.308 loading questions (dies and neck size bushing stuff) need advice

[Len5E1]

Hi,

So I am finally starting to get into loading for the .308, in the past i've stuck with easy cartridges like 223/300blk and pistols. For 308 I want much higher expectations to get the most out of my JP barreled semi auto. That said, when I went die hunting I was surprised to find out there's a lot more to choose from than I remember seeing for my other calibers.

So, I know many people like to shun a semi-auto lr308 style for accuracy but I want to do the best I can and not worry about the people that tell me to sell it and buy a bolt action. So far I was able to get a .33 MOA group at 300 yards with it so I know it's capable and that was with factory FGMM ammo. So my main questions regarding loading for the .308 is the dies. I was looking at forster first (which seems to be sold out everywhere) and then leaning towards the redding dies. Most of the better redding dies come with a neck bushing setup which asks you to choose a bushing size and explains how to choose. Well, I tried the measuring a factory rounds neck (got .3380) and subtracted .002 to get .336. I also tried measuring the neck of the same case from a fired round and got .015 wall thickness. By the math that would be .015+0.015+.308 then subtract .002 which surprisingly came out to the same .336 - so I assume that is the correct bushing size for this federal brass?

I don't have a lot of experience with adjusting things like neck tension or even bumping shoulders on the cases, I never really got that detailed with my 223 plinking rounds. Does anyone have any advice on a good die set and any extra tools that are good for precision loading? I was going to pickup a case bump comparator at the very least. I see a lot of people saying to measure the finished rounds COAL by base to ogive and not tip. Is there a special tool to measure this area besides trying to eyeball it with a micrometer which I don't trust myself to do consistently.

 

[straightshooter1]

Hi,

So I am finally starting to get into loading for the .308, in the past i've stuck with easy cartridges like 223/300blk and pistols. For 308 I want much higher expectations to get the most out of my JP barreled semi auto. That said, when I went die hunting I was surprised to find out there's a lot more to choose from than I remember seeing for my other calibers.

So, I know many people like to shun a semi-auto lr308 style for accuracy but I want to do the best I can and not worry about the people that tell me to sell it and buy a bolt action. So far I was able to get a .33 MOA group at 300 yards with it so I know it's capable and that was with factory FGMM ammo. So my main questions regarding loading for the .308 is the dies. I was looking at forster first (which seems to be sold out everywhere) and then leaning towards the redding dies. Most of the better redding dies come with a neck bushing setup which asks you to choose a bushing size and explains how to choose. Well, I tried the measuring a factory rounds neck (got .3380) and subtracted .002 to get .336. I also tried measuring the neck of the same case from a fired round and got .015 wall thickness. By the math that would be .015+0.015+.308 then subtract .002 which surprisingly came out to the same .336 - so I assume that is the correct bushing size for this federal brass?

I think .002 neck tension is a little too light for a semi, especially a .308. You want to make sure the seating of the bullet is not seated more as the round it loaded, which is not so unusual with semi and one of the reasons crimping is often done for cartridges used in semi's. I'd suggest going .003 or maybe slightly more so that you don't have to crimp them.

Whatever you use to get your neck tension, keep in mind that there is going to be some spring back. And every time you fire the case, it get work hardened a little more and spring back increases.

I don't have a lot of experience with adjusting things like neck tension or even bumping shoulders on the cases, I never really got that detailed with my 223 plinking rounds. Does anyone have any advice on a good die set and any extra tools that are good for precision loading?

One thing I'd suggest is for getting the right neck tension, use an expander mandrel. So, when your die, whatever type it is, sizes the case and neck down (without any expander ball), when you use an expander mandrel you can have more control over getting consistent neck tension, AND . . . it moves the neck thickness variation to the outside so you can get more consistent concentricity of your seated bullet.

I was going to pickup a case bump comparator at the very least. I see a lot of people saying to measure the finished rounds COAL by base to ogive and not tip.

Yes, you'll definitely want a comparator to measure your CBTO. The CBTO is more important as that's the part the hits your riffling first and you want that consistent. There's a much bigger variant in a bullet's overall length and the distance from base to ogive.

Is there a special tool to measure this area besides trying to eyeball it with a micrometer which I don't trust myself to do consistently.

Am not sure what you're referring to here. You don't really need a micrometer for anything other than the neck thickness measurements.

 

[Len5E1]

Am not sure what you're referring to here. You don't really need a micrometer for anything other than the neck thickness measurements.

First, thank you for your detailed reply, it was already helpful! To answer your question here - When I measure a COAL to the tip I just throw the whole round on a micrometer. If I wanted to measure only to the ogive and not the tip then I have nothing for the jaws of my micrometer to grab onto. Unless I have this wrong in my head, I'm trying to visualize how to measure from the base of the case to the ogive accurately? Pardon my ignorance.

One more side note - I think I saw that some of the redding or forster dies have some sort of neck ring in them in addition to the bushing which is supposed to allow you to adjust neck tension. Is something like that worth looking into or do you think it's best to have a separate tool (the expander madrel)?

 

[kingaling]

First, thank you for your detailed reply, it was already helpful! To answer your question here - When I measure a COAL to the tip I just throw the whole round on a micrometer. If I wanted to measure only to the ogive and not the tip then I have nothing for the jaws of my micrometer to grab onto. Unless I have this wrong in my head, I'm trying to visualize how to measure from the base of the case to the ogive accurately? Pardon my ignorance.

A very detailed explanation of CBTO vs COAL:

 

[straightshooter1]

First, thank you for your detailed reply, it was already helpful! To answer your question here - When I measure a COAL to the tip I just throw the whole round on a micrometer. If I wanted to measure only to the ogive and not the tip then I have nothing for the jaws of my micrometer to grab onto. Unless I have this wrong in my head, I'm trying to visualize how to measure from the base of the case to the ogive accurately? Pardon my ignorance.

Hmmm??? Sounds like you're referring to a caliper as a micrometer? They're not the same thing.

Nothing wrong with ignorance as long as one is willing to correct it.

One more side note - I think I saw that some of the redding or forster dies have some sort of neck ring in them in addition to the bushing which is supposed to allow you to adjust neck tension. Is something like that worth looking into or do you think it's best to have a separate tool (the expander madrel)?

Typically, they'll have a spindle with an "expander ball" that will go into inside of the case and will push the neck against the wall for its sizing. I have Forster dies and I use my Forster full length die with the spindle and expander ball removed. Then I run a die with an expander mandrel into the neck to get my neck tension, like I explained earlier.

Here are pics of an Expander Die and one of the Expander Mandrel that goes into it (this is what I use):

 

[Len5E1]

Hmmm??? Sounds like you're referring to a caliper as a micrometer? They're not the same thing.

Nothing wrong with ignorance as long as one is willing to correct it.



Typically, they'll have a spindle with an "expander ball" that will go into inside of the case and will push the neck against the wall for its sizing. I have Forster dies and I use my Forster full length die with the spindle and expander ball removed. Then I run a die with an expander mandrel into the neck to get my neck tension, like I explained earlier.

Here are pics of an Expander Die and one of the Expander Mandrel that goes into it (this is what I use):

Thanks, this information is very helpful! As for the micrometer thing, yes I mean calipers. I really don’t know where I picked it up but I have been calling calipers micrometers long before I got into reloading. It’s what our techs always called them for the equipment we worked on. I googled it just now and some manufacturers refer to them as “micrometer calipers” but I guess you can apply micrometer to all sorts of tools with that adjustment feature. I’ll try to watch my terminology in the future lol, sorry for the confusion. After watching part of the video the other guy linked I see that the Sinclair comparator has inserts that can measure the base to ogive on a loaded round which I didn’t know it could so that answers that question. I thought the tool only measured empty cases or bullets without a case depending on the insert.