Blowing primers

[SuperV]

Hi. I'm having trouble. I'm a novice TR shooter so please I need help from the fclass family.

I'm having trouble blowing the middle out of primers. It's not happening every shoot. I'm using lapua Palma brass with cci primers and 45.3 of 06h, hbc 5 thou jump. My loads are also molybdenum coated.

[AlanF]

Is that a small primer case? It does sound like a firing pin problem. I'd get your gunsmith to have a look at it.

Alan

[SuperV]

Alan do you or any one one if cci have soft cups. As it has only started it since I've been using the small rifle primer cases.

[johnk]

I've used CCI BR4 with the Palma brass both for FS loads & experimenting with my match rifle. I haven't had any such issues & some of the MR loads were brisk. On the other hand, small rifle primers of all denominations are known to be problematical when ignited by a standard firing pin (as opposed to a nice .06" diameter one in a snug firing pin hole).

What action are you using?

John

[AlanF]

...small rifle primers of all denominations are known to be problematical when ignited by a standard firing pin (as opposed to a nice .06" diameter one in a snug firing pin hole)...

That's what I'd heard. I'll hand-pass this one to you John

Alan

[SuperV]

It's my CG inch. I shot it over the Easter weekend at inverell using 44.4 06h and had no problem. But it didn't group as well. So I went back up to my pet load and its doing this. What I didn't mention is its a new batch of powder.

[Cameron Mc]

Need to know diameter of firing pin.

Cam

[bruce moulds]

is the inch firing pin capable of lengthening like some other actions?
if so, check for pin protrusion as well.
if protrusion has become excessive, this could be the least of anyones problems.
far better to blow a few primers than cop a bolt in the face.
keep safe,
bruce.

[Billy308]

Hi Ben,
That load in my barrel would be extremely hot. And probably why you are blowing primers.
44.6 of 2206H gives me similar velocity as 46.0 of 2208
Cheers Bill Naismith

[ned kelly]

G'day All,
had a similar problem with my Hall S 6ppc, essentially it was the area of the firing pin hole in the bolt face being large enough with a relatively light spring behind the firing pin AND coupled with a pressure in the primer pocket being high enough to push the pin back against the spring pressure, evidenced by cratered primer cups. This cratering is the cup extruding into the firing pin hole in the bolt face.
If the pressure became marginally higher it would cut a disc from the primer cup and it would usually end up in the bolt body somewhere.

It's all about the force applied to an area, e.g. how many pounds to shift the firing pin back into the bolt body and the area of the hole the fin passes through in the bolt face. Pounds per square inch of area. if the force from the primer pocket is higher than this force AND the effort to extrude the primer cup, the cup will deform, sometimes have the hole punched in it, just like a hole punch does to paper.

Now there are several options that are available (in no particular order)
1. heavier spring, but if your rifle is cock on opening, it will need more effort to open the bolt thus disturbing it on the bags.
2. bush the firing pin hole for a very close fit (reducing the area of the hole) to the existing firing pin diameter.
3. Bushing & reducing the firing pin hole and then reduce the firing pin diameter as well. This is why modern BR actions have pins less than 0.070" in diameter. I think the Barnard has 0.062" diameter pin
4. Back off the load and operate within the mechanical limits of you action/primer/case
5. try another primer, perhaps a magnum primer I use the CCI 450 in my 6x47lapua
6. buy another action designed to operate safely at these elevated pressures

hope this helps
Cheerio Ned

[RDavies]

I have started to get the same thing with my 6BR with loads which were not very hot. I used a loupe to look at the firing pin and found it has a small chunk out if it, so the firing pin is more like a chisel, than a nice round tip. Could be the same with yours.

[aaronraad]

If I was building a firing pin I'd make the tip seperately to hold a piece of music type spring wire. Best ejection pin material I've used compared to anything else you can easilly source in 0.062" diameter material.

[bartman007]

Hi SuperV,

As Billy308 put it, that load looks a bit hot.

Palma brass with cci primers and 45.3 of 06h, hbc 5 thou jump

You proved the point when you dropped back to 44.4 grains of 2206h, in that you didn't have the problem any more.

You mentioned your pet load, is that based on the fact that when the primers don't pop, that you get good groups? If so, that is simply because you have found a node point at the extreme end of the pressure for that case. If you alter your load from 43.8 to 44.8 grains, you'll probably find a more suitable load that has the same group size, but at a more reasonable pressure so that you don't pop your primers.

Take care. And as they always say, "START LOW AND WORK YOUR WAY UP".

[6.5x55ai]

Hi SuperV,

As Billy308 put it, that load looks a bit hot.

Palma brass with cci primers and 45.3 of 06h, hbc 5 thou jump

You proved the point when you dropped back to 44.4 grains of 2206h, in that you didn't have the problem any more.

You mentioned your pet load, is that based on the fact that when the primers don't pop, that you get good groups? If so, that is simply because you have found a node point at the extreme end of the pressure for that case. If you alter your load from 43.8 to 44.8 grains, you'll probably find a more suitable load that has the same group size, but at a more reasonable pressure so that you don't pop your primers.

Take care. And as they always say, "START LOW AND WORK YOUR WAY UP".

BR4 primers have a thicker cup than some other brands and are more accepting of hot loads, so if you are popping them, as already stated above, your load is too hot. In the early days of the 6BR popping primers for whatever reason was fixed by changing to BR4's.

[aaronraad]

What happened to the good ol' days when the bolt lift got sticky and you knew you were reaching the limit of the action. Rubber mallet employed when you'd gone way too far.

These super strong actions with effortless extraction use to be the domain of the elite BR shooters. Now every man and his dog can buy an action that will pop primers before breaking a sweat to lift the bolt handle.

If you miss the signs, you're going striaght off the cliff faster than you can blink. Bolt face pitting is not a design feature.