MANDREL AFTER BUSHING OR NOT ?

[Bill Norris]

Recently tried the mandrel after bushing when sizing brass for 3 of my rifles. Results simply don't show anything positive for me. Method I used was example: Fire-formed Un-turned Lapua brass Loaded neck diameter - .294 Used a .292 bushing in my die. When running a .262 mandrel in the necks after sizing there was little to no contact with inside of necks. Dropped down to a .291 bushing to feel slight contact. Noticed marginal opening with no difference in accuracy. My conclusion: Not worth the efforts nor moving the brass another .001. What say you?

EDIT: I repeated this same process with another 260AI and my 30BR with the same results. My 30BR requires turned necks down to .098

 

[rijndael]

I use a mandrel after a bushing, if I use a bushing that's .002" under loaded, my mandrel gets very little resistance on a couple pieces (out of 100 - Lapua). That tells me there's some inconsistency in the necks, even if it's only a couple of pieces. When I use a .003" under bushing, the mandrel feels most consistent for all of the brass.

 

[JMayo]

Same here. 6bra found no reason for the extra case handling. Another pice of reloading equipment is box.

 

[Bill Norris]

I use a mandrel after a bushing, if I use a bushing that's .002" under loaded, my mandrel gets very little resistance on a couple pieces (out of 100 - Lapua). That tells me there's some inconsistency in the necks, even if it's only a couple of pieces. When I use a .003" under bushing, the mandrel feels most consistent for all of the brass.

Absolutely my findings as well but with most of my brass. But I see no difference in accuracy at all.

 

[Straightshooter1]

Recently tried the mandrel after bushing when sizing brass for 3 of my rifles. Results simply don't show anything positive for me. Method I used was example: Un-turned Lapua brass Loaded neck diameter - .294 Used a .292 bushing in my die. When running a .262 mandrel in the necks after sizing there was little to no contact with inside of necks. Dropped down to a .291 bushing to feel slight contact. Noticed marginal opening with no difference in accuracy. My conclusion: Not worth the efforts nor moving the brass another .001. What say you?

I find it works best when the bushing produces a OD .002-003 less than the OD diameter that the expander mandrel will produce; maybe a little less if you brass is annealed.

 

[Bill Norris]

Using a mandrel was once a part of my process but I found it was redundant and possibly overworked the brass.

Now I only use them on new brass - to ensure the mouth is truly circular and to expand them if necessary when seating pressures are too high. With new brass springback I have found that my Lapua brass for the FTR needs a mandrel at either .308 and sometimes .3085 to get my seating pressure at a reasonable level (between 40-60lbs). I never had to go so large with any 6mm.

After the first firing I achieve the necessary NT with my choice in bushing.

Yes always run an expander in new brass to make sure it's completely round and reduce neck tension for initial fire-forming.

 

[rijndael]

I'll run a test this week with and without the mandrel, comparing groups and magneto numbers.

 

[Mark W]

I’ve been using a mandrel very successfully for my 12 twist 6BRA. I decided to just use a bushing when I got my 8 twist 6BRA running. So far I’m having trouble with inconsistent seating depths on the 8 twist. It’s one of the things I plan to dig into if the weather ever gets nice enough to do some shooting.

 

[Bill Norris]

I'll run a test this week with and without the mandrel, comparing groups and magneto numbers.

Please keep us posted with results.

 

[Mark W]

What seating die are you using?

I’m using the same Forster 6 Dasher seating die for both rifles. I’ve been meaning to pick up a Wilson seater to make it easier to do seating depth tests at the range.

 

[Mark W]

Then my next question would be what brand of bullets? And are you sorting them BTO?

Barts, Bergers, Sierra, and Speer in the 12 twist and so far just Berger and Sierra in the 8 twist.

 

[Dusty Stevens]

Make sure you are sorting them. If you are, then it is the seater that is likely the problem. If you are not sorting them then that is it. Possibly the stem is working better on some types than others.

I was using a brand of customs, not mentioned here, that were darn accurate (got me some 3-4" groups at 1K) but were a nightmare to sort - I don't know why they were that bad. The variance was all over the place. I gave up on them for that reason but they sure shot when I put in the effort.

So they shot real good but didnt measure good so you stopped using them? Do your bullets that sort right shoot better?

 

[JEFFPPC]

I’m using the same Forster 6 Dasher seating die for both rifles. I’ve been meaning to pick up a Wilson seater to make it easier to do seating depth tests at the range.

Mark W. You will be far ahead with a micrometer Wilson seating dies than trying to reinvent the wheel using a mandrel after sizing with a bushing, especially with turned necks..

 

[OmegaRed]

Mark W. You will be far ahead with a micrometer Wilson seating dies than trying to reinvent the wheel using a mandrel after sizing with a bushing, especially with turned necks..

I also found unacceptable variation when using other seating dies before switching to Wilson arbor style. After the switch it went away and now the arbor style is all I use...even for non BR guns.