Primer seating depth.

[Attica Jack #23953]

I got into a discussion with my shooting partner Onyx the other day, on this subject. He has been having some pistol rounds that FTF, with light hits. I checked his reloaded ammo, and said that the primers were not seated deep enough, they were above flush, with the case, he said he did not want to seat them deeper because they would be too deep, and would not fire. I stated that with a high primer, some of the hammer energy would be expended, seating the primer to the bottom of the primer pocket, and you would have a light hit on the primer, causing a miss fire. I don't think that you can seat a primer too deep, without destroying the primer. For discussion sake, lets say the primer pocket on a used case is 1" inch deep, the primer you are using is .995 thick, you seat the primer to the bottom of the case, leaving it .005 below flush, which is perfect, seated flush of above flush, the primer will have to move at least .005 or more to seat to the bottom of the primer pocket, before the primer anvil has a solid mass to strike and ignite. Any thoughts on this?

[Widder, SASS #59054]

Primers need to be seated "FULLY".

 

if the depth of that particular primer pocket allows a flush fit and no more, than that is FULLY seated.

 

But as with most properly produced brass, the primer pockets are alittle deeper than the thickness of the primers and therefore, the primers sit alittle deeper when FULLY seated.

 

I've helped a couple local pards set up their Marlins with proper hammer springs, etc....

 

Then when they use their reloads, they get misfires. In EVERY situation, it has been the primers not being FULLY seated was the cause. I would take my hand held RCBS primer gizmo and properly seat their ammo FULLY (below flush) and their ignition problems disappeared like magic.... Go figure!

 

 

..........Widder

[Garrison Joe, SASS #60708]

+1. FLUSH or deeper. Any less seating will hang up someplace or fail to fire.

 

If a primer seats more than about .005" below flush, you have some bad primers. Quit using them. This will happen maybe once in a lifetime.

 

Your pard is less than informed.

 

Good luck, GJ

[Driftwood Johnson, SASS #38283]

 

he said he did not want to seat them deeper because they would be too deep,

Howdy

 

Your pal is wrong. Widowmaker is correct. High primers waste some of the firing pin's energy fully seating the primer. That is why he is having FTFs. A primer is fully seated when the cup bottoms on the floor of the primer pocket. Most primer pockets are dimensioned so a primer will be subflush by a few thousandths when the cup is fully seated.

 

The other part of this situation is your pal has probably tuned his springs so light that a few thousandths of 'primer reseating' Re stealing enough energy to cause light primer hits. The problem will go away if he seats the primers fully. It would also probably be alleviated slightly if his springs were not so light.

 

A few thousandths of extra travel of the firing pin for a fully seated primer is not going to affect anything, so tell him to seat his primers all the way.

[Big Sage, SASS #49891 Life]

When primers are not seated flush (or deeper) I start having problems in my Ruger NMV's. The cylinder will bind up and won't rotate. It's flush or deeper for me!

[Warden Callaway]

I have a Dillon 550B that is less than a year old. It would only seat a primer flush. I had to slightly chamfer the primer post to get the primers to seat .002 below flush.

[Lead Ringer]

I wonder where your pard got his info? I'm confident it wasn't out of any reloading manual;)

Regards,

Ringer

[Yusta B.]

This is why, for me, seating primers by hand works. I can feel when the primer seats in the pocket. I would suspect that if your primers do not detonate when fully seated, you may have a head space issue or a firing pin that is a little short. YMMV

[Attica Jack #23953]

It doesn't happen all the time, which makes me think, an occasional high primer is the culprit. He never cleans his primer pockets..........but that is another issue altogether. Thanks for the responses.

[Hans Christian]

This is why, for me, seating primers by hand works. I can feel when the primer seats in the pocket. I would suspect that if your primers do not detonate when fully seated, you may have a head space issue or a firing pin that is a little short. YMMV

+1

 

Carbon buildup in the primer pocket can also factor in, but that's another can of worms.

[The Original Lumpy Gritz]

Primers MUST be seat'd to the bottom of the primer 'pocket' in the case

LG

[Delaware Drifter #36190]

A normal primer seating depth spec for most small arms cartridges is from flush to 0.008 inch below flush, but the majority of them probably do not run much beyond 0.005 inch below, and of course never above flush. I would not intentionally short-seat a primer, partly because there's really no point, but I am not sure if the firing pin force would further seat a not-fully-seated primer vice just igniting the primer, so I'll have to take someone elses word for it. Fully seat the primer.

[Widder, SASS #59054]

This is just my opinion, which might help or not.

 

But, in the instances where a primer is not FULLY seated and gives you a FTF when struck with the firing pin, its because it 'rolls with the punch'.

 

THEN, if the hammer is recocked for a 2nd strike, it will fire.

 

This is not a 'cast in stone' sure fire way of knowing. But in my limited experiences as mentioned in post #2, this has been the tale-tale sign of IMPROPER Primer Seating.

 

 

..........Widder

[Hans Christian]

Primer pockets are notorious for being inconsistent or having other flaws like off-center flash holes, dished bottoms or burrs.. I have culled out a few from my cowboy cases.

 

Varying pocket depths make seating by feel the best method IMHO.

 

One CAN use a primer pocket uniformer, but that is too much work for me on cowboy ammo. I save that chore for precision rifle ammo.

 

 

The best cases that I have encountered in 45 Colt came from Black Hills Ammunition.

 

Some of the worst 38 Special are S&B and some 1950's GI cases. The pockets were extremely tight on these.

 

Best of luck to your friend..

[Yusta B.]

This is just my opinion, which might help or not.

 

But, in the instances where a primer is not FULLY seated and gives you a FTF when struck with the firing pin, its because it 'rolls with the punch'.

 

THEN, if the hammer is recocked for a 2nd strike, it will fire.

 

This is not a 'cast in stone' sure fire way of knowing. But in my limited experiences as mentioned in post #2, this has been the tale-tale sign of IMPROPER Primer Seating.

 

 

..........Widder

This ^^^^^ + short stroking a pistol or possibly hammer dragging on thumb on the way down are some other possible causes. They will most probably fire if hit again.

[Driftwood Johnson, SASS #38283]

 

This is why, for me, seating primers by hand works. I can feel when the primer seats in the pocket.

To each his own, but I can feel just fine when a primer seats all the way on my progressive Hornady. And I can also feel if it does not seat all the way.

[Yusta B.]

To each his own, but I can feel just fine when a primer seats all the way on my progressive Hornady. And I can also feel if it does not seat all the way.

Totally agree - whatever works for the loader is the best way.

[The Original Lumpy Gritz]

To each his own, but I can feel just fine when a primer seats all the way on my progressive Hornady. And I can also feel if it does not seat all the way.

Same here on my D/550.

LG

[John Boy]

Primers MUST be seat'd to the bottom of the primer 'pocket' in the case

... and if they aren't when the cap is hit hard and fast - it will not crush the anvil because the cup is moving down. Law of Physics!

[Trailrider #896]

I agree wholeheartedly that primers should be seated flush or a little below. I seat my primers separately on an RCBS primer press, which uses the same shell holder as when I size/expand/seat/crimp. I can use a primer gage, but generally just run my thumb across the case head.

 

But there is one thing no one has covered: Use of the proper primer for the proper cartridge. Virtually all the cartridges we use in our sport which use LARGE primers use LARGE PISTOL primers, regardless of whether they are used in a rifle or pistol! Why? Because LARGE RIFLE primers can be as much as .009" LONGER than Large Pistol primers, and the primer pockets are shorter in the pistol cases by as much as .009". Using large rifle primers in pistol cases will result in HIGH PRIMERS, which can result in anything from tying up the cylinders in revolvers to promoting magazine explosions in tubular magazines in rifles! (Note, there os MO difference between SMALL PISTOL AND SMALL RIFLE primers and pocket depths. Don't ask me why, that's just the way it is.

[Keystone, SASS # 47578]

Howdy,

 

I reload with a Dillon 550 and have smooth below flush seating with Federal Large Pistol primers. However, Winchester primers require much greater effort to properly seat below flush. I recently cleaned all the primer pockets and still find Winchester primers more difficult to properly seat. I expect in the future to only purchase Federal primers.

 

Hasta Luego, Keystone

[John Boy]

Why? Because LARGE RIFLE primers can be as much as .009" LONGER than Large Pistol primers, and the primer pockets are shorter in the pistol cases by as much as .009".

Trailrider -Yes - LP's are the way to go for CAS. CCI 300 LP's are my primers for all CAS centerfires

What really is the issue is - the pocket depths between LP & LR primers - up to 0.014"

http://www.lasc.us/primerchart.htm

http://www.jamescalhoon.com/primers_and_pressure.php

[Rye Miles #13621]

This is why, for me, seating primers by hand works. I can feel when the primer seats in the pocket. I would suspect that if your primers do not detonate when fully seated, you may have a head space issue or a firing pin that is a little short. YMMV

Hey Yusta, how ya been pard?

 

I've been having some problems with high primers lately and I'm gonna have to go with your idea, HAND PRIME!!! Takes a little longer but I got more time than money anyway! Rye

[Yusta B.]

Been shootin smoke like my hero Rye ! I prime while watchin TV. I also deprime before tumbling - you know me - always against the grain !

[Grizzly Dave]

flush or deeper for me too, had some folks who had to borrow ammo from me have problems and they said my primers were seated too deep...strange I didn't have the same problems...

[Ventura Slim, SASS #35690]

Federal primers...no problemo

[Colt McCloud, SASS #65003L]

Attica Jack!!! Next match I will show the big guy my rounds. Primers (Federal) are fully seated and just below flush. I never clean the primer pockets just throw the dirty brass in the cleaner and reload. Use a Dillon SD. No problems!!! See you at Lapeer or DSC

Colt

[Trailrider #896]

Trailrider -Yes - LP's are the way to go for CAS. CCI 300 LP's are my primers for all CAS centerfires

What really is the issue is - the pocket depths between LP & LR primers - up to 0.014"

http://www.lasc.us/primerchart.htm

http://www.jamescalhoon.com/primers_and_pressure.php

I could be wrong on the depth difference, but IIRC...and it's been a few years...somebody at Olin quoted me .009". Maybe it's changed, but I also could be wrong. Regardless, there sure is a difference, and using LR primers in large pistol cases is asking for high primers. I worry more about magazine explosions, especially in M1860 Henry rifles, but also in the others with tubular mags. Another reason I also like using bullets with a flat meplat of .250" or larger. So long as they'll feed okay.

[John Boy]

Trailrider - no need for apologies ... I have trouble remembering what I had for breakfast and I'm eating lunch now

The majority of the magazine fed RNFP bullets are 0.125 with no chain explosions. And they slide easily into the chamber

[Nate Kiowa Jones #6765]

A normal primer seating depth spec for most small arms cartridges is from flush to 0.008 inch below flush, but the majority of them probably do not run much beyond 0.005 inch below, and of course never above flush. I would not intentionally short-seat a primer, partly because there's really no point, but I am not sure if the firing pin force would further seat a not-fully-seated primer vice just igniting the primer, so I'll have to take someone elses word for it. Fully seat the primer.

 

 

... and if they aren't when the cap is hit hard and fast - it will not crush the anvil because the cup is moving down. Law of Physics!

 

Well sort of.

 

flush or deeper for me too, had some folks who had to borrow ammo from me have problems and they said my primers were seated too deep...strange I didn't have the same problems...

 

They should be fully seated whether they are flush or deeper. What happens if they aren't is the cup doesn't really move but the anvil inside moves back when the primer is hit with the firing pin. The anvil has to be seated in the bottom of the primer pocket in order for the firing pin to crush the priming compound into it. If that anvil is not seated to the bottom it will move back without crushing the compound.

If a person is having to seat them high so his firing pin will reach them then he has a gun problem. Most likely the springs are too light. With most of the guns we use, firing pin protrusion is minimal so changing to lighter springs you get poor detonation. I see folks say they have to run the softer fed primers or their guns don't fire. To me that is just taking them too close to unreliable. Lighter springs can be used but you better make sure you have enough firing pin protrusion first.

 

Headspace can cause this too but not as common as light springs and poor protrusion.

[Widder, SASS #59054]

 

 

 

They should be fully seated whether they are flush or deeper. What happens if they aren't is the cup doesn't really move but the anvil inside moves back when the primer is hit with the firing pin. The anvil has to be seated in the bottom of the primer pocket in order for the firing pin to crush the priming compound into it. If that anvil is not seated to the bottom it will move back without crushing the compound.

If a person is having to seat them high so his firing pin will reach them then he has a gun problem. Most likely the springs are too light. With most of the guns we use, firing pin protrusion is minimal so changing to lighter springs you get poor detonation. I see folks say they have to run the softer fed primers or their guns don't fire. To me that is just taking them too close to unreliable. Lighter springs can be used but you better make sure you have enough firing pin protrusion first.

 

Headspace can cause this too but not as common as light springs and poor protrusion.

 

Well Stated Nate!

 

 

..........Widder

[Cpt Dan Blodgett, SASS #75655]

It is amazing how many folks in SASS are much more educated and informed than those idiots who wrote the reloading manuals. I care not that the conventional wisdom is fully seat primers, which is actually below flush. Slam fires are a myth. Those loonies that wrote the manuals and the corporate lawyers and safety committees that approved the manuals know nothing despite having Engineering Degrees etc.

 

If your gun will not shoot properly assembled ammunition, there is a problem with the gun!!! The hardest primers out there really don't need a lot of force to set them off, not really the best of Ideas to tune the gun so finely that it does not fire first time every time. Ok you save 15 nano seconds cocking the hammer with a lighter spring, but the hammer falls 10 nano seconds slower due to lighter springs. Wow you have netted 5 nano seconds per round for the match 5 x 120 = 600 nano seconds fantastic. Did you really? Well maybe not when one takes into account the 3 failure to fires and the 15 seconds it took to go around the cylinder to get the round to fire each time.

 

Can anyone say penny wise - pound foolish?

[Hans Christian]

It is amazing how many folks in SASS are much more educated and informed than those idiots who wrote the reloading manuals. I care not that the conventional wisdom is fully seat primers, which is actually below flush. Slam fires are a myth. Those loonies that wrote the manuals and the corporate lawyers and safety committees that approved the manuals know nothing despite having Engineering Degrees etc.

 

If your gun will not shoot properly assembled ammunition, there is a problem with the gun!!! The hardest primers out there really don't need a lot of force to set them off, not really the best of Ideas to tune the gun so finely that it does not fire first time every time. Ok you save 15 nano seconds cocking the hammer with a lighter spring, but the hammer falls 10 nano seconds slower due to lighter springs. Wow you have netted 5 nano seconds per round for the match 5 x 120 = 600 nano seconds fantastic. Did you really? Well maybe not when one takes into account the 3 failure to fires and the 15 seconds it took to go around the cylinder to get the round to fire each time.

 

Can anyone say penny wise - pound foolish?

 

Well said. Reliable ammo and gun function is the priority in CAS, right behind safety.