Case Gauge / Headspace Question

[bearstatearmory.com]

I recently purchased a Wilson case gauge to verify headspace and to the naked eye they looked great so I re sized and trimmed about 500 cases. I went to the range yesterday and had about 1/4 of them not firing (it didn't even look like the primer was touched at all). When I got home I checked the case gauge and it's SLIGHTLY below the gauge (about .003 was average of the ones not fired).

Does this make sense that the .003" would be enough that the firing pin in my AR wouldn't even make contact with the primer?

[J-cat]

So much for trusting a case gauge.

Does the bolt rotate and lock? If not, the firing pin won't go forward.

[bearstatearmory.com]

So much for trusting a case gauge.

Does the bolt rotate and lock? If not, the firing pin won't go forward.

Its in my AR, it just clicks like a dry fire

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[FLIGHT762]

When you say slightly below the gauge, what do you mean? There is a top step and a bottom step. If you were slightly below the top step, it's very likely you didn't size quite enough and the bolt wasn't locking/going into battery. That would be my guess. If that is the case, you need to turn your F/L die into the press another 1/12th-1/24th of a turn. It can be that small of an adjustment.

I've shot ammo that was sized slightly below the bottom step and they all fired, but any cases sized that measure below the bottom step will have excessive headspace and those cases, if fired, could case head separate.

I F/L size my cases where they are close to the bottom step, but not below the bottom step. I only use the drop in gauges as a guide. I prefer use a Hornady or the Sinclair headspace/ bump gauges.

With a set of calipers, I can size a case and then make a dummy round and try it in the rifle. I will make a note as to what the numbers are to the threshold of where the cases will/ /will not chamber in the rifle and I can set my F/L die to those numbers.

[bearstatearmory.com]

There is the top step, bottom step, and middle of the gauge. I'm saying that some of my ammo that didn't fire were about .003 below the middle

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[mark501w]

Run the ram all the way up touch the shell holder with die, back off ram add1/2 to1/4 turn on die to make up for press stretch. Size cases,go shooting.

[J-cat]

There is the top step, bottom step, and middle of the gauge. I'm saying that some of my ammo that didn't fire were about .003 below the middle

Those that did not fire, were they hard to extract from the chamber?

[bearstatearmory.com]

Those that did not fire, were they hard to extract from the chamber?

[J-cat]

Looks to me like the bolt isn't even rotating. That's why the firing pin isn't striking the primer.

Do what mark said and report back.

[GeoffLinder]

Yeah, agreed, bolt out of battery (not fully locked) will keep firing pin from coming through enuff to ignite primer. BUT, are your primers on the unfired rounds showing any sign of a primer hit? If so, maybe the issue is with primers not seated all the way. Try chambering the rounds a second time and if they go bang then it's a high primer issue. The primer is getting seated properly by the first strike but not igniting, the second strike works because the primer is now all the way in and doesn't absorb the firing pin force by moving forward. Even if a round is just hanging by the extractor and not right up against the chamber shoulder, it will usually fire as long as the firing pin hits the primer well.

[Munny$hot]

Sounds like your bolt didn't fully seat. Is it a new bolt? If so lube your bolt and fire away. It should break in fairly quickly

[bearstatearmory.com]

Yeah, agreed, bolt out of battery (not fully locked) will keep firing pin from coming through enuff to ignite primer. BUT, are your primers on the unfired rounds showing any sign of a primer hit? If so, maybe the issue is with primers not seated all the way. Try chambering the rounds a second time and if they go bang then it's a high primer issue. The primer is getting seated properly by the first strike but not igniting, the second strike works because the primer is now all the way in and doesn't absorb the firing pin force by moving forward. Even if a round is just hanging by the extractor and not right up against the chamber shoulder, it will usually fire as long as the firing pin hits the primer well.

There is no sign of a primer strike at all. My bolt isn't brand new, it probably has 500 rounds through it.

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[J-cat]

Adjust your sizer die to cam over the shell holder. Make a dummy round. Gently chamber it. Use the forward assist to close the bolt. Make sure the bolt is rotating forward.

Then, adjust the sizer die to only touch the shell holder on the up stroke. Make another dummy round. Try to chamber that one.

Is this how you have the die adjusted tight now: barely missing the shell holder on the up stroke?

[bearstatearmory.com]

Yeah, agreed, bolt out of battery (not fully locked) will keep firing pin from coming through enuff to ignite primer. BUT, are your primers on the unfired rounds showing any sign of a primer hit? If so, maybe the issue is with primers not seated all the way. Try chambering the rounds a second time and if they go bang then it's a high primer issue. The primer is getting seated properly by the first strike but not igniting, the second strike works because the primer is now all the way in and doesn't absorb the firing pin force by moving forward. Even if a round is just hanging by the extractor and not right up against the chamber shoulder, it will usually fire as long as the firing pin hits the primer well.

Here are some pics, as you can see the primers aren't touched at all in the first two pictures. In the second two pictures, I'm trying to show that it's below the bottom of the middle by about .002-.003; therefore, I think I ruined about 300 cases. The last pic with the calipers, I'm trying to show how I got the .002-.003 number, I'm making sure the caliper is sitting flush to the bottom and NOT on one of the steps.

I am thinking that the extra .002-.003" that I've sized my case too short is the problem?


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[bearstatearmory.com]

So I just went to test some thing, I tried firing the same 5 rounds that wouldn't fire last week and they fired fine this time (I changed nothing, didn't clean my gun or anything). I also made some new rounds and the headspace was slightly longer this morning and they also fired fine. Hmmmm

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