Bullet stabilization issues? .300 Norma Mag

F

FrenchPewPiou

Private
Minuteman
Feb 4, 2024
29
35
Paris, France
#1
Hi,

After solving my "super weird issues" which were due to bad primers, I have a new problem with my .300 Norma Mag reloads... my groups are very bad (between 1.7 and 2.7 MOA at 109 yards/100m) and it seems that literally all bullets land sideways on the paper target:
487500748_9528591027220202_6024409072926055085_n.jpg


Here's my reloading recipe:
  • Neck-turned Lapua Brass, trim to length 2.482in, neck OD 0.3355in for a loaded round at OD 0.3375in
  • Hornady A-Tip 250 grs, tried bullet jumps from 0.020in to 0.065in
  • RWS LRM primers
  • Vihtavuori N570 powder (77.9 grains) -- it seems low compared to some guys here on the forum but I'm already above Vihtavuori official max which is at 76.1 grains

I shot twice 15 bullets (plus like 3-5 fouler shots at the beginning):
  • String one (15 shots):
    • Average: 2703 fps
    • Std dev: 9.8 fps
    • Extreme Spread: 34.8 fps
  • String two (15 shots):
    • Average: 2703 fps (same as string one)
    • Std dev: 8.2 fps
    • Extreme Spread: 30.2 fps
I'm shooting with a silencer, but concentricity looks good:
487842999_996522142450608_1349494398747456024_n.jpg


And my barrel is a 26" 1:10 twist.

While my velocities aren't the best, they aren't terrible either, they're pretty stable... I really don't understand what's causing this.

I tried factory 230 grainers from Norma ("match grade" ammo) and it gave better groups (all holes touching at 109 yards), although I couldn't go to the target to check how they landed.

In your experience, what could cause this?
 
#2
Wow ... something is very wrong here. Step-1 for me would be to shoot some match-grade factory ammo and see if it's still key-holing the target. That would at least rule in or out something in your reloading components or processes.
 
#4
FrenchPewPiou said:
I just noticed Hornady recommends a minimum twist of 1:8.5" for their 250 grains A-Tip... my barrel is a 1:10". Isn't that the issue :confused:?
Click to expand...
My guess would be "No". If a 1-10 is tumbling at 100 yards, then a 1-8.5 will be tumbling at 100 yards. I think you've got something physically wrong with the rifle (canted chamber, defective crown, etc.).
 
#5
FrenchPewPiou said:
I just noticed Hornady recommends a minimum twist of 1:8.5" for their 250 grains A-Tip... my barrel is a 1:10". Isn't that the issue :confused:?
Click to expand...
Yes the twist is incorrect. Most guys are running at least 1:9 and often 1:8 twist. Depending on your density altitude and with enough velocity you might get away with it at high altitude but I assume you are near sea level. It sounds like the 230 grain bullet is as heavy as you are able to stabilize.
 
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#12
Thank you everyone for your inputs! I tried hard to find a bullet which:
  • Gives a stability factor of > 1.5 in my configuration
  • Is >= 230 grains to keep the advantages of these heavy bullets with high BC
  • Is available in France (hardest part)
These criteria narrow it down to a single bullet: the Sierra MatchKing #2251.
I ordered some, I'll post an update next week when I try it. If it doesn't work, I'll have to go to 220 grains bullets but the choice is extremely limited (almost non-existent actually) where I live, so... not ideal. Then that would be 185 grains next... but that's not at all what I originally wanted for this rifle.
Hopefully Sierra #2251s will work!
 
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#13
FrenchPewPiou said:
Thank you everyone for your inputs! I tried hard to find a bullet which:
  • Gives a stability factor of > 1.5 in my configuration
  • Is >= 230 grains to keep the advantages of these heavy bullets with high BC
  • Is available in France (hardest part)
These criteria narrow it down to a single bullet: the Sierra MatchKing #2251.
I ordered some, I'll post an update next week when I try it. If it doesn't work, I'll have to go to 220 grains bullets but the choice is extremely limited (almost non-existent actually) where I live, so... not ideal. Then that would be 185 grains next... but that's not at all what I originally wanted for this rifle.
Hopefully Sierra #2251s will work!
Click to expand...

But that bullet needs a 1-8” barrel

 
#14
918v said:
But that bullet needs a 1-8” barrel

Click to expand...
Yes, but all the stability calculators I tried give a result saying it should be fine (stable) given the muzzle velocity I'll have. Maybe Sierra mentions the 1:8 twist rate for other calibers with lower muzzle velocities which would not be enough to stabilize the bullet.

I just hope it will work, if not, I'll go for 220s if I can find some.
 
#15
FrenchPewPiou said:
Yes, but all the stability calculators I tried give a result saying it should be fine (stable) given the muzzle velocity I'll have. Maybe Sierra mentions the 1:8 twist rate for other calibers with lower muzzle velocities which would not be enough to stabilize the bullet.

I just hope it will work, if not, I'll go for 220s if I can find some.
Click to expand...
Marginal even at 3k, may fly true but bleed bc over distance
IMG_3415.jpeg
 
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#17
www.bluecollarreloading.com

Sierra 30cal 230gr HPBT

Product Information Caliber: 30cal Bullet Diameter: 0.308” Bullet Weight: 230 Grains OAL: 1.775" Bullet Style: Hollow Point Boat Tail MatchKing Recommended Twist Rate: 1 in 8" or Faster G1 BC: 0.800 Part Number: 2251 or 2261C Quantity: 50 or 500
www.bluecollarreloading.com www.bluecollarreloading.com

According to this it’s 1.775” long
 
#18
918v said:
www.bluecollarreloading.com

Sierra 30cal 230gr HPBT

Product Information Caliber: 30cal Bullet Diameter: 0.308” Bullet Weight: 230 Grains OAL: 1.775" Bullet Style: Hollow Point Boat Tail MatchKing Recommended Twist Rate: 1 in 8" or Faster G1 BC: 0.800 Part Number: 2251 or 2261C Quantity: 50 or 500
www.bluecollarreloading.com www.bluecollarreloading.com

According to this it’s 1.775” long
Click to expand...
Indeed, I found this page a few minutes ago... then I found a french gunshop website stating it was 1.620in (specifically the 2251s) like QuickLOAD. This is very confusing, I can't understand how different sources can have different lengths for the exact same bullet reference (#2251). I guess I'll have to wait 2 more days to find out the truth when I receive the box... but yeah, this smells a bit bad for me...
 
#19
FrenchPewPiou said:
Yes, but all the stability calculators I tried give a result saying it should be fine (stable) given the muzzle velocity I'll have. Maybe Sierra mentions the 1:8 twist rate for other calibers with lower muzzle velocities which would not be enough to stabilize the bullet.

I just hope it will work, if not, I'll go for 220s if I can find some.
Click to expand...

NO it won't be fine !. Minimum recommended twist rate 1:8.75 ,You're on the low end of marginal at best . :(
 
#20
Well... anyway, I received the box by mail just now and QuickLOAD and all the french websites screwed me: the bullet is 1.735in on average (not 1.620in), so all hope is lost on this bullet.
Screenshot 2025-04-08 082650.png


Looks like my only hope if I want to throw 230s is the Berger #30112 which lists 1:10 as the minimum twist rate but... it's not available in France. I may have to move to the US if I want to shoot properly...
 
#23
FrenchPewPiou said:
Well... anyway, I received the box by mail just now and QuickLOAD and all the french websites screwed me: the bullet is 1.735in on average (not 1.620in), so all hope is lost on this bullet.
View attachment 8659503

Looks like my only hope if I want to throw 230s is the Berger #30112 which lists 1:10 as the minimum twist rate but... it's not available in France. I may have to move to the US if I want to shoot properly...
Click to expand...

What bullets in the 215-220gr range can you get?
 
#24
Long Range 338 said:
You mentioned shooting factory 230gr Norma with good results. Try shooting the Norma factory load at distance to see where it falls apart.

Theory is great but real world results speak with full authority.
Click to expand...
Good idea yes! I kept one factory bullet which I disassembled and I just took a closer look at it... it really looks like the Berger #30430, which is very close to the Berger #30112 I want, except the twist rate calculator predicts a lower stability for the #30430 (1.38 vs 1.53, both at 2850 fps). Berger states both are ok for a 1:10 twist... which is a bit weird because their calculator only gives "marginal stability" (1.38) for the #30430.
The bullet I have from the factory cartridge measures 1.663in, vs. 1.668in theoretically for the #30430, it's pretty close!

secondofangle2 said:
Or change the barrel
Click to expand...
To be honest that was what I wanted to do at first, but... here in France a barrel change is 3-9 months (very few gunsmiths do it, then it has to be proof fired in a specific place, there is only one place in the entire country... a nightmare) and it's going to cost me about 1500-2000$. In the end I'm better off selling the rifle and buying a new one.

918v said:
What bullets in the 215-220gr range can you get?
Click to expand...
Only the Sierra #2240 I believe.
 
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#25
You could also shoot the 208ELD – M really fast.

If you run the ballistics calculations, you will see that doing that will keep up with the heavier bullets and all, but the most extreme scenarios

The owner of this site, the head motherfucker in charge of this shit, is a big fan of sending lighter bullets faster. And he is not wrong very often and not hear in particular.
 
#26
1:10 twist is too slow for the 250's to stabilise. The actual stability factor calculation needs a lot more than just bullet length. Miller and Greenhill are poor approximations at best.

Also, WTF are you doing with a 300 norma if it's so time consuming, difficult and costly to replace a barrel over there? That cartridge has a very short barrel life.
 
#28
As there are lots of information and lots of bullets to compare, I compiled everything in an Excel sheet here.
Screenshot 2025-04-11 105839.png


secondofangle2 said:
You could also shoot the 208ELD – M really fast.

If you run the ballistics calculations, you will see that doing that will keep up with the heavier bullets and all, but the most extreme scenarios

The owner of this site, the head motherfucker in charge of this shit, is a big fan of sending lighter bullets faster. And he is not wrong very often and not hear in particular.
Click to expand...
Indeed, one of the best performing bullets in the list above! Thank you!

PB&J. said:
1:10 twist is too slow for the 250's to stabilise. The actual stability factor calculation needs a lot more than just bullet length. Miller and Greenhill are poor approximations at best.

Also, WTF are you doing with a 300 norma if it's so time consuming, difficult and costly to replace a barrel over there? That cartridge has a very short barrel life.
Click to expand...
It's not my main rifle, it's just one I use when I want to have fun, feel a bit more recoil than my 6.5 Creedmoor. It's like when you go to a starred restaurant and pay $250 for a meal. But yes indeed, I'm at ~10% barrel life (which is ~800 shots from what I read) and still looking for the right load.

Ledzep said:
230 Atip should be Okay in 1:10 (but barely). 250's will not be.
Click to expand...
Barely ok I believe (C.F. the Excel sheet above).

I'll update this thread when I do more tests.
 
#29
208 AMAX was the go-to bullet for 300 RUM for many years.

(And 300 RUM has WAY more case capacity than 300 NM)

Most all of them are built as hunting rifles w 1:10 twist, which is why the Hornady manual doesn’t go above 225 ELD-M

If I were you, I’d get some 208 grains, push up the velocity, and roll with it
 
#30
If you ever have questions about stability with Hornady bullets or bullets in the 4DOF library, use 4DoF to check gyro. It uses a physical model of the bullet, not a generalized Miller style formula.

Here's the 230 in a 10 twist at sea level. Should shoot groups fine but will probably have some extra drag.
1000000301.png
 
#33
FrenchPewPiou said:
Hi,

After solving my "super weird issues" which were due to bad primers, I have a new problem with my .300 Norma Mag reloads... my groups are very bad (between 1.7 and 2.7 MOA at 109 yards/100m) and it seems that literally all bullets land sideways on the paper target:
View attachment 8656429

Here's my reloading recipe:
  • Neck-turned Lapua Brass, trim to length 2.482in, neck OD 0.3355in for a loaded round at OD 0.3375in
  • Hornady A-Tip 250 grs, tried bullet jumps from 0.020in to 0.065in
  • RWS LRM primers
  • Vihtavuori N570 powder (77.9 grains) -- it seems low compared to some guys here on the forum but I'm already above Vihtavuori official max which is at 76.1 grains

I shot twice 15 bullets (plus like 3-5 fouler shots at the beginning):
  • String one (15 shots):
    • Average: 2703 fps
    • Std dev: 9.8 fps
    • Extreme Spread: 34.8 fps
  • String two (15 shots):
    • Average: 2703 fps (same as string one)
    • Std dev: 8.2 fps
    • Extreme Spread: 30.2 fps
I'm shooting with a silencer, but concentricity looks good:
View attachment 8656445

And my barrel is a 26" 1:10 twist.

While my velocities aren't the best, they aren't terrible either, they're pretty stable... I really don't understand what's causing this.

I tried factory 230 grainers from Norma ("match grade" ammo) and it gave better groups (all holes touching at 109 yards), although I couldn't go to the target to check how they landed.

In your experience, what could cause this?
Click to expand...
You need an 8 twist to shoot 250 a Atips and a 9 twist to shoot 230 Atips.
The 250 gr Atips will not stablize in a 10 twist even at 2985 fps, in 300 RUM 26" barrel.

But I shoot them at 2500fps in a 308 8 twist with accuracy, and the 9 twist 308 22" 230 Atips 2600 fps with accuracy.

You're twist rate is too slow...elevation helps on hot days shoot at very high altitude 8000 to 10,000 ft. This summer, give it a try.
I've gone to 8 and 9 twists in 308 Win cause I shoot heavy bullets...the 8 twist works well from 130 gr Speer Varmint to 250 gr Atips, versitle and accurate.
 
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