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308
.275 member

Reged: 26/01/07
Posts: 61
Loc: Wangaratta/Victoria/Australia

505Gibbs barrel twist?
#84353 - 21/08/07 02:40 PM

Does anyone know what the rifling measurements are for a .505Gibbs ? I will soon be building one and will be using original reloading data 535g@2300fps .Thanks

308

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szihn
.400 member

Reged: 24/06/07
Posts: 2118
Loc: Wind River Valley, Wyoming

Re: 505Gibbs barrel twist? [Re: 308]
#84658 - 26/08/07 06:24 AM

I don't know what Gibbs did, but the new CZs are rifled 1-10"
Now, I would think a 1-14" or 1-16" would be better, as it would lower pressure, but that's just my theory. A 535 grain bullet of .505" doesn't need to spin as fast as 1-10" to stabilize.

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500Nitro
.450 member

Reged: 06/01/03
Posts: 7244
Loc: Victoria, Australia

Re: 505Gibbs barrel twist? [Re: szihn]
#84660 - 26/08/07 08:27 AM

It was quite a slow twist.

Mine and others I have seen are slow twist.

Not sure what it actually is though.

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mhb
.275 member

Reged: 20/09/05
Posts: 77
Loc: S.E. Arizona

Re: 505Gibbs barrel twist? [Re: 500Nitro]
#84768 - 28/08/07 09:28 AM

Barnes lists 16" as the pitch used in his test barrels. 14" to 16" pitch should work fine.

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hoppdoc
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Reged: 02/03/06
Posts: 1791
Loc: Southeastern USA

Re: 505Gibbs barrel twist? [Re: mhb]
#84774 - 28/08/07 10:15 AM

I assume pressures would be higher vs a slower twist shooting the 600 gr bullet at 2200fps in a new gun. Any load data from old vs new guns??

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308
.275 member

Reged: 26/01/07
Posts: 61
Loc: Wangaratta/Victoria/Australia

Re: 505Gibbs barrel twist? [Re: hoppdoc]
#84781 - 28/08/07 12:35 PM

Thanks for the info everyone............so if using 535g or 600g bullets a 14" to 16" would be ok? I would most likely only be using 535g.

308

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500grains
.416 member

Reged: 16/02/04
Posts: 4732
Loc: Salt Lake City, Utah USA

Re: 505Gibbs barrel twist? [Re: 308]
#84783 - 28/08/07 12:52 PM

I would go with a quicker twist, especially if (i) you may use monolithic bullets, (ii) you may use 600 grain Woodleighs, (iii) you wish to optimize penetration by reducing the chance of bullet tumble when it hit bone.

However, the pre-war guns were all slow twist. But that doesn't automatically make it the best choice.

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500Nitro
.450 member

Reged: 06/01/03
Posts: 7244
Loc: Victoria, Australia

Re: 505Gibbs barrel twist? [Re: 500grains]
#84784 - 28/08/07 01:11 PM

600gn bullets work fine in old 505 Gibbs.

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Whitneymr
.224 member

Reged: 26/08/07
Posts: 4
Loc: Colorado, USA

Re: 505Gibbs barrel twist? [Re: 500Nitro]
#85022 - 01/09/07 12:20 PM

Krieger lists 14' and 16" twists for the .505. Never had much reason to argue with him.

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