How Do I Set the Proper Head Space

[Cat 64]

Soon I will have received all the necessary components toassemble a factory Savage 12 target rifle in a 6 mm BR. I asked the supplierabout determining headspacing and I was told that "Whenyour barrel is installed your head spacing will be the Go Gage plus .001 –.0015".
My question to you guys is, what is the best method to ensure Ihave achieved that fine of a headspace. I know that the common sense approachis to use the Go/NoGo gages but I believe the difference between those two isgreater than the above measurement. Do I even need a NoGo gage? I saw a fewYouTube videos where some smiths are using Scotch Magic Tape at the end of theGo gage to assess the proper measurement. However the tape is 0.0022thick...so I am in a quandary. I need some direction please.

[memilanuk]

I think what they're getting at is if you snug down the barrel against the bolt, that would be right on the measurement of the GO gage. When you tighten the barrel nut, it will take up a (very small) certain amount of slack in the threads between the nut, the barrel and the receiver, which typically 'pulls' the barrel forward 0.001-0.002"... which is right about what they described.

GO/NO-GO gages are generally the best option. If you do it as described above, the bolt handle should even begin to close on a NO-GO gage, which is a good safety check just in case. If you do use tape, try using something a fuzz thicker like masking tape - typically 3-4 thou thickness, which is about the difference between a GO and a NO-GO gage.

If you don't already have 'em, you really really should get some sort of comparator for measuring cartridge headspace - mainly for use when setting up your sizing dies (I recommend either the Hornady LnL tools, or the Sinclair inserts if you can swing the $$$). It will also come in handy when checking the relative dimensions of your GO & NO-GO gages (or whatever substitutes you end up using).

[Cat 64]

Thank you. I have all the Hornady comparator already.

[earl39]

Cat, as Monte said if you have never installed a barrel before the best way is with both the go and no-go gauge.

[tiny68]

Here is my simple method that hasn't failed me yet. Screw the barrel down firmly against the go-gauge. Make a witness mark on the action and barrel with a sharpie. I back off 3/64 of a turn and make a new alignment mark on the barrel. That is 0.0023". I tighten, recheck with tape on the go-gauge (starts to get tight right after bolt head engages the lug). I only shoot reloads and resize to my chamber. Doesn't matter to me if it is not perfect for factory specs. I have a piece of masking taking that I have made 1/64 of turn marks on the I just line up with the witness mark of the action and then I can easily and accurate repeat the same headspace every time I put the barrel back on. Been using the same piece of masking tape for 5 years.

Luck, Tim