Is using a custom sized expanding mandrel a good option in place of having to grab a FL bushing die. I see some use them and was wondering what the consensus is. Thanks.
Using custom diameter expanding mandrel for neck tension
- Thread starter Tacticaldonkey
- Start date
Sure is, if it works for your needs!
Sometimes using an expanding mandrel - factory or custom - after a bushing die works even better.
Please explain this. dedogs
The case is not supported and run out may become a problem. I have used an expander after FLS but never got run out to be much less than 0.004. With a FLS bushing die or a Lee Collet I am typically <0.002 and usually 0.001.
This has been my experience also.
Sure.
I went from 'factory' bottleneck dies - complete with expander ball - to neck bushing dies, expecting to get better results from sizing. Got better yet I thought I could do better.
Took expanders out first, figuring they were 'pulling' shoulders and necks out of position desired, contributing to sizing issues I was still seeing.
About this time I took up neck turning as much to reduce variances in neck thickness as to get a better handle on consistent neck tension. Same with annealing.
Even with all that attention to uniform necks & shoulders I was seeing inconsistent 'parallelism' in the shape of necks after bushing-die sizing. Most frequently I'd see a very slight bell-mouth where they either weren't being sized enough or were springing back some after exiting the bushing.
What I do now is choose a bushing one or two sizes smaller then use a carefully selected expander mandrel to open necks up at the last sizing step. Haven't felt a need for custom mandrels yet, but have been close.
Lately with a Very Short Necked wildcat I built this year (284INCH) I'm finding more neck tension than I'd otherwise use for say 308 Palma loads to work better. So I go farther down for bushing diameter when neck-sizing then use a 7mm expander just barely into necks to bring them back to desired diameter for seating.
Now I understand this may be counter to common practice but for my needs (match sights w/sling for score) it works fine. I lose cases to head stretch rather than split necks, seating force is very consistent & what's most important I trust my rounds to perform well. 49 times out of 50 the nine's I see when my target comes up are what I expect to see after calling the shot being scored. It's not my hand loads....
BoydAllen
Gold $$ Contributor
Getting back to the original question, it has been my experience that substituting the use of an expander die and mandrel for the the expander ball when using a one piece FL die, gives better runout.
Some time back, I needed to load some ammo for a .22-250 varmint rifle, and all that I had was a set of RCBS dies, which included a one piece sizer. After using my concentricity gauge to evaluate test cases' neck runout, I decided to try removing the die's expander and expanding after sizing with the expander die and mandrel that were a part of my neck turning setup. The results were clearly superior.
Back in the late 90's I spoke with an experienced, successful and well known thousand yard benchrest shooter who told me that even though he used bushing dies, that the last step in his sizing process involved expanding with a mandrel, and that he had a set that were graduated in half thousandth intervals. He told me that he got better results with that method.
The reason that expanders of various types can increase neck runout is usually that the amount of push or pull exceeds the yield strength of cases' shoulders, and they yield asymmetrically, cocking the neck relative to the case body. If necks are lubricated, and the amount of expansion is minimal, there is no problem, as long as alignment is decent, and the press is operated with an eye toward minimizing force applied to the case.
On a related matter, one time I tried my friend's Forster press for expanding up .220 Russian brass to 6mm and the results were a lot worse than I had gotten with conventional presses. I took that as an indication that while letting the die float might be a good thing when sizing a case, that a more positive alignment system was better for expanding necks with a mandrel. The best results that I had gotten have been with a Harrell Combo Press, that is very well aligned, due to the manner in which it is manufactured, and which has a very close ram fit.
Some time back, I needed to load some ammo for a .22-250 varmint rifle, and all that I had was a set of RCBS dies, which included a one piece sizer. After using my concentricity gauge to evaluate test cases' neck runout, I decided to try removing the die's expander and expanding after sizing with the expander die and mandrel that were a part of my neck turning setup. The results were clearly superior.
Back in the late 90's I spoke with an experienced, successful and well known thousand yard benchrest shooter who told me that even though he used bushing dies, that the last step in his sizing process involved expanding with a mandrel, and that he had a set that were graduated in half thousandth intervals. He told me that he got better results with that method.
The reason that expanders of various types can increase neck runout is usually that the amount of push or pull exceeds the yield strength of cases' shoulders, and they yield asymmetrically, cocking the neck relative to the case body. If necks are lubricated, and the amount of expansion is minimal, there is no problem, as long as alignment is decent, and the press is operated with an eye toward minimizing force applied to the case.
On a related matter, one time I tried my friend's Forster press for expanding up .220 Russian brass to 6mm and the results were a lot worse than I had gotten with conventional presses. I took that as an indication that while letting the die float might be a good thing when sizing a case, that a more positive alignment system was better for expanding necks with a mandrel. The best results that I had gotten have been with a Harrell Combo Press, that is very well aligned, due to the manner in which it is manufactured, and which has a very close ram fit.
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So if I measure a FL sized case then had a few sized mandrels that stepped down gradually in neck tension could this possibly work? I don't know why I feel so inclined to try this, maybe it is slightly outside the norm in a way and would be a fun experiment. Any experience with the Whidden expander ball kits?
http://www.whiddengunworks.com/product/expander-ball-kits-and-sets/
Agreed.
Forcing necks down 0.010" or more then pulling on them while also opening once again is just not acceptable.
Until reading your post TD, I wasn't aware of John's kits. I've gone over to using his dies for most of the cartridges I shoot so will be looking at these closely. If I can save time and get results with their use equal or better than now it'd be a good thing.
I am going to order a kit in 308, as well as some custom mandrels just for the sake of experimenting, I figure I will learn a thing or two and can pass the info on to others. Also John will be getting an order for a bullet pointing system very shortly, I think it is a cool concept and it is another thing get me to learn something new and test results.
What dies did you get from them? I am going to be in the market for a 243 and 7mm08 very soon and have heard great things about their dies.
OK I'll bite, Who is John?
[QUO TE="spclark, post: 36802744, member: 744926"]
What I do now is choose a bushing one or two sizes smaller then use a carefully selected expander mandrel to open necks up at the last sizing step. Haven't felt a need for custom mandrels yet, but have been close.
.[/QUOTE]
If you're doing this, why a bushing die? Why not use a regular neck sizing die and then run the separate expander thorough the necks. Regular neck sizing dies are usually cheaper too than bushing dies.
What I do now is choose a bushing one or two sizes smaller then use a carefully selected expander mandrel to open necks up at the last sizing step. Haven't felt a need for custom mandrels yet, but have been close.
.[/QUOTE]
If you're doing this, why a bushing die? Why not use a regular neck sizing die and then run the separate expander thorough the necks. Regular neck sizing dies are usually cheaper too than bushing dies.
I already had bushing dies so buying neck dies's kinda wasteful, and as they don't size the case body either (by my understanding at least) I'd rather use what I know works.
Too I find I need only size the first 0.100" - 0.150" rather than the full neck length to get the results I like on paper; leaving the neck just above the shoulder unsized helps cases align better when chambering it seems.
John Whidden?
Got it Thanks, I use his dies, best I have ever had.
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