Resized Brass Neck Size Issue

[jackstrawIII]

I'm a relatively new reloader, and am attempting to form 260 Remington brass out of spent 308 cases (of which I have many). I resized them this evening and it went well, using a simple 260 FL sizing die. However, I have one major concern.

The neck opening measures only .2595" on (average) after sizing. That's .0045 thinner than the .264" bullet that will be going in. From what I've read, that's going to give me too much tension on the bullet. I've read that .0001-.0002 smaller than bullet diameter is the goal.

Does this mean I have to ream the inside of the necks? Or is there something I can do during the sizing process to fix this?

I have to outside neck trim them anyways (neck walls are too thick), so do I go ahead and just trim the neck thickness down on the outside and not worry about the bullet tension?

Any help is appreciated. Thank you.

[ammo.crafter]

Did you use the neck expander die before seating bullets?

Measure the neck before and after using the expanding die and see what you get.

[jackstrawIII]

Ammo.crafter, the measurement I posted was right after resizing. I haven't seated any bullets yet. All I've done is run the brass through a FL sizing die with tapered expander.

[Snyper]

If you need to turn down the necks anyway, I'd do a few then seat some bullets to see what happens.

You may just need to use a larger expander.

I wouldn't worry about "too much tension" as long as you can seat the bullets without causing problems such as distorting the cases or scraping the bullets.

Consistency is more important than "how much" tension there is.

[nhyrum]

As long as you chamfer and or use boat tail bullets, you should be OK. I'd bet my hornady dies had about the same neck tension.

[JeepHammer]

REAL common for people that have a micrometer and actually bother to check...
Since 0.0001" won't show up on the 'Horror Fright' digital calipers they usually crunch & shoot, then complain never knowing what they are actually building.

Depending on the die maker,
Some will tell the you "Tough..., what do you expect for $30"
Some will want a few bucks for a rod/larger ball,
Some will send you the ball or rod for free.
It will probably be oversized & you will have to hone/Lap it to exactly what you want... OK with me, I can easily take a little off, I find it VERY difficult to add more!

The upper end 'Competition' die companies will apologize and build an expander to YOUR specification and you will have it, usually for free, in about a week.
I know $150-$300 a set for dies hurts, but you really do get what you pay for.

[old roper]

Your using fired brass. You already mention necks are thicker and you have to turn them. You may have to anneal them also.

I don't think I fire one as is in that chamber unless loaded dia is same as you use before.

[ShootistPRS]

I'm a relatively new reloader, and am attempting to form 260 Remington brass out of spent 308 cases (of which I have many). I resized them this evening and it went well, using a simple 260 FL sizing die. However, I have one major concern.

The neck opening measures only .2595" on (average) after sizing. That's .0045 thinner than the .264" bullet that will be going in. From what I've read, that's going to give me too much tension on the bullet. I've read that .0001-.0002 smaller than bullet diameter is the goal.

Does this mean I have to ream the inside of the necks? Or is there something I can do during the sizing process to fix this?

I have to outside neck trim them anyways (neck walls are too thick), so do I go ahead and just trim the neck thickness down on the outside and not worry about the bullet tension?

Any help is appreciated. Thank you.

Since you measured the cases after sizing and you know you have to turn the necks, I would turn the necks and then fire the cartridges. After that the cases with the turned necks will have a larger inside diameter and the same outside diameter after sizing. You will find less tension on the cases with the turned necks. Be sure to chamfer the inside of the necks just about to the outside and then lightly deburr them on the outside. You may find that removing the extra material on the outside keeps the die from over sizing the necks.

[Unclenick]

Agree. Outside neck turning will give you better neck wall thickness uniformity than inside reaming. The main reason for inside reaming, to my mind, is to eliminate a donut. If you have one, you should be able to probe for it with a paper clip.

The upper case in this photo has a very visible internal donut formed by multiple resizings.



For outside neck reaming, a common procedure is to size the inside of the neck for the turning mandrel with a slightly larger expander mandrel held in a mandrel expander die body. Sinclair sells these (749-011-715WS
17 thru 338 Caliber Expander Die Body) and the mandrels. The same mandrels will get your OD opened up where you want it at the same time they set the slip fit for the outside turning mandrel.

Note that the Sinclair turning mandrels also fit in that die body, and I find that expanding a neck with one rather than using the expander inside the sizing die is less prone to bending the neck off-axis with the rest of the case.

[Snyper]

JeepHammer:
REAL common for people that have a micrometer and actually bother to check...
Since 0.0001" won't show up on the 'Horror Fright' digital calipers they usually crunch & shoot, then complain never knowing what they are actually building.

They're building ammo that fits their gun.
That's all they need to do.
The rifle's chamber is the best case gauge anyone could ask for.

[jackstrawIII]

Several of you guys have mentioned inside reaming. I looked up an inside reamer for my Forster tool and it says that the reamer is "several thousandths" larger than the diameter of the bullet.

I don't understand how that would be useful? Would I have to resize, ream, then resize again? Makes no sense.

[Pathfinder45]

If you can resize a 308 case to 260 and load it without trimming the neck thickness, will it chamber in your rifle? If it will, I don't see the need to thin the necks out. I have used a heck of a lot of 30-'06 cases in my 270 Winchester by simply resizing and loading as if they were correct 270 cases without any trouble whatsoever.

[mehavey]

I've ...run the brass through a FL sizing die with tapered expander.

I'm confused. It's the expander that opens up the neck to a specified inner diameter. So the wall thickness is interesting-but-irrelevant at this part of the problem.

Here's the test for neck tension:

- Measure the OUTside neck diameter of the currently sized/expanded case.
- Seat the desired bullet.
- Measure the OUTside neck diameter again.

How much difference is there between the two measurements?
(postscript: THAT's the measurement where the "1-2 thousandths" number comes from)

[F. Guffey]

Several of you guys have mentioned inside reaming. I looked up an inside reamer for my Forster tool and it says that the reamer is "several thousandths" larger than the diameter of the bullet.

I don't understand how that would be useful? Would I have to resize, ream, then resize again? Makes no sense.

I did not mention inside neck reaming but I have dies that are designed to be used when reaming the inside neck diameter. Size again? NO; the die is a sizing die with a guide in the top of the reamer. First the case is sized and then the neck is reamed, after the neck is rearmed the ram is lowered. There are different diameter reamers for reloaders with bad planning, again, I am not the fan of putting new reloaders into a dead run from the jump start.

That goes for the tension thing; no one can measure tension, tension is a new internet reloader term. I never got started with tensions, I started with bullet hold because I can measure bullet hold in pounds; again I do not have a conversation for tensions to pounds. One more time, I have tension gages; problem, my tension gages are calibrated to pounds.

And then there is the necking up and or down, most reloaders believe the neck gets thicker and or thinner with no consideration to the possibility the neck could get longer and or shorter with one exception; me.

Another consideration when forming and or necking a case neck up and or down, that comes under the category or working the brass. When forming cases I use new cases, even then there is no guarantee after forming and seating a bullet the case neck will not split in time and or split when fired.

F. Guffey