Light primer hits or.....

[#40Fan]

How about a BTO measurement? Are they the same as when you loaded them? Does your ejector pin move freely?

Ledd, I do think it is an optical illusion on the primer depth.

 

[luckeeshot]

you haven't stripped your bolt yet ? some old grease could cause a light strike

 

[Texas10]

I'm with Ledd Slinger here. Did you use a uniformer tool in the pockets and if so, what depth did it cut to? They do look waaaaay deep to me too.

 

[ridgeway]

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

I'm talking about the roll pin that holds the cocking piece to the pin. Can't see it untill you compress the spring. They can work loose and drag inside cocking piece.

 

[randyc]

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

I recently had new fire form Lapua brass that would fire on virgin firing and then would not. 15 out of 100 had a different look in primer pocket after resize and cleaned, almost like raised in the middle of primer pocket. I could see this easily and no matter if seated bullet .020 longer could I get it to fire. Trashed these 15.

 

[ShootDots]

My bet: You have tiny bits of primer cup material INSIDE the bolt body. These fragments are inhibiting the free forward movement of the firing pin! Pull the firing pin mechanism from the bolt and tap the bolt upside down and watch what comes out!

 

[JohnKielly]

I recently had new fire form Lapua brass that would fire on virgin firing and then would not. 15 out of 100 had a different look in primer pocket after resize and cleaned, almost like raised in the middle of primer pocket. I could see this easily and no matter if seated bullet .020 longer could I get it to fire. Trashed these 15.

I did that once when the primer pin on my sizing die was set too deep & it domed the pocket.

 

[mtang45]

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.

I do believe that even though I set the seater up for "touching" the lands, there were a few that were off the lands because of bullet length variation. That combined with the new brass may have allowed the case some extra movement.

As far as the primer seating depth, they were done on a Co-ax to a mechanical stop, so hopefully they were all the same.

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?

That's a good idea. I'll try that at the range this week.

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?

Yep, blasted the bolt out last night. I'll measure the firing pin fall tonight. I'm thinking maybe a combination little things created the perfect storm. New cases .065 short of the chamber, bullets seated a few thou short of touching, some gunk in the bolt not allowing a full fall or at least slowing the firing pin down. I'll do some testing at the range this week.

 

[Lucky Shooter]

I went through a similar experience shooting new Lapua 222 brass-----dented primers but no ignition.

The bolt would partially close on a GO gauge.

Using a headspace comparator, I checked 100 new cases against the GO gauge

85 cases measured .002"-.003" shorter than the GO gauge.

10 cases measured .004"-.005" shorter than the GO gauge.

5 cases measured .000"-.001" shorter than the GO gauge.

In my case, not being a commercial operator, this usually results in a decision to
ignore the GO gauge and SAAMI and cut the chamber to a depth that will have a
slight crush fit on the new brass.

The firing pin protrusion was measured and reported to the action manufacturer, who
confirmed it to be in the proper range. I was also sent a new firing pin spring, which hasn't
been installed yet.

The chamber was shortened by .002" and there have been no failures-to-fire------yet.

I'm waiting to see if we'll hear from alinwa on such as this.

There is more for me to do but I'm trying to wait for some cooler weather.

Good luck to you.

A. Weldy

 

[Ggmac]

Your new cases are .065" shorter than chamber ? And firing pin protrusion is ?

 

[Uncle Ed]

Your new cases are .065" shorter than chamber ? And firing pin protrusion is ?

That's a typo mtang45 dropped a zero.
New case 1.1565
Fired case 1.1630
Difference .0065

NOTE, see mtang45 photos of cases.

 

[Lucky Shooter]

Ggmac,

Per the posted numbers----the cases were measured on a headspace comparator
and compared to the same measurement on the GO gauge----100 cases were measured.

The headspace comparator measurements resulted in the posted distribution.

The shortest cases were .005" shorter than the GO gauge.

The longest cases were EQUAL to the GO gauge----don't remember the exact number of
cases that measured equal to the GO gauge but there were less than 5.

My thinking was that 95% of these cases were significantly shorter than the only hard
reference I had----the GO gauge.

My wording-----(chamber was shortened by .002") might have been misleading. The breech
face was set back .002" closer to the bolt face----in effect "shortening" the chamber. This was
accomplished by taking .002" off the tenon shoulder. No reamer work was required.

I don't remember how much firing pin protrusion the bolt had but the action manufacturer
said it was within their range. This protrusion was arrived at with 2 measurements with a depth
micrometer-----1) measure from bolt nose to bolt face 2) measure from bolt nose to tip of
protruding firing pin. The difference between these measurements is the protrusion. This was
the only method available to me with the tools I have.

I hope this adds some clarity.

A. Weldy

 

[mtang45]

That's a typo mtang45 dropped a zero.
New case 1.1565
Fired case 1.1630
Difference .0065

NOTE, see mtang45 photos of cases.

Yes, typo on my part. Sorry about that!

 

[Albany Mountain]

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

That will happen. I bought a box of 100 lapua (which was probably headspaced correctly) and had about 50% FTF (or 50 rounds). After checking the chamber was about .008+ longer. Tried seating into lands but only 25 of the 50 went off. Tried seating into lands with high primers, only 13 of the 25 went off. Tried again with the long bullet and high primers, only 4 of the remaining twelve went off. I then got pissed and pulled paper out of my scorebook, licked to wet the paper, and wrapped it around the shoulder and rechambered. DONE! haven't had a problem since with the same brass ever, when I resized .003 undersized from this chamber.

 

[Ledd Slinger]

Not trying to argue with or offend Mr. Albany Mountain, but I would advise against putting anything on the shoulder of a case. The whole point is to fire-form the cases. Putting a foreign object in the chamber is not only dangerous, but will not allow for true case formation to the chamber. Then there will also be debris left in the chamber after each round is fired. Not good

The ejector plunger is what pushes the case too far away from the boltface when there is excessive headspace. Remove the ejector plunger and spring in the bolt face (not the extractor claw), place each case in the bolt face before chambering, and fire the rounds. They should go BANG!

If not, the best option, although a little more time consuming, would be to expand the case necks up with a .257 expander mandrel, then gradually FL size the neck back down in the 6BR die until you have tight headspace where the bolt closes firmly on the case. This is the "false shoulder" method I use for fireforming certain cases. Still remove the ejector plunger to ensure the cases are seated firmly against the bolt face when setting headspace on the false shoulder.

 

[mtang45]

Alright folks, I measured CBTO on all the misfires and all but one were up against the lands, one was .002 short. So probably not pushing the case forward. I then pulled all the misfires down and fed the primed cases through the action. All went POP except for one CCI-450. Tried it 2 times and no-go. The firing pin crater in the primer kept getting bigger but it still wouldn't go. So with cleaned out bolt and no bullet to keep the primer up against the bolt face, all but one went bang. I think the problem was a fouled bolt and maybe one bad primer.

For those that asked the firing pin fall was .225

Thank you all for all the problem solving help!

 

[Webster]

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

All the hits look the same to me. Whenever I had a problem it always turned out to be not seating the primers deep enough. All Lapua cases pockets uniformed. No longer adjust the seater to a fixed position. I always seat by feel now. I have the primer tool adjusted so that when the primers feel properly seated the tool handle is about 1/4" from the tool body. With a few cases the handle touches the body. Pressure to seat doesn't feel the same on all cases probably because the pockets are swaged in place and not machined for depth or diameter. If the firing pin has to push the primer forward a little energy is lost that would crush the primer charge. Same FP dent?