Light primer hits or.....

[mtang45]

I was at the range yesterday doing some load testing on my 6BR and fired 35 rounds, no problem. Ran a brush and a couple of patches down the barrel to get semi clean for the next load. Shot 4 foulers and started in on the next set. I immediately started getting FTF. Out of 30 rounds in the next test 10 failed to go bang. 15 rounds were loaded with CCI BR4 primers and 15 with CCI-450. At first I thought I had a bad lot of BR4's as 7 of the 15 failed. But when I started in on the 450's I also had 3 of them fail.

New Lapua brass and all bullets seated touching the lands. I have checked the firing pin protrusion and its roughly .050". In my opinion the hits in the photo look pretty good, but I don't often examine primer strikes where there was a FTF so maybe they are light.

In the picture the 7 on the left are the BR4's and the 3 on the right are the 450's

 

[LVLAaron]

Any chance you loaded the primers when the cases were at all wet or lubed with something?

 

[mtang45]

Any chance you loaded the primers when the cases were at all wet or lubed with something?

I don't think so. They are new Lapua cases so no lube involved. Definitely no water.

 

[Ggmac]

What make rifle , who installed barrel , have you had any blanked primers in the past ? Could be a little long on headspace

 

[mtang45]

What make rifle , who installed barrel , have you had any blanked primers in the past ? Could be a little long on headspace

Its a Borden action, Bartlein barrel put together by Gordy Gritters. The rifle has roughly 300 rounds through it without a problem until yesterday.

 

[Ggmac]

Its a Borden action, Bartlein barrel put together by Gordy Gritters. The rifle has roughly 300 rounds through it without a problem until yesterday.

Was it a new box of Lapua ? Do you have any way of checking a fired case vs unfired case for length from base to datum ? Knowing no good way but a Wilson cartridge case gauge or a few other devices on the market .
No new triggers , so still leaning to a case length to chamber .

 

[Ggmac]

If you had any Plastigauge , you could take a new unfired case , place the Plastigauge on the base an close bolt , just to eliminate the possibility .

 

[Ggmac]

Any chance your primers or powders got infected ?

 

[Rsadams]

Firing pin channel gunked up or maybe a broken pin etc...?

 

[lpreddick]

New brass possibly not headspacing and bullet only touching, so firing pin strike pushes case forward? Use a headspace gauge and measure new vs fired brass. I'm currently fireforming brass for a wildcat whose shoulder is quite short in the chamber, so i seat bullets .020 into the lands. A few are ftf, so i cock the firing pin and they go BOOM. What's the condition of the firing pin spring?

 

[mtang45]

Was it a new box of Lapua ? Do you have any way of checking a fired case vs unfired case for length from base to datum ? Knowing no good way but a Wilson cartridge case gauge or a few other devices on the market .
No new triggers , so still leaning to a case length to chamber .

Hornady gauge measuring base to datum on virgin case and fired case (pic attached).

Any chance your primers or powders got infected ?

Can't say zero chance, but honestly believe zero chance. I'm very careful with powder changes and do the same routine every time. Primer storage is isolated and I can't think how contamination would be possible.

Firing pin channel gunked up or maybe a broken pin etc...?

Pic of firing pin attached

 

[mtang45]

New brass possibly not headspacing and bullet only touching, so firing pin strike pushes case forward? Use a headspace gauge and measure new vs fired brass. I'm currently fireforming brass for a wildcat whose shoulder is quite short in the chamber, so i seat bullets .020 into the lands. A few are ftf, so i cock the firing pin and they go BOOM. What's the condition of the firing pin spring?

Yes, I have had this happen to me fire forming a wildcat cartridge. But is the roughly .007 difference between virgin cases and the fired cases enough to do that? As far as the spring, its 300 rounds old. When I took it apart there was some grease in there but why would it suddenly change from the first 35 shots

 

[ridgeway]

Install a new firing pin spring and check roll pin to see if it's dragging inside shroud.

 

[Uncle Ed]

mtang45

Any chance even though you seated the bullets into the lands, you might not had enough bullet grip. Meaning if the bullets moved when the firing pin hit the primers it might have softened the blow.

The new unfired cases were .0065 shorter than the fired cases so I do not think that amount had any effect.

Does your priming tool have a adjustable mechanical stop or are the primer all seated by feel.

 

[Prose]

I had the same problem yesterday. My before and after was about 10 thousandths. At what difference in headspace would one start to blame headspace?

 

[Rsadams]

Is it just me or does it look like the strikes were getting lighter in the pictures on the OP..?

 

[Bc'z]

Is it just me or does it look like the strikes were getting lighter in the pictures on the OP..?

Could be camera angle, but yes.
All seem to take out the "B" to the same degree, also look to be seated to equal depth by photo.
Could you put a couple thin strips of tape on shoulders and see if they'll fire to check if it's a headspace issue?

 

[338rumshooter]

I'm with Ridgeway, have you checked for firing pin drag and/or protrution?

 

[Ledd Slinger]

You can try removing your ejector spring and plunger then place the cases in the bolt face prior to chambering then fire. Should work. If you get FTF on fired cases, then you definitely need to try other primers and maybe change out your firing pin spring.

Of course strip the bolt down and give it a good cleaning first. CRC "Mass Air Flow Sensor Cleaner" works awesome for that task. Can get it at any Auto Zone

What's the length of fall on your firing pin?

 

[Ledd Slinger]

How deep are those primers seated in the FTF cases? They appear to be sitting pretty deep in the pocket. Maybe just the photo playing tricks on my eyes...