300 norma imp v 30-338 lapua imp

[Buttermilk]

What do these two rounds offer that's an advantage over the 300 RUM properly setup on throat and magazine (ie 4" box)?

Serious question. Trying to understand the draw to the other two rounds.

Thanks!

 

[E4aker]

What do these two rounds offer that's an advantage over the 300 RUM properly setup on throat and magazine (ie 4" box)?

Serious question. Trying to understand the draw to the other two rounds.

Thanks!

Lapua brass mainly.

A 300rum throated properly for a 245 isn't going to fit in a 4" mag box.

That being said I love a RUM

 

[Marine sniper]

I had a 300 and a 30-378 Wby's that both were very accurate, but I got tired of spending all that time on brass prep (both were turn neck chambers) only to have the primer pockets die in 5 rounds. I won't even consider a cartridge now if high quality brass isn't available for it.

In addition, as E4aker pointed out getting the throat correct in re: to the boat tail junction is important as well, although inside neck reaming is an option I have used in the past with very good results (donuts).

FWIW; just got back from the range and 90 grains of US 869 that I had laying around produced 2750 FPS with 240 SMK's in a 26 in barrel during fire forming in my new 300 NMI.

 

[Alex Wheeler]

I've shot groups in the .1s at 1k with both cartridges multiple times in different rifle. The 300nmi excels in hunting weight rifles.

I feel like both cases are as big as I like to go for their bore size.

Something worth mentioning that adds value to me, is the 300 nmi is easier on optics and mounts. Especially these big 40oz scopes that guys like to use. I've built a few 33xcs for guys and they wreck optics…especially in the lighter weight rifles.

Over on accurate shooter theres threads I started on each one. With group pictures. Ones at 1k from these kind of guns dont happen too often. I wish I could find the one I shot comparing annealed vs non annealed. One was a 1.6 the other was a 1.7, back to back ones from a bipod gun. As much as I love the big 30, it just wont hang with the 338limp. But its so close it makes no difference in the real world. We also had both chambered in heavy bench guns for 2k group shooting. If weight it not a concern I will do the 338 every time. It so good I have been close to building a 1kBR rifle in it but the 10 shot groups would kill it. If we change to 5, it would be competitive. But ya, if you need a 8-10 pound gun, 300s are the way to go.

 

[Marine sniper]

Over on accurate shooter theres threads I started on each one. With group pictures. Ones at 1k from these kind of guns dont happen too often. I wish I could find the one I shot comparing annealed vs non annealed. One was a 1.6 the other was a 1.7, back to back ones from a bipod gun. As much as I love the big 30, it just wont hang with the 338limp. But its so close it makes no difference in the real world. We also had both chambered in heavy bench guns for 2k group shooting. If weight it not a concern I will do the 338 every time. It so good I have been close to building a 1kBR rifle in it but the 10 shot groups would kill it. If we change to 5, it would be competitive. But ya, if you need a 8-10 pound gun, 300s are the way to go.

In general annealing is overrated, although necessary at times. It is certainly not the magic bullet to extreme accuracy.

On paper the 300 NMI "should" be a little better than the 338 LAI at extreme range due to very similar MV and a slightly higher BC. In ELR there is an argument for the 338 due to increased splash signature.

Why do you figure the 10 shot groups would kill the 338 at 1K benchrest? I can say that one of my early concerns with a 33 XC was velocity migration due to quick shot barrel heat. I was surprised that ended up not being true. 10 shot strings over 6 minutes showed no migration at all.

 

[Alex Wheeler]

In general annealing is overrated, although necessary at times. It is certainly not the magic bullet to extreme accuracy.

On paper the 300 NMI "should" be a little better than the 338 LAI at extreme range due to very similar MV and a slightly higher BC. In ELR there is an argument for the 338 due to increased splash signature.

Why do you figure the 10 shot groups would kill the 338 at 1K benchrest? I can say that one of my early concerns with a 33 XC was velocity migration due to quick shot barrel heat. I was surprised that ended up not being true. 10 shot strings over 6 minutes showed no migration at all.

Well, we did it. We had a 2000yd group and score match for a while. I wish it would have taken off more. We used 1000yd F class targets and shot 3 5 shot groups for group and score per class. The 300 NMI was good, but the 338 LMI was better. In BR we shoot fast, so 10 shots would be less than 30 seconds. You would smoke the throats fast. When kept to 3 shots and then a cool down the throats last a long time. 5 wasnt too bad but those were bipod guns too, they take a little longer to shoot so you have a built in time delay between shots. But even with 5 shots, at 2k if you had a nasty day and could not see the sighters impact you had to shoot too many sighters and then you got really hot.

 

[QuietTexan]

What do these two rounds offer that's an advantage over the 300 RUM properly setup on throat and magazine (ie 4" box)?

300 LIMP has a 9% increase in case capacity over the RUM.

300 NMI has same case capacity but shorter length due to larger case head, so more bullet room at any given length. But to be fair that probably doesn't matter, especially if you never go past a 245 Berger. I think Kirby played with custom heavier-than-250gn cup and core 30 cal bullets in one of his mega-30 designs. CE's 240gn Lazer monos require a 6 twist, that's about the longest 30 cal I'm aware of in production.

My 300 NMI is a repeater and very similar to what my 300 RUM does, enough so I don't think there's a meaningful difference between those two. Just another 30 magnum box to check really. The LIMP is a toy to me, something bigger to try to wrangle. I have a 30XC reamer in hand next

Trying to understand the draw to the other two rounds.

Because they're big, uncommon, not everyone has one, and just a big general "why not"?

Some people want the 7 Rem Mag instead of a 300 Win Mag, which is probably a fair comparison between these and standard 338s. Very specific differences in limited cases that matter a lot to the individual making their choice. It's not like any of these are being bought at Kmart off the shelf, right? So we each get to pick and choose as we want to.

 

[Alex Wheeler]

I have chambered the 30xc. I really wanted feedback. I figured hed smoke em by the time he got them tuned. Never did hear back. But he didnt have me chamber any more. That usually tells the story.

 

[Marine sniper]

Well, we did it. We had a 2000yd group and score match for a while. I wish it would have taken off more. We used 1000yd F class targets and shot 3 5 shot groups for group and score per class. The 300 NMI was good, but the 338 LMI was better. In BR we shoot fast, so 10 shots would be less than 30 seconds. You would smoke the throats fast. When kept to 3 shots and then a cool down the throats last a long time. 5 wasnt too bad but those were bipod guns too, they take a little longer to shoot so you have a built in time delay between shots. But even with 5 shots, at 2k if you had a nasty day and could not see the sighters impact you had to shoot too many sighters and then you got really hot.

Ok, that makes sense, we shoot pretty fast in ELR, but nowhere near that fast.
If you ever get that going again let me know, I will probably make the drive a few times for that event.

 

[Alex Wheeler]

If I ever move back to Mt. I would be a big part of getting that 2k match going again. It was extremely interesting, a totally different ball game than 1k.