243 AI-Any Input?

[PathFinder]

I'm currently working on putting a 243 AI together on a Tikka. The plan is to hand ream a factory Tikka 243 20" threaded 1:8 barrel (already on hand) to 243 AI. It won't have the slightly shorter chamber of a typical AI, but I'll be starting with Alpha 260 brass so using a false shoulder to fireform will be pretty easy. Is it completely unreasonable to go to the 243 AI with the added cost of a reamer rental, fire forming, and more expensive dies? My reasoning for going to the AI is:

• Better brass life with little to no trimming. I despise trimming.
• ~10% capacity increase
  • Pushes it farther into slow powder territory (more on that below)
  • Velocity increase
• Use of H1000
  • Extended barrel life. Same idea as the 6 Comp Match and 6 SLR.
• The chamber needs more free bore anyways, may as well do both.
• The Alpha brass benefits from a fire form anyways, so that doesn't change much. I have lots of extra bullets and powder to do that with.

Basically the idea is to exceed 6 Creedmoor performance, but keep excellent long term barrel life. Even if I stick with the standard chamber, H1000 is going to be the powder of choice. Is the gain worth the time to ream the chamber, reamer rental, and more expensive dies?

 

[Bater]

Do it! I have never regretted any of my Ackleys and the 243 is quite possibly the raddest of the rad. The AI’s have an odd level of efficiency that is hard to explain and the 40° shoulders make trimming largely go away. My last build was a 260 AI using Alpha OCD, you will not be disappointed in that brass.

 

[sveltri]

Doing it right and setting back the chamber is the way to go. However, if you're not going to do that H1000 is ok H4831SC is better especially if going with a shorter barrel. What bullet are you planning on using?

 

[PathFinder]

Either the 115 DTAC or 112 Match Burner initially. The 109 ELD is an option too, but I'll test the 115 and 112 first.

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[Cahunter805]

I agree with above. You need to set it back if you’re going to go AI. If not you might run into problems sizing or excessive brass stretch/overworked issue.
That said the AI is a fun cartridge and H1000 is a great choice as is Retumbo.

 

[pods8 (Rugged Stitching)]

Will the necks need to be turned or will the reamer accommodate the 260brass necked down?

 

[xsn10s]

Instead of creating a false shoulder you could jam the bullet hard to keep in against the boltface. That's what i do with my 260 AI.

 

[PathFinder]

Will the necks need to be turned or will the reamer accommodate the 260brass necked down?

Not sure yet, but based on past experience going back and forth between 6/6.5 probably not.

 

[PathFinder]

Instead of creating a false shoulder you could jam the bullet hard to keep in against the boltface. That's what i do with my 260 AI.

That's another good option. I'm planning to do the false shoulder initially since the brass will be starting as 260 anyways.

 

[HandgunHTR]

Since you are handloading, having the chamber be a little long isn't an issue unless you want to sell it later.

Where I do have some advice, however is your plan to hand-ream. The AI reduces the body taper as well as putting a sharper angle on the shoulder, so it is going to take you a good while to hand ream as you have a good amount of metal to remove. To the point where you may get frustrated and want to use a drill, which could lead to over reaming really quick.

When I hand reamed a short chambered 7 Mauser barrel, I was only finishing the last 0.050" of the chamber, but it still took me about 2 hours and I am a very mechanical guy. I would assume that to clean up a regular chamber with an AI reamer you would be looking at 4-5 hours.

 

[PathFinder]

Since you are handloading, having the chamber be a little long isn't an issue unless you want to sell it later.

Where I do have some advice, however is your plan to hand-ream. The AI reduces the body taper as well as putting a sharper angle on the shoulder, so it is going to take you a good while to hand ream as you have a good amount of metal to remove. To the point where you may get frustrated and want to use a drill, which could lead to over reaming really quick.

When I hand reamed a short chambered 7 Mauser barrel, I was only finishing the last 0.050" of the chamber, but it still took me about 2 hours and I am a very mechanical guy. I would assume that to clean up a regular chamber with an AI reamer you would be looking at 4-5 hours.

That's what I figured about the length. My plan is to color in the shoulder area of the chamber after the body of the chamber is reamed out to diameter and the shoulder of the reamer starts to engage. Then slowly ream until all of the marker is gone. It may go over a few thousandths, but that should be ok. It's unlikely to ever be shot with any factory 243 ammo, only the Alpha brass that will be formed for it.

Thanks for the info on hand reaming. It sounds like it's a fairly common practice, but I couldn't find anywhere that said how long it takes. You are spot on about the drill, that already crossed my mind Hopefully I'll stay patient and go slow. Is a T-handle the best tool to use? I'm planning to clamp my barrel vise onto the side of a table vertically and ream with the barrel standing up.

 

[pods8 (Rugged Stitching)]

I didn't realize you were planning to hand ream this. What is the cost of the reamer rental and all versus just having a smith do it whom already has the reamer? I feel like this one might turn into a case of spend the extra $100-200 and not have the headache?

 

[Ramem7mm]

out of ignorance why are you starting with the 260 brass instead of lets say 243 lapua? I think I have an idea of why but curious the explanation from yourself.

I am on the search for a new 6mm and debating on 6 creedmoor which is an easy button or maybe a 243 AI

 

[PathFinder]

I didn't realize you were planning to hand ream this. What is the cost of the reamer rental and all versus just having a smith do it whom already has the reamer? I feel like this one might turn into a case of spend the extra $100-200 and not have the headache?

Cost of renting the reamer, gauges, and a throater is under $75. Mostly because I don't want to get told 6 months and the wait a year to get it back. I'm planning to get my own lathe soon, but this needs to be done ASAP. If a gunsmith were the only option, I'd leave it as a standard chamber.

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[PathFinder]

Two reasons. One, that's what Alpha makes. Two, it helps set up the false shoulder for fire forming.

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[pods8 (Rugged Stitching)]

I am on the search for a new 6mm and debating on 6 creedmoor which is an easy button or maybe a 243 AI

IMHO just go 6cm, it has lots of brass options and is turnkey. Unless you want a project.

Cost of renting the reamer, gauges, and a throater is under $75. Mostly because I don't want to get told 6 months and the wait a year to get it back. I'm planning to get my own lathe soon, but this needs to be done ASAP. If a gunsmith were the only option, I'd leave it as a standard chamber.

I bet kampfeld would be 1-2mo but point taken, keep us posted!

 

[Bater]

out of ignorance why are you starting with the 260 brass instead of lets say 243 lapua? I think I have an idea of why but curious the explanation from yourself.

I am on the search for a new 6mm and debating on 6 creedmoor which is an easy button or maybe a 243 AI

Isn’t Lapua 243 LRP? That’s why I went with Alpha in my 260 AI, SRP will last twice as long in my experience. When I build a 243AI it will be fed Peterson SRP

 

[PathFinder]

6 CM was the original plan, and if @hereinaz had any 18 or 20 inch prefits in stock I would have bought one weeks ago. May still end up with one in the next batch if this barrel doesn't work out.
The other reason is the ability to use H1000. It's more for barrel life than velocity. Basically testing if the claims from the competition crowd are right about a huge jump in barrel life with mid-capacity 6mms and H1000.
Plus 1:8 threaded 20" Tikka barrels are cheap and widely available.
I'm in a bit of a hurry and impatient if you can't tell The rifle I was going to hunt with didn't end up doing what I wanted, so now I'm in a pinch getting something else ready.

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[pods8 (Rugged Stitching)]

Isn’t Lapua 243 LRP? That’s why I went with Alpha in my 260 AI, SRP will last twice as long in my experience. When I build a 243AI it will be fed Peterson SRP

Have you had any issues in cold temps with the SRP? Seem to recall a few folks have.

Basically testing if the claims from the competition crowd are right about a huge jump in barrel life with mid-capacity 6mms and H1000.

Do it for science! Report back.

 

[Karl B]

H1000 in the .243 case is magic. I've considered 6 creedmoor before but can't come up for a valid reason being a handloader.

Different but similar, I recently did a 6x284 on a factory 8tw tikka barrel and the false shoulder is more consistent for forming than just jamming the bullets. At least it has been for me. With jamming I always got some pieces that didn't fully form vs the false shoulder that all came out perfect. Good luck on your project. I've got a set of .243ai dies on the bench that have been staring me in the face for years now that I probably need to put into use at some point. Looking forward to seeing your results.