300 NMI Chamber Version Advice.

[Mike D Texas]

Might as well go 40 degrees and reduce brass growth to the maximum extent possible, lower bolt thrust and slightly more capacity are also benefits.

All minimal gains at best. And I have several 40° Ackley cartridges and the 35° shoulder feeds noticeably better.

 

[Alex Wheeler]

The shoulder angle has little to do with capacity in this case. Reducing the body taper is the main improvement here. If chambered properly, you will have a crush fit on virgin brass so fireforming is all the same. I recommend just making 50 pieces of brass if its a hunting rifle. You will wear out the barrel with those 50 cases if your die is working. Its been a very successful cartridge. I chamber a lot of them. Its also a very good choice in some of the elr style matches.

 

[7.62 Gunner]

All minimal gains at best. And I have several 40° Ackley cartridges and the 35° shoulder feeds noticeably better.

Ok

 

[dhbikerczar]

I bet @Elk Hunter 338 probably has one dialed in.

I have an LPR 300 NMI that I'm running 180 gr hammer hunters through. I took one elk at 225 yards and one at 357 yards. Both shots performed perfect. I get honest 1/4 -1/3 moa 5 shot groups at 100 yards off the bipod and bench doing load development. I couldn't ask for a better build.

 

[EFouraker]

I have built 300nmi rifles with both 35 and 40 deg shoulders. Both feed like butter if the rifle is setup right.

I build a lot more 35deg 300nmi rifles because a lot of guys have it in their heads that the 40deg shoulder don't feed.

My current rifle has a 40deg shoulder and it hammers…..245s and n570!

 

[Quicksilver338]

245's and N570 is magic

 

[hwy1strat]

I have built 300nmi rifles with both 35 and 40 deg shoulders. Both feed like butter if the rifle is setup right.

I build a lot more 35deg 300nmi rifles because a lot of guys have it in their heads that the 40deg shoulder don't feed.

My current rifle has a 40deg shoulder and it hammers…..245s and n570!

What velocities are you getting with that? I have some N570 sitting around and that's got me thinking now

 

[EFouraker]

What velocities are you getting with that? I have some N570 sitting around and that's got me thinking now

2950 87.5gr. 26" suppressed. Max pressure in my rifle is around 3k

N570 is the best powder for the 300nmi imo.
It always give me the best precision/velocity and low ES whether i shoot 215s, 230s or 245s

 

[waveslayer]

I love N570 for the 300 NM. It's dirty, but velocity is good. I like 215's and 230's, haven't tried the 245's. Velocity 3052 from my standard 300 NM

 

[7.62 Gunner]

I have built 300nmi rifles with both 35 and 40 deg shoulders. Both feed like butter if the rifle is setup right.

I build a lot more 35deg 300nmi rifles because a lot of guys have it in their heads that the 40deg shoulder don't feed.

My current rifle has a 40deg shoulder and it hammers…..245s and n570!

Exactly
I always chuckle when someone claims 40 degree shoulders don't feed well..
I'll be sure to tell that to the 70% of dudes running 6 Dashers in my squad next match.
It's all about using the right parts and mags for your build.

 

[Huntnpack]

Thanks for the input. Appreciate it.