.300 aac neck expansion

[The mailman]

I just loaded my first small batch of .300 blk using converted LC brass.  Set hornady sst .308 125 gr. The brass checks out on the case gauge. After I set and crimp the bullet the cartridge will no longer seat in the case gauge.  Neck is .334 after seating bullet.  Is it the shoulder? What's the remedy?

[The mailman]

I've been reloading handgun ammo for a few years but am relatively new to rifle.  The oal of the cartridge is 2.107. The bullet is seated to just where part of the cannulure (sp?) shows which I think is right.  I am using Lee dies but not the sizing die.  I bought LC 5.56 converted brass that was already processed.  The brass will seat properly in the gauge prior to seating the bullet.  Haven't tried to load these in the gun.  Using a Lyman case gauge.  I'm now wondering if the shoulder is compressing when I seat the bullet.

[my82cam]

I use a case length gauge, I had to grind the bottom of the resizing die to get the case where it resized enough.

[Omega]

I've been reloading handgun ammo for a few years but am relatively new to rifle.  The oal of the cartridge is 2.107. The bullet is seated to just where part of the cannulure (sp?) shows which I think is right.  I am using Lee dies but not the sizing die.  I bought LC 5.56 converted brass that was already processed.  The brass will seat properly in the gauge prior to seating the bullet.  Haven't tried to load these in the gun.  Using a Lyman case gauge.  I'm now wondering if the shoulder is compressing when I seat the bullet.

I would play with your COAL a bit, I found the same thing with some bullets I had to seat just a hair deeper to get them to load.  Use a black marker on the bullet to see if it is touching the lands and grooves and seat accordingly.

 

Here are some OALs I garnered from others, confirm these as they are off the web:

 

• Hornady 110 V-Max, OAL: 2.000
• 110 TAC-TX, OAL : 2.015 Others say 2.250 and claim anything shorter is heavily compressed.
• Nosler Ballistic Tip 125 grain, OAL: 2.085
• Remington AccuTip 125 grain, OAL: 2.085
• Sierra H2120 125 ProHunter, OAL: 1.950
• Sierra 125 OTM, OAL: 2.215
• Speer TNT 125 1986, OAL: 2.010
• Hornady 130 SP #3020, OAL: 2.010
• Hornady 150 FMJ-BT 3037, OAL: 2.065
• Sierra 155 Palma, OAL: 2.150
• Lapua B416 200 grain, OAL: 1.960
• Hornady 208 AMAX, OAL: 2.150
• Sierra 220 SMK, OAL: 2.089