.243 to .243 ackley
- Thread starter Bro.D
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Cheechako
Guest
Bro
It's not that simple. A correct Ackley Improved chamber is made by setting the barrel back one thread and re-chambering so that a standard 243 cartridge is a crush fit. That is what gives the necessary headspace control while fire-forming. Otherwise the cases will stretch upon firing leading to possible seperations.
Before going ahead, think about this. The 243 Ackley Improved offers virtually no gain over the standard 243 W. The shoulder on the 243 W is already the maximum diameter so the only change is increasing the shoulder angle from 20 degrees to 40 degrees. This may look snazzy but it doesn't do much to improve the ballistics.
JMHO
Ray
It's not that simple. A correct Ackley Improved chamber is made by setting the barrel back one thread and re-chambering so that a standard 243 cartridge is a crush fit. That is what gives the necessary headspace control while fire-forming. Otherwise the cases will stretch upon firing leading to possible seperations.
Before going ahead, think about this. The 243 Ackley Improved offers virtually no gain over the standard 243 W. The shoulder on the 243 W is already the maximum diameter so the only change is increasing the shoulder angle from 20 degrees to 40 degrees. This may look snazzy but it doesn't do much to improve the ballistics.
JMHO
Ray
I hear
what you are saying about the advantage but, as they say, this is what the customer wants. I do agree though that brass life will be longer, this is somewhat an advantage.
So, what I'm hearing you say is push the reamer in about .0625 and this will clean everything up and then set the shoulder back and set the headspace to a crush fit (.004 short)? Thanks, Bro.D
what you are saying about the advantage but, as they say, this is what the customer wants. I do agree though that brass life will be longer, this is somewhat an advantage.
So, what I'm hearing you say is push the reamer in about .0625 and this will clean everything up and then set the shoulder back and set the headspace to a crush fit (.004 short)? Thanks, Bro.D
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Ackman
Guest
You'll want to set the barrel back far enough to cut a complete new chamber including neck/throat and web. Then make sure the new chamber is short enough to have plenty of "crush." The standard number thrown around is .004" but that's nowhere near enough. Brass can vary that much within the same headstamp and twice that much between different headstamps. Set it up with .010"-.015" crush. That sounds like too much but it really isn't. Case contact is only at the neck/shoulder junction radius and it won't feel like a lot on the bolt handle.
It's true the .243 is semi-improved already and that the AI version doesn't blow the case out as much as some other AI's. But to say there's "virtually no gain" is just not true. The simple answer is that a 243AI can shoot 70's the same velocity as a std. 243 will shoot 60's. That's a gain. In real life....the accuracy load in one of my 243AI's is a 70BT at 3746. In another one the accuracy load is a 70TNT at 3858. A std. 243 won't do that.
It's true the .243 is semi-improved already and that the AI version doesn't blow the case out as much as some other AI's. But to say there's "virtually no gain" is just not true. The simple answer is that a 243AI can shoot 70's the same velocity as a std. 243 will shoot 60's. That's a gain. In real life....the accuracy load in one of my 243AI's is a 70BT at 3746. In another one the accuracy load is a 70TNT at 3858. A std. 243 won't do that.
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.243 to .243 Ackley
Before you do this, you need to check the neck diameter of the reamer versus the neck size of the factory chamber. It is rare for a custom .243 Ackley reamer to be ground with as large a neck diameter as most factory chambers. If the reamer neck is smaller than the present chamber neck, your barrel setback needs to be at minimum equal to the neck length or there will be a step in the neck which will leave a ridge on the brass.
Back in years gone by, military rifle team gunsmiths set back barrels one or two turns and rechambered them with a "Match" reamer. Most of them had a step in the chamber neck but the service team members were not bothered in the slightest because the rifles shot great and none of the military teams reloaded. Things have changed a lot since then.
Scott Roeder
Before you do this, you need to check the neck diameter of the reamer versus the neck size of the factory chamber. It is rare for a custom .243 Ackley reamer to be ground with as large a neck diameter as most factory chambers. If the reamer neck is smaller than the present chamber neck, your barrel setback needs to be at minimum equal to the neck length or there will be a step in the neck which will leave a ridge on the brass.
Back in years gone by, military rifle team gunsmiths set back barrels one or two turns and rechambered them with a "Match" reamer. Most of them had a step in the chamber neck but the service team members were not bothered in the slightest because the rifles shot great and none of the military teams reloaded. Things have changed a lot since then.
Scott Roeder
You've gotten some good info here......
I'll add my vote for leaving it alone, there is NO-ZERO-NADA "added brass life" and no significant velocity gain.... (anyone who claims great velocity gains simply hasn't loaded the standard .243 up to the same pressure!)
Also, this whole "I'll push the reamer in about .0625 and this will clean everything up and then set the shoulder back and set the headspace to a crush fit (.004 short)?" sounds like you really do not get it yet??? I'm guessing this is a factory barrel?
FIRST OF ALL you've got to go at least one full turn to get the lettering (and sights??) indexed and this may not be possible depending on how it's threaded......
Then you've got to "push the reamer" whatever it takes to get a solid crush-fit on all types of brass. As Ackman says, ".004 ain't nearly enough!!" You'll find it to be something more like 8 to 12 thou UNDER a .243 Go Gauge.... or maybe even 15 thou! (I've never seen one THIS short but evidently Ackman has.....)
Good Luck
al
I'll add my vote for leaving it alone, there is NO-ZERO-NADA "added brass life" and no significant velocity gain.... (anyone who claims great velocity gains simply hasn't loaded the standard .243 up to the same pressure!)
Also, this whole "I'll push the reamer in about .0625 and this will clean everything up and then set the shoulder back and set the headspace to a crush fit (.004 short)?" sounds like you really do not get it yet??? I'm guessing this is a factory barrel?
FIRST OF ALL you've got to go at least one full turn to get the lettering (and sights??) indexed and this may not be possible depending on how it's threaded......
Then you've got to "push the reamer" whatever it takes to get a solid crush-fit on all types of brass. As Ackman says, ".004 ain't nearly enough!!" You'll find it to be something more like 8 to 12 thou UNDER a .243 Go Gauge.... or maybe even 15 thou! (I've never seen one THIS short but evidently Ackman has.....)
Good Luck
al
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frwillia
Guest
I was following and pretty much understanding it till here. Why can't a .243AI Go-Gage be used?
Fitch
I suppose somewhere, somebody makes a ".243 Ackley" go gauge. But one design parameter of Ackley chambers is you can fire factory rounds in them, and they are designed to be fitted (headspaced) with the standard gauges.
Al may comment on this, but the "real" problem with the standard (Winchester factory) .243 probably isn't so much the shoulder angle, but the freebore/throat numbers. Compare them against a standard (Remington factory) .244.
If that's correct, tighten them up and much of the barrel life issues of the .243 disappear. And keep them the same, with the only change an Ackley shoulder, and barrel life will only get worse.
As for brass life, shorter case life is usually a die/use of die issue. And of course pressure & its effect on primer pockets, which the Ackley doesn't address.
Of course, you can't tell this to a customer who only watches the "what some guy said" channel.
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frwillia
Guest
Yup. For sure PTG does. Go and no-go gages both. They are listed here:
http://www.midwayusa.com/Search/Default.aspx# gage .243 Winchester Ack____-_1-2-4_8-16-32
The go-gage is the third one down the list, at least it was when I did the search.
I don't have any indispensible ego attached to this. I'm just trying to make sense of what I'm reading, to understand it and maybe learn something.
PTG's gage, if it is properly made, should take care of that and reduce all SWAG crush numbers to a repeatable process. I can't imagine it wouldn't be properly made, Kiff would heat cherry red, beat it flat, and throw it out himself if it wasn't. This thread contains crush numbers from 0.004" to 0.015" - that's almost a factor of 4. That seems like a lot of range for something that ought to be reduced to practice by now.
So, why not use the go-gage? If it doesn't work, work with PTG to get them to make one that does and get on with it. Then it can be done the same every time.
Some good points.
I'm not debating the .243AI vs .243Win thing. I just bought a PTG reamer to do a barrel in .243Win and intentionally did not buy the AI reamer.
The reamer I got from PTG has a throat that is ~.034" shorter and a neck that is 0.001" tighter than the Savage factory chamber had as I recall. I didn't order it that way, that's how they made it - and I like it. I think I posted a dimensional comparison between the factory chamber and the one I reamed. The chamber is headspaced so there is very little difference between FL sized brass and fired brass. But the bolt closes freely on FL sized brass or factory ammo. Hopefully this will at least give me better brass life.
I suppose there is some non-zero but very small probability this will also help with barrel life, but if it doesn't, I can live with it.
Fitch
A .243AI Go-Gauge "can" be used but it isn't necessarily the best way. Your reasoning is good, or would be in MOST cases where an item gets "standardized" over time. The problem inherent to the whole thing is that the initial fireform headspace is set on a tiny portion of the neck/shoulder junction and it is such that even a slight change in neck diameter changes the "headspace." IMO you need not only to chamber to your choice of brass but also to chamber such that you have to just bump the new cases........ these operations have the added benefit of leaving you as short a gap-space as is possible.
AI's have got a real problem with pulling back at the neck.... ANYTHING you can do to jam that corner helps to make better brass. The whole AI concept is flawed for producing rifles of target accuracy but if you insist on it then you must take steps to produce as straight as possible cases. The biggest step IMO is to absolutely ensure a tight JAM on the n/s junction for the fireform process.
Next problem to surmount will be how to maintain that brass over time, how to size it. How to get that long 40* shoulder to compress straight back.
Now at this point someone's no doubt going to jump in with "THE .243AI HAS WON IT'S SHARE!!!!!!......" which is true. So has the 6x.284.......
But watch closely NOW as they're both supplanted by better rounds.
IMO even the bone-stock .243 built to Match standards is a better round.
al
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Big Al
Guest
Why not talk the guy into a re-chamber to a ctg with a longer/better neck? If I was going to do one, I would set the barrel back and go to the .244/ 6mm Remington and call it good. I'm not a fan of short necks, but thats just me.
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frwillia
Guest
Thank you sir. That explains a lot. I had wondered if there was a downside to the AI concept, you just pointed it out.
Good thread.
Fitch
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thorp
Guest
You are mistaken.
In Fact, the .243 Ackley is a big improvement over the standard .243. I have both and the ackley rifle shoots lights out and is around 300 fps faster. The Ackley cartridge holds 2 grains more powder than my standard .243.
In Fact, the .243 Ackley is a big improvement over the standard .243. I have both and the ackley rifle shoots lights out and is around 300 fps faster. The Ackley cartridge holds 2 grains more powder than my standard .243.
Boyd Allen
Active member
On the Ackley heaspace thing, a friend had a .22-250 AI built that was undoubtedly headspaced using an AI gauge. He had had two different brands of factory ammo in large quantities that he intended to fire to make his cases, Remington and Winchester I believe. When he got to the range and started fire forming he found that one brand (I forget which) fired every time, and the other had a lot of failure to fires. It turned out that the difference was their head to shoulder dimensions. One was significantly longer than the other. With full shoulder contact I do not think that this would have mattered, but with the AI chamber only contacting at the neck shoulder junction the problem occurred. If I were going to build an AI I would buy one brand of brass in a large quantity, enough to take care of my needs for a long time, and measure a large sample of the cases, and then choose one to use as a GO gauge, so that with the shortest case, I would still have some feel. I know that the problem with this approach would be that I might not be able to bump the shoulders of cases without shortening a shell holder slightly, but they are inexpensive and that is easily done.
So what is the gain-velocity.
so what is the loss-about 10-15% more powder, more recoil, more barrel wear(burning)??
How far do you want to shoot?? Maybe another gun (caliber) would be as good/better than AI.
In my case and other shooters Ive talked w/ recently we seem to think that a load of 85-90% max is more accurate than 95-105% of listed loads.
so what is the loss-about 10-15% more powder, more recoil, more barrel wear(burning)??
How far do you want to shoot?? Maybe another gun (caliber) would be as good/better than AI.
In my case and other shooters Ive talked w/ recently we seem to think that a load of 85-90% max is more accurate than 95-105% of listed loads.
243 Win or something faster
I really like the 243 Win. I also like the 243 AI. But if your going from the 243 Win to something faster, I suggest the 6mm Remington Ackley Improved or the 6mm/284. To convert a factory barrel. From 243 Win to Ackley Improved is a waste of money.
Rustystud
I really like the 243 Win. I also like the 243 AI. But if your going from the 243 Win to something faster, I suggest the 6mm Remington Ackley Improved or the 6mm/284. To convert a factory barrel. From 243 Win to Ackley Improved is a waste of money.
Rustystud
I use 6 mm REM AI for longer ranger varmint shooting.
I also use tight neck chambers requiring turning shells.
I had Kelbly put the rifle together with R-bolt, L-port Panda action.
Heavy barrel, 26 inch.
The Redding bushing dies with the sleeve can easily be altered.
The sliding sleeve is not hardened and can be cut with the AI reamer to make up a die set.
The 'body die' is not hardened either and can be modified to AI.
It does very well with plenty of longer range first shot kills on groundhogs from a portable shooting bench on bags and front rest.