I've lurked for a while but this is my first post here. I've fallen in love with a CZ 550 mannlicher in 6.5 x 55 swedish. I've seen a few references here to an ackley improved version of this cartridge. The problem is I can't find hardly anything on the web about it. Can anyone post some ballistics, comments, sites for reloading dies, brass etc? Thanks for the help. What sort of gain will this give over the standard cartridge.

The 6.5x55AI was designed by Bob Jourdan, or at least the most popular version of the AI swede anyways! Ackely himself never thought it was worth the time to do it. However it has been getting more and more popular among the competitive shooting sports.

BJ does some writing for Precision Shooting magazine. I think the first time he wrote about the swede was in 92 sometime?? Maybe someone else can help out on that. In July 2003 he wrote more of a general article on the ackleys. This is what it says about the swede.

Standard ackley, factory load, 140 gr=2550fps
6.5x55BJAI, 140 grain=2900fps
Thats a 13.7% gain. And ranks #4 among top percentage gain ackleys behind the .25-35WCF, .30-40 Krag and .250 Savage versions.
(That is percentage gain of ackley version over the standard factory loading.)

I too have contemplated building a swede ackley. Agreed that data isnt the easiest to find. A good starting point would be standard swede data and work your way up from there. Brass is made by fireforming standard brass into the ackley chamber, then use AI dies for reloading.

Hope this helps.

I have never worked with a 6.5X55 AI, but have worked with other improved cartridges, and a stock 6.5X55.

Studies have been done that show it takes an increase of 4% powder capacity to increase velocity by 1%. If you gained 8% with an ackley chamber, then you can expect a 2% increase in velocity, which means a std chamber velocity of 2500 fps will increase 50 fps, and a std chamber velocity of 3000 fps will increase 60 fps.

Where has all the magic increased velocity in the ackley chamber come from? It comes from running higher pressures, in some cases, very high pressures. The 6.5X55 is loaded to low pressures in defference to the over 100 year old rifles that were made in actions that can't handle modern high pressures.

The CZ-550 action can handle modern high pressures, so long as you don't have an M-96 swede that a high pressure round could land in, you can load the stock 6.5X55 within 50 fps of the ackley.

If you're going to the trouble and expense of re-chambering, you might as well go with a case that has a signifigant increase in case capacity. My suggestion would be the 6.5X284. There is lots of data for this round, and superb brass and dies are available. For the same cost as re-chambering to the ackley, why not go for a bigger chamber still?

I had a bit of a brain fart. A 6.5X284 won't clean up a 6.5X55 chamber. Still, if you're going to re-chamber, go with a round that has a signifigant increase in case capacity. Perhaps a 6.5-06, or 6.5-06AI.

There were a series of cartridges based on the 6.5 Swede back in the day, the Arch line. Ackley mentions them in his book more then a few times, and has data for them there, and they are basically an improved, blown out 6.5 x 55 case, necked up and down to different calibers, as well as the 6.5. I believe that it would be basically equal to the 6.5 BJ. - Dan

does anyone know the case capacity of the 6.5x284?
I recently finished building a 6.5x55AI and I'm very happy with the results
120gr Barnes TSX at 3260fps from a 27in bbl,very mild in recoil
I used starting data for the 6.5x284 shooting ALL load's over a chronograph

I don't have the capacity of the 6.5X284, but considering the body is about the same length as the 6.5X55, but it is larger in dia, it is a larger capacity case. 6.5X284 starting loads might still be too high for max loads in the 6.5X55 ackley.

Your velocities are about what a maxed out 6.5X284 will do, so I'd imagine you're probably opperating in the 70,000 psi range. It would be a good idea to back of the loads, or put a strain gauge on your barrel to see where you are opperating at. At the very least, see if you can get someone to run your loads through quickload, or get a copy for yourself.

Found according to Haas Interactive reloading guide the 6.5x284 holds 68gr of water however I don't know what case they're measureing.I was hopeing someone else had measured their's

My Lapua 6.5x55 reformed brass hold's 62.3 gr of water
So Paul with 6gr(water) differance I didn't think I was that far off base (BTW I did mention that I was useing a 27in bbl)

I did catch you mentioned a 26" barrel. If you look at data for a 264 win mag, you'll see that you're within 100 fps of it with a 26" tube.

Given the case capacities you mentioned, I'd expect at the same pressure and barrel length as a 6.5X284, you should be 50 fps slower, or with data from a 24" 6.5X284, you should have about the same velocity in your 26" 6.5X55imp.

For instance, Hodgdon shows their top 120 gr from a 24" 6.5X284 is 2900 fps(seems a bit slow). Their 26" 264 win mag data is 120 gr @ 3350 fps. Their 6.5 rem mag is 120 gr @ 3286.

Considering your case is smaller than the 6.5X284, and much smaller than the 6.5 rem mag and 264 win, I don't see how you can get the same speed as the magnums without running at very high pressures. You're probably just shy of loosening up primer pockets, if not already loosening them up. As I recall, I read about pressure tests that were done, and they indicated modern brass cases don't start looseing up primer pockets or giving sticky extraction until pressure in the 80,000 psi range. That would be running approximately 20% higher pressures than the gun is designed for.

I once loaded up my .308 to a level that corrected for barrel length, would be about 50 fps slower than a 300 WSM. I also loosened up the primer pockets on the cases.

I would think 3000 fps would be a realistic top speed for a 6.5X55 imp firing 120 gr in a 26" barrel.

go over to www.longrangehunting.com and do a search for the member (Steve Shelp). he is an accomplished 1000yd shooter as well as a respected BR gunsmith. He was the one who convinced me to go the route of the 6.5x55AI for a 600-1000yd rig. He has a lot of data (H4831 and 4831sc) are the accuracy powders he suggested. I won't dispute the mathmatics given on any Ackley improved topic,.but I can say that I get far higher velocity increases than the naysayers would suggest and I also don't lose my brass to loose primer pockets. I may be running a higher pressure, but I am getting magnum type velocities with less powder and good brass life.

Give Steve a hollar,..he has multiple match rifles in this caliber and in his own words,.."I love this caliber".

The base diameter of the -06 class cases are smaller than the 6.5x55 and so these won't clean-up a Sweede chamber.

I've just finished making a 6.5 x 55 BJAI. I'm still working-up loads. There's no doubt that the stock 6.5x55 is an excellent cartridge when loaded to modern pressures. We'll see how much better the AI does. If nothing else it sure looks cool. Case capacity of mine is 64.86 grains.

Link to pix of my 6.5x55 BJAI - scroll down