Gunsmithing TL3 cratering primers

[stangfish]

Curious if this is common. After working up loads I noticed that all of my primers were cratered. It is a 6.5 creedmoor, light to medium loads of H4350( 40.3 - 41.5). Firing pin indentations were shallow. Cratering on all loads. No pressure signs. Ignition was consistent as some loads were 3/4" at 400yds.

What i did notice was the radius on the firing pin was long. I would assume that that is what is allowing the flow around the pin and into the hole. Did Bighorn have an issue with firing pins with too large of a radius at one time? I would attempt a repair if the protrusion was adjustable. Thanks in advance for responses from people that understand the issue.

 

[Threadcutter308]

A pic or two of a spent primer would be helpful.

 

[stangfish]

I didn't take the time as I am pretty sure the primer is cratered. And I am fairly certain the firing pin caused it.
How I came to this conclusion. The firing pin will rarely penetrate the plane of the base of the primer .025". The Firing pin has a radius that is almost .040" long on the firing pin tip. The diameter of the radius at the plane of the bolt face is considerably smaller than the firing pin bore. This allows room for the primer cup material to flow around the firing pin radius. It has the largest(longest axially) radius of any firing pin I have ever seen.

The question surrounds the Bighorn action specifically and experience with that action and it's firing pin radius. Thanks in advance for responses from people that understand the issue.

 

[Supersubes]

I own a few and have built a few. None have issues. Call them, they’ll straighten it out.

 

[Awesymoto]

With FG215M primers in my TL3 I get the same cratering on very low loads. Factory ammo does it too, I’m not worried.

 

[Threadcutter308]

I didn't take the time as I am pretty sure the primer is cratered. And I am fairly certain the firing pin caused it.
How I came to this conclusion. The firing pin will rarely penetrate the plane of the base of the primer .025". The Firing pin has a radius that is almost .040" long on the firing pin tip. The diameter of the radius at the plane of the bolt face is considerably smaller than the firing pin bore. This allows room for the primer cup material to flow around the firing pin radius. It has the largest(longest axially) radius of any firing pin I have ever seen.

The question surrounds the Bighorn action specifically and experience with that action and it's firing pin radius. Thanks in advance for responses from people that understand the issue.

You're welcome.

 

[stangfish]

Sorry Threadcutter. I tried to weed out the inexperienced.

 

[Threadcutter308]

Sorry Threadcutter. I tried to weed out the inexperienced.

Just call Zermatt. I have 3 TL-2's and they are exceptional in every way. If you can get a hold of A.J., he's a great guy and will take care of you. If you get someone else, I am highly confident you will still be well taken care of.

Good luck and please post results as a follow up. It helps all of us others that have taken an interest in your situation.

 

[stangfish]

Will do. I will probably let it ride unless they want to replace the pin. I am going to pull the pin assembly and see if the protrusion is adjustable without cutting the back of the bolt head here in a minute. With everything being modular I don't think I would modify any dimentions and the price of a firing pin assembly is prohibitive. But if I could shorten that radius and bring the protrusion to somewhere around .035" I would be happy.

 

[DairyDictator]

Got my TL3 last year and have about 1500 rounds of 6. 5 creed through it. Nothing dangerous, but some berger factory rounds had some raised edges I could barely catch with a fingernail on a hot day. Never had a problem with cratering. They'll flatten but generally not crater like 700's do. My guess is the firing pin is on the smaller edge of tolerance and firing pin hole is on the larger side. Nothing to be terribly worried about (All the 700's have been doing it for decades and they're just fine), but it may be worth a call.

 

[Threadcutter308]

Will do. I will probably let it ride unless they want to replace the pin. I am going to pull the pin assembly and see if the protrusion is adjustable without cutting the back of the bolt head here in a minute. With everything being modular I don't think I would modify any dimentions and the price of a firing pin assembly is prohibitive. But if I could shorten that radius and bring the protrusion to somewhere around .035" I would be happy.

Are you reloading and is your brass possibly headspaced on the "short" side ? (re-reading your original post, looks like you answered that, as well as my squib question below.....).

My experience with Bighorn/Zermatt has been exemplary. I doubt (but it's always possible......you know, humans and such) that your action/FP left the factory in an out of tolerance condition. But, pretty unlikely.

I very much doubt the F/P "protrusion" is "adjustable", unless you were to remove it from the bolt and alter it in a lathe, or grind it. Which, I would advise against doing. You'd be altering it from the original condition that it left the factory in and you'd be assuming any/all liability.

Did you ever have any Squibs/failure to fire ? (re-reading your original post, looks like you answered that.....).

What is the Firing Pin OD in the area where it protrudes through the hole in the bolt head and what is the ID of the FP hole in the bolt head ? (I'd measure mine, but I'm not home right now.....)

I tend to think that if you are not having any squibs that you don't actually have any problem. If there is a "ring" at the diameter of the firing pin indentation on the primer and there are no other pressure signs (difficult to extract/ejector indentations), you should be OK. If there is reasonable/light drag on your bolt when closing on a reloaded/neck sized round, that can help, if your first round was short on headspace.

 

[stangfish]

You are rambling brother and you missed the object of the post.

 

[Threadcutter308]

Unbelievable.

 

[stangfish]

Threadcutter, I have an issue that I know what is causing it. You started your first response trying to troubleshoot it. Happy fathers day man and I love you.

 

[Tokay444]

I’d honestly be surprised if pin protrusion isn’t adjustable in an TL3.

 

[Sheldon N]

Curious if this is common. After working up loads I noticed that all of my primers were cratered. It is a 6.5 creedmoor, light to medium loads of H4350( 40.3 - 41.5). Firing pin indentations were shallow. Cratering on all loads. No pressure signs. Ignition was consistent as some loads were 3/4" at 400yds.

I've got a couple TL3's and the primers look cratered on moderate loads, nothing severe but there is a slight lip to the primer shape around the firing pin strike. I'd say it's normal/common, likely for the reason you outlined.

 

[Zack_va248]

I've got a couple TL3's and the primers look cratered on moderate loads, nothing severe but there is a slight lip to the primer shape around the firing pin strike. I'd say it's normal/common, likely for the reason you outlined.

I get the same on factory loads and reloads alike. slight lip. never caused any issues thus far.