Thoughts on bushings

[savageshooter86]

It appears were are at the mercy of how precise a bushing is made. I did some "small testing" today with my Whidden FL bushing die and 2 different size bushings and expander balls.

My fired necks are 342"(Savage FTR factory chamber) and have runout of 0005 or less. Lapua necks turned to 0.014. A loaded neck is 3364" IIRC

My 335 bushing with OUT expander gave 1.5 thous runout and sized necks to 3336.
My 336 bushing with OUT expander gave me 2.5 thous runout and sized neck to 3347

I would have thought it would have been other way around.

With Whidden's 0.307 expander mandrel I get a neck of 334". With his 0.3084 expander I get 3055" neck. Runout stayed basically the same with the expander VS without.

So I believe even with several of the same size bushings your runout will most likely not be the same.

 

[jelrod1]

Are you certain that the bushing is not contacting where you stopped turning? Did you snug to the bushing and then back off a little to let the bushing float? Curiosity has me asking why you are turning Lapua brass for a factory chamber? The more you have to size back down in one step has been known to cause more runout. May try using a bushing neck sizer first with a little larger bushing before running through the FL. Also may try putting an oring under the die. Just throwing out ideas.

Usually in my experience you get a little more tension without the expander, but less runout.

 

[savageshooter86]

turned the necks barely to clean them up about 90% because I was wanting to use bushing die and no expander ball. And this was before I knew what I know now about sizing more than 5 thous neck size will cause some issues and inconsistency.

I turned necks all the way down so it just made cut into shoulder. Bushing is floating in the die. Can hear it rattle and is only sizing about 3/4 of case neck

 

[22BRGUY]

Have you fired these cases yet (twice is better)? I've found that all of the benefits I'm trying to get don't show up on the measuring tools all that well until the cases have actually been fired a couple of times and then run through the process.
Best Wishes

 

[LCazador]

Try an o-ring on the shell holder so it will float. Bringing the neck down more than 5 thousand is going to result in some inconsistent run out. Some of the brass will spring back more than others. If you have already shot this brass more than twice, then I'd be talking to Whidden about his bushings.

 

[Bart B.]

It's the opinion of some folks that a one-piece full length sizing die makes straighter cases than a die with a floating bushing in it (RCBS and Redding bushing dies have a couple thousandths clearance to the die's bushing chamber walls). The one-piece die keeps the case body and neck well aligned when sizing them down a thousandth or two.

As bottleneck cases headspacing on their shoulder center up front in the chamber as its shoulder fits perfectly in the chamber shoulder being driven there by the firing pin, the case neck has to be well centered on the case shoulder else it'll be off center in the chamber. Case necks float clear of the chamber wall when the round's fired. Even a .243 Win case centers perfectly up front in a .308 Win. chamber. And the back end of most cases is pressed against the chamber wall by the extractor pushing it there.

Measuring bullet (or neck) runout is best done by having the case shoulder resting in a V block instead of the case body behind the shoulder. As there's no such thing as perfectly round case bodys or chambers, any out of round the case has will get transferred to the bullet if the case body's front part is the forward reference spinning ammo for bullet runout. When fired, the case behind the body-shoulder juncture has a bit of clearance to the chamber wall.

 

[savageshooter86]

Whidden doesn't make bushings. They are starting to offer different size expander balls for their FL dies. I am using Reding TN bushings. This brass is fired 5 times(annealed at 3 firings).

I found it interesting that the 335 bushing(sized necks slightly more) had better runout than the 336 bushing. Because sizing necks more than 5 thous, like others have mentioned, tends to induce runout and inconsistencies. So I had though the 336 bushing would have shown the better runout over the 335 bushing.

I was saying I bet if you bought 3 bushings at the same time, from the same company, they would give you different runout on the same brass.

**I am using a Forster Coax press which allows the dies to float. Whidden's new decapping assembly also allows the internals to float somewhat better. He beefed up his decapping assembly and his expander is shaped differently

 

[jelrod1]

I see what you're saying, however I think it would take a much larger sample size to determine the extent of inconsistency. Seems like you have good equipment. I would be curious to see what would happen if annealing every time and sizing the neck in two steps. Sizing down too much at once coupled with possible inconsistent hardness to me seems like that could be part of it. You may be totally right but I would want to eliminate some other variables before committing to it.

 

[savageshooter86]

yep I just did this as a quick test and though it was interesting. I know it would take more testing to prove this 100%. I hope I can get a Bench Source soon and will anneal each firing.

I also checked necks with my mic and over 10 cases the necks did not vary more than 0005". Which for my level of tools/skill and shooting, I don't believe this is causing me any headaches right now. I turned the necks a when I first got them so I would have more consistent necks and try to take out the variance.

 

[searcher]

The runout differences between the two bushings seems far too large, in my mind, to be caused by the bushings themselves. Most likely here are other inconsistencies such as, as another noted - the bushing not being allowed to "float", the die being screwed in tighter (or looser) than when the other bushing was being used causing the mis-alignment- or perhaps your expander ball or rod got tweaked. Try running the cases through your neck die again WITHOUT the expander ball - just sizing the neck. Also apply a bit of graphite on the bottom of your shell holder and remove the shell holder retainer on your press allowing the shellholder to slide around freely. Also try the O-ring as another noted. All these little things combined can tighten up to reasonable levels.