New 338 NM Build and Load Work Up Advice

JW74

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Joined
Jun 12, 2014
Messages
229
Location
Western, USA
I just had a 338 Norma magnum built and am in the early phases of my load work for it. If others here that have loaded for the 338 NM could give some feedback it would be greatly appreciated.

The rifle is built on a Defiance Deviant action with a Bartlien barrel (27” heavy varmint contour @ 1:9.3” twist).

I went with 300 grain Berger bullets to start and H1000 powder as this seems to be a very common combo in the 87-88 grain range at 2700+ fps. I started very conservatively, and the loads and velocities are as follows:

300 grain Berger Hybrid OTM
H1000
Fed 215M
New un-fired Norma brass
2.836” to ogive (0.018” jump)

1) 81.0 gn @ 2584 fps
2) 81.5 gn @ 2595 fps
3) 81.8 gn @ 2618 fps
New Lot of powder used (velocities dropped)
4) 82.1 gn 2540 fps
5) 82.5 gn 2590 fps
6) 82.8 gn @ 2585 fps
7) 83.1 gn @ 2610 fps
8) 83.4 gn @ 2620 fps
9) 83.7 gn @ 2627 fps
10) 84.1 gn @ 2630 fps

This was over a couple of range sessions. I am still ~4 grains and 100 fps below what most people are getting with H1000 and I am starting to see signs of pressure with flatish looking primers, no cratering of the primers though and no stiff bolt lift yet. All of these groups were close to 1/2” at 100 yards with SD’s from 4-12. I still have a little room to go up in charge but don’t think I will get close to 87-88 grains without high pressure. I am wondering if I may have a tight barrel and that is why I am seeing pressure earlier than most?

I also tried the same loads but substituted Reloader 33 for H1000.

300 grain Berger Hybrid OTM
Reloader 33
Fed 215M
New un-fired Norma brass
2.836” to ogive (0.018” jump)

Those loads were:

1) 91.0 gn 2559 fps
2) 91.5 gn 2574 fps
3) 92.0 gn @ 2601 fps
4) 92.5 gn @ 2610 fps
5) 93.0 gn @ 2642 fps

The Reloader 33 produced these velocities with no real signs of pressure but the groups were not as promising as with H1000 and the SD’s averaged higher at 15-20.

Thanks for any feedback or advice on these loads and further load development as it is greatly appreciated.
 
Last edited:

WeiserBucks

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Joined
Aug 16, 2016
Messages
1,770
I've had excellent results with Norma brass in 7 RM and 300 WM. However when I had my 300 Norma the brass was substandard to say the very least.

If you don't reach your velocity goals , which are very realistic, I recommend getting some Peterson brass. It's incredibly tough, lasts 5x longer than Norma and is available.
 

JW74

Well-Known Member
Joined
Jun 12, 2014
Messages
229
Location
Western, USA
WeiserBucks,

Thank you for the info. I will grab some Peterson brass and try it out. With your 300 Norma do you use magnum primers or standard large rifle?
 

Cuz

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Joined
May 18, 2014
Messages
219
Location
Magnolia, texas
I have 2 338 norma mags and both shoot 88 grains of h100 at 2750 with 27 1/2 inch barrels. Primers are a little flat, but cases ar lasting 5 plus reloads. Norma brass. Both chambers were cut with the same reamer and headspaced the same. 300 berger otm bullets. I tried retumbo, but stayed with h1000. They have shot well from Texas heat to colorado cold. I would load some once fired brass and work with that. New brass might be undersized enough to slam back into the boltface, causing the flattened primers.
 

JW74

Well-Known Member
Joined
Jun 12, 2014
Messages
229
Location
Western, USA
I have 2 338 norma mags and both shoot 88 grains of h100 at 2750 with 27 1/2 inch barrels. Primers are a little flat, but cases ar lasting 5 plus reloads. Norma brass. Both chambers were cut with the same reamer and headspaced the same. 300 berger otm bullets. I tried retumbo, but stayed with h1000. They have shot well from Texas heat to colorado cold. I would load some once fired brass and work with that. New brass might be undersized enough to slam back into the boltface, causing the flattened primers.

Cuz,

Great info! I will work up some loads with my once fired brass and see if there is a change in the primers. I definitely want to try and stay with H1000 as well as the accuracy has been excellent so far.
 

codyadams

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Joined
Jan 7, 2015
Messages
3,389
Location
Southwest Wyoming
In a 28" 338 nm I put together for a friend, 88.5 grains netter 2813 fps and grouped like this.

I wouldn't rely on flat primers to tell you pressure, go until you have increase in bolt lift, ejector mark, or a combo there of. Primers aren't the most reliable pressure indicator, take all the signs together. You may reach max lower, but 85-85 grains seems very low.
20190423_073739.jpg
 

jrock

Well-Known Member
Joined
Mar 12, 2014
Messages
1,229
Location
Idaho
I use Retumbo with the 300 Bergers. Gets about 30 fps more than H1000 with the heavies. 89.9 grains @ 2780 fps from a 26" barrel. Can't find Retumbo any more so will try some IMR 8133.

H1000 and RE22 shot the 285 EDLMs about 25 to 30 fps more than Retumbo at 2850 fps. 88 grains of H1000

All loads are about 1/4" MOA from my gun.
 

436

Well-Known Member
Joined
Mar 22, 2009
Messages
1,065
Location
NorthWest
I just had a 338 Norma magnum built and am in the early phases of my load work for it. If others here that have loaded for the 338 NM could give some feedback it would be greatly appreciated.

The rifle is built on a Defiance Deviant action with a Bartlien barrel (27” heavy varmint contour @ 1:9.3” twist).

I went with 300 grain Berger bullets to start and H1000 powder as this seems to be a very common combo in the 87-88 grain range at 2700+ fps. I started very conservatively, and the loads and velocities are as follows:

300 grain Berger Hybrid OTM
H1000
Fed 215M
New un-fired Norma brass
2.836” to ogive (0.018” jump)

1) 81.0 gn @ 2584 fps
2) 81.5 gn @ 2595 fps
3) 81.8 gn @ 2618 fps
New Lot of powder used (velocities dropped)
4) 82.1 gn 2540 fps
5) 82.5 gn 2590 fps
6) 82.8 gn @ 2585 fps
7) 83.1 gn @ 2610 fps
8) 83.4 gn @ 2620 fps
9) 83.7 gn @ 2627 fps
10) 84.1 gn @ 2630 fps

This was over a couple of range sessions. I am still ~4 grains and 100 fps below what most people are getting with H1000 and I am starting to see signs of pressure with flatish looking primers, no cratering of the primers though and no stiff bolt lift yet. All of these groups were close to 1/2” at 100 yards with SD’s from 4-12. I still have a little room to go up in charge but don’t think I will get close to 87-88 grains without high pressure. I am wondering if I may have a tight barrel and that is why I am seeing pressure earlier than most?

I also tried the same loads but substituted Reloader 33 for H1000.

300 grain Berger Hybrid OTM
Reloader 33
Fed 215M
New un-fired Norma brass
2.836” to ogive (0.018” jump)

Those loads were:

1) 91.0 gn 2559 fps
2) 91.5 gn 2574 fps
3) 92.0 gn @ 2601 fps
4) 92.5 gn @ 2610 fps
5) 93.0 gn @ 2642 fps

The Reloader 33 produced these velocities with no real signs of pressure but the groups were not as promising as with H1000 and the SD’s averaged higher at 15-20.

Thanks for any feedback or advice on these loads and further load development as it is greatly appreciated.

"JW74,
Do you neck-size after the first firing? If yes, does it show flattened primer still? Have you run a set of, Go No-Go and Field gauges in the rifle? I doubt that's the problem but you never know. My last thought(s), have you double-checked your scales? and do you live in a hot climate when you test your loads? Good luck, Cheer's
 

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