Outside neck dia. of loaded 25-06?

[RangerBrad]

Hey fellas, Am trying to order a bushing for a Redding S bushing fl die. The man at sinclair support said to measure the outside of a already loaded round and order that bushing size. He also stated that for my 25-06 it should be between .280-.283. When I got home I measured and am comming up with .284 on most rounds with an occasional .285 popping up. I am using WW super brass and 115gr bergers though the bullet should make no diffrence. Do any of yal have some rounds with this brass you could measure and tell if I'm on? Thank's, Brad

 

[flashhole]

Bullet diameter ((0.257" + (2 times neck wall thickness)) - .003").

If neck wall thickness = .010" it would be (.257" + .020) - .003" = .274".

If neck wall thickness = .015" it would be (.257 + .030) - .003 = .284".

Measure the thickness of the neck wall and buy accordingly.

 

[rscott5028]

Your measurement is within reason. But, I disagree with the Sinclair tech.

If you just measure the loaded OD and get that bushing, I think you've got a problem because you would be sizing the ID to .257" not accounting for spring back. Hence, you'd likely end up with more than a few at .258" ID which is really bad.

Based on your .284" measurement, I'd order .280-.282" bushings expecting to use .281" with your current lot of brass.

-- richard

 

[chucknbach]

Your measurement is within reason. But, I disagree with the Sinclair tech.

If you just measure the loaded OD and get that bushing, I think you've got a problem because you would be sizing the ID to .257" not accounting for spring back. Hence, you'd likely end up with more than a few at .258" ID which is really bad.

Based on your .284" measurement, I'd order .280-.282" bushings expecting to use .281" with your current lot of brass.

-- richard

Your suppose to subtract .001 from that reading. Or just buy a bunch keep the one you need send the rest back.

 

[rscott5028]

Your suppose to subtract .001 from that reading. Or just buy a bunch keep the one you need send the rest back.

Subtracting .001" is cutting it close with non-turned necks.

I would subtract .003" allowing for .001" spring back leaving you with an ID of .255" for most of your cases.

Smaller will lead to runout and larger may leave you with .257-.258" ID if your brass lot is not consistent.

I prefer to having extras on hand.

-- richard

 

[RangerBrad]

If I buy several sizes, how will I know which one is the right one I should be using? Brad

 

[rscott5028]

If I buy several sizes, how will I know which one is the right one I should be using? Brad

Do the math above to identify the desired bushing.

Confirm by sizing and measuring the neck IDs.

You want the neck ID to be .001-.002" smaller than the bullet diameter.

Larger IDs may lead to loose bullets.

Smaller IDs won't improve neck tension, but it may cause increased runout as you seat bullets.

-- richard

 

[chucknbach]

From RCBS instuction manual

NECK BUSHING SELECTION​

Neck bushings are not included. Proper neck bushing size
can be determined two ways. Measure the outside neck
diameter of a sample loaded cartridge, subtract .002" to
.003". This allows approximately .001" of brass spring
back for correct neck tension. The other is to measure the
neck wall thickness of your case, multiply by two, add the
diameter of your bullet and subtract .001". For example:
loaded case neck diameter is .333-.002=.331 neck bushing
or .012 case neck thickness, .308 diameter bullet is
.012+.012+.308 =.332-.001=.331 neck bushing. RCBS
suggests that you have neck bushings one to two sizes
above and below your target diameter.​

 

[chucknbach]

Subtracting .001" is cutting it close with non-turned necks.

I would subtract .003" allowing for .001" spring back leaving you with an ID of .255" for most of your cases.

Smaller will lead to runout and larger may leave you with .257-.258" ID if your brass lot is not consistent.

I prefer to having extras on hand.

-- richard

You are correct, I was going off my memory which isn't to good, apparently.

 

[lever-hed]

IMO the bushing dies should be used with non-factory bbl's. Even so, I dont believe in the neck tension theory, I believe you get more out of a standard neck sizing die such as Lee, or some of the newer full length custom dies, depending on your rifle ..

 

[rscott5028]

IMO the bushing dies should be used with non-factory bbl's. Even so, I dont believe in the neck tension theory, I believe you get more out of a standard neck sizing die such as Lee, or some of the newer full length custom dies, depending on your rifle ..

What is your description of the "neck tension theory?"

Do you not believe that neck tension exists?
Or, that it doesn't need to be consistent?
Or, that it doesn't matter?

-- richard

 

[RangerBrad]

Found a new problem. I measured the neck thickness of my used brass and it shows .013 which would give me a loaded out side neck diameter of .283 which is really close to my measured out side diameter of .284

Then I measured my new virgin brass neck thickness and it measured .016 which should give me a loaded out side neck diameter of .289

This is a diffrence of .005, these measurments were taken with a regular set of calipers however, the used brass measured just what I expected it to.

According to this I would have to re-measure and install a new bushing at $15 a piece, after every few reloads.

This is also outside of what the sinclair tech. stated it should be which was .280-.284.

What say yal to this? Brad

 

[Nimrod]

What say yal to this? Brad

Neck turn, I would rather have the necks too thick on new brass than too thin, then you have the option at least.

Bob

 

[wallypedal]

All good info, just want to mention a couple things I didn't see brought up. First, some of the $20 calipers aren't great, and measuring with the knife edges takes some practice. I like using a regular micrometer on case necks. Second, not all .257" bullets are .25700". With as many variables involved here, the numbers can stack either direction enough to require a bushing change for a bullet/case batch. Neck turning helps remedy some of that.

It does get down to how much neck tension you want, how much neck re-working you want going on and how anal you want to be about it. Some of us enjoy chasing the ultimate, but there is a point of diminishing returns. Really good match and hunting ammo is made all the time without worrying about .001" of additional tension. Loose is no good obviously.
Wallypedal