firing pin has time to retract. The pressure from the burning powder, which was ignited by the explosion of the primer pellet, pushed the case back against the back plate/bolt and reseats the primer into the pocket. Then the rest of the stuff happens to get the bullet down the bore.

The bottom line is you have to seat your primers completely, which means below flush, not flush. Look at an unexpended primer sideways and you'll see that the legs of the anvil stick up above the edge of the primer cup a few thousandths of an inch. When properly seated, the legs of the anvil will be flush with the edge of the cup, both of which will be resting on the bottom of the primer pocket.

Hope this helps.

Fred

 

[Herman B]

...why would seating the primer some small distance further into the primer pocket result in a deeper strike (from the firing pin)...

Energy from the pin striking a high primer is absorbed by the primer sliding deeper into the brass cup. Once fully seated/bottomed-out, the primer cup absorbs all pin energy, resulting in a crush against the anvil and a pleasing sound.

That rounds ignite on the second strike is often symptomatic of high primers.

 

[Rule3]

OK lets review:

Why are you using rifle primers?
Do the rounds fire when you do a second strike on them?
If you use Pistol Primers do they work?
Is the main spring screw tight? Have you messed with the spring?
Primers need to be bottomed out so the force of the firing pin ignites it.

 

[9mmepiphany]

Guys, riddle me this: why would seating the primer some small distance further into the primer pocket result in a deeper strike (from the firing pin) on the aforementioned primer?

Re-read the first paragraph of Post #10

 

[9mmepiphany]

The primers are seated into the case primer pocket so as to be flush with the case head.

Seated Flush might be part of the problem. Primers need to be seated until they have bottomed out...a little extra doesn't hurt either. It also doesn't hurt to run a Primer Pocket Uniformer into your cases

BTW, From what I gather the CCI small magnum rifle primers and CCI small magnum pistol primers come off the same production line. They are identical.

They're not. While CCI Small Magnum Pistol Primers are very much like CCI Small Rifle Primers, they are not identical to CCI Small Magnum Rifle Primers...see Post #12

The is a new 686 but is there a mechanical problem that could account for this?

You could always add an Apex Tactical Specialties Extended Firing Pin

 

[cw308]

No problem in using rifle primers in pistols only difference is the cup is thicker on the rifle primers.

 

[George P]

jski said: ↑
The primers are seated into the case primer pocket so as to be flush with the case head.
Seated Flush might be part of the problem. Primers need to be seated until they have bottomed out...a little extra doesn't hurt either. It also doesn't hurt to run a Primer Pocket Uniformer into your cases

Exactly, I have never seated primers flush, they have always been seated just a smidge below flush