260 in a 6.5cm chamber?

birdiemc

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There's a smith in Montana who runs a creedmoor reamer deep enough to chamber a 260 rem round in it. Fireforms the 260 in it. I believe it has 56-57gr capacity. I'm wanting to try this as it may allow RL26 H1000 or N565 to really shine.
This comment popped up in the latest manbun thread and got a little attention, but then passed over...but it interested me. If I understand correctly, the 30degree shoulder is what all the hype is about in the creedmore package so this seems like a cool idea...but I know nothing at all about wildcatting (I suppose would be the best term) so what's the deal, would cutting the chamber deeper with 6.5cm reamer then running fireformed 260rem brass have a true advantage?
 

highdrum

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This comment popped up in the latest manbun thread and got a little attention, but then passed over...but it interested me. If I understand correctly, the 30degree shoulder is what all the hype is about in the creedmore package so this seems like a cool idea...but I know nothing at all about wildcatting (I suppose would be the best term) so what's the deal, would cutting the chamber deeper with 6.5cm reamer then running fireformed 260rem brass have a true advantage?
Yes it will essentially give the low case wall taper and 30° shoulder of the creed to the 260 parent. Will add 3-4gr powder capacity, reduce case growth, add performance over the creed and 260 saami chambers. You can still use regular 6.5 creed dies from all that I've read.
 

nkyshooter

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What is the advantage of this over a 260 Ackley?

The only 6.5 Creedmoor advantage I am aware of VS 260 Remington is the shorter case length permitting the long bullets to be seated without intruding into the case capacity... So by doing what you are describing it would seem to me the sole advantage is being forfeited?

Am I missing something?
 

highdrum

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What is the advantage of this over a 260 Ackley?

The only 6.5 Creedmoor advantage I am aware of VS 260 Remington is the shorter case length permitting the long bullets to be seated without intruding into the case capacity... So by doing what you are describing it would seem to me the sole advantage is being forfeited?

Am I missing something?
No need for special reamer or dies. 30° shoulder may feed better than 40° other than that, little. I didn't intend for this thread to spin into a creedmoor wildcat thread.
 

birdiemc

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No need for special reamer or dies. 30° shoulder may feed better than 40° other than that, little. I didn't intend for this thread to spin into a creedmoor wildcat thread.
That's why I started a different thread to be able to discuss what you mentioned outside of the original thread you posted in.
 

highdrum

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That's why I started a different thread to be able to discuss what you mentioned outside of the original thread you posted in.
Hmmm well started cooking and drinking at about 9am today, just now noticed my quoted post brought me into a new thread. Good on you for etiquette. There was a fella on here that did the same thing with a 25 creedmoor reamer ran deep to where necked down 260 brass chambered. Perhaps @JTB can opine in on this he is running speeds 100'/sec faster in his 22" 25 creed ultra that I run from a 26" 25 creed. So the extra case capacity may be worth another 150fps. I have a long freebore 6.5 creed and I can't get 143eldx to 2950 w/ rl26 before pressure signs in a 24" barrel. If the extra case capacity gets me anoyebr 4gr I bet 3050-3075 is possible and that will run neck and neck with 6.5prc velocity. Should be doable with 51gr rl26 in srp 260 brass, or necked down/formed lapua 308 palma.
 

Hespco

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Consider this. Savage model 16 260 Rem 22" Bbl. CCI # 250 mag primer, Rem 260 brass, 47.5grs Rel 26, Badlands Precision 125gr bullet = 3032 fps. In picture , bullet on the left is a Nosler 140gr AB. On the right is the Badlands 125gr mono. Very high BC. My rifle produce's three shot groups between 1/2" & 3/4" at 100. Need to play with the seating depth to see if I can tighten the group.
 

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nkyshooter

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No need for special reamer or dies. 30° shoulder may feed better than 40° other than that, little. I didn't intend for this thread to spin into a creedmoor wildcat thread.

If it isn't SAAMI then isn't it by definition a 'wildcat'? ... even if using a SAAMI reamer, as soon as it is taken deeper it is no longer SAAMI right?

Just my thoughts on this - appreciate you have challenged me to think/rethink about and through it ...

- a special die for full length sizing will be required if the chamber is deeper than the SAAMI in order to shrink the body near the base as it grows over time
- other 'wildcat' cartridges (i.e. 260 rem AI) can often use standard dies except for body or full length (i.e. Lee 260 collet neck and seater for 260 AI) ... design and function of the die will drive this
- 30 vs 40 degree shoulder for improved feeding is arguable but I do agree the 'potential' exists for improved feeding with 30 vs 40 ... there is also a 260 Improved 30 deg shoulder and if not mistaken also a 35 ... and all the above applies to them as well.

Since the creedmoor case was created off the shorter 30TC case (as compared to 308) in order to have the advantages of the shorter case and subsequent ability to seat the long bullets without intruding into/reducing the case capacity, it doesn't make sense to me to try and "revert" the length back to the 308 case length ... unless you just want to experiment with a wildcat. No judgement from me on that - my 6.5 ackley (wildcat) and 6BR (former wildcat) rifles are my favorites for the range ... And all the above being said - I'm curious who is doing it, to what success, what kinds of muzzle velocity and accuracy is being achieved, etc, etc ...

Cheers
 

del2les

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Back in "BC", Before Creedmoor, years, we called this a 260AI, and it was available in 30 and 40 degree shoulders. Hmmm, now that I think about it, I think I will rename and reintroduce my 260AI's as the 6.5"CMM", CM Magnum. It should sell like hotcakes! When at the range and people ask what caliber I am shooting, I can be all modern and cool with my "new" 6.5CMM.....
 

del2les

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@del2les - so what you're sayin' is ...

A 6.5 CM is basically a 260AI 30deg stopped a little short? And if we don't stop it short it is a 260 AI 30 deg - just like if we take a 6.5 CM a little deep? ... 😜

Basically, the 6.5CM is a 260AI teenager.
The 260AI, or now its 6.5CMM is an adult,
and the 6.5-06/AI is grandad.
 

codyadams

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If it isn't SAAMI then isn't it by definition a 'wildcat'? ... even if using a SAAMI reamer, as soon as it is taken deeper it is no longer SAAMI right?

Just my thoughts on this - appreciate you have challenged me to think/rethink about and through it ...

- a special die for full length sizing will be required if the chamber is deeper than the SAAMI in order to shrink the body near the base as it grows over time
- other 'wildcat' cartridges (i.e. 260 rem AI) can often use standard dies except for body or full length (i.e. Lee 260 collet neck and seater for 260 AI) ... design and function of the die will drive this
- 30 vs 40 degree shoulder for improved feeding is arguable but I do agree the 'potential' exists for improved feeding with 30 vs 40 ... there is also a 260 Improved 30 deg shoulder and if not mistaken also a 35 ... and all the above applies to them as well.

Since the creedmoor case was created off the shorter 30TC case (as compared to 308) in order to have the advantages of the shorter case and subsequent ability to seat the long bullets without intruding into/reducing the case capacity, it doesn't make sense to me to try and "revert" the length back to the 308 case length ... unless you just want to experiment with a wildcat. No judgement from me on that - my 6.5 ackley (wildcat) and 6BR (former wildcat) rifles are my favorites for the range ... And all the above being said - I'm curious who is doing it, to what success, what kinds of muzzle velocity and accuracy is being achieved, etc, etc ...

Cheers
As far as feeding, I have a .260 AI 40degree that I run with an AICS mag, and I can't see how feeding could get any smoother. Now if you were going to run as a BDL, this could completely change! I just know that feeding is very smooth from my American Rifle Company mags. And as far as custom dies, my Redding 3 die set was $100 on a good sale, but you can get a Redding full length bushing sizer die for around $100 even not on sale, and just use a standard .260, 6.5 creed, or similar seating die and be gtg, and with a proper .260 ai, you would be able to shoot factory ammo in a pinch.

But if you like the 30 degree shoulder but want a cartridge like that, the 6.5 SLR is a great solution, and still uses .260 brass, and also will fit better in a short action, as it gets the 30 degree shoulder from pushing the neck/shoulder junction of a .260 down, lengthening the neck.

As far as the 6.5 cm and .260 ai 30 degree being the same thing just longer or shorter, the 6.5 cm actually has a slightly larger diameter base, as in a properly spec'd .260 AI reamer would not clean up a 6.5 cm chamber without being set back. It is only slight, but they are different.
 

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