.243 Win chamber neck clearance

[B_Thomas]

I have two barrels chambered for .243 Win. Different smiths....different reamers. Loaded ammo measures .272"(no turn). Fired brass measures .274" in one barrel & .277 in the other. How much clearance would be preferred over the neck loaded OD? Thanks.

 

[XTR]

Most people cant see any difference in accuracy/precision.

Some will tell you that you are working the brass more with a larger neck, but I've loaded thousands of rounds with .007 clearance in my F-TR rifles and never split a neck. (though I have thrown half a bucket of brass lost to loose primer pockets over the last 5 yrs. (I do anneal)

Both will work, the .002 clearance is a little on the tight side for me. How deep do you seat? If you seat deep watch out for doughnuts forming at the base of the neck. Check your loaded rounds measurements there. When you seat you could end up getting .275/6 at the base of the neck and getting into over pressure if the bullet is seated deep and has a hard time releasing.

 

[B_Thomas]

Most people cant see any difference in accuracy/precision.

Some will tell you that you are working the brass more with a larger neck, but I've loaded thousands of rounds with .007 clearance in my F-TR rifles and never split a neck. (though I have thrown half a bucket of brass lost to loose primer pockets over the last 5 yrs. (I do anneal)

Both will work, the .002 clearance is a little on the tight side for me. How deep do you seat? If you seat deep watch out for doughnuts forming at the base of the neck. Check your loaded rounds measurements there. When you seat you could end up getting .275/6 at the base of the neck and getting into over pressure if the bullet is seated deep and has a hard time releasing.

Thanks. The tighter clearance barrel does shoot better. I may start turning the necks a bit. Maybe turn for .270"-.271"?

I seat the 105 hybrids at 2.875".This puts the bottom of the bearing surface slightly above the neck to shoulder junction.

 

[expiper]

OP,,,the fired brass that measures .274 prolly means that you chamber neck is .275"....just rite,,that is what I use with great results,,,,,I try to keep the shank of the bullet ~.030" above the neck/shoulder junction becasue the donut is not just at the exact corner but is "fat"....I like to take a bullet and insert it in the unsized case neck and locate the donut area and record this actural contact point as the minimum safe seated length with that particular bullet ,,,,Roger

 

[XTR]

As expiper notes, my 6SLR has a .275 neck and I get .274 on my fired brass. My WW brass is .270 or .271 loaded I think.

 

[B_Thomas]

Great. Thanks for the replies.

My chamber throat is cut for a 105g hybrid touching at 2.900". Been loading for .040" to .010" jump. I'd like to have a little more throat...I guess it will grow as I'm less than 100 shoots into this barrel.

Thanks again!

 

[expiper]

"B"...if you dont have enough throat ,,,deepen it now,,,that is a fairy tale waiting on it to grow/wear to where you want it,,,with a .243 it will take 1000 rds to get .040" of wear,,,guess what the bbl is also wearing out all the way down the bore,,,,get it right for the bullets you are wanting to use and enjoy it while it lasts,,,(no matter what the cal. !!)...Roger

 

[jaygorski]

My .2767" chamber shoot as good or better than my 274 neck, loaded rounds are .2715-.272

 

[B_Thomas]

"B"...if you dont have enough throat ,,,deepen it now,,,that is a fairy tale waiting on it to grow/wear to where you want it,,,with a .243 it will take 1000 rds to get .040" of wear,,,guess what the bbl is also wearing out all the way down the bore,,,,get it right for the bullets you are wanting to use and enjoy it while it lasts,,,(no matter what the cal. !!)...Roger

The 105's are positioned above the junction at 2.865". That's gives me a .035" jump. I'd try a little more jump but will be getting close to the junction point. The groups really tightened up each time I have seated deeper. It's loving .030"-.040" jump.

 

[TAJ45]

Tubb uses .005" from what I've read.

 

[B_Thomas]

Tubb uses .005" from what I've read.

Sounds like I might be better off turning the Lapua brass a bit. I'm measuring. 0134"-.0137" neck thickness. If I turn for a .012" thickness....that should put me close to .269" Loaded and .005" clearance. Thoughts?

 

[spife7980]

Sounds like I might be better off turning the Lapua brass a bit. I'm measuring. 0134"-.0137" neck thickness. If I turn for a .012" thickness....that should put me close to .269" Loaded and .005" clearance. Thoughts?

Go for it unless you use the same brass in each chamber in which case I would probably leave well enough alone.