My Ackley Improved Adventure

[dlutter]

I just wanted to share my experience in case it might help someone interested in AI cartridges.

I have had a .338-06 AI for about a year. It is my first foray into the non-factory chambered cartridges. I also want to note that, though I had help from various internet forums including this one, I know no one personally with Ackley Improved experience. There were some people who were very right in their advice and some who were very wrong. Also there are more than two ways to do things.

To form the cases I necked up new Nosler .30-06 brass to .338 in one step in my .338-06 AI full length sizer die. Then I used 200 gr Accubonds and 225 gr Interbonds with published middle of the road loads of H380 for a regular .338-06. Bullets were seated 0.020 inches off the lands. When I fireformed, all cases had beautiful shoulders but some would have flattened primers, some would have primers slightly pushed out, and a few formed cases would be normal. ??? Primers were much easier to seat in most of the cases, though I wouldn't call the primer pockets loose. :-\

Here is what I learned that may account for my primer difficulties:

1. When necking up the original brass I must have run some of the cases all the way into the full length die, thus setting the shoulder back and creating a head space problem. I think this accounts for the slightly pushed out primers.

2. Even though the H380 load was from published data, I believe it is much too fast a powder to be used in this case. I think I created a high pressure situation, which accounts for the flattened primers. For those wondering why I used H380, my .22-250 doesn't like it so I had it to burn.

I have since fireformed new cases(necked up with the necksizing die) with the same bullets plus 200gr Speers and IMR 4350. I had no primer issues and the cases formed nicely.

Here as some other things I have learned in my Ackley Improved Adventure:

1. Even though you can go directly from 30 caliber to 338 caliber, I think you will get more consistent case necks if you take an intermediate step of necking up to 8mm. I haven't done this yet but I have some cases with crooked necks due to the uneven pressure from the expander ball.

2. You really should have a chronograph when finding max loads for you wildcat/improved cartridge. There is no way you can go by the rule that AIing you cartridge adds x%(I have heard between 3 and 6% for the .338-06). You can go from a normal fired case to a blown primer in less than a grain of powder. I think individual guns vary too much and brass varies too much between manufacturers and lots. Start a grain or two below max with published data if you can find it and work up in 0.5 grain increments or even 0.3 gr once you get towards the top. I load one round per powder weight up to my set limit. I don't have a chronograph yet, so after one blown primer I am limiting myself to 1.5 gr over published max in the unimproved cartridge until I save up. That works out to about a 2% increase for me.

3. Unless you have a good amount of first hand experience with someone, you never really know who's advice to believe. There are many experienced people who are "right" about alot of things. That doesn't mean they are "right" about your gun/cartridge. By all means, ask questions and learn from others but take everything with a grain of salt. Most importantly, try get to know someone with experience in what you are doing(like I didn't). If you don't have that opportunity(like me), these forums are great. Just be smart.

I will try to post any other info I find interesting as I stumble along. Hopefully this is useful to someone. Thank you all for previous and future help.

Dylan

 

[BHarvey]

I found that going to AI in the same cartridge required me going to a lower powder. For instance....


260- 47 grs of H4831SC gave 2750 fps.
260AI- netted over 2850 fps with the same charge, and a 1" shorter barrel.
(Used the same barrel, just cut tenon off and re-chambered)

Same results with lots of other powders I had chronoed in the 260.
The sharper shoulder does indeed seem to either burn the powder more efficiently, or bring about a faster pressure peak that gives the extra velocity.

 

[flatlander]

I'll wager that once you've saved enough to purchase a good chrono, and gotten used to having the data it provides, you'll wonder how you ever got along without it. I bought a used M33 Oehler from a friend back in '86 when we got into IPSC pistol shooting and needed to know whether our loads were making major power factor. Since then, I've built rifles for AI versions of 250, 6.5x55, & 280, plus several 6 Dashers. Though Sierra's 5th edition loading manual gives data for several AI cartridges, you're still pretty much on your own when it comes to fireforming & working up loads.

I feel having a good, reliable & accurate chrono is also very beneficial when testing new lots of powder & primers, as well as for comparing different brands of primers. I'll set up a chrono more often than not when shooting off the bench at 600-1000, even when I've already got chrono data for the load being fired. It's always interesting - and sometimes educational - to get additional data for a known load whether conditions are different or not. And it's always helpful to have chrono data when you get unexpected results, whether on target, or in the pressure signs on fired cases.

 

[Rust]

I've always fireformed new brass seating the bullets into the lands with a fair amount of neck tension. There can be some pretty large variances in the base to shoulder dimensions in fresh brass, and if it's on the short side the case can sort of bounce around in the chamber otherwise. Protruding or flattened primers can result.