Headspace question for new Carbon6 prefit barrel

[epoletna]

Please keep us informed what you find out and what you decide.

 

[Longtine88]

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!

Did you send them dummy rounds to cut to and did you use new Adg brass when you did?

 

[cohunt]

Did you send them dummy rounds to cut to and did you use new Adg brass when you did?

He said it was a pre-fit

 

[arrow179]

Did you send them dummy rounds to cut to and did you use new Adg brass when you did?

I did not send them dummy rounds and it was supposedly cut to SAAMI specs

 

[Mike D Texas]

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.

I've heard more than one person say a comparator is a poor messing tool. So what is a good tool to use for measuring shoulder datum and/or seating depth?

 

[Longtine88]

I did not send them dummy rounds and it was supposedly cut to SAAMI specs

Do you have depth mic's to pull us a few measurements?

 

[arrow179]

Do you have depth mic's to pull us a few measurements?

I do not. I only have basic tools and do not consider myself any sort of gunsmith. This is my first forte into building anything custom or semi-custom myself. My gunsmith is about 4weeks out on being able to take a look at it so I was trying to learn and figure it out on my own. I appreciate all the responses and feedback as I've learned a bunch on this forum (and probably spent way more in the classifieds than I should have )!!

 

[MagnumManiac]

I've heard more than one person say a comparator is a poor messing tool. So what is a good tool to use for measuring shoulder datum and/or seating depth?

I have made my own, but Larry Willis at Innovative makes one for most datum sizes.
The problem with a comparator is the radius left on the edges of the hole and if you run a bore gauge into them, they're not exactly what they say they are.
Other than what I made for myself, the best measuring tool that is easily sourced is the RCBS Precision Mic, very accurate to .001"and I have never found a bad one.
I have also found bad go gauges in the past, not common, but sent them back.
Comparators are only good for comparing fired and sized case datum measurements, but measuring headspace, nope!

Cheers.

 

[Mike D Texas]

I have made my own, but Larry Willis at Innovative makes one for most datum sizes.
The problem with a comparator is the radius left on the edges of the hole and if you run a bore gauge into them, they're not exactly what they say they are.
Other than what I made for myself, the best measuring tool that is easily sourced is the RCBS Precision Mic, very accurate to
.001"and I have never found a bad one.
I have also found bad go gauges in the past, not common, but sent them back.

Cheers.

I guess I'm not following on how to mic a shoulder datum? At least not with some other tool needed?

 

[MagnumManiac]

I guess I'm not following on how to mic a shoulder datum? At least not with some other tool needed?

My point is in regard to using a comparator tool to measure a go gauge. Each headspace datum is at a particular diameter, .375" for 30-06, .420" for belted mags and WSM/RUM etc.
A RCBS Precision Mic is the most accurate measuring device on the market, it has precise graduations and you can easily see .0001" if you use them often enough. It will even measure go/no go gauges accurately.

Cheers.

 

[joelpend]

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 would not be concerned at this point. If the headspace was too long then yes I would not want that. If you can resize your cases sufficiently then no issue going forward.

 

[ntsqd]

Since I wasn't familiar with the RCBS tool I looked it up. I can see how it would be the ideal tool for this sort of measuring. Unfortunately I don't see the .30 RSAUM listed. They can likely make one, but it'll be a special order.

Interested in what the results of removing the ejector does for testing with the no/no-go gauges.

 

[joelpend]

Sometimes the ejector does not snap around the case head of the gage as easily as it does with a brass case so just make sure the case head of the gage is behind the extractor.

 

[FullCurl8]

Sometimes the ejector does not snap around the case head of the gage as easily as it does with a brass case so just make sure the case head of the gage is behind the extractor.

That's not what an Ejector does. Proper headspace gauge use can never occur with the Ejector in place if it's a spring loaded bolt face plunger style ejector. And Extractors sometimes make contact as well, but with less frequency. But removing both from the bolt will ensure your feeling everything there is to feel.