how can I figure neck bushing size, without loading a case ?

[Riss]

Need dies to properly load a bullet in a case to determine the proper bushing size to get. But cannot size a neck without a bushing in the die. Which I need in order to load the bullet to.... ARGHHHHHH. Bullet is 308 exactly. Inside hole mic'd the case, while outside mic'ing the case neck. Is close but not really sure I am getting a good reading. Reads about .335 on the OD of the 308 Win case. Anyone have suggestions. I have a set of 308 dies, but no loader handy.

 

[dave from mesa]

Not sure what kind of dies you have but I think Hornady has a formula that they use. Might be on there website.

 

[Riss]

Have Dillon dies. Not going to use them. Getting Redding S bushing FL size, neck bushing die. Need to figure out proper OD of case over loaded bullet to figure proper neck bushing. Guess I may just have to load one with the Dillon dies and go from there.

 

[NuJudge]

A lot will depend on your brass and your bullets.

I have a set of the Redding .223 dies. I don't know what others do, but I bought several bushings on either side of what I though would work.

Start with determining bullet diameter and case neck thickness (remember to double it as it is on both sides of the bullet), then guess how much smaller than bullet diameter you want the case neck to be. This will vary depending on how violent bolt closure will be, and other things. I guessed that I wanted case neck ID to be .004" smaller than .223 bullet size. After all this, you need to guess how much the neck will spring out after being compressed by the bushing.

Someone here may have experience with this type of die. It will help them to know what specific bullet diameter you have, and case neck thickness.

CDD

 

[plinky]

Bullet diameter + neck wall thickness X 2 equals loaded round diameter. Subtract .002 to .003 from that should give you your bushing size. Brass hardness (and neck wall thickness variation) will affect the result though, so you probably want to bracket the ideal bushing on the bigger and smaller sides.

Edit: yeah what Nujudge said.

 

[Walkalong]

Figure it up, but be prepared to buy more than one bushing, it just works out that way. Besides, you will want to experiment with different neck tensions anyway.

then guess how much smaller

NuJudge gave a good description of what to do.

 

[USSR]

Riss,

One of the things with bushing dies (without an expander ball), is that the finished OD is dependant upon the as-fired OD. Once you start trying to reduce your OD much more than .005", you end up getting a finished OD .001" less than the bushing size. For example, my fired brass comes out of my FN SPR with a OD of .346". Using a .338" bushing, gives me a finished OD of .337". You don't say what platform this ammo will be used in, but as a general rule, I use a bushing .001" under the loaded cartridge's neck OD for a boltgun, and .002" under for an autoloader. Hope that helps.

...be prepared to buy more than one bushing...

+1.

Don

 

[kelbro]

Your bushing size will vary with your brass selection and the differences in their neck thickness. I like .002 smaller than the OD of a loaded round.

 

[243winxb]

308 Win Bushing Size .333" Just a Guess.

My Guess is a .333" diameter bushing should work for starters. I measured 3 different neck/brands diameters. One WRA64 GI factory new ammo. Another Winchester ammo reloads. The third box is Federal American Eagle reloads. The all run close on OD of the loaded rounds. Necks have NOT been turned on the reloads, just loaded with standard RCBS dies. The OD's run from .337" to .335" So my guess may be close. Here is the bushing range that Redding list for each caliber.http://www.redding-reloading.com/pages/bushrangechart.html It does NOT list what i have guessed is the correct bushing to start with. The drawings for the 308win list a loaded neck diameter as .343" But most all factory loaded ammo does not come close to what i consider the MAXIMUM loaded neck diameter. You will end up buying maybe 3 bushing. http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm

 

[243winxb]

Neck Wall Thickness can change

The neck wall thickness can change when loading with standard dies using an expander. I first noticed this when some new brass when loaded in 243win measured .276" This is the drawing measurement. Brass has never before or since been this thick in the neck wall diameter. I load the new factory brass as it comes out of the box of 100. No flsr, no expander touches it, except maybe a kiss on the case mouth with the expander to make the mouth round. The lot of brass was exceptionally accurate on first firing. I measured the necks loaded OD at each loading. The neck wall thickness keep getting thinner each loading till at a certain point it stopped. As the neck wall thickness got thinner, the groups got bigger. With each loading the neck became more loose in the chamber degrading accuracy. This alone is a great reason to buy bushing dies, even if you do use the expander. This way the neck is not overworked, thining it and pulling it off center from the body of the case. IMO

 

[Strongbad]

Here's another link... the link with Redding's instruction on how to determine the proper bushing size.

http://www.redding-reloading.com/pages/necksizebush.html

 

[Riss]

Gun will be a M1A chambered for the M118LR. Will be springing later (tax time) for a Remington 700, also in 308. M1A is already in the shop so I currently so not have anything in 308. Bushing direction said to measure OD of case neck with a loaded bullet that you are going to use. Since I am using the 175gr SMK and LR118 brass I still have something to measure. Talked to the guys in the machine show today, will take a case in tomorrow and inside mic the case for wall thickness with a ball mic x2 and add the diameter of the bullet to get a start at proper bushing size and prepare to get additional bushings if needed. BTW the links in this thread and another thread here gave me a lot more insight into what I need to do to reload for the M1A.

 

[USSR]

Riss,

I shoot ammo loaded using LC M118LR brass almost exclusively. Loaded cartridge necks will measure ~.338. For a M1A, I would get a .337" bushing. This will likely produce a ready to load .336" OD neck, which is sufficient for your use.

Don

 

[Riss]

The M118 LR is all I have sxcept for some mixed commercial once fired. I have enough of the LR stuff that I do not need to use anything else. I got it mic'd today. Wall thickness was 15 thou on the nose. That and an exactly .308 diameter 175gr SMK gives me .338 OD of the neck. Redding directions say to go 1 or 2 thou under that OD to get the bushing size.