neck tension

[zx10mike]

guys looking for some advice please .i'm running a 307 bushing in my shehane that gives me 3 tho neck tension.i tried a 308 bushing and it made no difference to group size but cost me 30 fps.my load is 57.9 n165 that gives a tame 2798 fps with great accuracy and a nice full case.i'm now thinking about 5 tho neck tension ,this might give a bit more fps and at the moment my cases seal on the shoulder not the neck and more neck tension might help this too.
would be greatfull for any words of wisdom/pointers/negatives ,any one found running more neck tension is better? i'm using whidden dies and the reading bushing only sizes 50-60% of the neck to 307 so really 5 tho neck tension might equate to same preasure as 2.5 if the bushing sized the whole neck.
please fire away with any words if wisdom and sorry if this is a basic dummy question.
mike

 

[22BRGUY]

Are you jumping or jamming? and if jumping how far?

 

[zx10mike]

10 tho off the lands shot great and i have had no need to tweak so might be 15 tho now but not a big jump

 

[mikecr]

Are you sizing more neck length than seated bullet bearing?

 

[zx10mike]

no i can see a ring where the bushing sizes up to %60 down the neck

 

[jsthntn247]

Are you sizing more neck length than seated bullet bearing?

What affect does this have?

 

[22BRGUY]

Just MHO, but I would try jamming 5 thou with the 308 bushing.

Best Wishes

 

[zx10mike]

thanks for the idea that might be a better option than more neck tension just to get that better burn.i'll try that and report back.

 

[mikecr]

Are you sizing more neck length than seated bullet bearing?

What affect does this have?

If he's only sizing neck length that is gripping bullet bearing(no more so), then he's getting no more than ~1thou of actual tension anyway(springback from expansion). This, regardless of sized to interference fit(unless less than 1thou).
So 1thou or 3thou or 5thou interference fit makes no difference -unless,, his reported interference fit isn't actually what he thinks it is.

 

[zx10mike]

which in simple dummy terms means ????lol

 

[mikecr]

Just gathering information about the actual condition.
What cal?
What do your loaded necks measure?
What do your fired necks measure?
what do your sized necks measure?

 

[zx10mike]

284 shehane sized is 307 loaded 310 fired sorry all prepped for f class sat and cant remember off top of my head.by monday i'll have tried touching the lands (during blow offs) and i'll have plenty of fired cases to measure.here is a pic of the problem.thanks for the help chaps.