Totally confused about bushings

[repiv]

I am trying to get between .0015 and .002 neck tension on my bullet. When I measure my case with a bullet seated it measures .337 (this is for a .308 BTW) I got a Redding FL sizer die with .336 bushing.

Redding says:

<span style="font-weight: bold">To Determine Bushing Size</span>
The Proper busing size can be determined by measuring the outside neck diameter of your loaded cartridge with a micrometer. From this measurement subtract .001" . This allows for a small amount of brass spring back and creates a proper press fit for the bullet.


However after I size the brass I measure it and I am expecting a measurement at the neck around .3355-.335 but its <span style="color: #FF0000"><span style="font-weight: bold">.333</span></span>.

The expander has been removed and this is once fired brass measuring .343 before sizing. Its Lapua brass and SMK 175

What am I doing wrong? Do I just need to get a larger bushing?

 

[Quicky06]

Re: Totally confused about bushings

Read the instructions you posted. It says measure a loaded round

 

[427Cobra]

Re: Totally confused about bushings

You got the right bushing, I use a .336 for lapua brass, where I think the problem is coming from is from not step sizing, I size from a fired case of .342, first bushing I use is a .339, then .336 for lapua, win brass gets .333 and a final .331, yes it's a lot of work, the .339 bushing lives in my FL die, I use a neck die for the rest.

 

[repiv]

Re: Totally confused about bushings

Quicky I said "When I measure my case with a bullet seated it measures .337 "

Cobra Is it really necessary to step it? I have not read that anywhere before. I dont doubt you I have just not heard this before. Just curious though what is the diameter of the neck after you complete your sizing?

 

[mdmp5]

Re: Totally confused about bushings

How many cases has this happened with? I don't step size either, and with a 336 bushing and Lapua brass, I measure about 336 after sizing. Did you clean the inside of the die with acetone or suitable solvent before using? Are you over lubing the cases? That is the only way I can ponder that your neck is getting smaller than your bushing.

 

[mdmp5]

Re: Totally confused about bushings

cobra, i think that if his necks were measuring noticeably bigger than the bushing size, your argument would be valid. However, I don't think that his problem is not step down sizing.

 

[427Cobra]

Re: Totally confused about bushings

IMHO step sizing aids in concentricity, and works the brass less, I had the exact problem repiv is talking about until I read to only size no more than .005 at a time, I picked .003 at a time beause that is half way between .342 and .336, the expander barely touches the inside of the neck, and since been removed, before step sizing the expander pulled very hard, and with it removed the seating die would distort the hell out of the bullets indicating too much neck tension.

I find step sizing a PIA, I spec my new 260 to have a tight but no turn neck and a very short lead, .003 expansion from loaded to fired case.

 

[repiv]

Re: Totally confused about bushings

I took the die apart and cleaned everything and resized a few more cases. Now I am getting .335 and these cases have not been trimmed. I think I will go ahead and get a .337 busing and just call it a day. I still dont understand why im not getting .336 from a .336 bushing. I think I also may need to trim this brass a tiny bit. It reads between 14.5 and 15 on the neck.

 

[Victor N TN]

Re: Totally confused about bushings

It doesn't hurt to keep an extra bushing or two if you can afford it. I have several for each caliber. Usually a -.001, -.002, -.003" plus a couple if I am turning the case necks to a thinner wall thickness.

The new bushing will probably take care of the situation.

 

[GreatGonzo]

Re: Totally confused about bushings

German Salazar's take on 2 stage sizing

Note that he says that going too far in 1 step will usually lead to od's smaller than the die. Interesting.