Question for y'all, just got a 300 RUM put together on a defiance action. After shooting the gun is showing slight ejector marks on the brass. This is both with factory loads and with minimum hand loads (88gr H-1000, Berger 205). Contacted barrel manufacturer and they claim this is common? Not something I've seen before on a tame load. Any advice?
Ejector marks
- Thread starter Cohunter9887
- Start date
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At first glance, your primers don't look excessively pressured.
I see Peterson brass, and I presume relatively tough case heads. Supposedly first rate brass. Which should be resistant to ejector plunger marking. But I haven't yet used Peterson brass.
Have you measured any muzzle velocities. MVs will generally correlate well with cartridge pressures. High MVs ~ high pressures. Low MVs ~ low pressures.
Since it sounds like a custom build, I suggest this simple test. Make sure bullets can be inserted into your fired case necks without difficulty, to help ensure you have sufficient chamber neck - to loaded cartridge case neck clearance.
Maybe contact Peterson. See what they think about those plunger marks on their 300RUM brass.
About all I have to offer at this time...
I see Peterson brass, and I presume relatively tough case heads. Supposedly first rate brass. Which should be resistant to ejector plunger marking. But I haven't yet used Peterson brass.
Have you measured any muzzle velocities. MVs will generally correlate well with cartridge pressures. High MVs ~ high pressures. Low MVs ~ low pressures.
Since it sounds like a custom build, I suggest this simple test. Make sure bullets can be inserted into your fired case necks without difficulty, to help ensure you have sufficient chamber neck - to loaded cartridge case neck clearance.
Maybe contact Peterson. See what they think about those plunger marks on their 300RUM brass.
About all I have to offer at this time...
Last edited:
Let Her Eat
QuietTexan
Well-Known Member
Steel or CF barrel?
Little more info for y'all, the Peterson brass I originally shot was virgin brass never shot. I have since shot it with the hand loads for my other rum which is Norma brass on its 3rd firing, same result. Velocity is ~120 fps slower out of the problem gun versus my other. Both 26" light palmas. Via bore scope bore is comepletly clean, no carbon, copper etc.
If the brass isn't a good fit to the chamber on the first firing it can cause ejector marks on the next reload either don't bump the shoulder at all or only .001"
Not all barrels will produce the same speed some are fast some are slow. I've also had several barrels pick up speed as they mature. For the most part they seem to plateau around 150-200 rounds. That's if they are going to pick up speed, some don't.
Not all barrels will produce the same speed some are fast some are slow. I've also had several barrels pick up speed as they mature. For the most part they seem to plateau around 150-200 rounds. That's if they are going to pick up speed, some don't.
Mikecr
Well-Known Member
Maybe it's an action issue, or a slippery chamber.
RockyMtnMT
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Some rifles show ejector marks on everything. This is why I like to start low and work up. When the mark starts to change/get more pronounce then you know you are pushing.
Creedmoor shooter
Well-Known Member
My experience with peterson is exactly this. Seems to show pressure early in the case head. Good brass but it shows ejector marks very easily.
Good to know
