6mm PRC TWIST rate

[HABU 1]

Hi there, what would the ideal twist rate for the above calibre shooting 90G ELD X
bullets , 8twist or 7twist thanks Lee

 

[jackieschmidt]

A regular 6BR will shoot that bullet just fine in a 8 twist, so I suppose a case as large as the PRC would do the same. Just at a higher velocity.

 

[mike mccormick]

I would think an 8 twist way too fast. I played with a 6mm06 a few years ago. I made the error of going with an 8 twist, and proceeded to blow up a lot of 90 to 105 grain bullets. Defeats the purpose of having 3500+ plus MV when the bullets won't handle the rotational speed.

 

[HABU 1]

Thank you Gents, not a lot of info on the 90g in 6mm on the Internet, will send email to hornady and ask the question .

 

[Kurz]

Hornady ELD-X bullets are supposed to be similar to the AMAX line of bullets from the past except for the newer tip. I have hunted with the 105 AMAX for years but I haven't bothered with the lighter bullets seriously. A published comparison might be the 6-284 cartridge which has more data and is similar to the PRC.

https://press.hornady.com/assets/site/hornady/files/obsolete-data/6mm-284.pdf

Some exploring led me to find a velocity in the neighborhood of 3500 - 3550 fps. from a 26" barrel. Feed this information into the Berger Calculator and you find that a 1:9" twist will provide a 1.51 stability factor which is minimum without losing BC. So, if you don't plan on running them this hard or you want a shorter barrel (not bright), then I suggest the possibility of a 1:8.75" or 1:8.5" to be on the safe side.

RPM at 3500 fps with a 9" twist = 280,000 approximately.

RPM at 3500 fps with an 8.5" twist = 296,500 approximately.

If you can't contain yourself and you have to have this cartridge and bullet combination, I suggest trying VVN-160 or N-165 powder. Cool burning to attempt to control throat erosion...

Your choice.

 

[HABU 1]

Thanks for your reply Kurz.

 

[Tommie]

I’d go slower than 8

 

[HABU 1]

I would think an 8 twist way too fast. I played with a 6mm06 a few years ago. I made the error of going with an 8 twist, and proceeded to blow up a lot of 90 to 105 grain bullets. Defeats the purpose of having 3500+ plus MV when the bullets won't handle the rotational speed.

Hi Mike what twist did you swap it too may I ask, cheers Lee

 

[mike mccormick]

Hi Mike what twist did you swap it too may I ask, cheers Lee

I stuck with Sierra 110s and Berger 115s and was able to keep those together at 3400

 

[HABU 1]

I stuck with Sierra 110s and Berger 115s and was able to keep those together at 3400

Thanks for your reply, Mike what bore size were you running 236 or 237 cheers Lee

 

[mike mccormick]

Thanks for your reply, Mike what bore size were you running 236 or 237 cheers Lee

I don't honestly remember, sorry