Berger - Twist Rate Recommendation Update

[royinidaho]

Pac Nor says:

375 (.375")
3 groove 12" 15"
5 groove 8" 12"
6 groove 10" 14" 15" 18"
Polygonal 10"

I have no idea of what I actually have as I purchased from a fellow forum member and don't recall specifics.

I'll be checking twist rate.

Here's what the seller quoted. I'm confident in the numbers.

Pac-Nor super match 1/10" twist
31" 6 groove
1.350" for 4" tapered to 1.25@7" and then taperedto 1" @ 31"
6 flutes.

Nothing but questions on this end...

 

[Kiwi Greg]

Have you recovered a fired bullet to see how much engraving is going on, it could be slipping in the bore.

Get a CEB projectile & offer it up into the muzzle nose first it should be a nice snug fit between the lands on the bore rider up until about an 1/8 of an inch or so from the seal tite band.

Like this,



If it is loose it probably won't engage the rifling properly which could/should reduce the RPMs & effect stability

I have shot 425s in the 1-9 no problem out to 2K & a friend has shot them further so 1-10 & 377 or 400 shouldn't be a problem if the projectile & barrel hold hands properly.

 

[DocUSMCRetired]

Out of curiosity how did you measure the MV?

I would also like to add, how far are you jumping? If it hits the lands at an angle, it can cause problems.

 

[royinidaho]

Out of curiosity how did you measure the MV?

I would also like to add, how far are you jumping? If it hits the lands at an angle, it can cause problems.

MV is SWAG validated by Beta Chrony :roll eyes: Magnetospeed arrived today. Will see.

Seated per CEB instructions w/"ring" touching case mouth. That bullet is awful long and can't be off by much. However, will delve into this further.

Kiwi,

I check the fit prior to shooting. Here's what she looks like now.

 

[Kiwi Greg]

MV is SWAG validated by Beta Chrony :roll eyes: Magnetospeed arrived today. Will see.

Seated per CEB instructions w/"ring" touching case mouth. That bullet is awful long and can't be off by much. However, will delve into this further.

Kiwi,

I check the fit prior to shooting. Here's what she looks like now.

The seal tite band hits on the end of the chamber neck, it has miles of jump.

Is the projectile tight in the muzzle or can you wiggle it around a wee bit ?

 

[royinidaho]

The seal tite band hits on the end of the chamber neck, it has miles of jump.

Is the projectile tight in the muzzle or can you wiggle it around a wee bit ?

When pressing the projectile into the muzzle with only as much finger pressure as I can she does wiggle a wee bit.

The projectile doesn't "ease" into the bore but stops all at once, which seems reasonable for metal on metal.

 

[royinidaho]

Out of curiosity how did you measure the MV?

I would also like to add, how far are you jumping? If it hits the lands at an angle, it can cause problems.

Just shot 3 shots over the MagnetoSpeed V3, Pretty darn sweet rig I'd say.

149 gr H 50 BMG
377 CEB MTAC
Seated as far forward as rifling would permit. Maybe 0.001" jump.

Velocities: 3075/3099/3073

Group right at 1 MOA vertical and 0.67 MOA horizontal @ 300. Not the best of groups I've shot. She shoots better with the seal tite band at the case mouth.

Going to attempt to retrieve a fired bullet. That should be fun.