260 AI

[Kevin11mee]

Greetings all. I recently built a 260 AI on a R700 short action and I'd like to get any info on load data that anyone has for this cartridge. I do have a pretty good load with the Barnes 127 LRX around 3000 FPS (H4350) but need to tune seating depth to tighten groups a bit. I'm looking to shoot either the 147 ELDM or the 143 ELDX. Berger 140 and 135 are also available but I don't like that they are so difficult to find. Also, what length are you trimming brass (Lapua .260 Rem)? After fireforming, cartridge length is about 2.013-2.014 which is shorter then .260 Rem trim length of 2.025.

 

[Wind Gypsy]

Trim length on an AI should be the same as the parent cartridge unless your reamer used a different case length.

 

[Addicting]

Greetings all. I recently built a 260 AI on a R700 short action and I'd like to get any info on load data that anyone has for this cartridge. I do have a pretty good load with the Barnes 127 LRX around 3000 FPS (H4350) but need to tune seating depth to tighten groups a bit. I'm looking to shoot either the 147 ELDM or the 143 ELDX. Berger 140 and 135 are also available but I don't like that they are so difficult to find. Also, what length are you trimming brass (Lapua .260 Rem)? After fireforming, cartridge length is about 2.013-2.014.

Use Lapua 243 brass in the future, it will give you more neck.

N555 is pure magic in the that cartridge. There are several post on here from me and @p_ham on it. I am running that 127lrx at 3150 with N555.

 

[Kevin11mee]

Use Lapua 243 brass in the future, it will give you more neck.

N555 is pure magic in the that cartridge. There are several post on here from me and @p_ham on it. I am running that 127lrx at 3150 with N555.

Ok. Forgive my ignorance but how do you fireform with a .264 bullet? Resize neck first?

 

[Kevin11mee]

Trim length on an AI should be the same as the parent cartridge unless your reamer used a different case length.

The problem is the fire formed brass is shorter than .260 REM trim length of 2.025.

 

[Addicting]

Ok. Forgive my ignorance but how do you fireform with a .264 bullet? Resize neck first?

I run a .264 mandrel in the neck, and then use the cream of wheat method to get a case ready to load.

As far as trimming cases, there’s really no need in the Ackley once it’s fire formed. If you want to get deep in the weeds and make them all the same length you can. In my experience, it hasn’t been worth it for a hunting rifle.

 

[ImBillT]

You don’t NEED the neck length. I’d stick with 260 brass if it was mine. Being a little short isn’t going to hurt anything.

 

[Kevin11mee]

I run a .264 mandrel in the neck, and then use the cream of wheat method to get a case ready to load.

As far as trimming cases, there’s really no need in the Ackley once it’s fire formed. If you want to get deep in the weeds and make them all the same length you can. In my experience, it hasn’t been worth it for a hunting rifle.

Ok. Thanks

 

[MTGunner]

I have necked up .243 Lapua brass to .260 and fire formed successfull. I load 120 grain BT and 130 grain VLD. Both shoot extremely accurate out of my 260 AI, 24” Lilja, SS bbl. This is on a Rem. 700, Mountain rifle platform. It has accounted for many a critter.
I have loaded 107 grain Sierra SMK for long range shooting targets. Another very good projectile. Mostly I load H4350. MTG

 

[p_ham]

I run a .264 mandrel in the neck, and then use the cream of wheat method to get a case ready to load.

As far as trimming cases, there’s really no need in the Ackley once it’s fire formed. If you want to get deep in the weeds and make them all the same length you can. In my experience, it hasn’t been worth it for a hunting rifle.

Rather than the COW method, I prefer to load up varmint bullets over IMR4064. I get trigger time that way and they consistently group in the .3-.4 MOA range for me.

@Kevin11mee like @Addicting said N555 is magic in this cartridge. It does really well in the 130 class bullets. H4350 and RL26 do well in the 140 class.
Personally I would stick with the 127LRX over anything Hornady makes. If you want cup and core go to Nosler or Sierra.
Hammers are hard to hold onto unless you start with 243 brass and hit them with a Lee FCD.

 

[Kevin11mee]

Rather than the COW method, I prefer to load up varmint bullets over IMR4064. I get trigger time that way and they consistently group in the .3-.4 MOA range for me.

@Kevin11mee like @Addicting said N555 is magic in this cartridge. It does really well in the 130 class bullets. H4350 and RL26 do well in the 140 class.
Personally I would stick with the 127LRX over anything Hornady makes. If you want cup and core go to Nosler or Sierra.
Hammers are hard to hold onto unless you start with 243 brass and hit them with a Lee FCD.

Yea, I like to shoot so I usually shoot matchburners.

 

[Wind Gypsy]

The problem is the fire formed brass is shorter than .260 REM trim length of 2.025.

If case length is below the trim length that means you don't have to trim it.

 

[Wind Gypsy]

Use Lapua 243 brass in the future, it will give you more neck.

N555 is pure magic in the that cartridge. There are several post on here from me and @p_ham on it. I am running that 127lrx at 3150 with N555.

Does necking up ever result in thicker brass (donuts) where the shoulder becomes neck?

 

[Addicting]

Does necking up ever result in thicker brass (donuts) where the shoulder becomes neck?

It can and has for me in the past. I turn my necks if I notice it. Not all of them do it and I don’t know why some lots do and some don’t.

I went down last night and checked my brass and this last batch is all 260, not turned, and measured 2.018. Thought they were all 243 but I must of cycled thru those.

 

[Kevin11mee]

I use .260 Rem brass (Lapua) to fireform and it measures 2.013 after fireforming. What is the advantage of using .243 brass?

 

[Wind Gypsy]

I use .260 Rem brass (Lapua) to fireform and it measures 2.013 after fireforming. What is the advantage of using .243 brass?

You get a longer neck. How important that is, I'm not experienced/qualified to say.

 

[MTGunner]

Even with the longer neck it is not an issue to chamber. If necessary necks can be trimmed to length required. I anneal after two firings to avoid work hardening the brass. For that matter each and every caliber that I load gets same treatment. Brass life is essential and brass has gotten darn expensive. MTG

 

[Addicting]

You get a longer neck. How important that is, I'm not experienced/qualified to say.

It matters when you shoot certain bullets and if you have a deep throated chamber where you can seat bullets far out. Hammers need every thousandth it can get.

 

[Kevin11mee]

It matters when you shoot certain bullets and if you have a deep throated chamber where you can seat bullets deep. Hammers need every thousandth it can get.

Makes sense

 

[Don Fischer]

Greetings all. I recently built a 260 AI on a R700 short action and I'd like to get any info on load data that anyone has for this cartridge. I do have a pretty good load with the Barnes 127 LRX around 3000 FPS (H4350) but need to tune seating depth to tighten groups a bit. I'm looking to shoot either the 147 ELDM or the 143 ELDX. Berger 140 and 135 are also available but I don't like that they are so difficult to find. Also, what length are you trimming brass (Lapua .260 Rem)? After fireforming, cartridge length is about 2.013-2.014 which is shorter then .260 Rem trim length of 2.025.

Think about it a bit, if the cartridge length is shorter than the trim length, the bullet tip will be inside the case! Looking in my Hornady manual the trim length for the 260 is 2.025. The COL is 2.800! Need to rethink this a bit! Are you saying after firing the case length is 2.013-2.014? Case length and cartridge length are two different things. Probably case length of 2.014 would be fine and as the case is fired and resized it will grow. My thought is probably resizing then firing your blowing out the case walls some and when doing that pulling back the neck a bit. The shoulder will go ahead and fill out the chamber. Just might result in a bit shorter COL! if you take a 260 case and fire it in a 260 chamber, firing will srtetch the case a bit to fill the chamber. Then the neck would get pushed forward and at some point need trimming. Think you'll find that now when you fire these case's again the cace will already fit the chamber much better so rather than pull the neck firing by expanding the case walls, it will push the neck a bit. result is the case will grow a bit!