Rough "single stage" bullet seating on 6.5 Creedmoor (with Arbor Press and force gauge)

[FrenchPewPiou]

Hi everyone,

I'm on my 3rd reloading batch, the first two ones being with brand new Lapua brass each time. I have a K&M Arbor Press with the 0-150lbs force gauge pack.

With my first two batches (brand new brass), the seating would be what I'd call "two stages": first stage would be at ~20 lbs of force to start inserting the bullet into the neck, and then more force, about 50 lbs of force, was required to finish seating the bullet. This matches pretty well what I saw on another forum where the guy did a thorough analysis of the seating force using a force gauge connected to a computer and got two stages: first one at 25lbs and second one at 40lbs.

Today, I did my third batch, and I re-used the brass of my 2nd batch. I prepared the brass mostly the same way (differences below), but for some reason this time when seating the bullets I only got a single, 50lbs, stage. And it was pretty "rough": the bullet wouldn't move at all until 50lbs where it would go in all at once. It was pretty consistent over 100 bullets (45-55, less than 5 above 60lbs).

Differences in brass prep between previous and current batch:

• Didn't trim (case actually shrank after firing...)
• Didn't chamfer/deburr because I didn't trim
• I sized only half of the neck

Have you ever experienced this? Is it good, bad, irrelevant? What could cause this?

Thanks!

 

[Supersubes]

How did you clean the cases? How much neck tension?

 

[FrenchPewPiou]

How did you clean the cases? How much neck tension?

I use a wet tumbler with Frankford Arsenal cleaning solution and stainless steel pins for ~2hours. Neck tension is 2 thou like the first batch (brass thickness: 0.015in, outside diameter: 0.292in, bullet diameter: 0.264in).

 

[Supersubes]

I dont know anything out that cleaning solution in particular, but id guess the necks are too clean. Raw brass in raw copper is a pretty sticky combo.

 

[Rocketmandb]

Neck lube

 

[918v]

The reason for this is you only sized half the neck using a bushing die, I presume. If you had sized the whole neck you would have seen two levels of resistance.

The reason the seating pressure increased over new is because the brass is harder after firing and subsequent resizing.

 

[918v]

When you size the whole neck you reduce the diameter of the neck/shoulder junction to some amount less than the bullet diameter. This causes the secondary increase in seating pressure when the bullet passes through it.

When you size the neck partially the neck/shoulder junction remains larger than the bullet so there will not be an increase in seating pressure when the bullet passes through.

 

[FrenchPewPiou]

I dont know anything out that cleaning solution in particular, but id guess the necks are too clean. Raw brass in raw copper is a pretty sticky combo.

Indeed, much better now with Neolube 2!

The reason for this is you only sized half the neck using a bushing die, I presume. If you had sized the whole neck you would have seen two levels of resistance.

The reason the seating pressure increased over new is because the brass is harder after firing and subsequent resizing.

When you size the whole neck you reduce the diameter of the neck/shoulder junction to some amount less than the bullet diameter. This causes the secondary increase in seating pressure when the bullet passes through it.

When you size the neck partially the neck/shoulder junction remains larger than the bullet so there will not be an increase in seating pressure when the bullet passes through.

I think you are right on everything! I put some Neolube 2 now to ease the seating, I'm at 25lbs.

Thanks everyone!