The topic of misfires is a frequent one which I try to address in the forums. The questions are frequently posted on various forums in relation to the Russian primers (KVB, PMC, Wolf) as they have a harder cup than most US made primers and this is a factor in the misfire situation. I'll start this post with a recent question posted on
http://www.6mmbr.com/ and my answer. I hope to add more to it over the next few days.
Question posted by Ridgeway:
I have 5k of the new Wolf SRM primers with the gold cups. I used almost 100 primers and I had a missfire! I never had an issue with CCI, Fed or Remington since I've been reloading in '90. I even have primers from the early '80's that I use for fire forming that work! Anyone else have missfires with Wolf? I hope this is not a trend for 5k worth of primers!
There was not a problem with seating...I use a K&M priming tool. The cup definitely bottomed out. I'm on my 8th firing on a Dasher case...the primer pockets aren't as tight as they used to be and its easy to feel.I even re-cocked with the dud in the chamber and re-fired. Nothing. Did that like 3 times. Once I removed the round...the cup was a little distorted from being hit numerous times with the pin.
Answer 1 (German):
Ridgeway, have you installed a light firing pin in the rifle? Has the spring been checked lately?Either condition (light pin, worn spring) can lead to misfires. This is assuming that the primers are properly seated since you indicated that you are confident of that.
Reply 1 (Ridgeway):
German...the action is a new Panda with about 375 rounds on it. No modifications have been made to the bolt spring or pin. I re-cocked like 3-4 times and nothing happened other than smash and distort the primer. Is the spring in a Panda bolt on the light side?Primer seating...I can definetly feel them bottom. This is just one incident...not going to worry unless it happens again. Maybe its a fluke?
Answer 2 (German):
I don't know if the Panda firing pin and spring are lighter than "standard" which I define as a Remington 700. I'll see what I can dig up, Otteson's book The Bolt Action Rifle might have those specs. I'll check.
Let's take a look at some specs from: Otteson, The Bolt Action Rifle,
Vol. 1, pg. 138, Rem. 700 (short action, post 1968):
Lock Time: 2.6 ms
Firing pin fall (to impact): 0.213 in.
Impact velocity: 15.2 ft./sec.
Impact energy: 87.2 in.-oz.
Impulse: .96 oz. sec.
Unfortunately, Otteson didn't specify the weight of the firing pin on the 700. Impact energy and impulse, by the way are important to proper ignition, but often overlooked in the overemphasized quest for fast lock time. All modern rifles have darn good lock times and improvements are nearly meaningless - except as they reduce energy and impulse and thus reduce ignition reliability.
As we move on to the Panda, we run into a brick wall, because Otteson covered that action in his later book Benchrest Actions & Triggers, and the level of detail provided on the basic action functions is greatly reduced.
Lock Time: 2.7 ms
Firing pin fall (to impact): 0.24 in.
Beyond those scant figures, we are told: "The firing pin assembly follows a Remington pattern except for a smaller diameter striker tip, which allows better primer support." Indeed, the closeness of the figures indicates a great similarity in the underlying mechanism. Let's bear in mind however, that while the Remington probably hasn't changed in the 30+ years since the review, the Panda may have evolved a bit, so let's not assume these specifications necessarily remain valid for current production Pandas.
I don't have a Remington firing pin to weigh, other than the one in my 40X. If you want to take your Panda apart and weigh the firing pin with the cocking piece and separately weigh the spring (1/2 the weight of the spring should be considered in the weight of the striker) then I will do the same with the Remington.
While you have ruled out primer seating as an issue, for the benefit of others, I will say that primer seating is the primary area to examine in these situations and only after it has been determined that you are doing it correctly should your attention turn to the firing mechanism. The primer should bottom in the cup and then a slight additional forward movement, which gives a small degree of pre-compression to the pellet, should be felt. I have never been able to get this degree of "feel" from a press mounted priming tool. I use the Sinclair tool, but the K&M tool is equally good; the RCBS hand tool will do, although its heavy spring reduces feel to a certain degree.
One last thing - you asked if it might be a fluke, a bad primer or two in the lot. Generally speaking, no. Modern primer manufacture in the US and abroad and especially in the Murom plant where the Wolf primers are made, is held to such a close standard that the possibility of a bad primer is infinitesimal, the odds of more than one are essentially zero. When misfires are experienced, the primer is generally the last place to look for the cause. I'm not suggesting it is impossible to have a bad primer, simply that the probability of that is exceedingly low.
That the primer would not fire with repeated hits is normal. Once a primer has been struck, the pellet is complressed to a degree. If the impact energy and impulse were insufficient to ignite, there is not enough compression distance remaining in the primer (between the cup and anvil) to ensure ignition on a subsequent strike. In some cases it might, but it shouldn't be counted on.
UPDATE 09-06-09
It's a good thing we never stop learning - even if the lesson is delivered via a good helping of crow. I went to a match today and got 100% misfires with Russian primers in my .30-06, a first occurence. I stopped trying after 5 cases because I thought I knew what happened and it would be a 100% failure rate. When I got home and checked things out, I was right - a bad case of tolerance stack. Read on...
As some of you know, there is 0.010" manufacturing tolerance from the minimum to the maximum headspace length in a .30-06 chamber in accordance with SAAMI standards, so that is the acceptable range for a chamber. By measuring fired brass versus a "Go" gauge, I know that the chamber in this rifle is at 0.003" over minimum, OK, still good. The new brass measured -0.002", so there's a built-in 0.005" clearance from case shoulder to chamber shoulder on the first firing of this brass (see the Headspacing article here if this concept isn't clear).
The new lot of Russian primers is a bit lower in height than the old ones. The primer pockets on the new Winchester brass might be a bit deeper than the old brass. Whichever is the cause, the primers are noticeably deeper in the primer pocket than the old brass and primers.
I seated the bullets to jump 0.020", so there was no resistance to forward movement.
So.... with the 0.005" headspace, deep primers with hard cups and no resistance, I got misfires despite my heavy long-action Remington factory firing pin with a fresh spring. Man, that's sure some tasty crow. I'll pull the bullets, reseat them to jam into the lands in order to press the case head against the bolt face and that should take care of it. On the next firing, with headspace reduced a few thousandths it should be no problem. We'll see...
