Velocity Effect of Bullet Tension

[Hugnot]

Some stuff that I have found.

Checking out some same lot brass, with equal powder charges and same bullets and same neck wall thickness, that after firing, some were coated with powder residue down to the rim also with residue on bolt head. Subsequent examination showed that if a bullet was inserted into the neck of these smudged fired cases the bullet would not easily slip fit into the mouth. Other cases were clean and easily allowed slip fit bullets. Annealing all cases, 15 seconds all around, propane flame, brass contacted outside of reducing part of flame, fixed the problem - everything was happily clean and accuracy returned.

My guess is that some necks were work hardened and brass spring back occurred just after passage of bullet from case and a good brass/chamber seal did not happen. I would guess that the annealed necks had uniform neck tension and little spring back and a good seal occurred upon firing.

My routine is to anneal after 3-4 firings, full length size using a body die, lubing the lower part of the case, lube the inside of the neck with 3-In 1 graphite lock lube, neck size using a Lee Collet Die (5 applications, 5 seconds apart, for spring back), then carefully and slowly seat the bullet using a seater plug that grips the bullet ogive. I can feel by the amount of force the degree and uniformity of neck tension.

 

[ButterBean]

I will admit I'm not familiar with Hammer bullets and the amount of neck tension required. Thank you for pointing that out!

The correct powder charge (and seating depth) cures a lot of problems....In my experiences less neck tension required more powder to achieve consistent results and vice versus. I have never personally found the need or any added benefit to adjust neck tension on a FINISHED load. That said if your are struggling to get a good consistent shooting load...changing to more or less neck tension could certainly alter the course of initial load development.
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The problem with seating force gauges like the K&M and 21St Century are those numbers can be easily manipulated with the amount of speed with which you seat the bullets and the amount and type of lube used.

With consistent reloading practices the variance in seating force probably doesn't vary more than 10-15psi and that is being generous. I doubt many if any could/can shoot the difference unless the numbers were on the opposite ends of the spectrums.

I'll give you one example, With the 124 HH in a 300WSM, I was getting great groups at 3636fps but a .003 neck tension I could feel the bullet just falling in to the neck , I polished my mandrel down ( Lee Collet Die) to .0045 and added the Lee FCD at 1/8 of a turn from contact and gained 174fps ( 3810fps) with no change to anything else, I do agree with you on the gauges, To many variables but if your consistent with everything they should work but IMHO I think they are unnecessary

 

[Tiny Tim]

I'll give you one example, With the 124 HH in a 300WSM, I was getting great groups at 3636fps but a .003 neck tension I could feel the bullet just falling in to the neck , I polished my mandrel down ( Lee Collet Die) to .0045 and added the Lee FCD at 1/8 of a turn from contact and gained 174fps ( 3810fps) with no change to anything else, I do agree with you on the gauges, To many variables but if your consistent with everything they should work but IMHO I think they are unnecessary

I'm @ 0.0025 neck tension. After the season I'll try increasing it to see if es/sd tightens up. If not, I'll join you starting campfires with Staball.

 

[iRock]

I love this forum. So much learned!