Need help/advice - primer seating


January 29, 2010, 08:39 AM
I've been reloading 357 Mag cartridges for my revolver and I'm having a big problem with misfires; about 30%- 40%. I originally thought it was the prime system on my turret press so I bought a RCBS hand primer; I'm still getting the same results. I have no way to measure the seating depth; I'm just relying on the tool. I'm using Magtech small pistol primers. Any advice is welcomed. Thanks.:banghead:

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January 29, 2010, 08:47 AM
Make sure the primers are below flush in the pockets.

January 29, 2010, 08:48 AM
I normally do that by feel; they all appear to be below being flush, thanks.

January 29, 2010, 08:50 AM
Are you seating to the bottom of the pockets? You should be able to "feel" them bottom out.

Are you over seating (crushing) the primers?

Does this specific firearm have a problem with factory loads or loads with different primers?

Recent trigger job or spring replacement?

Any possibility the primers were contaminated.

What did I forget, guys?

January 29, 2010, 09:02 AM
I do feel the primers bottom-out; I also apply a lot of force, I may be crushing the primers; the revolver is fairly new (about 1000 rounds through it), it's a S&W 627; no trigger job or spring replacement; thanks.

January 29, 2010, 09:19 AM
Sounds like you're crushing the primers. Seat one and gently remove it and look at the compound pellet under magnafaction. The anvil 'the three pointed thing' should be pushed just flush with the cup without damaging the pellet.

January 29, 2010, 09:22 AM
That's good info, something I didn't know, thanks!

January 29, 2010, 10:04 AM
The S&Ws I own are all more than 20 years old, so I don't know if this still applies.

If the FP strikes look shallow, check the spring tension screw. It may have backed out.

January 29, 2010, 10:10 AM
Thanks EddieNFL; without any manuals right now, is this screw easily accessible, and how would you adjust?

January 29, 2010, 10:16 AM
It takes a lot to crush a primer to the point it won't fire. It can be done, but it takes a lot of pressure.

Eddie had a really good suggestion about checking the tension (strain) screw. Is the gun new to you? Does it fire factory fodder OK? Weak aftermarket spring?

January 29, 2010, 10:27 AM
The gun is factory new, and I've never had a factory round misfire.

The Bushmaster
January 29, 2010, 10:33 AM
SEAT the .... primer!! Don't be afraid of setting it off. You won't!! It must be just below flush with the case head. You will be able to either see it or feel it. BUT SEAT THE DAMNED PRIMER...

I bet that if you struck the primer a second time it would go off...

DO wear safety glasses when ever you are reloading.......

January 29, 2010, 10:53 AM
Hey Bushmaster, is it a good idea as indicated before that as a test case to look at the anvil as being just flush with the cup. I've seated the primers in all cases by squeezing the manual priming tool extremely hard with the result that the primers are below flush with the case head, I'm just not sure if I'm crushing the primers, if in fact, that could cause this many misfires; thanks.

January 29, 2010, 11:16 AM
Gun Problem? The hammer should be able to lift about 4 lbs. if i remember corrrectly. New gun, lube it so the hammer has no drag. Break Free CLP.

January 29, 2010, 11:29 AM
If you can't tell if you're seating them flush or not try this: Put a primed case into a pair of calipers like you were measuring case length and hold the rimmed end up to a light. Since most calipers are thinner than the primer pocket if they are just below flush you should be able to see a small slot of light right where the primer is. Not terribly scientific but usually how I check mine.

January 29, 2010, 11:41 AM
This is in the gun, not your technique. Seating primers just isn't rocket science and really doesn't require a micrometer. If you press until it stops -- it's SEATED. That's it.

Either your gun's strain screw is backed out causing too little tension on the mainspring, or the hammer is hanging up and not getting enough speed on the fall to deliver enough energy, or you need a heavier mainspring.

The screw is in the lower front of the frontstrap of the grip. (Depending on what grips your revolver wears you may have to remove the grips to see the screw.) If you put a well-fitting screw driver on it and tighten it firmly, it's tight enough. If it wasn't tight, there's your problem.

If it lights all factory primers (try several brands), it could be that the MagTech primers are much harder than normal. On the other end of the spectrum, Federal brand primers are very soft and will light off pretty consistently even in guns running light springs. If it lights off all factory ammo, S&W is probably going to say that it's within specs.

If it isn't consistant with factory ammo, S&W may take it back, replace the mainspring, and even polish up the hammer channel to help it move faster.

If it is still an issue, you could replace your factory mainspring with a Wolff "Type 1" spring and see if it improves anything. The Type 1 springs aren't heavier, but they do feel different/better than stock. Just might work better, but for $12 they could be worth a try.


January 29, 2010, 11:50 AM
Thanks for all the advice!

January 29, 2010, 01:16 PM
The gun is factory new, and I've never had a factory round misfire.
Then a 30%- 40% mis-fire rate with reloads almost has to be defective primers.

1. Check the strain screw.

2. Change primer brands.

* A properly seated primer should be below flush.
* The anvil should be crushed into the primer pellet slightly to "pre-load" it.
* The firing pin should make a good dent in the primer.

If you are doing all that and still getting mis-fires, you have a bad batch of MagTech primers.

BTW: A severly crushed / flattened primer is generally more sensitive, not less sensitive.


January 29, 2010, 01:25 PM
Thanks rcmodel; I just bought some CCI primers which I'll be trying next, but I will first check the strain screw.

January 29, 2010, 01:33 PM
Sounds like a plan. Hoever, be aware that CCI primers are on the harder end of the spectrum. The "up side" is that, if you gun will light off CCI primers, it will light off anything that's made properly.

As rc said, certainly could be a bad batch from MagTech.


January 29, 2010, 01:36 PM
I'll post a follow-up as soon as I get some results; thanks to all.

January 29, 2010, 01:37 PM
If a factory stock S&W 627 won't light CCI primers, or any other good brand of primers, you need to send it back to S&W for repair!


The Bushmaster
January 29, 2010, 01:46 PM
Garth64...I just went into my reloading/gun room (Man Cave) and pressed a primer as far as my Lee Auto Prime II could. The primer ended up .012" below the flush. Loaded it in my S&W Mod 10. Pulled the trigger and it went off.

I've seated primers sideways (oops), which definately crushes them. Out of curiosity, loaded them in one of my revolvers. Pulled the trigger. Guess what? They went off...

January 29, 2010, 02:18 PM
It looks like I either have a batch of bad primers or my strain screw is out of adjustment, thanks.

January 29, 2010, 02:26 PM
For the last 54 years I have seating my primers with authority and never have a problem,a few miss fires along the way, but few and far between.

The Bushmaster
January 29, 2010, 02:34 PM
I guess you get the missfires after the first 25 years then. Right floydster? I've been reloading for 24 years and haven't had one missfire [yet]...:D

January 29, 2010, 03:08 PM
For me, something must really be out of whack; I'll check what I listed before and report back what I find; thanks.

January 30, 2010, 12:02 PM
I can count the missfiers on one hand in all the many years reloading.

I actually started reloading on an old Delta drill press when I was 11 years old,

lots of memories.

January 30, 2010, 12:27 PM
I haven't had one.......yet.

The Bushmaster
January 30, 2010, 12:33 PM
Floyd...Guess I pretty safe then...I'm not 72 yet. Have a few years until I have to worry about primer missfires.;)

January 30, 2010, 12:51 PM
In 30 years of reloading I hate to admit that I've had two failures to fire. Both my fault! One was in a Colt Python .357 Magnum and was because of a high primer. Fired the second time. The other was in an AR-15 in bitter winter weather. Firing pin mark on the primer was very very light. Fired the second try. Had been carrying the AR for a few hours in cold and snow before taking a shot at a target before calling it a day. Only thing found was that the firing pin and channel was dirty and oily. Probably a stiff firing pin due to the cold making the oil and dirt stiff. Learned both lessons and now make sure guns are ready for freezing temperature and that primers are closely inspected for proper seating. Both mis-fires were when I first started loading and (knock on wood) I haven't had another in the last couple decades.

February 14, 2010, 03:33 PM
Thanks to all; my problem with misfiring was that the strain screw was out a full 2 turns; after tightening the screw, had ZERO misfires today for 120 rounds; thanks again for the info!

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