What were your before and after velocities with Ackley improved cartridges?

Thanks,
ASS_CLOWN

My Ruger #1 (26"bbl) did an honest 4040 fps. 223 AI 40 gr BT and H335/win 748.

Normally you get 60-80 fps increase with AI cartridges when you rechamber the SAME barrel to the improved versions. Any case with considerable taper will exceed this and probably get you 125-150 fps extra(.250 Savage,6mm Remington,.257 Roberts,7x57,30-30,.300 H&H). Some people claim a lot more than this, but experiments by a lot of writers have shown these claims of 300 fps are usually not valid.

I would add a couple of points about the "gain" from an "improved" case design over the original.

1. How much gain is possible depends on how close the original was to being at maximum bore capacity. If a cartridge was already overbore capacity, then adding MORE powder in the case isn't going to do much beyond increasing blast, barrel erosion and recoil.

2. The gain with any "improved design" is also going to vary according to how the original case was. Most modern cartridges don't leave much room for improvement to begin with. Very little taper in most cases and usually a pretty sharp shoulder.

Many so called "improved cartridges" are really just ego trips for the guy who dreamed them up. It's fun to have a cartridge named after you or your pet dog or whatever........even if the cartridge doesn't really do a thing over the factory original.

Clearly the world can take the majority of "improved cartridges" and flush them down the drain as being of no consequence.

www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Number=536103

Go to this thread and see boilerroom's post. He's listed 25 AI catridges showing velocity gains (fps & %) for each.

I find that most folks havn't taken advantage of the sharper shoulder of the AI calibers. The sharp shoulder (read this somewhere) allows more powder to be burned inside the case and not the barrel. This can be taken advantage of by using much slower powders than the parent caliber could make use of. I have been working with a 6.5-06AI and 140gr a-max pills. I am shoving them through a 26" 1:8 twist tube and getting almost 3100fps with no pressure signs yet. This is with H1000. I can't ignore the fact that magnum level performance is now taking place with far less powder being used and much less muzzle blast. My 280AI exibits the same characteristics as well. There are, as stated, many calibers which make very little use of the AI change however,..the WSM's are good examples. They have No body taper and very sharp shoulders from the start. One can say that these are a 35 degree version of the AI calibers,..but are offered in factory chamberings with multiple ammunition choices available.

I tell my customers that they can expect to get 75 fps more velocity with an Ackley Improved chamber.

This is what you will generally get with the AI rounds such as the 308 family which are not blown out a great deal.

THe 22-250 and 250 will often get twice this amount as will the 257 Roberts and similiar rounds. These are the highest performance gainers. The Swift is another big gainer but bore size limits some of this.

THe '06 family will generally get 100 fps gains.

There are other advantages with the AI chambers then just velocity though!!!

50

Not enough for it to be worth the trouble, IMHO. I enjoy my .280 AI, but if I had to do it all over again, I would not have bothered with the AI bit. To me, what ever extra velocity I might have gained, be it 60-75-100 or 120 fps, was not worth the extra hassle with the cases. Heck, there are few things I can do with the .280 AI that I could not have done with the regular .280 Rem. I put it down to "youthful exuberance", it was fun while it lasted...

- mike

David White has a thread on another forum that gives his opinions on the Improved cartridges. It deals mainly with Thompson/Center handguns, but is interesting reading to say the least.
http://www.bellmtcs.com/forum/index.php?act=ST&f=24&t=1206&s=174ddf084e59447b1a9d6101f2a9bb33