Seating depth changes after seating a bullet?

[seidersjoden]

I had this issue so bad with my 338-416 Rigby Improved 45* with H50BMG, I had to change powder. As soon as the rounds came out of the press, they would start backing out while in the loading block!
My 300WM has this issue with 230gr Berger OTM's with just about every powder I put in there. I haven't lengthened the throat yet, and it is a SAAMI chamber, I will probably set back and run the A191 reamer in to fix it, but I just re-seat prior to shooting them.
I will also add that there is an important part of the loading procedure often overlooked. It is called the "Powder Packing Scheme". If you just dump powder into the case, especially powder that will be compressed, each dump of powder will be a jumbled random height in the case, the level of compression will also be different. This changes the burning of the powder between shots, which affects ES.
The best technique is to swirl the powder into the case with a powder funnel, no drop tube is required. This technique stacks the powder so uniformly that it is more consistent than a long drop tube. I did a test with clear 1/4" plastic pipe, as dumped loads varied in height quite a lot, the swirled charges practically stayed exactly the same height each time.
My ES dropped on untuned loads without even doing seating depth tests first using this method. Now this is only useful on loads that will be compressed, whether only slightly or heavily, although it works best on bulky powder loads like RETUMBO, RE33 & H50BMG or ANY compressed loads.

Cheers.

Interesting...thanks for the advice!!

 

[seidersjoden]

After reading this thread initially, I wasn't 100% convinced. I went back and remeasured my rounds I loaded the week before and found no movement or variation (Moved on).

I recently returned from Wyoming. I flew out, and flew back. I went to the range today to verify my zero. Needless to say my zero had shifted (Separate Issue).

After getting back home tonight, I decided to measure all my leftover rounds that I had taken to Wyoming and noticed they had moved out .001 - .002 thousands from 2.989. Ran them back through the seater, all good to go.

So that being said, I believe something happened to my rounds in flight. Not certain what if any effect pressures would have on ammo being transported onboard a plane.

must be the overpressure of altitude with the rounds, or, maybe they would have moved out regardless..?

 

[seidersjoden]

Did you do anything to necks that would reduce friction?

Nothing with necks but I do dip the Bullets in dry lube.

 

[C.O. Shooter]

must be the overpressure of altitude with the rounds, or, maybe they would have moved out regardless..?

Yea I have no clue! Maybe someone who has an upcoming flight could test this theory! Or someone answer who has experienced this!

 

[seidersjoden]

I would get the drop funnel above^^^^^. One trick i used with compressed loads, was to hang up in the seat die for 4-5 seconds and let the brass get a grip on the bullet before extracting it.

makes sense, a lot like keeping tension on the bullet when adjusting bullet run out. I noticed quickly straightening the bullet without holding tension that brass spring back would occur and the bullet wouldn't straighten as much

 

[misterc01]

Pressure - or possiby how the baggage handlers treated whatever they were being transported in!

 

[elf]

How are you measuring them? CBTO or bullet tip? If the latter, you will always find some variance. Do you use a comparator?

 

[Savage 12BVSS]

I've had this happen on compressed loads. Means there is too much compression if this is a compressed load.

Thats the reason alright, if you reseat they can still push out again but not as bad. Drop tube and vibration both help this problem by lowering powder level in case. I never liked dealing with it so found powder I could run lower charge weight on, problem solved. Magazine and distance to lands can cause problems with bullets sticking into lands if close or failing to feed right.

 

[C.O. Shooter]

Pressure - or possiby how the baggage handlers treated whatever they were being transported in!

My rounds were transported in a hard MTM ammo box.

How are you measuring them? CBTO or bullet tip? If the latter, you will always find some variance. Do you use a comparator?

CBTO w/Comparator.