300PRC +P Load development

4O6shootist

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Perfect explanation, I run 90% improved cartridges and hardly ever have to trim brass. You will get min brass growth running improved! As with any cartridge I load for, I do keep a close eye on the case head expansion at the .200 line and primer pocket depth. Pressure tested NO but a caliper and constant measuring will tell you when your into some excessive pressure.

300 NM has some of the worst brass flow or case growth I have ever seen. More case taper = less grip on the chamber walls. More bolt thrust perhaps.

I believe Jim Boatright has written a article on this matter.
300nm was designed to be run through belt fed machine guns(as well as bolt guns), hence the reason for taper and low shoulder angle. Before tearing down the original design, a bit of understanding needs to known of its original intended purposes.
 

Carole Baskins

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elkaholic

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That's really fast for a 250 and only 89 grains!

I have RL33, 250's and a 29" RUM barrel throated for 4.155 COAL that I have yet to install... wasn't expecting more than 3050 with 10-15 grains more capacity.
Thats why a lot of folks like the SM
 
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BCX

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  • Mar 18, 2018
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    300nm was designed to be run through belt fed machine guns(as well as bolt guns), hence the reason for taper and low shoulder angle. Before tearing down the original design, a bit of understanding needs to known of its original intended purposes.
    Thanks for the information, see I learned something new today. Never had I read it was designed and put in service for a belt fed machine gun.
     

    BCX

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    Tom Sarver was the original designer. Next time I shoot at Thunder Valley I will get more info on the 300 NM.
     

    4O6shootist

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    Thanks for the information, see I learned something new today. Never had I read it was designed and put in service for a belt fed machine gun.
    Multi purpose, bolt gun, but able to run in automatic belt feeds. There are a few large machine guns chambered in the 300nm. I think it'd be a lil hard on barrels lol
     

    BCX

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    Yeah that was my next question on barrel life in a machine gun w the 300 NM. Maybe Frank stole the modBB formula 😂😂😂😂 I know Sig has a 338 Norma mag machine gun.