Twist Rate Question

[17remhunter]

Looking at a 6 CM with a 1.8 twist............... I understand that you cant over stabilize a bullet but what happens when you run a 75gr V-max with the 1x8 twist will the bullet hold together. looking at over 3700fps.............. Just wondered if anyone has feed back on what would be the lightest bullet you could shoot with that twist rate in the 6 CM

 

[lancetkenyon]

Looking at a 6 CM with a 1.8 twist............... I understand that you cant over stabilize a bullet but what happens when you run a 75gr V-max with the 1x8 twist will the bullet hold together. looking at over 3700fps.............. Just wondered if anyone has feed back on what would be the lightest bullet you could shoot with that twist rate in the 6 CM

I doubt you will get near 3700fps from a 6CM and 75 V-Max. But a 1:8" should work fine with the 75 V-Max.
I got 3350+ with an 87 V-Max in my 24" 1:7.5" 6CM.

I had the 87 V-Max vaporize 10' from the muzzle from a 1:7" 6SST @ 3650fps+.

 

[Rosebud]

I doubt you will get near 3700fps from a 6CM and 75 V-Max. But a 1:8" should work fine with the 75 V-Max.
I got 3350+ with an 87 V-Max in my 24" 1:7.5" 6CM.

I had the 87 V-Max vaporize 10' from the muzzle from a 1:7" 6SST @ 3650fps+.

Wow, heard of that happening but never seen it!

 

[lancetkenyon]

Wow, heard of that happening but never seen it!

It was really cool. 1st shot, I didn't see, but no bullet hole in the target. Second shot, I kept my left eye open, and about 10' from the gun, I saw the shimmer in the sunlight and dust rise in a horizontal line from the ground. Crazy looking.

 

[Hugnot]

Stuff on the 6mm 75 & 87 VMax

I never shot the 75 6mm VMax but have shot 1,000's of 6mm 87 VMax's. I blew some 87's up from an 8 twist 6mm-06 at about 3,500 fps. I usually shoot 87's out of my 10 twist 6mm AI & it is good for 600 yards plus at nice velocities just under 3,500 & ballistic data indicates the 87's pass 75's velocity about 400 or so. I re-barreled the 6mm-06 to an 8 twist 6.5-06 it shoots 95 VMax's fast enough as well as 140's.

RPM's of 324,000 for the 75 out of an 8 twist are spinning like crazy & good results would be uncertain.

Don't think the 6 CM could get 3700 with a 75 but if it could:

A 10 twist would probably save the 75 from blowing up.

 

[MagMan]

It was really cool. 1st shot, I didn't see, but no bullet hole in the target. Second shot, I kept my left eye open, and about 10' from the gun, I saw the shimmer in the sunlight and dust rise in a horizontal line from the ground. Crazy looking.

Sounds like a shotgun too.

 

[nralifer]

Looking at a 6 CM with a 1.8 twist............... I understand that you cant over stabilize a bullet but what happens when you run a 75gr V-max with the 1x8 twist will the bullet hold together. looking at over 3700fps.............. Just wondered if anyone has feed back on what would be the lightest bullet you could shoot with that twist rate in the 6 CM

No problem from my 243Win from 3648-3801 fps shooting 80 gr Badlands BD2 copper bullet. Shoots <0.75 MOA at 600 yds. 1963 Rem 700 ADL, 22" factory barrel.

 

[spladi]

Looking at a 6 CM with a 1.8 twist............... I understand that you cant over stabilize a bullet but what happens when you run a 75gr V-max with the 1x8 twist will the bullet hold together. looking at over 3700fps.............. Just wondered if anyone has feed back on what would be the lightest bullet you could shoot with that twist rate in the 6 CM

Because the 6 MM Creedmoor can produce such high velocity, information about the 87 V Max's ability to stay together at high RPM's might be best discovered from some gunsmith who has built a similar variety, say a 6mm .284 or a 6mm o6.

 

[Randy Tidwell]

Hugnot, I was getting ready to post the spread sheet built that calculates bullet RPM, you beat me to it.

Most do not realize how fast we are spinning bullets from these fast twist barrels.

I stopped shooting Bergers from my 6Dashers, 105s were coming apart at 3350.

Switched to Scenars, never had one come apart.

 

[jasent]

I think the rifling has a lot to do with whether they hold together. I've shot the 64gr beget column from my 1:7 28" 243 with no trouble and 58gr vmax from my 1:7.5 26" 243 at 3800. No blow ups even out to 500 yards. 6 groove button rifled. Jme.

 

[Eric H]

Stuff on the 6mm 75 & 87 VMax

View attachment 421393

I never shot the 75 6mm VMax but have shot 1,000's of 6mm 87 VMax's. I blew some 87's up from an 8 twist 6mm-06 at about 3,500 fps. I usually shoot 87's out of my 10 twist 6mm AI & it is good for 600 yards plus at nice velocities just under 3,500 & ballistic data indicates the 87's pass 75's velocity about 400 or so. I re-barreled the 6mm-06 to an 8 twist 6.5-06 it shoots 95 VMax's fast enough as well as 140's.

RPM's of 324,000 for the 75 out of an 8 twist are spinning like crazy & good results would be uncertain.

Don't think the 6 CM could get 3700 with a 75 but if it could:

View attachment 421490

A 10 twist would probably save the 75 from blowing up.

What site are you getting your SG numbers from?

 

[nralifer]

Hugnot, I was getting ready to post the spread sheet built that calculates bullet RPM, you beat me to it.

Most do not realize how fast we are spinning bullets from these fast twist barrels.

I stopped shooting Bergers from my 6Dashers, 105s were coming apart at 3350.

Switched to Scenars, never had one come apart.

Remember, copper bullets are a lot tougher, penetrate better, can have better BCs, are more lethal, damage less meat and can't fly apart at high twist rates which actually enhances their lethality.

 

[skipglo]

It was really cool. 1st shot, I didn't see, but no bullet hole in the target. Second shot, I kept my left eye open, and about 10' from the gun, I saw the shimmer in the sunlight and dust rise in a horizontal line from the ground. Crazy looking.

Not nice....But Nice! ( to see at least)

 

[Fiftydriver]

Looking at a 6 CM with a 1.8 twist............... I understand that you cant over stabilize a bullet but what happens when you run a 75gr V-max with the 1x8 twist will the bullet hold together. looking at over 3700fps.............. Just wondered if anyone has feed back on what would be the lightest bullet you could shoot with that twist rate in the 6 CM

Dont think you will reach the bullets integrity limits in that twist with a creedmore. At least not until the barrel gets quite worn. Would think you would be just fine. If you did run into issues, just step up to the 87 gr class, bring speed down a bit, drop rpm a bit but gain BC.