Failure to Fire Tikka 223

[rugger7622]

The only brass that is set back .007 are the one's that do not fire on the 1st attempt. All other brass essentially doesn't grow at all. If I measure .000 on the gauge, afterwards it's basically the same, maybe .0005.

 

[rugger7622]

OK, so are the same primers being used in both the LC and Starline brass?

And this still doesn't explain the .007 difference in the 'before' and 'after' on the LC brass.
The cartridge base to datum is .007 less, or the primer is seated .007 deeper in the pocket, or ..... ???

Yes sir

 

[rugger7622]

I would never have guessed with a fail to fire and re-cock would push the shoulders back that much, but I've seen it now 10-15 times in the last year. I've gone down the path of primers, crimped pockets, crush, etc. and thought it was potentially crush....but proved myself wrong today.

 

[M-61]

LC brass has been sized too much and your cartridge base to datum line measurement is under spec

That is the headspace. Using ‘effort’ to close the bolt means there is minimum headspace. Which is ok by me and won’t cause a FTF.
I agree 100% with your measuring requests. All of them.

 

[DShortt]

Yes means same primers?

Again, what exactly measures .007 different on the LC brass when you have a FTF? Cartridge base to datum line, or primer seating depth?

 

[rugger7622]

No effort in closing the bolt between those that fire and those that don't

 

[rugger7622]

The shoulder on the failure to fire pieces of brass, two of them today, are both .007 set back vs. where they started and the other 28 pieces of brass that did fire on the 1st attempt basically have no growth.

 

[M-61]

would never have guessed with a fail to fire and re-cock would push the shoulders back that much

Me neither. But just try my empty case request up above. It’s a reach but in order to a problem you have to know exactly what the problem is. Fixing a problem is well, easy…. correctly troubleshooting it is the skill.

 

[DShortt]

That is the headspace. Using ‘effort’ to close the bolt means there is minimum headspace. Which is ok by me and won’t cause a FTF.
I agree 100% with your measuring requests. All of them.

I agree, but something doesn't make sense. I can't imagine closing the bolt is making the case .007" shorter and even if it did, that would still mean the case is anything but sized too much.

So.... I presume we're talking about primer seating depth?

 

[rugger7622]

No, not primer depth. I load a measured piece of brass at .000, fire it, it doesn't go off, I re-cock, it goes off and between the two attempts when I get back home and measure the shoulder, the shoulder have been pushed back .007. It appears the firing pin is hitting with enough force to push the shoulders back .007 but not setting off the primer......makes no sense to me at all.

 

[rugger7622]

I agree, but something doesn't make sense. I can't imagine closing the bolt is making the case .007" shorter and even if it did, that would still mean the case is anything but sized too much.

So.... I presume we're talking about primer seating depth?

You are right, no additional force required to close the bolt on this brass, it's the same shoulder measurement as all the other brass that fires

 

[rugger7622]

Using this guage as well as a comparator. https://www.whiddengunworks.com/product/case-gauge-3/

 

[DShortt]

The shoulder on the failure to fire pieces of brass, two of them today, are both .007 set back vs. where they started and the other 28 pieces of brass that did fire on the 1st attempt basically have no growth.

I'm convinced you have at least some LC cases that are sized too much.

Measure 50 of them before priming and loading them. I bet some are short compared to the rest. In other words, the FTF cases were short before you chambered them and attempted to fire them.

 

[DShortt]

You are right, no additional force required to close the bolt on this brass, it's the same shoulder measurement as all the other brass that fires

We're going in circles.

Either the brass that fails to fire is. 007" shorter than the brass that does fire, or it isn't.

Which is it, because this is contradictory.

 

[rugger7622]

I'm convinced you have at least some LC cases that are sized too much.

Measure 50 of them before priming and loading them. I bet some are short compared to the rest. In other words, the FTF cases were short before you chambered them and attempted to fire them.

I agree with you, however, I sorted and measured 100 pieces of LC brass and only loaded 30 that were within .0005 of each other to rule that out. I've been having this issue over the past 8 months so over the winter this brass got the most attention I've ever given to any brass. The 30 pieces I fired today, shoulder measurement wise, were as close to identical as possible with two guages.

 

[rugger7622]

The brass starts off at the exact same should measurement size, I shoot it, the ones that don't fire have the shoulders pushed back at least .007 after they fire on the 2nd attempt. The ones that do fire have essentially no growth. No brass is starting off .007 shorter in should measurement.

 

[M-61]

I can't imagine closing the bolt is making the case .007" shorter and even if it did, that would still mean the case is anything but sized too much.

Yes. Something is really off with the measurements.
I just can’t get a handle on a number of the things that are going on therefore I’m all over the map trying to help as best I can

 

[DShortt]

I agree with you, however, I sorted and measured 100 pieces of LC brass and only loaded 30 that were within .0005 of each other to rule that out. I've been having this issue over the past 8 months so over the winter this brass got the most attention I've ever given to any brass. The 30 pieces I fired today, shoulder measurement wise, were as close to identical as possible with two guages.

So where is the .007" difference you mentioned in post #1 come from?

"The brass that failed has been set back .007" compared to starting."

There's NO WAY a firing pin strike is changing the headspace dimension by .007" on Lake City brass. That stuff is notoriously robust.

 

[DShortt]

Yes. Something is really off with the measurements.
I just can’t get a handle on a number of the things that are going on therefore I’m all over the map trying to help as best I can

It's one of 3 things.

You have some LC brass that has been sized too much and is below your necessary headspace dimension.

Or, you have some LC brass that has had the primer pockets cut too deeply and the firing pin can not strike the primer cap forcefully enough.

Or there is missing information.

Given what you've posted, it's a problem with the batch of LC brass you have because you've stated Starline brass fires every time. Or you have different primers in the LC brass.

There are only so many possibilities.

 

[rugger7622]

I agree it doesn't pass logic, but I'm seeing a minimum of .007 setback on FTF LC brass. I can't explain it but it is for sure happening.