Reamer Print reading

[RonS]

I am interested in building a 6mm ARC with a 1:12 twist. How do I determine how much freebore I will have in my chamber? What dimensions should I be looking at in the JGS print?

 

[TrxR]

Im not real experienced here but i believe its .0899 but it could be the .1057

 

[RonS]

Im not real experienced here but i believe its .0899 but it could be the .1057

Thx, I think I can work with those numbers...

 

[pintopete]

Thx, I think I can work with those numbers...

Technically the .0899. The difference between the .0899 and .1057 must be for case growth (.0158).

 

[WSnyder]

The number most universally referenced as "freebore" would be .0899".

 

[NZ_Fclass]

I am interested in building a 6mm ARC with a 1:12 twist. How do I determine how much freebore I will have in my chamber? What dimensions should I be looking at in the JGS print?

Ron - I'm interested in why you are limiting your options with a 12 twist? While it's clear that you wish to shoot lighter projectiles, I wonder if a 10 would be any disadvantage, allowing heavier bullets to be used.

 

[L.Sherm]

Look at the U and V numbers thats the freebore.

 

[wkdickinson]

I was looking at this exact question this morning. I would really appreciate those of you on the forum who really understand this stuff (and there are lots of you) lending you knowledge to those of us trying to learn and understand.

 

[gunsandgunsmithing]

.0899 is the freebore length. The .1057 number is freebore plus the length of the 45 degree chamfer at the end of the chamber neck.

 

[RonS]

Ron - I'm interested in why you are limiting your options with a 12 twist? While it's clear that you wish to shoot lighter projectiles, I wonder if a 10 would be any disadvantage, allowing heavier bullets to be used.

NZ, I’ve been shooting a 6mm Grendel with an 1:8 twist for about a year now using 90~105gr bullets. It does very well out to +600 yards. I was looking for something to use in local club matches at 100 yards, the only rule is no BR’s or PPC’s. They are shooting anything from 221 Fireball’s to 30-06 w/ reduced loads. Since starting this thread I switched from a 12 twist to a 1:11 twist to shoot 66~80gr bullets.

 

[RonS]

.0899 is the freebore length. The .1057 number is freebore plus the length of the 45 degree chamfer at the end of the chamber neck.

Thx for your help, now if anyone knows where I can get a go-gauge for the 6mm ARC it would be a great help as well. I’m building this one on a Savage SA with a 24” barrel.

 

[WSnyder]

if anyone knows where I can get a go-gauge for the 6mm ARC it would be a great help as well.

Brownells shows a Clymer go no-go set in stock.

CLYMER GO & NO-GO HEADSPACE GAUGE SETS | Brownells

Convenient kits contain “Go” and “No-Go” gauges for accurately checking chamber length to make sure it meets SAAMI specs. These gauges are essential tools for ensuring a tight, accurate, safe chamber when chambering a new barrel. Always have a set...

www.brownells.com

Manson keeps some of the popular SAAMI on the shelf.

 

[NZ_Fclass]

NZ, I’ve been shooting a 6mm Grendel with an 1:8 twist for about a year now using 90~105gr bullets. It does very well out to +600 yards. I was looking for something to use in local club matches at 100 yards, the only rule is no BR’s or PPC’s. They are shooting anything from 221 Fireball’s to 30-06 w/ reduced loads. Since starting this thread I switched from a 12 twist to a 1:11 twist to shoot 66~80gr bullets.

Thanks mate. Just interested. I have a 6.5 Grendel as a fun gun and planning a 6ARC in the future, but with a 7.5 twist...I do have a 222 with an 8 twist - it's a Tikka with a new take off Tikka barrel Shoots 55g just fine - i haven't tried a heavier pill in it as I dont waste 105's on rabbits and I have a pile of Hornady 55's I bought cheap years ago. I'm a bit of a fan boy of 6mm- have a few...BR, BRX, 243 and SLR. Best of luck with the ARC. Put up a pic when its done.

 

[RonS]

Brownells shows a Clymer go no-go set in stock.

CLYMER GO & NO-GO HEADSPACE GAUGE SETS | Brownells

Convenient kits contain “Go” and “No-Go” gauges for accurately checking chamber length to make sure it meets SAAMI specs. These gauges are essential tools for ensuring a tight, accurate, safe chamber when chambering a new barrel. Always have a set...

www.brownells.com

Manson keeps some of the popular SAAMI on the shelf.

Thx for the heads up, I ordered a set...