300 Norma vs 300 Norma Imp

I am still debating but almost ready to start acquiring parts so now is crunch time. I'm leaning towards the 300 NMI over the standard 300 NM. I am not really looking for the additional capacity so much as I hate trimming cases. Using quality brass such as Peterson or Lapua, how often does a standard 300 NM need to be trimmed? I need to determine once and for all if the Imp is worth the added cost and time.

When I first got my Peterson 300 Norma brass I torture tested 1 piece, fired it 10x and had to trim twice . Primer pockets were still good . Hope that helps you decide one way or another.

When you fireform into the improved versions, the over all length of the case gets shorter as material is pulled back to fill the new dimensions/shoulder angle, leaving you with a case length much shorter than the 2.492" trim to length (2.502" chamber depth) standardized for the original 300 Norma Mag and used for wildcats

Based on the improved body dimensions of my cases that pull back more material to fill new chambers, I haven't seen the need to ever trim when using Norma brass, typically primer pockets let go before trimming is required

With the new Peterson and Lapua 300 NM fireformed into my wildcat versions it's the same deal so far at 4 firings on cases except the primer pockets are still good , where the Norma brass would show loose pockets and be culled before trimming becomes necessary

with the harder case heads retaining integrity of primer pockets on the Peterson and Lapua brass I will most likely encounter trimming at some point in the next few firings but haven't yet got there

I'd move up to a 300 Lapua improved if entertaining a 300 Norma IMP

TXAoudadKlr said:

I'd move up to a 300 Lapua improved if entertaining a 300 Norma IMP

Click to expand...

The first super mag I looked at was a 338 LAI. Then I saw the 300\338 NM and NMI and honestly the straight 300 NM gives me plenty, I'm just looking at the Imp to reduce case stretch. Plus the NMI does not loose anything if I load them to fit in a 3.85" mag. My range only goes to 1900, still within the supersonic range of the NMI based on what I have plugged into JBM. I am looking to find some BLM land that might allow me to take it further from time to time but doubt that will happen often enough to justify the added powder of the LAI.

What are your thoughts on why the LAI over the NMI?

jb1023 said:

I am still debating but almost ready to start acquiring parts so now is crunch time. I'm leaning towards the 300 NMI over the standard 300 NM. I am not really looking for the additional capacity so much as I hate trimming cases. Using quality brass such as Peterson or Lapua, how often does a standard 300 NM need to be trimmed? I need to determine once and for all if the Imp is worth the added cost and time.

Click to expand...

I did a lot of research on the Norma improved, seems quite a few guys have burned the throat up really fast, like 600 rounds fast.
I guess in terms of being really over bore, going from a case capacity of 102 grains to 110 is significant
For that reason I'll be trimming my 300 NM cases.

jb1023 said:

The first super mag I looked at was a 338 LAI. Then I saw the 300\338 NM and NMI and honestly the straight 300 NM gives me plenty, I'm just looking at the Imp to reduce case stretch. Plus the NMI does not loose anything if I load them to fit in a 3.85" mag. My range only goes to 1900, still within the supersonic range of the NMI based on what I have plugged into JBM. I am looking to find some BLM land that might allow me to take it further from time to time but doubt that will happen often enough to justify the added powder of the LAI.

What are your thoughts on why the LAI over the NMI?

Click to expand...

I have one. OAL is 3.700 with 181gr HH .010 off.

My thoughts are, if I'm going to go through the trouble of running an improved Norma magnum for extra performance over the regular Norma Mag, I would go straight to the Lapua.

I guess I'm going that far to the extreme for 30's might as well go one more step and go with the LAI.

That said my next big 30 will be a straight up 300 Norma, no extra frills or thrills.

blackaj said:

I did a lot of research on the Norma improved, seems quite a few guys have burned the throat up really fast, like 600 rounds fast.
I guess in terms of being really over bore, going from a case capacity of 102 grains to 110 is significant
For that reason I'll be trimming my 300 NM cases.

Click to expand...

At 110gr capacity, it matches the 300 rum. I haven't heard of a lot of burnt 300 rum barrels in that round count. I think the 300nm imp rifles that were shot out that quickly may have been abused, long hot shot strings poor cleaning etc. My improved version has a 33° shoulder, CIP taper, might have picked up 3-4gr capacity, I doubt it'll have that much affect on barrel life. The sharper shoulder me help it by containing more flame in the case.

highdrum said:

At 110gr capacity, it matches the 300 rum. I haven't heard of a lot of burnt 300 rum barrels in that round count. I think the 300nm imp rifles that were shot out that quickly may have been abused, long hot shot strings poor cleaning etc. My improved version has a 33° shoulder, CIP taper, might have picked up 3-4gr capacity, I doubt it'll have that much affect on barrel life. The sharper shoulder me help it by containing more flame in the case.

Click to expand...

You're probably right I'm sure guys built them to hot rod.
I spoke with a few guys on here about the 300 RUM when I was considering the Norma, it seems 700 rounds was pretty typical for accuracy to start falling off.
One guy said his barrel had like a 4" firecrack up the barrel after about 500 rounds.
Your 33 degree shoulder sounds pretty cool, how fast are you able to push 230's or 225's?
Where did you find the reamer and dies?

blackaj said:

You're probably right I'm sure guys built them to hot rod.
I spoke with a few guys on here about the 300 RUM when I was considering the Norma, it seems 700 rounds was pretty typical for accuracy to start falling off.
One guy said his barrel had like a 4" firecrack up the barrel after about 500 rounds.
Your 33 degree shoulder sounds pretty cool, how fast are you able to push 230's or 225's?
Where did you find the reamer and dies?

Click to expand...

Ryan Pierce is building my rifle, he has the dies from whidden. He has pushed a 215 Berger as hard as 3275fps in lapua brass with N570. Accuracy is around 3200 on most builds. My rifle is almost finished. He has 300 rounds through his 300nm imp, and has zero throat erosion he says. I also have a standard 300nm built by Mesa that will be delivered in a week, it's a heavier target style rifle, but does have a proof 1:9 barrel, just like the rifle Ryan is building. I'll have a direct comparison between standard vs improved. I'll be running lapau brass and 215 Bergers in both builds.

highdrum said:

Ryan Pierce is building my rifle, he has the dies from whidden. He has pushed a 215 Berger as hard as 3275fps in lapua brass with N570. Accuracy is around 3200 on most builds. My rifle is almost finished. He has 300 rounds through his 300nm imp, and has zero throat erosion he says. I also have a standard 300nm built by Mesa that will be delivered in a week, it's a heavier target style rifle, but does have a proof 1:9 barrel, just like the rifle Ryan is building. I'll have a direct comparison between standard vs improved. I'll be running lapau brass and 215 Bergers in both builds.

Click to expand...

Highdrum, With Ryan's reamer, do you know if you will be able to fireform standard brass or will you need to do other prep first?

Ryans reamer was set up to shoot factory ammo/brass and fired brass becomes the Improved cartridge

jb1023 said:

Highdrum, With Ryan's reamer, do you know if you will be able to fireform standard brass or will you need to do other prep first?

Click to expand...

His rifles shoot factory Berger ammo sub half moa fire forming, after that it's FL size with his dies load and shoot.

@Swamplord would be the guy to elaborate on 300nm imp barrel life. His versions are about as aggressive as they get for max case capacity. I'm particularly interested in how his norma based short mags turn out.