Gun and/or reloading issues. Need help.

[1lessdog]

If there was some kind of obstruction in chamber he world never get a loaded round in the chamber. He never really said if that was after was fired or before.

I think he has a build up in his Full length sizing die that is causing it. If he is using the old RCBS lube pad and RCBS lube I have seen it like that many times. Take some Q tips and rubbing alcohol and clean your Die out. A dirty die does strange things.

 

[SupressYourself]

I beleive he said it was only after firing, but it seems more likely he just missed it, and it was there after resize.

Clean the gun, clean the sizing die, and try again.
And you should probably look into putting some more powder in that case.

 

[1lessdog]

I don't believe you can get any kind of blow by. Think of a 6MM and fire forming it to a 6MM Ackley Improved. It pushes the brass forward to form the case. If there was any kind of gap it would seal up at the shot.

I would really like to get my hands on that rifle and shot it.

Your load is on the low side. I would bump it up to 41 or 42 gr and see how it shoots.

 

[Tymurrey]

My guess is under pressure, once fired brass, which volume increased slightly even if full length resized vs the factory new brass and an already light load the brass might not be sealing the chamber. Slight variations can make a huge difference on an alrighty light load. Have you changed brass brands or cleaned the chamber recently or done anything different than previous. If dented from reloading from to much lube I’ve usually seen the dent more on the shoulder than the case body and the dents would pop out after firing. Do you have a different lot of powder to try as well.

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Also since it didn’t happen on all of them could have been a couple got mixed up that had multiple firings and the brass had work hardened enough to not expand and seal the chamber all the way. You didn’t happen to get H4350 instead of IMR4350 or something like that did you. My guess on accuracy is inconsistent pressures and powder ignition/burning.

 

[jokostel]

Low pressure dent... quite common when you're running at start charges in cooler weather.

 

[espringers]

yep. what these guys said ^^^