Short cases causing misfires

[urban]

I've had occasional failures to fire over the past 6 months - perhaps 1 in 70 rounds.

I shoot CSR competitions with a .223 Howa. Each competion is about 80 rounds and I've done 6 this season - all using reloaded ammo (i.e. approx 500 rounds). I used factory ammo last season with no issues.

I thought the problem was dodgy magtech primers because the primers had a reasonable indent from the firing pin. However, at the last competition I had 3 failures to fire and all were visibly light strikes.

I checked the rifle thoroughly and I can't see anything wrong with the bolt, firing pin or spring. So I started thinking about what else might be causing it. I wondered if perhaps I'm bumping the shoulders too far, resulting in too much headspace and cartridges that ride forwards slightly when struck.

I took one of the failed cartridges and stuck layers of tape onto the head until the bolt was hard to close. It took 7 layers. I did the same with a factory round. It took one layer. 7 layers of tape measured 0.33mm.

I don't have a comparator so I 3d printed one and sized it so that it would index on the case shoulder rather than the bullet ogive. It's a bit rough and ready but it seems to show the following:
1. Fired cases before resizing = 31.65mm
2. Factory rounds = 31.68mm
2. Handloads = 31.55mm

The absolute numbers cannot be referenced to the specs because the comparator is not calibrated, but it shows that my reloads have a shoulder that is more than 0.1mm (4 thou, if you must) further back than factory or chamber.

I'm using a Lee die that (I believe) unlike other makers dies doesn't provide any adjustment. You are meant to resize until the shell holder is touching the base of the die (reference) - and that's what I do.

I think the next steps are to buy a case gauge, which should allow me to confirm the above with greater confidence, and then to buy another die (not Lee this time).

Thoughts welcome.

 

[MarinePMI]

I've had occasional failures to fire over the past 6 months - perhaps 1 in 70 rounds.

I shoot CSR competitions with a .223 Howa. Each competion is about 80 rounds and I've done 6 this season - all using reloaded ammo (i.e. approx 500 rounds). I used factory ammo last season with no issues.

I thought the problem was dodgy magtech primers because the primers had a reasonable indent from the firing pin. However, at the last competition I had 3 failures to fire and all were visibly light strikes.

I checked the rifle thoroughly and I can't see anything wrong with the bolt, firing pin or spring. So I started thinking about what else might be causing it. I wondered if perhaps I'm bumping the shoulders too far, resulting in too much headspace and cartridges that ride forwards slightly when struck.

I took one of the failed cartridges and stuck layers of tape onto the head until the bolt was hard to close. It took 7 layers. I did the same with a factory round. It took one layer. 7 layers of tape measured 0.33mm.

I don't have a comparator so I 3d printed one and sized it so that it would index on the case shoulder rather than the bullet ogive. It's a bit rough and ready but it seems to show the following:
1. Fired cases before resizing = 31.65mm
2. Factory rounds = 31.68mm
2. Handloads = 31.55mm

The absolute numbers cannot be referenced to the specs because the comparator is not calibrated, but it shows that my reloads have a shoulder that is more than 0.1mm (4 thou, if you must) further back than factory or chamber.

I'm using a Lee die that (I believe) unlike other makers dies doesn't provide any adjustment. You are meant to resize until the shell holder is touching the base of the die (reference) - and that's what I do.

I think the next steps are to buy a case gauge, which should allow me to confirm the above with greater confidence, and then to buy another die (not Lee this time).

Thoughts welcome.

Back you die off 1/4 turn at a time (and retighten the lock nut), until you get the headspace you need. Dies do not have to be run until they hit the shell holder, but it's a good place to start.

And yes, that is probably your issue. If your load isn't near max, you can take any unused rounds and using a kinetic bullet puller, knock the bullets forward (but not out of the case). Then reseat so that the bullets lightly touch the throat. This will keep the case from moving forward as the firing pin hits. You're essentially fireforming the case to your chamber (this is a practice many wildcat reloaders use, when the wildcat case is a radical departure from the original parent case).

 

[jthyttin]

If you have a sturdy press, get locking ring for the die and find a correct amount of shoulder bump. DO NOT adjust 1/4 turn at a time, since outer thread on dies is 7/8"-14 i.e. single turn is 1.8mm and 1/4 turn still 0.45mm. The locking ring enables you to maintain the setting over reloading sessions. I recommend locking ring also for the seating die.

If you don't have sturdy press, or the end of stroke is "cam over", you can get set of Competition Shell Holders from Redding, or maybe some equivalent product. Redding set has 5 holders, .002", .004", .006", .008" and .010" thicker on the upside than standard. So you can still maintain contact between shell holder and die, while adjusting the shoulder bump.

 

[plumber01]

You are not alone, I have had the same 223 for over ten years, never a problem,and when using Magtec srp ive had about 2 or 3 per 100 fail to go bang.
When in the field its not a problem, but on the range in a comp, it isnt funny
Try, ,,,,,anything else!
good luck