headspacing a AI cartridge

[rsbhunter]

I read the stickey post above about headspacing, and still have some questions...IF using the case/feeler gauge piece method,or tape method on a 260AI, can i use the original caliber case(260Rem)???? As i won't have any fireformed cases. Thanks for the help, AGAIN.....rsbhunter

[dcloco]

YES! AI chambers should have the ability shoot original cases.

[kslefty]

For your 260 AI your gun should be set to put a .004" crush on a virgin piece of .260 brass. In other words the brass should chamber with a fairly light crush feel on the bolt. Basically you should use a set of gages if you have any real doubts.

[chap]

I've done it both ways, off brass and with a go gauge..........There will be those who disagree but the simplest method is to call Dave Kiff and have him make you a go gauge for the caliber you're using. It's a small investment for the security it offers where you do need the crush fit for fireforming brass.

[calib]

I just got done with a 243ai build and waited for the go gauge to get here until I head spaced the gun. It was very simple to do with just the go gauge then the tape

[nwkman]

I just use the parent go-gauge and test it with a piece of new brass.

[Eric in NC]

The parent cartridge "go" actually becomes the "no-go" for the AI version (because the AI chamber is shorter than the parent as kslefty pointed out).

How you can tell .004" crush on a piece of brass, how you can tell if your unfired factory brass is the correct dimension anyway, etc. etc. is beyond me.

Just rent/buy an AI go gauge or ask someone here for a piece of fired 260 AI brass, size it in your dies and roll from there.

[calib]

i think just my go gauge was 30$ and got here in a week now i have it in case i do another build or switch barrels or what ever (243ai)

[nwkman]

Works for me and I've never had any issued with my brass after doing it that way. A person could easily oversize brass .004.

[chap]

As pointed out above, If you headspace an Ackley chamber off a regular go gauge, you now have a chamber with at least 4 thousands headspace, likely more.........that won't give you a crush fit to hold the case neck against the chamber to allow the shoulder to blow forward to create the new Ackley dimensioned shoulder. That results in a situation where the brass grows in length and may lead to case separation problems with the brass down the road. The end result of a proper fireforming process is to create the Ackley dimension with a very slightly decrease in brass length (as the shoulder blows forward it pulls the neck towards the brass slightly).

[Burnin-Powder]

that won't give you a crush fit to hold the case neck against the chamber to allow the shoulder to blow forward to create the new Ackley dimensioned shoulder.

Can't you just seat the bullet long(well in contact with the lands) to hold the case agains't the bolt face? Just wondering? No dog in this race i would just like to know. I would just like to gain some knowledge, please help.

[Ray Gunter]

Can't you just seat the bullet long(well in contact with the lands) to hold the case agains't the bolt face? Just wondering? No dog in this race i would just like to know. I would just like to gain some knowledge, please help.


Short Answer...... yes

There are a couple of methods of artificially creating a tight headspace.
One, as you mentioned, is seating a bullet long so it contacts the rifling holding the case tight against the bolt.

Another method would be to creating a false shoulder that would also hold the case tight against the bolt. In this particular example it would be necessary to neck up the case to a larger size. maybe a 6.5 cal. then using the 243AI sizing die neck it back down. That would create the false shoulder.

[bigedp51]

Having collected and shot the British Enfield rifle that can have as much as .017 head gap clearance and used every method possible to keep from having case head separations I would like to add my 2 cents.

Buy real actual headspace gauges for you AI build and stop messing around with tape, shims or any other ballpark methods. You want a real actual calibrated gauge and not ballpark guesses, do you realise the type and amount of resizing lubricant can effect the "case" headspace after sizing by several thousandths. Do you realise different resizing gauges can effect your case headspace length.

The new Winchester .243 cases I bought for my Stevens 200 ran from .001 to .007 under minimum headspace on the GO gauge, so "HOW" can you use a new case or a resized case unless you know the actual case length.

http://i122.photobucket.com/albums/o254/bigedp51/IMGP7241.jpg

If you set your headspace using a cartridge case and set your headspace too tight (tighter than the GO gauge) your resizing dies will not push the shoulder back unless you remove material from the top of your shell holder.

Below lapped shell holder .003 shorter than normal.

http://i122.photobucket.com/albums/o254/bigedp51/IMGP6943.jpg

There are many ways to measure and set your cartridge headspace after you have fire formed your cases.

http://i122.photobucket.com/albums/o254/bigedp51/headspace_gauge_rs.jpg

http://i122.photobucket.com/albums/o254/bigedp51/7-17-201055522PM.jpg

http://i122.photobucket.com/albums/o254/bigedp51/7-17-201054719PM.jpg

Please notice these Redding shellholders come .010 oversized meaning ten thousandths "OVER" minimum headspace or the GO gauge.

http://i122.photobucket.com/albums/o254/bigedp51/7-17-201054345PM.jpg

NOW don't forget to grease your bolt lugs to prevent galling your bolt lugs from your tight fitting cartridge cases in your "custom" chamber.

http://www.accurateshooter.com/technical-articles/bolt-maintenance-methods-materials/