300 Norma Magnum Build – Solid Setup or Would You Do It Differently?

[ShowMe QTR MOA]

Hey Hide members,

I’m putting together a dedicated 300 Norma for ELR and long-range steel work — mostly prone shooting, with the goal of pushing consistent impacts past a mile. Weight isn’t a concern; I’m prioritizing stability, precision, and long-term performance.

Here’s the build so far:

Build Specs:

• Action: Kelbly Prometheus Magnum Long Action
• Barrel: 32” Bartlein MODBB, 1.25” straight contour, 5R rifling, hand-lapped, 1:8 twist (non-fluted)
• Muzzle Brake: EC Tuner Brake Gen 2
• Trigger: TriggerTech Diamond Pro
• Optic: ZCO 5-40x56 or Vortex Razor GEN III 6-36x56 MRAD. Probably go the vortex route snd save $2k.
• Mount: Area 419 One-Piece 36mm, 20 MOA built-in
• Chassis: Undecided — leaning toward MPA Matrix Pro II or Vision chassis or MDT ACC Elite (need weight tuning options, balance, and recoil control)
• Intended Use: ELR steel, occasional comps — not for hunting or field carry
• Looking at the black & acid red color by MPA or the Patriot color by Paramount Tactical for the MPA Matrix Pro II

Looking for your feedback:

1. Would you stick with the 32” barrel for 300 Norma or go shorter?
2. Thoughts on the MODBB contour vs MTU or other?
3. MPA vs MDT chassis — which has worked better for you at distance?
4. Any regrets with this action, brake, or optic choice?

Hoping to build something that stays tight past 1,500 yards and doesn’t fall apart after 500+ rounds. Appreciate any insight — especially from folks who’ve already walked this path.

Thanks ,

ShowMe-QTR-MOA

 

[Mike Tackleberry]

Remember, you have to make weight in the ELR Light class (26LBS) if you want to shoot in competitions. My 300 PRC with 28" MTU contour is 25.9lbs for reference. You also need a 36mm mount, not a 34mm for the ZCO.

 

[Shoots 700's]

I went 300 Norma with a 27” barrel. Not sure how much speed you would pick up going that long.

 

[Kopfjager1]

A 28" MTU contour is only going to be around 6.9 lbs, the 32" 30 cal, 1.250" straight will weigh 10.0 lbs, depending on the breach and muzzle threads. 28" straight cylinder will weigh around 8.7 lbs.

And its only going to yield approximately 100 fps over a 28" with the same cartridge components. Is 100-150 fps worth the extra $100-200 for each barrel? Just something you should ask yourself. If its occasional matches, I would forego anything longer than 28", until you reach the point where you're trying to find any advantage, slightly perceived or not, to get ahead.

 

[Schw15]

Hey Hide members,

I’m putting together a dedicated 300 Norma for ELR and long-range steel work — mostly prone shooting, with the goal of pushing consistent impacts past a mile. Weight isn’t a concern; I’m prioritizing stability, precision, and long-term performance.

Here’s the build so far:

Build Specs:

• Action: Kelbly Prometheus Magnum Long Action
• Barrel: 32” Bartlein MODBB, 1.25” straight contour, 5R rifling, hand-lapped, 1:8 twist (non-fluted)
• Muzzle Brake: EC Tuner Brake Gen 2
• Trigger: TriggerTech Diamond Pro
• Optic: ZCO 5-40x56
• Mount: Area 419 One-Piece 34mm, 20 MOA built-in
• Chassis: Undecided — leaning toward MPA Matrix Pro II or Vision chassis or MDT ACC Elite (need weight tuning options, balance, and recoil control)
• Intended Use: ELR steel, occasional comps — not for hunting or field carry
• Looking at the black & acid red color by MPA or the Patriot color by Paramount Tactical for the MPA Matrix Pro II

Looking for your feedback:

1. Would you stick with the 32” barrel for 300 Norma or go shorter?
2. Thoughts on the MODBB contour vs MTU or other?
3. MPA vs MDT chassis — which has worked better for you at distance?
4. Any regrets with this action, brake, or optic choice?

Hoping to build something that stays tight past 1,500 yards and doesn’t fall apart after 500+ rounds. Appreciate any insight — especially from folks who’ve already walked this path.

Thanks ,

ShowMe-QTR-MOA

I run a 300 norma improved 32 inch barrels i believe the vcc contour with a samson foundation long action Bat action with brass weights but the arca was non brass. With one set of back weights out im 25.9 or so...... I run a razor gen 3 area 419 mounts sent it level. I think bats are go to for the lapua cases and I'm a huge fan of stocks now since I went foundation

 

[BurtG]

Make sure you order a 36mm mount obviously

 

[Long Range 338]

300 Norma is all about performance and performance comes with a cost. The longer barrel length will certainly provide the best chance for best performance. Your specified rifle fills the bill well in my opinion and Its all personal preference anyways...

 

[demarpaint]

I like it, I might consider a 30" barrel as a compromise.

 

[ggmanning]

I just ordered a 28" 1:9 barrel. Medium Palma/DTA contour. I couldn't find enough benefit to go longer, unless a lot longer than 28", which I didn't want to do.

 

[Mike Tackleberry]

I just ordered a 28" 1:9 barrel. Medium Palma/DTA contour. I couldn't find enough benefit to go longer, unless a lot longer than 28", which I didn't want to do.

That should work well, mine is a 9T MTU 28" and I shoot the Berger 245 LRHTs, and it shoots very well.

 

[Mj1995]

I just got mine back from Keith at Phoenix custom rifles, did a 30" straight 1.25" 9 twist krieger. I think the next barrel it gets well be a mtu instead of straight.

 

[ShowMe QTR MOA]

I run a 300 norma improved 32 inch barrels i believe the vcc contour with a samson foundation long action Bat action with brass weights but the arca was non brass. With one set of back weights out im 25.9 or so...... I run a razor gen 3 area 419 mounts sent it level. I think bats are go to for the lapua cases and I'm a huge fan of stocks now since I went foundation

Sounds like a beautiful build , do you have any photos

 

[ShowMe QTR MOA]

I just got mine back from Keith at Phoenix custom rifles, did a 30" straight 1.25" 9 twist krieger. I think the next barrel it gets well be a mtu instead of straight.

What made you decide to go mtu next?

 

[Schw15]

Sounds like a beautiful build , do you have any photos

To me it's the perfect build for what I do.

 

[Schw15]

First time the pics didn't work

 

[Mj1995]

2 reasons. Was going to go mtu originally but the only barrel in stock anywhere that I could find at the time with the twist i wanted was the straight.

Second reason (I know i can't shoot good enough to tell, but science and physics) a tapered barrel should be stiffer than a straight wall and therefore should be more accurate.

I don't currently do any competitions but it could shave a decent amount of weight going to mtu like others have said.

 

[ShowMe QTR MOA]

I believe that isn’t accurate straight vs mtu, a tapered barrel like an MTU is not stiffer than a straight 1.25” barrel. From a physics standpoint, barrel stiffness is defined by flexural rigidity (EI), where E is Young’s Modulus (a material constant) and I is the area moment of inertia. For a circular cross-section, I = (π/64) × D⁴ — so stiffness scales with the fourth power of diameter. That means the thinner muzzle on an MTU contour (typically ~0.93”) is dramatically less stiff than a 1.25” straight profile, even though they may share the same breech diameter.

This matters because the muzzle is where barrel oscillation and harmonics have the greatest impact on accuracy, especially under heat or with a suppressor. The straight contour maintains maximum stiffness across the full length, minimizing deflection, POI shift, and harmonic disruption.

MTU is still a great compromise, offering solid stiffness with reduced weight (~1 lb less for a 26” barrel) and better handling for dynamic shooting like PRS. But if you’re strictly comparing stiffness, the straight profile wins by the numbers.

 

[HotrRod308]

I think the .300NM is excellent choice for what you are trying to do. I have a bone stock AXSR 27” barrel shooting 245 Hybrids at 2870fps and have run it out to 2500 with hits on steel in ELR match last weekend. You will also need to factor in a Prism if you wanna keep a 100 zero and shoot past 2500 yards.

Sounds like an awesome build you got going!!

 

[vh20]

I think the .300NM is excellent choice for what you are trying to do. I have a bone stock AXSR 27” barrel shooting 245 Hybrids at 2870fps and have run it out to 2500 with hits on steel in ELR match last weekend. You will also need to factor in a Prism if you wanna keep a 100 zero and shoot past 2500 yards.

Sounds like an awesome build you got going!!

What powder and charge weight?

 

[surgeon260]

I would pick an action with 1-1/8" tenon diameter for any Lapua bolt face cartridge. Based on my experience with Norma magnums in Defiance actions, and comparing them to Borden Bigfoot/Surgeon XLs, the 1-1/16" tenon actions just can't take pressure like the beefier actions that were designed for that bolt face. You will hit pressure earlier in a 1-1/16", and in the long run you will face lug set back.

 

[Evlshnngns]

What made you decide to go mtu next?

Going mtu or similar would help with balance and handling.

Go 1.25 for 5" then taper to 1". Like a proof comp contour. Still very rigid and darn heavy.

 

[surgeon260]

I would also look at an improved chamber. Those 20 degree shoulders stretch like crazy. A 35-40 degree shoulder will be much more stable.

 

[secondofangle2]

Just go 338

Seriously.

 

[Long Range 338]

Just go 338

Seriously.

Yes and no. Heavier bullets make seeing splash much easier but the cost to get there becomes prohibitive. 338 LM isn't enough enough to get it done and you have to go with something like 33XC. Speed matters.

 

[secondofangle2]

Both have Lapua bolt face (300nm and 338lm)
Brass and factory ammo more plentiful w 338
285 ELD-M will go 2950 w a 32” bbl, smoking the 225 30 cal

Is why I said. Not because I assume he wants to go to next level of 375CT or Tubby’s creations