300 Norma Improved 35 degree

[rhovee]

9

 

[L.Sherm]

Charles Greer confirmed my suspicion that a 10 was the best with 210-220 Bergers

 

[CBlack]

Looking to purchase a barrel for my 300 Norma improved. I live in Mississippi and want to stabilize 215/220 Berger hybrids.

What’s twist rate should I purchase

Depends on what you want to do with it. ELR...1:9. Hunting...1:10

 

[Alex Wheeler]

You can use either. I prefer to error on the side of a little more twist. Some of the best 1k group aggs ever shot are around 1.8 on the Miller scale. You will also find that some bullets open a little better with a bit more twist. I have never used a 220 Berger for hunting, but I have used the 215 and a little extra twist doesnt hurt it.

 

[WAMBO]

Charles Greer and I both use 1-10" twist on our 30 cal barrels for 1K BR, proofs in the targets but if I was going to shoot ELR like a few others have stated I'd choose a 1-9" twist.

 

[Bodhisafa]

This will be strictly ELR....what’s the best Berger with an 9 twist then?

 

[Alex Wheeler]

In this case Id start with the 230 hybrid.

 

[GlennK]

You can use either. I prefer to error on the side of a little more twist. Some of the best 1k group aggs ever shot are around 1.8 on the Miller scale. You will also find that some bullets open a little better with a bit more twist. I have never used a 220 Berger for hunting, but I have used the 215 and a little extra twist doesnt hurt it.

The miller scale is very accurate

 

[Bodhisafa]

Since we are talking about the barrel, any recommendations on contour. This is strictly a prone gun.

Action is a Jim Borden Denali.
Iam thinking 1.35 straight. Any disadvantage to this heavy barrel hanging off the end of the action?

 

[Ledd Slinger]

You guys have to remember that speed plays a big part in bullet RPM which equates to stability. With the speeds you get from the 300 NMI, there is NO reason to be twisting these things so tight. A 1 in 10” is plenty of stability for the 220gr Berger and even the 230gr.

I hated the 1 in 8” barrel on my first 300 NMI. It was really finicky. My current 1 in 9” on this NMI is definitely more accurate and forgiving, but I’ve still pushed the 220gr bullets fast enough for them to fly apart. My groove diameter might be a little tight too, but point is that I still have more twist than I need. All the other barrels I now have waiting for future builds are 1 in 10” and I know they will work perfectly fine, probably even better than the 1 in 9”

 

[Bodhisafa]

You guys have to remember that speed plays a big part in bullet RPM which equates to stability. With the speeds you get from the 300 NMI, there is NO reason to be twisting these things so tight. A 1 in 10” is plenty of stability for the 220gr Berger and even the 230gr.

I hated the 1 in 8” barrel on my first 300 NMI. It was really finicky. My current 1 in 9” on this NMI is definitely more accurate and forgiving, but I’ve still pushed the 220gr bullets fast enough for them to fly apart. My groove diameter might be a little tight too, but point is that I still have more twist than I need. All the other barrels I now have waiting for future builds are 1 in 10” and I know they will work perfectly fine, probably even better than the 1 in 9”

Where your speeds at max pressure or where you laying of the gas a little?

 

[taylorw]

Speaking of twist rates.. When’s the “bullet shredder” making another appearance
@tom?? Lol

 

[Alex Wheeler]

I dont think its going to run them fast enough to make any come apart. I think what Ledd saw with his 220s was an anomaly, possibly related to that barrel more than the twist. Unless that 220 has a tendency to do that, I have not shot those. Glenn has ran the 210 VLD in the low 3200s and shot in the 2"s at 1k, in a 9 twist. In all the playing we have done, still have yet to loose a bullet.

 

[Alex Wheeler]

Charles Greer and I both use 1-10" twist on our 30 cal barrels for 1K BR, proofs in the targets but if I was going to shoot ELR like a few others have stated I'd choose a 1-9" twist.

Are you both shooting 220s? How have they been agging?

 

[WAMBO]

Are you both shooting 220s? How have they been agging?

We were both shooting the 215's then Charles switched to the 220 but I still shoot the 215's.
I've been agging in the 5"-6" range with a best of 4.9", smallest group was a 2.9375"
You would have to ask Charles about his aggs, I don't remember.

 

[Alex Wheeler]

If your talking 10 shot groups thats a very respectable agg. Thanks for that. I wondered about the 220 but am skeptical about the factory point.

 

[WAMBO]

For me I only shoot LG which is 5 shot groups.
Also we always have wind in Tucson, we hope for a consistent wind but sometimes it switches badly, most times 2nd relay is so bad it's like having a totally different match between 1st and 2nd relay.

 

[tom]

As Alex said earlier, a lot of what we've seen agg out well, AND ON MULTIPLE BARRELS, has been around 1.8+- on the Miller scale.....not Miller Lite @GlennK

That being from pretty much strictly 6mm, fast twist benchrest rifles though, so who knows. What to watch for with marginal stability (around 1.5) is vertical that seems hard to tune out. Of course the one example in our 6mm world has been 105 hybrids in 8" twist barrels. Jim Richards shot the smallest 10 shot in history a few years back with that combo, and later a score record with the same gun. However most barrels would suffer from vertical problems at 1k....however they would shoot dots at 600! Alex ran them in a 7.5" back then and broke 2 different group agg records, which is a true testimony of how something is working, or not. I personally run 7.75" for shorter 103 class 6mm bullets, and in my opinion always error on the more stable side of things. I haven't seen any accuracy decay with a bit more stability, at least not with good bullets. I have seen a decay for certain if I miss it the other direction. In my opinion, something around 9.5 would probably be about perfect for these 1.6" 30 cals in question here, but I wouldn't be afraid of a 9".

Maybe @dkhunt14 can chime in here. I realize he mostly shoots 210 vlds in his 300s, and they're right around marginal in an 11" twist, but I would be open ears to his thoughts on his 30s. I can't think of anyone with a better idea on what makes 30 cals tick. Multiple agg and single target records, and a win percentage through the roof...What say you Matt?

Tom

 

[Ledd Slinger]

I wondered about the 220 but am skeptical about the factory point.

The 220 tips are way more consistent than the 215s and 230s. Hardly any of the jagged angled tips in the 220s like you get with 215 and 230. They will easily shoot as good as the 215s and 230s. Next time I’m home I can send you a hundred to play with if you wanna try them out.

I plan to spin up a Hart 10 twist and a Wilson 10 twist I have on hand this spring and do more testing with the 220s. A 9.5 would probably be a good twist choice too but I’m not going any faster than that anymore. Not at our elevation and with the speeds of the NMI.

 

[Alex Wheeler]

What concerned me was the amount of point. Tom has a lot of experience here. From his testing we have learned there is a correct amount of point for a certain bullet. So without testing different points I was skeptical they would get it right from the factory and we are kind of stuck with it at that point. So far the 245s have just not shot as small as other bullets. Maybe we just dont have them figured out yet. It will be cool to watch theses 220s agg out as I am sure a bunch of guys are gonna try them this year.