I recently fired some factory ammo in a .17 Rem that I received as a gift. It's a custom job with an aftermarket barrel.
All of the primers have a dimple that is .012"-.013" proud of the case head and none of them are pierced. All 90 cases have the same symptom.
I'm thinking it's either a long chamber or short ammo. Any ideas?

I would have a chamber cast made by a gunsmith to sort out your problem. Take the fired cases with you to show him.

Don

Could be a weak spring and or a large firing pin hole. This might be compounded with soft or thin primer cups. It could be a sign of over pressure but it doesn't seem likly. roger

sounds like your firing pin and firing pin hole don't match in size. When you fire a round the firing pin dents the primer ignighting the round the pressure in the case then pushes the primer cup into the firingpin hole and the firing pin is pushed rearward slightly when the pressure subsides the firing pin then pushes the primer cup back down. If the difference in the diameter of the firing pin hole and the firing pin isvery much the firing pin will only push the center of that dimple down leaving abit of a ring which is what it sounds like you are discribing. This tollerance can be tightened up by bushing the firing pin hole.

Are you familar with the term cratered, re primers? With hot factory ammo, a tight chamber etc. it's not unheard of.

It will probably go away with moderate hand loads, if not it may need a fireing pin bushing or something.

I doubt its caused by a long chamber or short ammo as you put it.

See Rhys's post, thats where the cause lies.

If chamber was too long or ammo too short the whle primer would start backing out. If thatw as the case you could just back off your sizing die to correct the ammo for that particular chamber.

It's not cratered primers. I know what that looks like.
I also don't think it's a headspace problem. Then I think there would be case stretching, etc.
I do think it's an oversized firing pin hole. I compared the hole on the .17 with the holes on my .222 Mag. The difference was huge!
So now I wonder if the gunsmith converted a model 700 that was originally chambered for a round with large rifle primers.
Does the firing pin hole on, say a .243, measure larger than a .223?

quote:

Originally posted by slancey:

Does the firing pin hole on, say a .243, measure larger than a .223?

Now that's a big,big hole. roger

My gunsmith said it's too dangerous to bush a firing pin hole because of the high pressure level.
Does anybody know of a fix for an oversize firing pin hole, or an undersize firing pin?

It can be done. It s done. Go to the gunsmithing board and ask for help/ advice.

Gre Tan Rifles offers the bushing service.

My old Vanguard .243 craters due to an oversized pin hole. I returned it to Weatherby and they sent it back saying it was "...within factory tolerances." I just use a harder primer and it's never been a problem, just an agrivation.

What does a "dimple" look like?

If it's anything like my old 30-30, it looks like a flattned out smooth ex-crater.

Another gunsmith suggested a new main spring. He said that .17s are notorious for primer issues when the firing pin spring is weaker than it should be.

Yep could be a few things, I'd get a good smith to start with the cheapest possibility (maybe pin protrusion) up to bushing if needed. He should be able to test fire it as he goes.