Headspace question for new Carbon6 prefit barrel

[arrow179]

I have a Tikka T3X action with a Carbon6 prefit barrel (SAAMI spec reamer) torqued to 80 ft/lbs. Using PT&G 300RSAUM go and nogo headspace gauges. Neither one will allow bolt to close. I checked the difference between the 2 gauges and the nogo is .004" longer using Hornady headspace comparator kit (.420" bushing). When I measure brand new ADG brass it is .0005" shorter than the go gauge and the brass will allow the bolt to close fairly easily. So is the rifle safe to operate? I'm assuming that it is but I would consider myself a novice when it comes to gunsmithing. Any help or advice would be appreciated!

 

[066wally]

Yes.

 

[FEENIX]

I have a Tikka T3X action with a Carbon6 prefit barrel (SAAMI spec reamer) torqued to 80 ft/lbs. Using PT&G 300RSAUM go and nogo headspace gauges. Neither one will allow bolt to close. I checked the difference between the 2 gauges and the nogo is .004" longer using Hornady headspace comparator kit (.420" bushing). When I measure brand new ADG brass it is .0005" shorter than the go gauge and the brass will allow the bolt to close fairly easily. So is the rifle safe to operate? I'm assuming that it is but I would consider myself a novice when it comes to gunsmithing. Any help or advice would be appreciated!

"I" am personally not OK with that. IIWY, I would want it properly head-spaced; the brass can be manipulated through sizing. Consult with C6 and explain your issue. But that's just me. Good luck!

 

[arrow179]

I sent C6 an email and will see what they say and report back. I agree I would like the barreled action to be properly headspaced.

 

[arrow179]

Got a response even on a Sunday! Sounds like they aren't worried about it being out of spec. I guess I'll load a few rounds up and fireform some brass and see how it shoots.

 

[cdherman]

You may have trouble resizing your brass. The gun will be safe to fire, but if you cannot resize the brass down with your dies then, you should research lapping a shell holder to allow a few more thou resizing. Other problem is that you might have trouble chambering factory loads in a pinch, though since so many factory brass is quite under spec, its doubtful you would have problems. And can you even get factory 300 RSAUM?

Look at this way: If you have to lap a couple thou off a dedicated shellholder (to this gun), you will end up with a shell holder and die set that is perfect for your gun. Your headspace will never change with this gun, and once you have a perfect shell holder, you can chuck the die into your press, screw it down to the dedicated shellholder, plus the usual 1/2 turn, tighten the ring and know you are getting correct shoulder setback forever.......

Since the RSAUM is kind to cases in terms of stretch, you should also see little to no case length growth, but do check especially at first since you potentially have a short chamber.

Me, I'd shoot it first and ask questions later. If it shoots, then its a keeper. If it doesn't then make an issue of the short chamber and make them replace the barrel.

 

[DoneNOut]

Are you removing the ejector and placing the go gauge under the extractor? Then inserting into chamber? Or are you just placing the go gauge in like a regular case and push feeding it in?

 

[MagnumManiac]

A comparator is a poor measuring tool, I suspect the numbers you get off of it are out by at least .003"…
If the bolt isn't closing on the go gauge, you have a serious problem, the headspace is far too short, even if you have a shell holder turned down by .010", you are still going to have issues because the web area on nearly all .550/.555" brass is difficult to size. I had this very issue on the first 25 Pronghorn (25/300WSM) I built, no amount of turning down shell holders worked very well, had to remove the barrel and run the chamber reamer back in.
I thought tight was gonna be a good idea…nope.
I would have that barrel properly headspace before proceeding.

Cheers.

 

[FEENIX]

A comparator is a poor measuring tool, I suspect the numbers you get off of it are out by at least .003"…
If the bolt isn't closing on the go gauge, you have a serious problem, the headspace is far too short, even if you have a shell holder turned down by .010", you are still going to have issues because the web area on nearly all .550/.555" brass is difficult to size. I had this very issue on the first 25 Pronghorn (25/300WSM) I built, no amount of turning down shell holders worked very well, had to remove the barrel and run the chamber reamer back in.
I thought tight was gonna be a good idea…nope.
I would have that barrel properly headspace before proceeding.

Cheers.

This!

 

[Ucsdryder]

on rokslide there's a thread with similar issues. If it won't close on the go/no go garages that is out of spec and I'd want it done right.

 

[FEENIX]

Got a response even on a Sunday! Sounds like they aren't worried about it being out of spec. I guess I'll load a few rounds up and fireform some brass and see how it shoots.View attachment 474599

"I" am personally not OK with that. IIWY, I would want it properly head-spaced;

I would have that barrel properly headspace before proceeding.

on rokslide there's a thread with similar issues. If it won't close on the go/no go garages that is out of spec and I'd want it done right.

I do not want to assume anything but is the ejector/firing pin assembly removed when you head-space it?

We can only advise, but you have the ultimate decision. I have never had a C6 pref-fit, but I have a C6 barrel on my last build (.338 Thor) that my gunsmith chambered with my custom-made reamers/go-no-go gauges from Manson's. Sorry you are going through this issue. Good luck; I hope you can resolve it.

 

[arrow179]

I do not want to assume anything but is the ejector/firing pin assembly removed when you head-space it?

It was not but I will try that today and see if that causes the go gauge to close.

 

[grouse]

Was your action trued?

 

[Dmagna]

I have a few prefits from them. Never had an issue, I would load up a few and shoot it. I have a .223 ai, 22 creed, 300 prc, 7prc, and 6.5 prc from them. All are hammers, but I have never had an issue with headspace. But if it was me I would shoot it. See what the brass looks like.