FC 308 Brass: Inconsistent Should Bumping

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capreppy

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I've got 1400 pieces of FC headstamped 308 Win brass.

Am processing 200 pieces currently. Using a Redding Body Die to FL size (not the neck) and bump the shoulders back. A fired round out of my rifle is 1.621 using the Hornady Headspace Gauge and a Frankford Arsenal Digital Caliper. I want to bump the shoulders back to 1.619. Out of 200, 50 or so bump back fine to 1.619. 140 or so bump to between 1.622 and 1.624. I cannot for the life of me get them to bump back further. I am not making any changes to the body die as I am processing these.

I am using a Giraud Trimmer (see me other thread, damn fine product) so it indexes off the shoulder. Since I can't get this brass to bump to the same shoulder length, I can't get consistent OAL. I checked the 1.619 pieces and they chamber fine. The 1.622 and over brass will not chamber (as expected).

I am using a Lee Collett Neck Die to do the necks (see previous thread on this topic).

I know FC brass has issues and is likely the brass. Any suggestions on how to correct, short of getting different brass (and yes I am considering that).
 
Most likely your de-capping stem is set too low.

This is preventing the case from entering the sizing die as far as it would but for the interference of the de-capping stem.

Back the de-capping stem out 0.050" and have another go at it.
 
W.E.G. said:
Most likely your de-capping stem is set too low.

This is preventing the case from entering the sizing die as far as it would but for the interference of the de-capping stem.

Back the de-capping stem out 0.050" and have another go at it.
Click to expand...
A redding body die does not have a decapping stem. Think FL sizing die without internals.
 
Slightly different spingback in the various cases - to do the whole batch, set the die a touch lower to assure the longest is 1.619 ... the trim difference for those that will end up at 1.617 is irrelevant to the loads or accuracy you'll end up with.

Alternatively if they're already segregated, just touch up the longer ones.
/Bryan
 
Different brass strengths.

Shoulders do not always bump to the same spot exactly, even when the same brand. With cases from the same lot you will get .002 to .003 spread or better. The better the brass, the tighter the spread.

Mixed brass which comes from different lots and may have been fired a different amount of times will vary more.

I sized some RP .300 BLK brass the other day and I got a .004 spread. All fired close to the same number of times. The average was where I wanted it, which is 1.140 with my home made shoulder gauge.

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I know FC brass has issues and is likely the brass. Any suggestions on how to correct, short of getting different brass (and yes I am considering that).
Click to expand...

What press? How is the die set up?
 
I think this is due to your lube, press window flex, and brass temper. Tolerance stacking can get you that much variance, but this is extreme.
 
Lee Breechlock and Imperial Sizing. I would believe flex and whatever, but I tried to resize and it did not change anything.

None of this brass has been fired out of my rifle yet so has not been fire formed.
 
You might have slightly better luck after FLR for the first time. But spring back and press flex both stack together to give you some variation when you're trying to partial FLR. If I was into partial FLR, as I bet you are since you have a body die, I'd consider a way to get rid of the press flex. You can use shims or buy competition shellholders that give you more consistency.

but I tried to resize and it did not change anything.
Click to expand...
Well, yeah. So? It won't change until you change the die settings or anneal the brass or use a different lube. The force causing press flex is equal and opposite to the force exerted by the brass. Each piece of brass is unique, so this force varies (and it affected by lube). Your longer pieces of brass are harder. They are exerting more force than the ones that sized all the way. This leaves the gap between the die and shellholder just a hair bigger; and then they also springback more on top of that. No matter how many times you try to size the case, the gap/flex/springback will remain consistent, because that's the "equalization point." Try annealing the shoulder and doing it again.
 
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Press flex is an issue for me. This is known and is something I will correct in the short term if possible. Brass spring back is something I'll check later tonight. I'll set the die down lower and push the shoulders a little further in the hopes of getting them to stay a little lower.
 
but I tried to resize and it did not change anything.
Click to expand...
Did you have the die down far enough to contact the shoulder? As 918v pointed out, that spread is pretty bad.
 
It could be the locking insert is not secure. Is the assembly moving? Get a magnifying glass and observe the joint while sizing.
 
The breechblock assembly.

Is the die loose in the assembly? Is the assembly loose in the press?

pressbushingarrange.gif


Is the die wobbling in there? I don't like this system at all.
 
I suspect you are picking up slack somewhere inbetween the shellholder and the die.

buy competition shellholders
Click to expand...

Yup.

It will remove slack from the system.
 
Ok so I did a little more investigating. I think the brass that were bumped weren't really bumped and were already good to go. I reran some of the long brass and realized they are not being bumped at all. The sides are being sized, but the brass isn't making it to where the shoulder would be bumped. The die is touching the shellholder so the die can't really go down further. :(

I hope what I said above makes sense. At the same time, I can't believe a redding body die would be too "tall" as to prevent the shoulder from being bumped because the shoulder didn't make it that far up the die.

Am I doing something wrong in the setup of the body die?
 
But the press is flexing.

Do this:

Raise the ram all the way up.

Screw the die in until it touches the shellholder.

Then add an additional quarter turn.

This will remove all slack and frame flex from the equation. Now resize the case and come back.
 
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