Seating Consistency w/ CO-AX and Redding Comp. Die

[Varangi]

I can't wrap my head around an issue I experienced this morning. I thought I'd share it with the Collective before I re-visit my bench.
I'm reloading 300win mag using a CO-Ax and Redding Comp S Seating Die. I use the fixed shell plate w/ a Redding #6 shell holder-
20 pieces of brass are sized, trimmed
208gr. A-max's( not sorted)- I'll sort next batch, never had issue before..

Seating Die prepped w/ dummy to seat the 208 at 2.767 to Ogive- Confirmed several times.
Die free floats in the press... set screw holding die in slot adjusted to min.(just enough to keep the die from sliding out.

Seated all bullets- same technique- checked measurement w/ digital calipers- +/- .003 on all 20 rounds-- 2.764-2.770...

Verified measurement on dummy- 2.767- calipers ok
Inspected Die- no visual issues..
Bearing Service and Meplat should not be an issue- die contacts bullet just above Ogive..

Any ideas?

Thanks in advance

Mike

 

[Mikecr]

Variance in neck tension can cause this. Seater plug wedging is dependent on tension.

 

[Varangi]

Variance in neck tension can cause this. Seater plug wedging is dependent on tension.

Thanks, that gives me a place to start- I did feel some resistance in a few of the cases. I had to bump the shoulder back on a few of the cases which were already primed. Ran them back through the bushing die but probably got sloppy- I'll pay more attention next time.

Mike

 

[bill123]

Variance in neck tension can cause this.

I agree. Had the same problem because I sized and expanded cases in a large batch and then let them sit for about 1 month. Try expanding just before seating. Maybe cases are ready for annealing?

 

[The Oregonian]

I agree. Had the same problem because I sized and expanded cases in a large batch and then let them sit for about 1 month. Try expanding just before seating. Maybe cases are ready for annealing?

New to reloading here...what you said makes sense but brings to mind a question. If you are not turning necks, would you expand the necks? And if you were tuning necks, would you neck size after turning, or neck size, expand, and turn?

If expanding the necks without turning, would you expand and then neck size? Or neck size and them expand?

From what I have read, the only time you would expand the necks is prior to turning, but curious to hear about your method if it is different.

 

[bill123]

New to reloading here...what you said makes sense but brings to mind a question. If you are not turning necks, would you expand the necks? And if you were tuning necks, would you neck size after turning, or neck size, expand, and turn?

If expanding the necks without turning, would you expand and then neck size? Or neck size and them expand?

From what I have read, the only time you would expand the necks is prior to turning, but curious to hear about your method if it is different.

I remove the button in the sizing die and use an expander as a separate step. It is supposed to control runout more effectively. It is also better to use an expander if you use a bushing die. Check out the articles toward the bottom of the page in the Reloading section here for a complete explanation:The Rifleman's Journal: Articles Index

Another great resource is Zediker's book Handloading for Competition.

 

[Mikecr]

You're going to expand necks no matter what. This, with either bullets or a hardened expander.
-Soft bullets wiggling off the end of a seater plug are terrible expanders-

Where you want low runout, and consistent seating, you pre-expand necks prior to bullet seating.

 

[The Oregonian]

Once cases are trimmed as needed, and assuming that no neck turning is done and a FL size is not needed, can you clarify the order of steps?

Is it expand with a mandrel (such as what would be used if you were turning necks), then neck size? i.e. you expand and then bring back down to size?

 

[WapitiBob]

I turn my seater back slightly for every bullet seating. The most consistent seating I get is with new brass and I still see a few thou so I just dial every one of the bullets in. Once fired vs twice fired use to make a big difference when my loads were at max.

 

[bill123]

Once cases are trimmed as needed, and assuming that no neck turning is done and a FL size is not needed, can you clarify the order of steps?

Is it expand with a mandrel (such as what would be used if you were turning necks), then neck size? i.e. you expand and then bring back down to size?

Other way around. Size first, expand second. This is what happens when you use a die with an expander ball installed as well. The expander ball is the last thing to touch the case neck.

 

[Mikecr]

There are a few reasons we should always expand before seating bullets, and as mentioned an expander mandrel is best for this(Sinclair's expander die sys).

Expansion:
-Pushes thickness variance in necks outward for straighter seating/lower loaded runout.
-It injects energy into brass that will try to release over time(back to balance). This release is called springback,, it's all that is gripping bullets,, and it continues over time. It's conservative to leave springback strengthening bullet grip over time(well, trying to), rather than weakening(much easier). When you downsize necks as the most significant action(rather than expanding last), springback is outward away from bullet grip.
-By expanding to ~1/2thou over cal, springback will provide plenty of bullet grip without excess seating forces. This allows best seating depth consistency.

You can pick a bushing that leaves the ideal interference fit without further expansion action, but this leaves greater seating force variance, especially over time. So it's best to pre-expand necks before seating.

Hope this makes sense..

 

[The Oregonian]

Makes sense...I have Redding comp dies and a Froster coax on the way, as well as a sinclair neck turning kit, so I have all the tools to do what was suggested. Appreciate the insight.