Pushing the bullet past the shoulder / neck junction

[swhiteh3]

Of course, we're talking about the full diameter section of the bullet.....

What is downside to a load which requires the bullet to be past the shoulder / neck junction?

I've heard lots of people say it's bad to push the bullet past this, but why? Anyone have data or really clear experiences why this is bad?

I have plenty of length available in my magazine, but just wondering if I should push the throat out a bit, and load the cartridges a bit longer to clear the neck / shoulder junction.

(For background, this is 6mm GT with a 115 DTAC. It was chambered with 0.170" freebore. After COAL / Jump testing it's happiest at 2.550", a jump of 0.042". And it's currently being pushed past the shoulder / neck junction by *ABOUT* 0.040", so I was assuming I'd add about 0.060" of freebore.)

 

[spife7980]

After a few firings the shoulder material migrates forward into the neck. If the shoulder is thick enough you end up with a donut of thicker material at the base of the neck. That can pinch the bullet a bit more than the rest of the neck would.
That said I dont care if the bullets down past the neck, some of my best shooting combos are way into the case.

 

[mtang45]

The only downside that I know of is reduced case capacity for your powder charge. Having a good part of the bullet sitting inside the case is pretty common in 300 WSM SAAMI chambers.

 

[orkan]

After a few firings the shoulder material migrates forward into the neck. If the shoulder is thick enough you end up with a donut of thicker material at the base of the neck. That can pinch the bullet a bit more than the rest of the neck would.
That said I dont care if the bullets down past the neck, some of my best shooting combos are way into the case.

If the firings get up past a dozen or so, it can start to be a real issue in some cartridges with certain dies.