Bushing Size for Mandrel

[Mikemontminy]

No if he sizes it down .002 it will expand at least .001 which makes that .001 too big if im reading it right. Gonna have to tighten it way up then let the expander mandrel set it right for the turning mandrel

After looking at the two posts from the OP I think he is looking for information on which neck bushing /expander mandrel combination to control neck tension before seating bullets. He feels like the mandrel isn’t making enough contact with the inside of the neck to open it back up and make all the necks uniform . If your cases are annealed every time prior to sizing and you don’t think the mandrel is opening the necks back up or making any difference . I would try going .001 smaller with your sizing bushing prior to using the expander mandrel and see if that helps. The final inside neck diameter is what your trying to keep consistent and it’s a good idea to have different size mandrels and neck bushings to get there. I always check the final inside neck diameter with gage pins prior to filling cases and seating bullets.

 

[Ned Ludd]

In my hands, a mandrel needs to be under bullet diameter by the amount of neck tension you're aiming for (i.e. under bullet diameter) plus half a thousandth. For example, I use a 0.336" bushing to give .002" neck tension (interference fit) in un-turned Lapua .308 Win Palma brass necks. When I use a mandrel as the final sizing step, I would select a 0.334" bushing instead, followed by a 0.3065" mandrel to give almost exactly the same neck tension (.002") as the 0.336" bushing will do by itself.

When using a mandrel as the final sizing step, the necks need to be sized down smaller than the mandrel by a sufficient amount that the mandrel can do its job and open the necks up properly. Too little difference between the mandrel and the bushing and you run the risk of excessive variance and/or simply not getting the neck tension you really want. Running a bushing that is tighter than necessary means you're working the brass more than you need to. I have determined empirically with Lapua 0.223 Rem and 0.308 brass having un-turned necks that a bushing that is .002" smaller than the bushing you would ordinarily use to achieve ~.002" neck tension by itself is just about perfect when you intend to follow with a mandrel as the final sizing step.

For example, with 0.308 Win cases, I use a 0.336" bushing by itself, OR I use a 0.334" bushing followed by a 0.3365" mandrel. With 0.223 Rem cases, I use a 0.248" bushing by itself, OR a 0.246" bushing followed by a 0.2225" mandrel. Both approaches yield similar results. This needs to be determined empirically as I mentioned above. Different brands of brass can have different neck wall thickness, as will brass with turned necks.

 

[Lucky Shooter]

I'm following this thread with great interest and curiosity----as a
non-competitive shooter who likes to shoot 100 yd bug holes.

My necks are sized with a collet die using pin gages----.0005" increments
dropped into the case. The next larger size pin gage---.0005 larger---is used
to verify that the neck has been resized.

A comment on this per Joe R's video and his remarks about dwell time when using bushings----dwell time appears to have similar effects on neck ID when
using collets. As expected, this method works better when necks are turned.

A Redding body die is used to resize the case body.

Question:
Other than having additional steps for FL (case body) sizing and depriming,
what does this method give up as compared to S-type bushing die sizing and
the use of expanders ?

BTW, I also have S-type dies and bushings---just trying something new to me.

Thanks for any comments.

A. Weldy

 

[Kraven]

Lots of good info here. Thanks fellas. Mikemontminy is spot on. my current setup is L.E Wilson FL sizing die with 0.267" bushing (0.269" loaded neck) and Sinclair E- Mandrel (0.001" under bullet). pretty much looking for the least amount of neck sizing while still making use of the mandrel pin. with this setup, the mandrel has 0.001" expansion after sizing. I do see the lower 1/3 of the neck is not touching the mandrel. not sure if this is critical but I think this is a byproduct of a bushing die. I have different size bushings and mandrel pins to experiment with. I do have a non-bushing FL sizer die that sizes neck farther down but it shrinks the neck quite a bit (off the shelf die) and would give me inconsistent run-out.

6 Dasher, Proof Barrel
Alpha brass (unturned)
AMP Anneal (every firing)
Giraud Trimmer (every firing)

been reloading for a long time but precision reloading is still new to me. I think I am heading in the right direction. thanks for all of the input fellas. last outing I shot a 1/4" 5 shot group at 200yds.

 

[whatwind?]

As an aside, a shooting buddy just did a micro test loading identical rounds (brass, powder, bullets, seating depth) with his .284 Shehane but varied using an expander ball versus a pin gage. He fired them blind alternating 5 shots at a time—40 rounds total. Again, this is a micro test, but a start. Consistency of the pin gage seems to win.
View attachment 1186376

@David Christian

What die set was he using for the expander ball test and how much below pin gauge did he go before using the correct pin gauge and how much neck tension for both? just curious, i use bushing plus expander ball from whidden and wonder if i should try the pin gauge/mandrel also...thanks