Help..Throat length / Freebore / bullet jump

[Colin78]

With the bullets you chosen the Bergers will shoot better closer to the lands and the LRAB and the LRX typically need a good bit of jump, I would consider that. I always just set up a couple dummy cases then send to ADG and when they get back to me with measurements based on the throat diameter and lead angle then I choose a freebore to cut.

I agree 100% on the jump difference between ABLR and Berger. Which is kinda causing me more of an issue because if I set the jump on the Berger's to be close to lands the ABLR's won't even chamber and if I set the jump for the ABLR's to be a long jump the Berger's will be a mile from the lands. Seems like lots of people are using a freebore of .195 to .220 on the XM length 7 SAUM's maybe I need to just do that and then worry about bullets / seating depth / and jump later when it's finished.

 

[bigngreen]

Mine is set at a .230 freebore for the 180 Hunting Berger.

 

[L.Sherm]

Big n Greens reamer is set up well for the 175 elite or 180 VLd if my math is correct. .230 touchs the lands with a 175 elite and .015 of with the 180 VLD.

 

[Colin78]

Mine is set at a .230 freebore for the 180 Hunting Berger.

Big n Greens reamer is set up well for the 175 elite or 180 VLd if my math is correct. .230 touchs the lands with a 175 elite and .015 of with the 180 VLD.

With your .230 freebore what is your COAL and jump?

 

[L.Sherm]

Same as post #14 and # 17.
175 touch and 180 is .015 off.
Keep in mind there could be some difference between lots but those are off Bergers dimension chart.

 

[Colin78]

Same as post #14 and # 17.
175 touch and 180 is .015 off.
Keep in mind there could be some difference between lots but those are off Bergers dimension chart.

With a .230 freebore 175's touch at what coal?

 

[L.Sherm]

You will be way past the case nk- shoulder junction on any of the bullets you mention at 3.1. Seating at the bearing surface boatil junction.
According to bergers dimension with there 180 VLD at boatail bearing surface- nk- shoulder junction on brass your OAL is 2.987 with the 175 Elite hunter its 3.02.
I know the 180 VLD isn't the hybrid but thats all they listed in there dimensions, I couldn't imagine it much longer than the 175 elite

3.02 or there abouts.

 

[Kimber7man]

I have a 7SAUM built on an anTi XM length action and 175 elites are in the lands at 3.04" COAL. They shoot very well at 2.99-3.00" COAL.

I think @Longtine88 has several 7 SAUMs and could/might chime in as well.

 

[Colin78]

I have a 7SAUM built on an anTi XM length action and 175 elites are in the lands at 3.04" COAL. They shoot very well at 2.99-3.00" COAL.

I think @Longtine88 has several 7 SAUMs and could/might chime in as well.

Do you know what your freebore is?

 

[L.Sherm]

I forgot to add in about .012 to the freebore for lead angle which comes to 3.032 and .299

 

[RidgeTop]

Push up against lands would give you massive pressure.

I'll see if I can find a pic of Weatherby Mk V freebore. This looks like some freebore.

 

[L.Sherm]

Increase pressure at or into yes but I wouldnt use the word " massive"

 

[Kimber7man]

Do you know what your freebore is?

nope. Just told the gunsmith I was going to shoot the 175 elites and 180 hybrids in it.

 

[Longtine88]

Well I do have several. And currently putting a XM length together with a saami chambered proof prefit.

With a saami chamber a 180 hybrid will have a CBTO of 2.284" touching lands and around 3.018" for a COAL. I have one rifle that has a freebore of 0.190 and the 180's touch at 2.354"CBTO and 3.088" COAL.

Honestly I have just started using saami chambered prefits because I have no issue getting the 180's to the 3,000' mark. The 175's to the 3,030' mark. So no need of longer freebore and I can load them longer time wise because of throat erosion. And I generally find the best length right just shy of the lands.

Greatest cartridge in my book. You picked a good one.