6mm GT chamber question

[StreetCred]

Welp. . . Things did not go well Saturday. Shot 2 rounds and both had pierced primers. There's something up with my receiver, bolt, firing pin, all of it, none of it. . . I don't know what the issue is. Had this problem with the previous barrel. Took it to a local gunsmith and they checked a few things - headspace is good, firing pin protrusion is a thou or two long. He measured a new Tikka and that was a thou longer than mine.

 

[Coleredding00]

Welp. . . Things did not go well Saturday. Shot 2 rounds and both had pierced primers. There's something up with my receiver, bolt, firing pin, all of it, none of it. . . I don't know what the issue is. Had this problem with the previous barrel. Took it to a local gunsmith and they checked a few things - headspace is good, firing pin protrusion is a thou or two long. He measured a new Tikka and that was a thou longer than mine.

Not sure in the tikka platform, but i know ive read that rem 700 actions need to have the firing pin hole bushed for the same reason. Too much clearance lets the primer flow too much.

Also, what primers are you using? CCI 450 is usually the go to, the cup is a little thicker.

 

[43.6N]

Welp. . . Things did not go well Saturday. Shot 2 rounds and both had pierced primers. There's something up with my receiver, bolt, firing pin, all of it, none of it. . . I don't know what the issue is. Had this problem with the previous barrel. Took it to a local gunsmith and they checked a few things - headspace is good, firing pin protrusion is a thou or two long. He measured a new Tikka and that was a thou longer than mine.

Can you take a picture of your bolt face and firing pin head?

Once a primer gets pierced, the hot gas can etch the bolt face and pin making pierced primers more likely to occur.

If you have a second tikka bolt, swapping it out can help isolate the problem to the bolt/pin assembly.

 

[StreetCred]

Not sure in the tikka platform, but i know ive read that rem 700 actions need to have the firing pin hole bushed for the same reason. Too much clearance lets the primer flow too much.

Also, what primers are you using? CCI 450 is usually the go to, the cup is a little thicker.

I had this same issue with the previous 6.5CM barrel using Winchester SR primers. Then I found out how horrible those were so I switched to CCI's. That's what I used Saturday.

One thing I though of today is the suppressor. Could that be causing enough back pressure to puncture the primer if the firing pin is just a hair too long? I didn't have any issue with the factory barrel. It wasn't threaded so I never used a suppressor with it.

 

[Lawnboi]

I had this same issue with the previous 6.5CM barrel using Winchester SR primers. Then I found out how horrible those were so I switched to CCI's. That's what I used Saturday.

One thing I though of today is the suppressor. Could that be causing enough back pressure to puncture the primer if the firing pin is just a hair too long? I didn't have any issue with the factory barrel. It wasn't threaded so I never used a suppressor with it.

How much powder?

 

[Coleredding00]

I had this same issue with the previous 6.5CM barrel using Winchester SR primers. Then I found out how horrible those were so I switched to CCI's. That's what I used Saturday.

One thing I though of today is the suppressor. Could that be causing enough back pressure to puncture the primer if the firing pin is just a hair too long? I didn't have any issue with the factory barrel. It wasn't threaded so I never used a suppressor with it.

I doubt its the suppressor, the primer is likely pierced at peak pressure shortly after detonation, long before the suppressor would have an influence.

 

[StreetCred]

How much powder?

38.0gr H4350 with a 105gr BTHP.

 

[wind gypsy]

I had this same issue with the previous 6.5CM barrel using Winchester SR primers. Then I found out how horrible those were so I switched to CCI's. That's what I used Saturday.

One thing I though of today is the suppressor. Could that be causing enough back pressure to puncture the primer if the firing pin is just a hair too long? I didn't have any issue with the factory barrel. It wasn't threaded so I never used a suppressor with it.

What CCIs? 400 and 450s/BR4/41s have a significant difference in cup thickness.

Like others said, prior pierced primers might have damaged the pin/bolt face and made it more prone to future pierced primers. To top it off, it sounds like you started with a hot charge that might be overpressure.

 

[StreetCred]

What CCIs? 400 and 450s/BR4/41s have a significant difference in cup thickness.

Like others said, prior pierced primers might have damaged the pin/bolt face and made it more prone to future pierced primers. To top it off, it sounds like you started with a hot charge that might be overpressure.

I'm using the standard CCI 400's. I spoke with another gunsmith and he said he's got another customer with the same issue. Different rifle and caliber. He switched from the 400's to the 450's and the problem went away.

I'm waiting for the gunsmith to look at my rifle. I think at the minimum I'll need to replace the firing pin or have it shortened a little. There is some minor pitting in the bolt face. Nothing protrudes and all the holes in the primers are in the firing pin dent.

I probably should back off on the charge a bit.

 

[Lawnboi]

Cci 400 are thin cup primers, not suitable for max pressure loads in standard bolt face tikkas especially.

Get some 450s, br4, 41s or rem 7 1/2s. I’d also start a little lower looking at velocity and signs of pressure.