why are standard loads to hot in my gun

[Yellerdog]

I have a 16 in 300 fireball barrel on my gun from modle 1 I can load up recommend 17.5 gn h110 behind 125 sst and blow the primer out of case. I drop to 15gn and no problem going to work up from there now but why would my gun be so different. All cases are trimed to proper length and case gauged.

[talonxracer]

You have a barrel chambered in 300Fireball ?

Trying to shoot 300BLK in it?

Sounds like the ammo is too tight in the neck of the fireball chamber causing overpressure. The common advice is do not shoot 300BLK in a 300 whisper/300-221/300 fireball rifles

[Yellerdog]

I was told all was basically the same. Factory 300 blk works fine in it just having problems with a hunting rnd setup.

[talonxracer]

They are not the same, close but not identicle. I would get a 300blk go, no-go gauge and check it out,

[WDA]

The max case length of Blackout is .018 longer. Chambering an in-spec blackout round into an in-spec fireball chamber will most likely cause that .018 to crimp down on the bullet and cause overpressure. Most of the case dimentions are different but that one is likley causing the "problem".

I wouldn't shoot that barrel with blackout anymore, even factory rounds. You may be able to get it reamed to blackout.

[BTP]

I have a 16 in 300 fireball barrel on my gun from modle 1 I can load up recommend 17.5 gn h110 behind 125 sst and blow the primer out of case. I drop to 15gn and no problem going to work up from there now but why would my gun be so different. All cases are trimed to proper length and case gauged.

I had the EXACT same issue with the exact same upper from model 1 in 300fireball a few years ago as well. I sent it off to get reamed to 300BLK specs and problem solved. Then I sold it and got an AAC upper. Fix the chamber and I bet you fix the problem.

[m4tt70]

I have a 16 in 300 fireball barrel on my gun from modle 1 I can load up recommend 17.5 gn h110 behind 125 sst and blow the primer out of case. I drop to 15gn and no problem going to work up from there now but why would my gun be so different. All cases are trimed to proper length and case gauged.

There are a few items to look at for high pressure, if you are loading within the manufacturer's specs. One is the chamber. Not all are the same. If the chamber is tight the pressure will go up. Another factor is the surface area of the bullet. Some bullets of less weight have greater surface area and pressure goes up. A good example of this is the Hornady 75gr OTM. It has more surface tension than the 77gr SMK and loads lighter. Another area is bullet seating depth. Just a couple of thousands can make a big difference. The deeper you seat, the more pressure. Try seating with less depth and check pressure. Just make sure you stay under the max OAL.

Just some thoughts. I never claim to be an expert at anything.