Twist Rate - 300 Norma
- Thread starter goosendmax
- Start date
What velocity have you seen the Berger 220’s give up on you.
of you haven’t been able to pass that velocity yet?
thanks
Can't answer that specifically. I'll say yes but at what distances, conditions etc....will it show it's ugly face. Now throw in the gun/barrels condition and what effect that is possibly having on the bullet.
I'm waiting for more data but there is data now showing that the 5R style rifling is helping the flight of the bullet vs an even groove barrel. If what they (ballistic testing (ammo/bullet makers) are seeing is accurate....by helping the flight of the bullet it has to be helping the BC in some shape or form you would think. I just cannot put a accurate description on it. What they are seeing is when the bullet hits the different velocity changes where the BC is effected (like the transonic range) the even groove barrels the bullet does what I'll call a weird dance but then settles back down again. The bullets fired out of 5R rifled barrels didn't do the funky/weird dance on the doppler radar. Only way I can describe it.
What I think is happening is at the boat tail junction/bearing surface area of the bullet when fired thru a barrel with conventional rifling like in a standard 4 groove, 6 groove etc... leaves like a burr on the jacket. This burr even though really slight is what my guess would be causing the bullet to do the weird dance/or what has been described to us as a hop. So it becomes a little erratic at times during the course of it's flight.
Not sure if I explained that good enough for you to follow?
Hi,
There is so much we can learn from certified and documented testing in the industry across the board.
@Frank Green Thank you for putting out the information you put out in regards to what the ammunition companies are doing, have done and want to do.
Sincerely,
Theis
There is so much we can learn from certified and documented testing in the industry across the board.
@Frank Green Thank you for putting out the information you put out in regards to what the ammunition companies are doing, have done and want to do.
Sincerely,
Theis
I'm not sure if auto-correct got the best of that but I went up to 92.5gr of N570 during load dev and hit pressure there (which was around 3200fps). Current load of 90.4 gr was at 3140 but sped up to 3200fps after 100 rds. This is at 2.820" BTO in Lapua brass with Fed 210M primers.
I run 90.7 of N570 with 200 gr Barnes all copper LRX in a 28 inch, eight twist barrel at 3,300 FPS. QuickLOAD tells me this is seriously over pressure but there are zero pressure indications on the brass in a Mausingfield action.
Since I don’t need that velocity, I backed down to 87.5.
We've haven't done any pressure barrels per say.
We have done gain twist barrels that started out at 0 and ended at 13.5 for 6PPC shooters. I told the guy it wouldn't shoot. He said yes it will. I'm a harmonic's vibration engineer and it will dampen the harmonics and it will shoot better. I said no it won't. The rifling doesn't even make one revolution! He said I was wrong. He had it all figured out!
Guess what...it didn't shoot!
Hi,
LOLOLOL Poor soul. His degree was more than likely in..
And NOT harmonics, lolol
Sincerely,
Theis
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Yup, 92.5 actually. I was going on the loading info Berger provided me. I'm pretty sure I posted it in the .300NM thread in the reloading section, I'll see if I can find it again.
That would be great. I know for the 215 they list 88gr as max. I'm going to run 85-88 tomorrow and see if there's any sign of pressure.
This is what I got from Berger/Capstone over the phone. My COAL is 0.057" shorter than theirs but I'm also almost 8gr below their max.
.300 Norma Mag, Berger 220 LRHT, 3.680" COAL
N570
Starting load: 83.5gr approx MV (26" barrel) 2692fps
max load: 98.1gr Approx MV: 2986. 97% case fill
Around 98 gr is what QuickLOAD is saying should be the max for a 200 gr Bullet. You might ask if Berger has shot that load are are they just giving you the QuickLOAD data.
I started at 90, saw no signs of pressure, but 10% higher velocity than expected. When I adjust the burn rate of my lot of powder for actual velocity, QuickLOAD is now saying 90 gr is seriously over pressure. I’m seeing 3,000 + FPS with 87 gr.
Be careful out there.
This came up in the 300NM thread in the reloading section. Viht's COAL is 3.406" vs Berger using 3.680". A 1/4"is a huge difference and gives you way more case capacity (at lower pressure). I too think 98gr would be absolutely cooking. I hit very slight pressure signs at 92.5. My COAL with 220s is 3.623" (2.820" BTO) and 90.4gr gives me 3200fps with no pressure. I had it out to 1608 yards yesterday. I guess we'll see as temps warm up. How temp stable is N570?
The only load data I have been able to find for 300 NM is from Sierra. Are there any other sources you know of and/or can suggest?
There is a bunch of data in the 300NM thread in the reloading section. All I personally have is the data I got from Berger for 220s with N570 and H1000.
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Just curious - seems weird to me that the MRAD and the AXSR off their 300NM barrels in 1:8 twist when it sounds like the consensus of the thread is that twist is too fast. Why do you think they decided to offer 1:8 in their factory configurations? Would I even be able to shoot factory Berger 215 300NM ammo out of that?
My MPA 300-NM is a 1:9 twist, and it shoots my 230-Bergers just fine. I get velocities just shy of 3,000 ft/sec and SD's aroun 6-ish. Great results at distance.
Twist rate can only be too fast if projectiles are exploding apart after leaving the barrel. Otherwise, more stability factor isn't going to hurt anything.
the 8 twist is why you stopped hearing them crow about the caliber
The 8 twist is not as good as advertised, not at all, I had more stealth inquires from the operator class asking why their results sucked with the Norma when everyone was crowing about it.
You can add in Spin but you can't include speed, Spin and speed work against the bullet in combination. why they went lighter instead vs the 230gr bullet. Same thing with the 260 when they had it, they wanted the 130 Berger hybrid, over twisted it, blew the Bergers up and switch to heavier jacket Lapua 139s, to try and recover the project.
9 is the most I would do with a 30 cal, especially if you want speed behind it.
They were over twisting because they were trying shorter barrels for urban shit, then they decided to do ELR and just made the barrel longer... can't do that, believe me you might get some decent results but not the results people talk about. My Norma does this at 100 yards, and hammers at 2500 yards, factory gun, factory ammo. 10 twist
The 8 twist is not as good as advertised, not at all, I had more stealth inquires from the operator class asking why their results sucked with the Norma when everyone was crowing about it.
You can add in Spin but you can't include speed, Spin and speed work against the bullet in combination. why they went lighter instead vs the 230gr bullet. Same thing with the 260 when they had it, they wanted the 130 Berger hybrid, over twisted it, blew the Bergers up and switch to heavier jacket Lapua 139s, to try and recover the project.
9 is the most I would do with a 30 cal, especially if you want speed behind it.
They were over twisting because they were trying shorter barrels for urban shit, then they decided to do ELR and just made the barrel longer... can't do that, believe me you might get some decent results but not the results people talk about. My Norma does this at 100 yards, and hammers at 2500 yards, factory gun, factory ammo. 10 twist
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