Guys,

I have a rather nicely done pre-64 Model 70 in 338 Win Mag. Has a 24" SS Kreiger bbl that has magnaported. Sights are a single blade fixed DGR middle, with a flip change front sight bead. Has a nice pillar bedded McMillan stock and has been black teflon coated. Weighs about 8 1/4 pounds with a 2.5-8 Leupold VX III. Good elk rifle.

Shoots 250 grain factory Remington Core-Lokts like a banshee ... 2" groups at 300 yards. Primers look fine.

Primers look fine with factory Federal 250 Nosler HEs. Not as accurate, but that's expectable.

Have been loading it for practice and have noticed an oddity. With Remington cases, 225 grain Hornadys, and CCI 250 primers I can load to 66 grains of IMR 4350 (yielding 2623 +-7 fps) with normal response. The velocity is about what is predicted by the loading manuals too. At 66.5 grains of IMR 4350, it begins to show the bottom of the firing pin cavity is getting thin ... black is visible ... to the firing pin indent being completely burned out (pierced primer).

This is a pretty light load for 225 Hornadys in the loading manuals. Otherwise cases and primers look more or less normal.

Something is wrong here. Is the firing pin exposure too great? How do I measure it?

Is the shape of the firing pin incorrect?

Do I have some more profound problem?

What additional testing should I do to identify the problem before sending it to a smith?

Thanks VERY much!

I just checked a pre 64 magnum for you and mine sticks out .063". It has a round nose to the firing pin tip with a flat "meplat" on it. This rifle does not pierce primers.

Put the safety on 1/2 and remove the bolt from the rifle. Hold the firing pin upside down under the jaws of a vise and tighen on it. Pull back on the bolt body, depress the spring loaded bolt lock on the bolt shroud and twist the bolt until the firing pin falls into the bolt in the fired position.

I have no idea how to get it back together. Just kidding.

mstarling---

It sounds like you need a new firing pin spring. You should probably have a 'smith check it out to makes sure the FP protrusion is right and the pin is the right shape. Everytime a primer is pierced it erodes the FP.

Jack,

Do you have the tolerances on the firing pin protusion and suggestions on it's shape?

How did you determine that the firing pin spring may be weak?

Of course even the primers might be made wrong but firing pins can be a problem.

Guys,

The firing pin protrusion is 0.060" with the bolt out of the rifle.

The shape of the pin seems a little odd ... not a full hemisphere ... more a flattened done with a pretty sharp edge that seems rolled (rivetted) very, very slightly.

Have done a lot of auto pistol pins but not a rifle pin. On a pistol I'd make sure the end is hemispherical and then flatten the end slightly to reduce cratering. Same idea here?

Have also read, and it is supported by Belk's comment, that the problem could be the firing pin spring. Is there a current Winchester production model whose FP spring would bit my pre-64 M70? (Brownell's lists a bunch of models in their catalog.)

Thanks!

[ 07-01-2003, 08:30: Message edited by: mstarling ]

I have found CCI primers soft-shelled,they cratered on a large firing pin holed rifle.The WLR didn't.I still use CCIs.