Setting COL without the proper modified case

[Nomad47]

My 6-284 barrel is due to arrive today. I will be making my own modified case for the Stoney Point (now Hornady) OAL gauge. Of course, it has to be a fired case, but I want to load up three loads at .020 off the lands BEFORE making the modified case.

So I think this will work.

I will use a 6XC modified case and measure from the case base to the ogive and also case base to datum point on the shoulder of the case. Then subtract to get datum to ogive. Then I will seat bullets in the 6-284 cases to match that datum to ogive measurement minus .020".

Comments?

 

[CanusLatransSnpr]

Maybe I'm looking at it wrong but, if you're measuring from base to ogive with one case, and then base to ogive from another case? The measurement, in application, should be the same? The points of reference are no different whether it is a 6xc case, or a 6x284 case! Cartridge head stamp and ogive being the points of reference. Just my thoughts.

Mike

 

[357Mag]

Nomad -

Howdy !

Say... have you by chance, ever tried using a Sinclair bullet " comparator "
( looks like a big hex nut w/ holes in each flat ) ?

I've used these for 35+yr, and they work great ( IMHO ).
Simplicity, itself.


With regards,
357Mag

 

[Alex Wheeler]

Sounds like it should work fine. I find the most accurate way for me is to strip the bolt of firing pin and ejector. F.L. size the brass so the bolt closes on it with no resistance. Then seat a bullet long, countinue seating deeper in small incriments untill the bolt drops with gravity. Then you have your touch length. Im sure you know about this method, just saying.

 

[GSPV]

You can make a dummy round, then seat the bullet progressively deeper till the rifling marks just disappear. You'll have to view the bullet with a magnifing glass. Polish the bullet with #0000 steel wool between tries.

Mark that round to being your "index" round for that bullet. Then, you can always get back to that point if you, say, change seaters, change seater stems, etc. If you want .020" off, then you can set the seater to the index round, then go 20 marks deeper on your micrometer, or use the bullet comparator and calipers.

 

[Nomad47]

I think a couple of you may have misunderstood my question. I have the Stoney Point tool to measure cartridge OAL. And I will have a chambered barrel in my possession by the end of the day. The first round fired after screwing on the barrel will be the one that gets made into a modified case. But in the meantime, I want to seat some test loads to .020 off the lands (and before I have made the proper modified case).
So basically I want to measure COL to lands using a 6XC modified case, then measure datum point to ogive and apply that info to 6-284 cases. Again measuring from datum point to ogive on the 6-284 cases, but seating .020 deeper.

 

[Alex Wheeler]

Ah, datum point of the shoulder to the ogive of the bullet. Would work great (asuming the shoulder angles are the same) . How will you measure that?

 

[Nomad47]

Well, I think they both are 30 degrees. I will be using the Hornady headspace gauge for the 6XC. Not sure if that is the same one for the 6-284 or not. I know the straight 284 uses a different one, and I have both. But I think I should use the same gauge on both cases.
If I end up .015 or .025 off the lands, its no big deal. I'm just after a starting point that is close to .020 off.

 

[tazzman]

Nomad47,

Load cartridges to the load STANDARD(- 10%) in accordance with your 6-284 reloading book , and then fire them to provide you with cases formed to your chamber. Then you will have cases, formed to your chamber, that will give you the dimensions you require to load +/- 20 thou. to the rifling.

Cheers, Phil aka tazzman

 

[Nomad47]

It would appear that my method worked.

Using the 6XC modified case and the datum to ogive measurement, I got an ogive to lands of 2.381". I then inserted a bullet in a split case and let the rifling seat the bullet. That measurement came out to 2.391" and would be partially jammed.
So I am going to seat my test loads to 2.361". That should be .020" off the lands give or take .010".

 

[CanusLatransSnpr]

Glad it worked out for you Bill! Just out of curiousity, how are you getting the threads in the modified case that you're going to make? I have looked for a tap that size and thread pitch, which the size eludes me right now, and I couldn't find one! Thanks!

Mike

 

[fdshuster]

Mike: 5/16" x 36 tpi

 

[CanusLatransSnpr]

Thank you sir! I need to acquire a tap like that for future endeavors!

Mike

 

[fdshuster]

Mike: As I learned, you won't find a 5/16 x 36 tap at the local hardware store. Companies like Granger will have them.

 

[garywfisher]

Anyone seeking to purchase the needed tap should be sure to search the internet and compare prices. When I did this a few months ago I was quoted prices as high as $90 but found one for about $9 (don't remember the source). I have used it a couple of times and it obviously works properly. It is high speed steel in case you are wondering.

 

[CanusLatransSnpr]

Good looking out Gary!

Mike

 

[Nomad47]

I got the drill bit and tap for $27 from Tanner Bolt & Nut in NY thru the internet. Someone on this forum linked me to them.

 

[Nomad47]

Now I have another problem with this barrel I just bought. The neck is .277 and so are my loaded rounds. Looks like I will have to buy a neck turner. WAS trying to keep things simple.