300 Win Mag in 1:7 Twist Barrel

[Qbanmissilecrissis]

I had a barrel made for my 300 winny in a 1:7 twist rate with 30” length. I had the barrel built for 230gr Hornady A-tips. My shooting buddy talked me into it. I have not found much in the web in regards to others using this twist rate except for 1:8 twist is more than enough to maintain stability. I have access to a 2000yard range and I have been successful with consistency at 1300 yards with my current 1:10 twist barrel. At the mile im starting to struggle hitting the plate and at 2000 I’m wasting bullets. Has anyone tried using the 1:7 with this or similar bullet with any success. My thoughts are with the advancement of these high velocity bullets nowadays the jacket should hold. Any constructive thoughts?

 

[gnochi]

Jackets won’t hold above ~300,000 rpm, so double check that your velocity is below ~2900fps. The other problem with faster twists is you get worse spin drift if the bullet centers of mass and drag aren’t perfectly aligned (read: it’s a copper jacketed lead bullet).

That said, copper solids should be very interesting, especially if you can load to longer overall lengths.

 

[jetmd]

I would venture to guess that optimum performance with that twist rate will only come from shooting solids.

YMMV

 

[Taylorbok]

Are you able to spot your misses? There is a lot more that goes into making impacts at 2k than 1000.
What is your MV that is pretty fast twist for cup and core bullets but I don't think you should be tearing them apart.
How's your s/d and e/s?

 

[Dogtown]

1:8 will generally stabilize everything up to 250s. 1:7 is necessary for heavy solids (ex: 240gr) though because they're longer than jacketed 250s.

 

[GIXXER2000]

I run a 1-8 in my 300NM with 230 hybrids and A-Tips and 1-9 in my 300WM shooting 220's hybrids. I would think 1-7 is too fast for jacketed bullets fine for solid's as Dogtown stated.

 

[Taylorbok]

I doubt he's getting much over 2800 fps which still puts him in the "manageable" range for RPM. Also if he's tearing jackets off you'd see issues much before 2000 yards.

 

[GBMaryland]

I'm using 180Gr Warren Tool Bullets - solid copper bullets. I'm starting out at 3200FPS, and I'm supersonic to ~1800 yards.

With a 1:7 twist I'm shocked that you can get jacketed bullets to hold up. That being said, solids would work ALOT better for your application. Not to mention, that with a 1:7 you can probably use some nice and heavy solids... with insane BCs.

For example:

.30 198gr FLAT LINE BULLET | Warner Tool Company

The WTC .30 198gr Flat Line Bullet is a CNC lathe-turned copper solid, designed to boost speed and BC - shooting farther, faster, flatter.

www.warner-tool.com

 

[GBMaryland]

FWIW:

 

[Taylorbok]

I wish OP would come back and give his MV. again if he's blowing up bullets that usually happens about 100 feet out of the muzzle.
IMO solids can't beat a cup and core at the distances they are effective out of a 30 cal.
However if you gonna try solids someones gotta give these a good try...

FLM 30c 241gr "Seneca" Competition Bullets - 50 ct

[email protected]

patriotvalleyarms.com

 

[GBMaryland]

I haven't played with PVA yet... bought some in 6.5 and need to give them a whirl.

I've used the WTC 180s in my 300WM, and they are nasty bastards at 3227 FPS (ADV)...

 

[Qbanmissilecrissis]

Are you able to spot your misses? There is a lot more that goes into making impacts at 2k than 1000.
What is your MV that is pretty fast twist for cup and core bullets but I don't think you should be tearing them apart.
How's your s/d and e/s?

With my current 1:10 twist barrel I’m getting MV of 2850 fps ES 26 and SD 6-7 on my reloads. The new 1:7 twist barrel hasn’t been installed yet.

I guess maybe the question should be, has anyone actually had first hand experience and can actually speak on their results shooting jacketed bullets out of a 1:7 twist.

If not I’m going to be the Guinea pig and will be glad to report my results.

 

[GBMaryland]

Just take off your suppressor when you start shooting those bullets… just in case they fragment early

 

[Taylorbok]

With my current 1:10 twist barrel I’m getting MV of 2850 fps ES 26 and SD 6-7 on my reloads. The new 1:7 twist barrel hasn’t been installed yet.

I guess maybe the question should be, has anyone actually had first hand experience and can actually speak on their results shooting jacketed bullets out of a 1:7 twist.

If not I’m going to be the Guinea pig and will be glad to report my results.

Ok, I was under the impression the barrel was on and you thought you were having issues. But essentially you can't hit the target at 2k with 1:10 twist and 230 a-tips. With the setup you are currently running are you able to spot your misses?

1:7 twist at 2850 gives you 293K RPM I've never spun the A-tips that hard but they should hold together. I don't know if it's going to make you hit the target tho. If you are having bad stability issues you'll usually see that much closer in. Typically slightly under stabilized will just sacrifice some BC not like it starts flying sideways at tranz. I've shot the 250's from a 1:9 with no problems out to 2500 yards, currently using a 1:8.5
I'd say more likely you are fighting wind and shooter error.

 

[kb300w]

I shoot 300WinMag with 225gr ELD-M in a 1 in 9" twist. Good results out to 1910 yards.

 

[Fig]

^^^ and @GIXXER2000 are approaching the limits of the rifle/cartridge IMO. I run 1-8 twist on 230 Juggernauts moving at 2,750, out of a GAP Hospitaler, and I can bang steel at 1,800 yds as long as my wind call is correct. That gun shoots as well as any of my match rifles. That's also about the limit of my turret (and eyesight), as that's well on the backside of the parabola. I'd also be interested to see how that would shoot some 'spensive boolets.

 

[GIXXER2000]

I have taken both my 300NM and 300WM out to 1979 yards with good accuracy. The hardest part is spotting your misses. When I spoke with Robert Vestal about my 375CT and what bullet I could use in a 1-7 twist he told me the 375, 350 gr SMK's would come apart in if I push them very hard. It's just to fast for the jacketed bullet. I shoot 400 CE Lazer's. I believe what he had to say.

 

[Taylorbok]

I have taken both my 300NM and 300WM out to 1979 yards with good accuracy. The hardest part is spotting your misses. When I spoke with Robert Vestal about my 375CT and what bullet I could use in a 1-7 twist he told me the 375, 350 gr SMK's would come apart in if I push them very hard. It's just to fast for the jacketed bullet. I shoot 400 CE Lazer's. I believe what he had to say.

300k RPM is usually the limit. Depending the velocity with those smk you'd likely be 310-330k RPM in 1:7.
If he keeps the velocity down at 2850 he should be fine

 

[GIXXER2000]

If I remember right that's about what Vestal had to say. I sold the 350 SMK's and got some Leigh 370 something solids for barrel break in.

 

[cameljockey230]

I don't think the 300 win mag is going to push those bullets to destruction.
At 3000 fps the centrifugal force is in the neighborhood of 28,000 psi while the acceleration is roughly 128,000 g's.
Friction causes heat and heat kills bullets.
Try them and see what happens.

 

[Pete Cefalu]

Are you able to spot your misses? There is a lot more that goes into making impacts at 2k than 1000.
What is your MV that is pretty fast twist for cup and core bullets but I don't think you should be tearing them apart.
How's your s/d and e/s?

He /we haven't installed the pipe yet. his rig(setup) should allow him to spin the 230 AT at 2900MV and entertain the 212 Mono's to 2K with a nice jump.

FWIW:

View attachment 8171141

Can you calculate at sea level in 90*F and 70%humidity for comparison? I'm curious.

 

[Pete Cefalu]

I wish OP would come back and give his MV. again if he's blowing up bullets that usually happens about 100 feet out of the muzzle.
IMO solids can't beat a cup and core at the distances they are effective out of a 30 cal.
However if you gonna try solids someones gotta give these a good try...

FLM 30c 241gr "Seneca" Competition Bullets - 50 ct

[email protected]

patriotvalleyarms.com

The solids arethe alternate plan. he is sitting on a boatload of the 230AT's. I have a bunch of Josh's 212 and 241's to try, As I have the same setup albeit a 28' bbl. i shelved them when 300PRC was built. Hope to share our results weather/time permitting.

 

[GBMaryland]

 

[Qbanmissilecrissis]

UPDATE:

I just want to give you guys a little update so that I don't leave you hanging. The 230 Atip's work flawlessly.

74.5gr of H1000 gives me 2885fps which keeps it just under (300000rpm) actual number 296742rpm's. This rig shoots like a F'ing laser. I'm also playing with PVA's 241gr mono and they are most def a game changer.

Once I have more to share, I will make sure to post.

 

[PB&J.]

UPDATE:

I just want to give you guys a little update so that I don't leave you hanging. The 230 Atip's work flawlessly.

74.5gr of H1000 gives me 2885fps which keeps it just under (300000rpm) actual number 296742rpm's. This rig shoots like a F'ing laser. I'm also playing with PVA's 241gr mono and they are most def a game changer.

Once I have more to share, I will make sure to post.

Got any long term updates on the 7 twist?

I'm rebarreling my win mag shortly and am thinking of going 7 twist with 225 ELDM's, Hornady seems to think they'll take the RPM's.

 

[Fig]

Honestly, with that BC and that weight there is absolutely no need to try to squeeze excessive speed/pressure, start blowing primers, deforming brass, Etc.. If you are going to spin heavies fast then you shouldn't be as concerned about MV. I'll take a solid, predictable rainbow over a flatter, shakier parabola any day. Since the goal is obviously more stability and predictability with a faster twist this only makes sense. 1:8 is stabilizing a 230 fine in my rifle.

I've never found precision trying to push the limits of pressure in any rifle. At 2,750 Fps I get no signs of pressure with H1000. The Berger calculator says I'm still fully stable with a 1:9.5, and at 1:10 goes marginal.

My thinking is that rather than trying to squeeze and push the MV of the very capable .300WM it makes more sense to go with the up horsepower versions NM, WM, and RUM. For me the squeeze isn't worth the juice, but for many it is.

 

[Pete Cefalu]

It was my understanding and reasoning for having 2 barrels spun at 1:7 in order to stabilize the much longer and heavier solids with very high BC's. If your running heavy for caliber jacketed bullets, and your target is in transonic or subsonic zone of flight path, you will want them holding their spiral. If that's the case, then I go .5 additional to what the bullet manufacturer requires(requests?). If your target will always remain in supersonic distance, than the manufacture's recommendation should be fine(I still reduce by .5). The only time I played with high MV is when the manufacture's listed high BC was measured at a given/known speed. I am by no means an expert here, but did spend thousands of dollars experimenting with solids and 1:7 twist on my 300WM. I have since moved on and hand load Horny 230 A-Tips @2940fps out of a heavy 28" 7 twist pipe. The 1 mile plates I engage are planted in trans flight and I easily hold 1.5 MOA. I am on the 2nd 7tw barrel, and have ordered another in 7.5tw and 30". Lastly, I have shed the jackets on some bullets by not accounting for the brutal heat I sometimes run in. The RPM formula that most of us use(>300,000 RPM) does not account for excessive heat added into the included heat equation from friction. Hope this makes sense.