Barrel length on a big 30...

[Ledd Slinger]

FYI, here is a cutaway i did on my milling mchine of Lapua and ADG brass in 300 Norma Mag. Normally ADG is built very strong like Lapua, but in this particular cartridge, Lapua is much stronger around the primer pocket where you need it most when pushing speeds. No idea why ADG did this in the 300 Norma.

Peterson and Norma brand brass is garbage in the 300 Norma

LEFT: Lapua RIGHT: ADG

 

[ISS]

Thanks.

I am concerned with the Improved version about using quite a bit of accurate barrel life fire forming, and getting the Improved die set. Where did you gentlemen acquire yours?

 

[Ledd Slinger]

Thanks.

I am concerned with the Improved version about using quite a bit of accurate barrel life fire forming, and getting the Improved die set. Where did you gentlemen acquire yours?

You just start shooting while fire forming to zero optics and get your range dopes.
And I would not fireform ALL your brass at once. No sense in that. I usually only have 50 formed pieces at a time. When those wear out, i start using another 50.

But if you must, Whidden makes a hydro forming die and he should still have my specs on file. My chamber dimensions ended up being nearly identical to Alex Wheelers design so if you go that route, my die on file will work for that chamber. Tho John might have Alex’s chamber design on file as well since it was made public a while back

 

[Sgt. Brumbaugh]

I am concerned with the Improved version about using quite a bit of accurate barrel life fire forming, and getting the Improved die set. Where did you gentlemen acquire yours?

I am the team lead for the USMC Scout Sniper Association ELR team. My entire team other than I run standard 300 Norma's, we compare data a lot and I can say there is virtually no "improvement" running the 300 NMI over the standard 300 Norma. We all run long throats (.275) and my improved might run 25 fps faster (max) over the standard Norma's. We have a total of 5 standard Norma's on the team, so lots of different barrel lengths, to compare.

If I had it all over to do again, I would run the standard Norma. If you are going to do the improved, I load up 100 pieces of brass to fire 50 at a time during a range session. I bring a cooler full of ice water and towels and use the towels to cool the barrel down between strings of fire. You can get a barrel that is hot to the touch to cool in a few minutes when you wrap it in cold towels.

Make sure that your fireforming loads are jammed a few .000 into the lands so the brass fireforms correctly. I personally don't like the hyrdo dies, a piece of brass is not usefully fireformed until the shoulder is at the same length as fully fireformed pieces of brass. I can get it there in one fireforming. I use blem 220 SMK's from Midway (.30 cents each) and 93 grains of US 869 (2900 FPS)

When I fireform I will normally try to get some wind call practice in or something more using than just pulling the trigger.

Surprisingly, wrapping the barrel in cold towel does not seem to change the POI much.

 

[Matt_3479]

I run 230 hybrids in my norma with a 26” barrel at 3000-3050fps. Had them up to 3150 with rl33 but this shot so well with n570 I never went higher

 

[ISS]

Jeez, I knew it Brumbaugh! Jarhead! My third tour in RVN we moved from Chu Lai to Danang and took over the 1st Marine Force Recon Bn's AO. We got their hooches, and they were kind enough to leave us a full foot locker of brand new KaBars. Still in the cosmolene!

Seriously, the Corps has always performed well in the field. Force Recon is/was about the equivalent of the Army Rangers.

I was wondering about the benefit of the NMI. I am going to stick with the standard chambering.

What do your rifles weigh? Maybe post a picture one of these days...?

Thank you for your service.

 

[Ledd Slinger]

I am the team lead for the USMC Scout Sniper Association ELR team. My entire team other than I run standard 300 Norma's, we compare data a lot and I can say there is virtually no "improvement" running the 300 NMI over the standard 300 Norma. We all run long throats (.275) and my improved might run 25 fps faster (max) over the standard Norma's. We have a total of 5 standard Norma's on the team, so lots of different barrel lengths, to compare.

Well we’ve been testing this cartridge long before the military ever its greasy little hands in it so i can confidently say that your data is WRONG!

Are you stating that you shoot a NMI and have only compared your ONE single NMI against many other standard Normas to draw your conclusion? Thats very weak and inconclusive. Either your NMI chamber is a poor design, or you have a slow barrel if that has been your experience.

My NMI chamber design holds about a 10gr capacity advantage over the standard Norma and the makes quite the difference when running the slower powers with heavy bullets. The standard Norma cant touch the NMI. I guarantee i can run the same weight bullet well over 100 fps faster than any of the standard Norma rifles you have in your group and i will do it with a shorter barrel and probably still have throttle to spare!

 

[FireMedic]

Well we’ve been testing this cartridge long before the military ever its greasy little hands in it so i can confidently say that your data is WRONG!

Are you stating that you shoot a NMI and have only compared your ONE single NMI against many other standard Normas to draw your conclusion? Thats very weak and inconclusive. Either your NMI chamber is a poor design, or you have a slow barrel if that has been your experience.

My NMI chamber design holds about a 10gr capacity advantage over the standard Norma and the makes quite the difference when running the slower powers with heavy bullets. The standard Norma cant touch the NMI. I guarantee i can run the same weight bullet well over 100 fps faster than any of the standard Norma rifles you have in your group and i will do it with a shorter barrel and probably still have throttle to spare!

Sgt. Brumbaugh knows what he’s talking about. I have burned through several barrels with 300 Norma imp and I’m currently running a standard 300 Norma and 300 nmi 40deg

The improved version pressures out with 2gr more powder and only only runs 25fps faster Maybe. I see more variation between individual barrels than the two chamberings.

The standard Norma has a capacity of 105gr. H20 to the neck. The improved version 110gr

My reamer is about as improved as you’d want to make it also. .08 body taper and 40deg shoulder I don’t think you could make the case 10gr bigger and still have enough body taper for good extraction.

 

[Ranger188]

What diameter and taper barrels are you running with the 300 NM or NMI ?
Will a 1.25 breech dia. work, or larger?

 

[FireMedic]

What diameter and taper barrels are you running with the 300 NM or NMI ?
Will a 1.25 breech dia. work, or larger?

1.250 is fine, as long as then tenon is not larger than 1-1/8”. I do prefer it larger if you can get away with it.

 

[SKWERLZ]

Thanks.

I am concerned with the Improved version about using quite a bit of accurate barrel life fire forming, and getting the Improved die set. Where did you gentlemen acquire yours?

I’d just shoot them at distance, it’s surprising how good fire form loads can shoot and you get good practice and dope.

1.250 is fine, as long as then tenon is not larger than 1-1/8”. I do prefer it larger if you can get away with it.

^^^^^

 

[Sgt. Brumbaugh]

FWIW; I also communicate with a lot of guys who run the standard and improved Norma's outside my team that I communicate with re: velocities, barrel lengths, powders, etc comparing the two chamberings. The data I have gathered outside my team mirrors the data in my team in that there just isn't much difference in velocity between the two.

The one advantage I do see with my 40* NMI is virtually no case growth between firings.

 

[Ledd Slinger]

Sgt. Brumbaugh knows what he’s talking about. I have burned through several barrels with 300 Norma imp and I’m currently running a standard 300 Norma and 300 nmi 40deg

The improved version pressures out with 2gr more powder and only only runs 25fps faster Maybe. I see more variation between individual barrels than the two chamberings.

The standard Norma has a capacity of 105gr. H20 to the neck. The improved version 110gr

My reamer is about as improved as you’d want to make it also. .08 body taper and 40deg shoulder I don’t think you could make the case 10gr bigger and still have enough body taper for good extraction.

Wheres is all this data??? What speeds are you achieving with identical bullets and barrel specs using the standard Norma and Improved?

 

[FireMedic]

Still not buying it. You guys have something wrong in your design or barrel specs.

Have you compared them side by side? Just curious. I felt the same way as you until I did.

I have wildcatted a lot. And I have probably 10 variations of 300 nmi reamers. Both 35deg and 40deg….and several 300 Normas with different freebore lengths and throat geometries.

To see big improvements with velocity in a wildcat, you need to either increase the capacity enough to go to a slower powder, or make the capacity grossly larger than the parent case. The 300 Norma imp does neither. You just add a couple grains more powder to make the same velocity.

I build a lot more 300nmi’s than 300 Normas in my shop(Probably 30 this year alone). It has a certain sex appeal about it to customers. 40 deg shoulder with a 250 Atip sticking out of it just looks cool….but the juice isn’t worth the squeeze IMO

 

[L.Sherm]

To see big improvements with velocity in a wildcat, you need to either increase the capacity enough to go to a slower powder,

I dont agree with this, the 280AI vrs the 280 Rem is easily a 150- 200 FPS gain the 2 280 Rems i had set back to 280AI did and same with the 20VT vrs the 20-221AI.
Some definitely benefit and some dont.

 

[FireMedic]

I dont agree with this, the 280AI vrs the 280 Rem is easily a 150- 200 FPS gain the 2 280 Rems i had set back to 280AI did and same with the 20VT vrs the 20-221AI.
Some definitely benefit and some dont.

Not agreeing doesn’t change the truth. You are hiding pressure with the 280AI, Plain and simple. If both cartridges are ran to the same pressure with the same freebore lengths, you won’t see near those gains.

And the 280 ai is one of those cartridges that sees a sizable gain because the capacity increase is around 3% more than you see by improving the 300norma

Here is pressure data from hodgdon comparing the two you mentioned. Roughly 92fps gains

 

[L.Sherm]

Not agreeing doesn’t change the truth. You are hiding pressure with the 280AI, Plain and simple. If both cartridges are ran to the same pressure with the same freebore lengths, you won’t see near those gains.

And the 280 ai is one of those cartridges that sees a sizable gain because the capacity increase is around 3% more than you see by improving the 300norma

Here is pressure data from hodgdon comparing the two you mentioned. Roughly 92fps gains
View attachment 1675437View attachment 1675438

How do 99% of us look for signs of pressure.
Do different actions handle pressure different? Brass?reamers? Barrels?
Hell look what there trying to do with the Backcountry.

 

[FireMedic]

people seeing 200fps gains in a 280ai has me wonder….lol

Seriously though, I’m not here to argue. I’m just trying to help some folks using actual experience from someone that does this full time for a living.

 

[L.Sherm]

people seeing 200fps gains in a 280ai has me wonder….lol

Seriously though, I’m not here to argue. I’m just trying to help some folks using actual experience from someone that does this full time for a living.

I'm not here to argue either, but if you have a cartridge that has a saami 65,000 psi and it shoots lights out with a custom action, Lapua brass and custom reamer, custom barrel at 68-70,000 and no typical pressure signs that we all look for were are you gonna shoot it at?
Compare Noslers load data 280AI vrs 280 Rem it mirrored exactly what I saw.

 

[Mike TackleBerry]

Well we’ve been testing this cartridge long before the military ever its greasy little hands in it so i can confidently say that your data is WRONG!

Are you stating that you shoot a NMI and have only compared your ONE single NMI against many other standard Normas to draw your conclusion? Thats very weak and inconclusive. Either your NMI chamber is a poor design, or you have a slow barrel if that has been your experience.

My NMI chamber design holds about a 10gr capacity advantage over the standard Norma and the makes quite the difference when running the slower powers with heavy bullets. The standard Norma cant touch the NMI. I guarantee i can run the same weight bullet well over 100 fps faster than any of the standard Norma rifles you have in your group and i will do it with a shorter barrel and probably still have throttle to spare!

I have to agree with you, there is absolutely an improvement with the Ackley improved version over the standard 300 Norma. my buddy has found that his ackley improved 338 lapua has significantly less donut formation in the neck/shoulder junction as opposed to his standard 338 lapua, Also the added powder capacity was a welcoming gesture as well. He also noticed a velocity increase of close to 80 fps.