30 SM Build Barrel Twist??

[huntinherrrington]

I have a 300 sherman 30" 1:9 but with the powder shortage load development is impossible so I am building a 30 Sherman Magnum. I picked up 8lbs of N570 and 200 Berger 245 EOL yesterday. Plan to order some 205gr badland SBD2 and possibly hammer bullets.

Question is get 30" barrel with 1:7 or 1:8 twist??
Also, Will 1:7 be an issue with bullets like 208 eldm or 215 bergers?

Thoughts or suggestions?

My elevation is sea level.

 

[MagnumManiac]

These are my thoughts...take them as you will.
1:10" twist for 30 cal bullets up to and including 230gr is fast as is.
The standard twist is 1:12".
Now, anything faster than 1:9" twist IS going to affect SOME bullets using a J4 jacket, which one's is an unknown until you try them.
I know many are going to chime in saying an 8" twist is optimal for 245gr+ bullets.
This is rubbish, the Berger stability program is flawed.
The JMB program spits out totally different numbers, so which is to be believed, I ask.
The ONLY time you will need a faster twist than 9" is if you're shooting solid copper or solid aluminium bullets.
I need a 9" twist in my 338-416 because I run a custom turned solid copper bullet in it, very similar to a Cutting Edge Laser.
A 10" twist was marginal, but still stable.
A 7" twist will likely tear many bullets to bits.
My 7" twist 22-250AI tears some Sierra bullets apart, mostly the 52gr Matchking, which is fun doing so, but that's just me messing about.
Anyway, consult some stability programs before deciding on your rate of twist.
I think 7" twist is way too fast.

Cheers.

 

[elkaholic]

I have a 300 sherman 30" 1:9 but with the powder shortage load development is impossible so I am building a 30 Sherman Magnum. I picked up 8lbs of N570 and 200 Berger 245 EOL yesterday. Plan to order some 205gr badland SBD2 and possibly hammer bullets.

Question is get 30" barrel with 1:7 or 1:8 twist??
Also, Will 1:7 be an issue with bullets like 208 eldm or 215 bergers?

Thoughts or suggestions?

My elevation is sea level.

I would not go tighter than 8 even for the new Atips. I run a 9 and it shoots lights out with 245 Bergers.

 

[Pdvdh]

Get an 8.5 to shoot the 205gr Badlands Precision. That's what I did, but whadda I know.

Agree with Rich. No reason to go any faster than an 8-twist.

 

[huntinherrrington]

I'll look for a 8.5" so I'll be covered for the badlands if no luck I'll get a 9" and stay with the 245 EOLs and lighter.

Rich, How fast do you think the 30" tube with N570 will push the 245s?

Also is your 30SM brass fully formed now?

 

[elkaholic]

I'll look for a 8.5" so I'll be covered for the badlands if no luck I'll get a 9" and stay with the 245 EOLs and lighter.

Rich, How fast do you think the 30" tube with N570 will push the 245s?

Also is your 30SM brass fully formed now?

Ive had guys run them up to 3100' with 30" barrels but that has to be warm.
I run them right at 3000' in my 28" and the brass lives well and shoots bugholes

 

[huntinherrrington]

Is the 30 SM brass fully formed or does it still need to be fire formed to form the 40* shoulder?

 

[elkaholic]

Is the 30 SM brass fully formed or does it still need to be fire formed to form the 40* shoulder?

Needs forming but will shoot great while forming

 

[nkyshooter]

Mine is due any day ... 26", 5r, 8twist ... I'm at about 800-1000 feet elevation.

Savage 300 PRC is an 8.5twist ...

I would 'probably' have been just fine at my elevation with a 9 ... for sure with an 8.5 ... but I don't think the 8 twist will be a hindrance as I don't expect to shoot anything lighter than 200's with it for my applications.

 

[huntinherrrington]

Get an 8.5 to shoot the 205gr Badlands Precision. That's what I did, but whadda I know.

Agree with Rich. No reason to go any faster than an 8-twist.

Have you worked up a load with the 205s yet?

 

[Pdvdh]

Might get out tomorrow. Got some shells loaded today. Supposed to be decent weather-wise.

 

[hugheserj]

9 twist should be fine for 245 EOLs

 

[Pdvdh]

Have you worked up a load with the 205s yet?

Initial ladder test, 30 SM with 8.5-twist 26" Bartlein barrel, 205gr Badlands Precision Super Bulldozer-2, and N570. Look's like it's gonna shoot. Ran up to 84.0gr & 3,126fps. Never reached maximum pressure.
One promising node at 2,975fps. Another so-so at 3,045fps.
But more load work is in order...

 

[L.Sherm]

This 10 shot group was shot recently with a 10 twist, 220 Bergers in a 300wsm at 2800fps at 1,000 yards pending new record.