primer seating depth and misfires

[s.stimson]

I have been having some trouble regarding misfires in my 300 win mag reloads. I'm getting a nice clean dent in the primer but no bang. If I try the round 3-4 times it will go off ok. In an attempt to sort out the issue I primed 10 cases and measured the primer depth (all were carefully primed so that they were flush with the bottom of the case)

So the 10 primed cases all fired 1st time so I'm thinking that the primer depth may be the route cause of the misfires. So the question is how far below flush with the bottom of the case is acceptable? For information I am using a rcbs hand primer.

Thanks

[Simon_S]

Try doing some a bit more deeper mate, if your still having trouble you could have some
faulty primer.

[lilguy43uk]

If your primer pockets are a tad on the loose (and large) size, the primer could be moving fractionally forward with the impact of the firing pin and not getting a clean strike.

Or it could be as has already been mentioned, faulty primers.

[Turnup]

Primers should be bottomed out. If they are not fully seated then they will move forwards with the impact of the firing pin, weakening the strike. Below flush is OK, above flush is not OK.

[Vermin Al]

About 5thou according to Chuck Hawks: When reloading, always seat primers slightly below flush with the head of the cartridge case. This insures that the anvil is properly pressed against the priming compound for reliable ignition. Failure to properly seat primers is the biggest single cause of misfires in reloaded ammunition. A good depth to aim for is .005" below flush. With some experience this can be determined by feeling the case head after the primer is seated. Any primer that is flush or protruding should be very carefully removed and the case reprimed. Decapping a live primer can set the thing off, so behave accordingly and take all necessary precautions, including ear and eye protection.

http://www.chuckhawks.com/primers.htm

Other references, 2-6thou.

[Mike95]

Are they Gynex primers! Bought a load for my club, very hard. My Marlin 30/30 needed several taps to ignite them. i have never noticed any problem with Sellier and Bellot, however they are seated.

Mike95

[ZAKDINGEL]

Sounds like a primer issue rather than the seated depth i always thought that a primer fits into the pocket as far as it will go? if you have had the same problem in another gun then i would have thought it was not the striker spring but the primer itself

[Simon_S]

You also need to keep the primer pockets clear of crud.
Should have one these

http://www.henrykrank.com/index.php?...oducts_id=1584

[zubuk]

Yep, clean out the primer pockets with a primer pocket cleaning tool or a primer pocket uniformity tool (which is what I use). Also all of the precision shooting reloading books suggest seating the primer to ensure the legs if the anvil inside the primer are firmly seated against the bottom of the pocket, this should involve crushing the primer anvil slightly. Also I would try using one of the more mainstream brands.

Anyway my 5 pence worth. ATB
Simon

[Parabuteo]

Ello flower

We dont uniform our primer pockets until after 2-3 firings, I am not sure why but I have been told by them that knows that it tends to wreck the pockets if you do. It may just be a palma brass thing but it carries weight apparently.

Primers must bottom out (or rather the anvils) and be just below the case head (you can feel it fairly easilly, about 5 thoug as stated).

Some people use a uniformer for cleaning, I am not sure if this is ideal as you keep digging away at the pocket, although if brass comes off I guess it has moved, but then how many then bother sorting any burring out round the flash hole. Personally I would shoot a few then unifor, then clean only (flat ended tool, does not cut but gets into corners).

If a primer si a bit reticent you can often see marks on the face of the primer, CCI are great for this as the little logo squishes a bit.

Another thought is this?

Is the sizing die set correctly for the headspace of the rifle?

I recently found I was setting my shoulders back further than a new, unfired case. Not the end of the world but not ideal with 4 thou of movement when you only need enough for a hassle free chambering (1-2).

If the shoulders are set too far back, a hard primer may well transfer the impact of the pin onto the case which (not being seated against the shoulders...winmag is not belted is it...) wont resist and will move, which may mean it does not ignite.

So, it could be that repeated firings are seating the thing for you (bad bugger!!) or that its headpsace and the compound is getting squished a bit more each time.

Or your firing pin/spring may need a ruddy good soak in solvent and a very light oiling as it may be dragging a bit.

I have used CCI and Federal in my Barnard and have only ever had one misfire accros 2700 rounds, Fed are quite soft, CCI harder.

SO

Check primers

Pocket depth

Seated primer depth

Bump setting on die

Firing pin for gunk and general bolt wear.

[Marten]

Seating too hard or too deep will cause misfires, you only need to seat flush or just below flush.
Seating too deep distorts the primer anvil.

[s.stimson]

Just as an update on the situation i have done some measurements on primer depths and confirm they are within the tolerance of "a gnat's below flush" brass was all clean and new with flash holes de-burred. I've been in contact with the gunsmith who built the rifle to discuss the situation, I will be trying a different batch or brand of primers (currently using Federal magnum large rifle primers) as the strike looks good on the primers and take it from there.

[Parabuteo]

If you are happy with the primers (I would not be if you say they are getting a good strike and still not going off)

Then I would strip the bolt a damned good strip, de grease (Possibly in a US cleaner) dry and re lube with very light oil.

You could (safely of course) fire some primed only cases to see if it makes any difference.

Possibly try this with some that have been re-sized and if they still chamber some fired, un re-sized ones (Logic being that the shoulders may be being bumbed too far back).

If it is intermittent, segregate those cases that cause the issue.

If it is not intermittent I would supect the rifle personally.

Grease and dirt can put hell of a drag on a pin.

[s.stimson]

Another update, I went to the range on Sunday with two batches of ammo, both using the same powder but diffrent primers (Remington 9 1/2M, and Fedral GM215M but a different batch to last time) I had seated them a little more gently than last time to make surre that i was not crushing anything.

The Remington primers would not go bang for love nor money, but the Fedrals all went off ok this time. I'm off the opinion that the pin is striking the primer on the lower limit of "just hard enough" so as i have seated the fedrals a little (and we are talking a max of 0.02mm diffrence here) shallower than last time it is just enough to make it go bang.

Simon

[Parabuteo]

Another update, I went to the range on Sunday with two batches of ammo, both using the same powder but diffrent primers (Remington 9 1/2M, and Fedral GM215M but a different batch to last time) I had seated them a little more gently than last time to make surre that i was not crushing anything.

The Remington primers would not go bang for love nor money, but the Fedrals all went off ok this time. I'm off the opinion that the pin is striking the primer on the lower limit of "just hard enough" so as i have seated the fedrals a little (and we are talking a max of 0.02mm diffrence here) shallower than last time it is just enough to make it go bang.

Simon

Simon, Federal primers are known to be soft. This is why Lee have a warning about using them in their auto prime (which most of us studiously ignore).

If the pin is setting off the softer primer, but not the harder, why not clean the bolt etc and consider a new main spring.

You could very easily carry out tests off the range with cases that just have primers in them.

Most if not all of the primers available will be used in factory loads of some sort which probably wont have the QC we have over seating depths yet they still fire reliably in many many different rifles.

Do you know anyone with a similar rifle you could interchange springs/bolts to test?

I have not had a single primer related missfire in 3000 rounds through my F/TR rifle, mostly all CCI BR4 Primers (hard). Likewise with my No4 or M67.

How do the struck primers look? I mention the bolt/spring as it is the easiest thing to fix. If all of the cases have overly deep primer pockets they are as likely scrap. If they are over bumped you may never get them to fire and re-form.