Factory 260 ammo in a 260 AI chamber?

[Kansas91]

I've got a 260 AI barrel and heard of folks using factory loaded 260 rem ammo to get their fire formed cases. Will this work? Is it safe? I'm pretty reluctant to try this, but want to ask the experts to see if this is possible or what's the best way to fire form for the 260 AI? Thanks!!

 

[Eddie Harren]

That's exactly how P.O. Ackley designed them to be made. AI shooters have been doing this for years.

 

[Sniper338]

load and shoot. that what its made to do

 

[Sheldon N]

With the cost of factory 260 ammo, you'll do far better buying some nice Lapua brass and loading your own standard 260 rounds to shoot and fireform. You'll likely find that your fireforming rounds can actually shoot quite well. You can work up an accurate load for fireforming that will let you get some shooting practice in.

Plus, then you end up with fireformed Lapua brass instead of something of lesser quality.

 

[savagedasher]

Changing from a 260 to a 260AI I had to seat the bullets in the lands. That is dependent on how the head space is set. Larry

 

[Brians356]

It depends an who chambered the AI. According to Ackley's method, they are supposed to chamber it to the No-Go 260 Rem gauge (i.e about .010" shorter than normal, or so that the bolt barely closes on the No-Go) so that there is a slight crush fit (a bit of bolt resistance when you chamber a factory round) resulting in zero headpace* when you fire the SAAMI round. (* Keep in mind it is not going to "headspace" on the shoulder at all, but only at the neck/shoulder junction!)

My 250 AI was not properly short chambered, and firing factory ammo does not create a nice sharp shoulder for me - the round is rattling around in the chamber. Yikes! Plus not all factory loads are as "hot" as they could be for fireforming. Finally, some loaded brass is not as soft as most new unfired cases.

Alternatively, you can take some good 260 Rem or even 243 brass and fire form "bulletless" w/ about 12-15% of a normal powder charge weight of very fast powder like Bullseye and a pistol (important!) primer. I have used inert filler (corn grits), tissue wad, wax neck plug etc. but if you use 15% charge weight and simply hold the rifle vertically when you fire it (so the powder sits in the head of the case) you don't really need all that claptrap.

 

['Freak]

It depends an who chambered the AI. According to Ackley's method, they are supposed to chamber it to the No-Go 260 Rem gauge (i.e about .010" shorter than normal, or so that the bolt barely closes on the No-Go) so that there is a slight crush fit (a bit of bolt resistance when you chamber a factory round) resulting in zero headpace* when you fire the SAAMI round. (* Keep in mind it is not going to "headspace" on the shoulder at all, but only at the neck/shoulder junction!)

My 250 AI was not properly short chambered, and firing factory ammo does not create a nice sharp shoulder for me - the round is rattling around in the chamber. Yikes! Plus not all factory loads are as "hot" as they could be for fireforming. Finally, some loaded brass is not as soft as most new unfired cases.

...

Shouldn’t that 260 Remington Ackley Improved be chambered such that the bolt will just barely close on the standard 260 Remington “GO Gauge” which corresponds to the SAAMI minimum head to shoulder datum length; instead of the stated “NO-GO” Gauge on which if the bolt will close, it’s gonna leave a factory loaded 260 Remington round a rattling around inside of a chamber that’s been cut real close to the SAAMI maximum head to shoulder datum length?

 

[KRP]

Parent cartridge go gauge becomes the no-go for an Ackley chamber. A no-go gauge is longer than a go gauge and shouldn't chamber, hence the no-go.

 

[Geno C]

Parent cartridge go gauge becomes the no-go for an Ackley chamber. A no-go gauge is longer than a go gauge and shouldn't chamber, hence the no-go.

This is correct. A no-go is longer.

 

[Brians356]

It depends an who chambered the AI. According to Ackley's method, they are supposed to chamber it to the No-Go 260 Rem gauge (i.e about .010" shorter than normal, or so that the bolt barely closes on the No-Go) so that there is a slight crush fit (a bit of bolt resistance when you chamber a factory round) resulting in zero headpace* when you fire the SAAMI round. (* Keep in mind it is not going to "headspace" on the shoulder at all, but only at the neck/shoulder junction!)

My 250 AI was not properly short chambered, and firing factory ammo does not create a nice sharp shoulder for me - the round is rattling around in the chamber. Yikes! Plus not all factory loads are as "hot" as they could be for fireforming. Finally, some loaded brass is not as soft as most new unfired cases.

...

Shouldn’t that 260 Remington Ackley Improved be chambered such that the bolt will just barely close on the standard 260 Remington “GO Gauge” which corresponds to the SAAMI minimum head to shoulder datum length; instead of the stated “NO-GO” Gauge on which if the bolt will close, it’s gonna leave a factory loaded 260 Remington round a rattling around inside of a chamber that’s been cut real close to the SAAMI maximum head to shoulder datum length?

Yes, I got the gauge designations wrong (dyslexia?). It needs to barely close on the "Go" gauge which (if I am now back on track) is the shorter of the two gauges. Thanks to all for the gentle correction.

 

[ShootDots]

It is true that P.O. Ackley designed the improved versions to be made by fireforming from factory ammo. Having said that, there are better ways of doing it. I use a "relatively mild load" with a V.L.D. bullet jammed 15-20K into the lands. This holds the base of the cartridge against the bolt face allowing for proper headspacing after fireforming. With properly tailored fireforming loads, you can shoot "High-Master" F-Open scores at 300 yards.

 

[Brians356]

It is true that P.O. Ackley designed the improved versions to be made by fireforming from factory ammo. Having said that, there are better ways of doing it. I use a "relatively mild load" with a V.L.D. bullet jammed 15-20K into the lands. This holds the base of the cartridge against the bolt face allowing for proper headspacing after fireforming.

The bullet will hold the base against the bolt face while the pin strikes the primer, which is good. But once the pressure expands the neck (rather soon) and releases the bullet, if there is not a crush fit at the neck-shoulder junction, it is not an ideal scenario. It may still form the case satisfactorily. In my "long" AI chamber, I noticed some lopsided stretching (thinning) in the usual place ~0.2" from the bottom of the body. If the case had been better held in place by a crush at the neck/shoulder junction, it might not have stretched noticeably. After that I switched to "bulletless" and lightly lubed the cases. The stretching was reduced, and became more uniform around the circumference. I assume the very quick/sharp impulse from the Bullseye was a positive factor. (These random thoughts brought to you from what passes for my mind.)

 

[KRP]

I would not want the bolt to close on the parent cartridge go gauge(it's now the no-go for the Ackley chamber remember)...especially not if I intended to shoot factory ammo.

 

[Brians356]

I would not want the bolt to close on the parent cartridge go gauge(it's now the no-go for the Ackley chamber remember)...especially not if I intended to shoot factory ammo.

Fair enough, and that makes sense. What Ackley must have stipulated was making a new AI Go gauge which was .010" (?) shorter than the parent Go gauge, and using the old Go as the new No-Go as you stated. And if anything, barely closing on the new Go would be better than splitting the difference. Thanks for the correction.

 

[Northridge]

There are two ways to approach this situation. First if I am building a rifle and client wants to use factory 260 brass and they have limited experience I will use a ackley go gauge which will cause a light crush fit on non formed brass. I like this application because it holds brass while fire forming & for liability reasons I prefer this method. If it is a 260 that someone all ready has chambered but wants to turn in to a ackley I will clean Up chamber with 260 ackley reamer but at this point a crush fit is out of the question as the 260 is a few thousands longer at body shoulder junction. In this situation running bullets a bit long to hold case in position while fire forming is your only safe option. I would use caution when using factory ammo as more than likely bullets will not engage lands at all and depending on chamber specs you may cause hangovers etc. the sammi spec 260 ackley is the shorter version as is the 260 ackley brass being produced. The original ackley version is slightly improved over sammi version.

Shawn williams

 

[Northridge]

Correction a few thousands longer at neck shoulder junction.

 

[KRP]

I would use caution when using factory ammo as more than likely bullets will not engage lands at all and depending on chamber specs you may cause hangovers etc. the sammi spec 260 ackley is the shorter version as is the 260 ackley brass being produced. The original ackley version is slightly improved over sammi version.

Shawn williams

I didn't realize there was a sammi(SAAMI?)version of the 260 Ackley or that brass was available. I've never had a hangover from an Ackley chamber...MGD is pretty much a guarantee though.

 

[Brians356]

I would use caution when using factory ammo as more than likely bullets will not engage lands at all and depending on chamber specs you may cause hangovers etc. the sammi spec 260 ackley is the shorter version as is the 260 ackley brass being produced. The original ackley version is slightly improved over sammi version.

Shawn williams

I didn't realize there was a sammi(SAAMI?)version of the 260 Ackley or that brass was available. I've never had a hangover from an Ackley chamber...MGD is pretty much a guarantee though.

And I never realized 260 Ackley brass was being produced. By whom?

 

[Sheldon N]

I bet he's thinking of the 280AI and Nosler brass.

 

[savagedasher]

When I had my 260 AI made the head space was too long for shooting factory loads.
I did the same process as I do with my dashers. Seat the bullet long and fire forum.
What a great cartridge does every thing a 284 does but with less powder an double the barrel life . Larry