Gunsmithing Proof CF prefit barrel on Tikka T3x - Bolt Closes on no-go gauge but not on Field gauge

[LANCER]

So I decided to install a Proof Carbon barrel on my T3x. Prior to install, I cerakoted both the action and the steel parts of the barrel. I did not tape off the action face nor the mating face of the extension, although I DID tape off the barrel threads. When I installed, I only had a go-gauge, and since the bolt closed on the go-gauge, I decided it was "good enough" like an idiot.
Few months later, I'm on my second firing of Lapua 308 brass in this chamber (but had 8 firings before in old factory barrel) and I had 3 case head separations on a mildly warm load.
Decided to buy No-Go and Field Gauges of the same brand just to make sure I wasn't having a headspace issue. They are Forster gauges.

The no-go gauge closes with slight bolt resistance.
Field gauge does NOT close.

I read that closing on a no-go is not necessarily terrible as long as it doesn't close on a field gauge. However it seems I have a "generous" headspace. Brass had previously been bump-sized and neck-sized after fireforming again in the new chamber. I've fired other ammo that I loaded for my semi-auto (LC LR brass) and of course did not have any issues. I have not measured my LC--LR brass which was new prior to firing.

Am I over thinking and my Lapua brass was simply shot out or had ICHS or is my headspace really that much off? Should I have a gunsmith turn a couple thou off my barrel to remove the cerakote so I can have tighter headspace? I want to make sure before I run new brass through this chamber. It shoots 1/3 MOA currently on my good days.

 

[DAVETOOLEY]

Your headspace is fine. I always recommend starting with new brass in a new barrel. Almost always leads to some problem if you don't.

 

[Raufoss]

Your fine, carry on and don’t worry.

A small DT said it’s better to start with new brass if you don’t want to experience some issues.

 

[LANCER]

Thanks guys. I'll get a new batch of Lapua or Peterson for it.

 

[JD. martin]

So I decided to install a Proof Carbon barrel on my T3x. Prior to install, I cerakoted both the action and the steel parts of the barrel. I did not tape off the action face nor the mating face of the extension, although I DID tape off the barrel threads. When I installed, I only had a go-gauge, and since the bolt closed on the go-gauge, I decided it was "good enough" like an idiot.
Few months later, I'm on my second firing of Lapua 308 brass in this chamber (but had 8 firings before in old factory barrel) and I had 3 case head separations on a mildly warm load.
Decided to buy No-Go and Field Gauges of the same brand just to make sure I wasn't having a headspace issue. They are Forster gauges.

The no-go gauge closes with slight bolt resistance.
Field gauge does NOT close.

I read that closing on a no-go is not necessarily terrible as long as it doesn't close on a field gauge. However it seems I have a "generous" headspace. Brass had previously been bump-sized and neck-sized after fireforming again in the new chamber. I've fired other ammo that I loaded for my semi-auto (LC LR brass) and of course did not have any issues. I have not measured my LC--LR brass which was new prior to firing.

Am I over thinking and my Lapua brass was simply shot out or had ICHS or is my headspace really that much off? Should I have a gunsmith turn a couple thou off my barrel to remove the cerakote so I can have tighter headspace? I want to make sure before I run new brass through this chamber. It shoots 1/3 MOA currently on my good days.

I have 390 rds on new 6.5CM Proof research carbon barrel installed by smith. I happen to just notice although I had Forster field Guage but no,go/No Go Guage’s so I did same bought go and No go Forster Guage’s and SAME PROBLEM!! Closes with little resistance
On no go but NOT FEILD GUAGE!! Man I was worried till I found you all and the ole boys saying “ CARRY ON”Thanks
Tremendously you all

 

[Shooter71]

Your headspace is likely long, which isn’t a big deal if you’re setting your fl sizing die properly. If you don’t know exactly how much back you’re setting your shoulder, for that chamber, you need to.

 

[JD. martin]

Your headspace is likely long, which isn’t a big deal if you’re setting your fl sizing die properly. If you don’t know exactly how much back you’re setting your shoulder, for that chamber, you need to.

Thanks MR!!! I appreciate your input Sir.
never thought to ask on here plenty
shooters that have FORGOTTEN MORE THAN ILL EVER KNOW. Even though been dabbling in long range for 8yrs now. Yea I bum shldr .020 thou with an average of 2.30,95” proof prefit in tikka
Tac A1. Thanks agin my freind

 

[Shooter71]

Did you mean .002”, instead of .020”? Might’ve been a typo. .002” would be appropriate, .020” would definitely lead to case stretching and separations. You probably know, but for anyone that might be reading, head separations can be pretty dangerous and potentially hurt you and the rifle. If your setup and brass control is good you’ll get loose pockets after a while, but not head separations.

 

[308pirate]

This is why I won't consider shouldered pre fits, regardless of the action, for DIY rebarreling.

 

[Mike Casselton]

Thanks MR!!! I appreciate your input Sir.
never thought to ask on here plenty
shooters that have FORGOTTEN MORE THAN ILL EVER KNOW. Even though been dabbling in long range for 8yrs now. Yea I bum shldr .020 thou with an average of 2.30,95” proof prefit in tikka
Tac A1. Thanks agin my freind

Please, for the love of all that's holy, please use complete words and sentences.

There's no reason to abbreviate that much if you want anyone to have a chance a understanding what you're trying to say.

Thank you,
Non-Management


Also, yeah, I'm pretty sure you meant .002, not .020.
Although, I've seen it done, the brass becomes 2-pc brass very quickly.
Glad you got it sorted out.

 

[JD. martin]

Did you mean .002”, instead of .020”? Might’ve been a typo. .002” would be appropriate, .020” would definitely lead to case stretching and separations. You probably know, but for anyone that might be reading, head separations can be pretty dangerous and potentially hurt you and the rifle. If your setup and brass control is good you’ll get loose pockets after a while, but not head separations.

Shooter71:
Yes SIR!! Thanks most definitely typo on my part,nice catch. It’s .002” thou
Not .020” thou. Have always run lapua brass so this barrel was no exception after second firing case growth has stopped not much of any trimming. Tube is averaging .371” to .405” as long as I’m doing my part!! Been happy with it. Thanks again MR. Shooter71: thanks for response and corrections. Have great day Brother. J. Martin

 

[JD. martin]

Please, for the love of all that's holy, please use complete words and sentences.

There's no reason to abbreviate that much if you want anyone to have a chance a understanding what you're trying to say.

Thank you,
Non-Management


Also, yeah, I'm pretty sure you meant .002, not .020.
Although, I've seen it done, the brass becomes 2-pc brass very quickly.
Glad you got it sorted out.

Thousand pardons Sir, Never been very good at grammar/punctuation in any form of writing. Not sure this is correct
Lmao. Hate typing txting the whole Ball, so always just half ass my writing more shooting. I’ll get ir fixed oops, Get it fixed. Thanks MR. Much appreciated
J. Martin.

 

[Mike Casselton]

JD,
I wish more people on the Hide would take a good natured ribbing like you did.

On a serious note though, lots of people ask questions and can't even form a proper sentence. Yours wasn't like that, just hard to follow with the texting style abbreviations.

It's all good.

 

[LeftyJason]

Just a heads up. "0.002" thou" is redundant. Pick one or the other. "2 thou" or "0.002" " works.

-sincerely someone who regularly works in tenths (0.0001") or ten millionths (0.00001") increments.

 

[LANCER]

A small update:
I was tired of getting insipient case head separations at 3 firings, so I decided last weekend to pull the barrel and fix my headspace issues. Since I cerakoted the action face, I tackled the low hanging fruit by getting my flattest stone and carefully removing the cerakote on the face. Took a few passes until I saw shiny metal all around. Retorqued the barrel, and with my new go/no-go gauges I stripped the bolt and snuck up to the no-go gauge, each time taking two or three passes on the stone. Once the bolt wouldn't close on the no-go gauge, I wanted to use the scotch tape method on the go-gauge until I felt resistance.
It took two more passes on the stone until the bolt wouldn't close on the go-gauge with one layer of scotch tape on it. I don't know how thick the cerakote was, but it was enough to cause the no-go gauge to close the bolt. I retorqued the barrel to 65 ft/lbs, then loosened it, then retorqued to 85ft/lbs. I loosened it again, and retorqued to 85ft/lbs. Previous torque was 100ft/lbs and contrary to my non-machinist belief, it may have actually "stretched" the chamber by having higher torque. So I checked with go/no-go gauges after everything was put together, and it fails on the no-go (as expected) and will not close on a go-gauge with one tape layer without some resistance. Remove the tape and the bolt closes smoothly on the go-gauge.

I shot the rifle this weekend with my loads, and a few rounds loaded on the previously-fireformed brass had a tad of resistance chambering, but I was confident I wasn't over stretching the brass this time around. I'll buy a new box of Lapua and I should be good to go. Not sure what change this made to precision and accuracy, but did a first-round hit at 1000 yards with the .308.

So, check your prefits, there obviously has to be a little bit of tolerance for function on multiple actions, but if you cerakote or paint your action, be mindful of that front action to barrel interface, as well as the barrel shoulder. I would mask those off before coating. Don't do what I did.

 

[LANCER]

Your headspace is fine. I always recommend starting with new brass in a new barrel. Almost always leads to some problem if you don't.

I bought two bags of starline (Lapua out of stock when I posted initially) and on the third firing I had ICHS on 30% of the cases. I have since fixed the generous headspace issue and will buy new brass again.

 

[KnowNothing256]

Yeah I was reading the beginning of this thread just now, and was surprised at how many people were telling you you were good to go, when case head separations are not good to go. Seemed like they skimmed right past that part. They were correct that closing on a no-go (esp with resistance) but not closing on a Field gauge is generally acceptable; however, case head separations throws that right out the window in my mind.

I don't think you need new brass on a new barrel, although it's nice to have. The only real risk with going with fired brass is that you might have to bump the shoulder further back; I expect you WILL have to do this if you use fired brass in your reduced-headspace setup, since you basically took it down to right around SAAMI minimum.

If this doesn't fix it, it's possible you have an out-of-spec chamber near where you're seeing the separation start; if there was a machining error, you can end up with a chamber that's out-of-round and too large, causing bulging, case thinning, and possible/eventual separation at that location. I'm not sure the best way to check this, other than to measure the diameter of your fired cases that are showing separation signs; if they're notably larger than the SAAMI diagram, you might have a chamber issue rather than a brass issue. I'll be honest, I suspect this is more likely than a headspace problem, since after all, not closing on a field gauge is usually fine. If you're resizing your brass all the way back down to SAAMI spec though, after firing in a chamber with longer headspace, then yeah you might just be overworking the brass and it gets hard and brittle, then starts to fracture. Now that I think about it, is this what you're doing?

What's your resizing method? Are you bumping the shoulder, or are you fully sizing your cases with an unmodified FL sizing die? If you're FL resizing brass from a long chamber, then yeah you might just be sizing too much. The Redding Competition Die Holders are the best fix for this in my opinion.

 

[Ledzep]

Full disclosure, I don't know what you have going on lancer, but I've done fire-form wildcats before that blew the shoulder out .030 and never had ICHS issues on subsequent sizings until I got well over 10 firings on the cases. Granted, I was seating bullets long on purpose to form those cases....

Do you have a comparator attachment for your calipers to measure headspace when you resize? This reminds me of when I first started reloading for old .30-06 milsurps and just ran the die all the way down and got case heads to pop in 4 firings.

 

[LANCER]

Yeah I was reading the beginning of this thread just now, and was surprised at how many people were telling you you were good to go, when case head separations are not good to go. Seemed like they skimmed right past that part. They were correct that closing on a no-go (esp with resistance) but not closing on a Field gauge is generally acceptable; however, case head separations throws that right out the window in my mind.

I don't think you need new brass on a new barrel, although it's nice to have. The only real risk with going with fired brass is that you might have to bump the shoulder further back; I expect you WILL have to do this if you use fired brass in your reduced-headspace setup, since you basically took it down to right around SAAMI minimum.

If this doesn't fix it, it's possible you have an out-of-spec chamber near where you're seeing the separation start; if there was a machining error, you can end up with a chamber that's out-of-round and too large, causing bulging, case thinning, and possible/eventual separation at that location. I'm not sure the best way to check this, other than to measure the diameter of your fired cases that are showing separation signs; if they're notably larger than the SAAMI diagram, you might have a chamber issue rather than a brass issue. I'll be honest, I suspect this is more likely than a headspace problem, since after all, not closing on a field gauge is usually fine. If you're resizing your brass all the way back down to SAAMI spec though, after firing in a chamber with longer headspace, then yeah you might just be overworking the brass and it gets hard and brittle, then starts to fracture. Now that I think about it, is this what you're doing?

What's your resizing method? Are you bumping the shoulder, or are you fully sizing your cases with an unmodified FL sizing die? If you're FL resizing brass from a long chamber, then yeah you might just be sizing too much. The Redding Competition Die Holders are the best fix for this in my opinion.

I've always taken care to FL size my brass "the right way" as best as I'm able. I use the Hornady comparator set on all my bolt gun brass, as well as the RCBS precision MIC set and can confirm that my brass doesn't get shoulder-bumped more than 2 thou each time. I use 2 dies to size: A Lee collet neck sizer, and then a Redding body die adjusted to bump 2 thousandths. This is done on a Redding T7 which does have a slight flex on the turret when sizing. Saving up for a zero or a Prazi.

There is the occasional one that gets 3 thou when setting up the dies, but usually at 2 thou. There is no unusual deformation of the cases as far as I can see (haven't measured) but the runout is within 2-3 thou across the necks, and around the shoulder area when measured. I don't believe it's the chamber, but I will compare to a SAAMI diagram on the fired brass before resizing to see if I have any off-axis dimensional changes. I have borescoped the chamber and it looks clean, smooth, and no indication of runout or issues (visually)

Thanks for all the suggestions, I will try a few things out and post again.

(I have not yet resized the fired brass out of the "corrected" setup, but will be able to tell against my notes on my previous fired brass whether I'll have to bump excessively now or not.) My resized prepped brass from the old headspaced settings chambers snugly, but without resistance.

 

[LANCER]

Full disclosure, I don't know what you have going on lancer, but I've done fire-form wildcats before that blew the shoulder out .030 and never had ICHS issues on subsequent sizings until I got well over 10 firings on the cases. Granted, I was seating bullets long on purpose to form those cases....

Do you have a comparator attachment for your calipers to measure headspace when you resize? This reminds me of when I first started reloading for old .30-06 milsurps and just ran the die all the way down and got case heads to pop in 4 firings.

It's possible that on the first resize, I may have just done a FL size using the setting from the previous factory barrel. I don't recall at this time but I agree, I shouldn't have the issue so I must have done something wrong initially, and then "tolerance stacked" from then on

I was aware of the proper sizing procedures even before the new barrel, but I have so much brass and calibers, that I may just have said fuck it, and cranked out a compromised batch of brass which shortened its life.