Printable View
Im going to start fireforming new lapua brass for my new AI and looking for some load info. I have 75amaxs and wandering what powder and charge will be best for fireforming. I have onhand varget, benchmark, win 748, imr 4064, imr 4350, imr 4166, h322, re15 and vi140. Also is it possible to do load development while fireforming? Any help would be great.
Use at least an upper window ( 75%-80%) load for the parent 22-250. As P.O. said, "Use a good stiff load". What powder-bullet combination is up to you.
I don't do any development until I have formed brass. To form the last batch of 22-250 Imps I used Varget and some 45g Hornets I had laying around and some using Unique, TP and a soap bullet. :p
Bill
I used 75gr Amax's, CCI BR2 primers and a near max load of Varget to fire-form my Norma brass and the load shot better than most all of my tweaked AI loads. Unfortunately I can't tell you an exact powder charge as it's been probably 9-10 years since I've had to form any new brass for that rifle.
I have always found that a near max load for the parent case of a given bullet and powder (I liked varget in all the 22-250's and 22-250AI's I have had so far) gave me a great forming load and was normally very accurate. Often times with my AI loads in most cases, I end up settling on a max or just over max charge for the parent case as an accuracy load and from there on out that's what the barrel gets regardless of formed or unformed brass. Accuracy is normally very good either way. I often fire form loads in the field popping at varmints and use the formed loads for target work.
L1986, I'm in the same boat that you are in. I'm anxiously waiting on an 8 twist 22-250AI barrel myself. I, too, would love to hear from the AI gurus around here about their fire forming loads! Being an "Ackley-Newbee" , I'm looking for a bit of insight when it comes to loading for this cartridge. I've loaded quite a bit for standard cartridges, but, never for an "AI". Thanks in advance for any info supplied! Idaho-45
I've found some excellent loads using IMR-4064 & 55 grain bullets. So that would be my pick. Expect your F/F loads to be from 100 to 200FPS slower than the same charge in a formed case. So don't be discouraged with low velocity readings when fire forming. Like others, I'd F/F with a max charge for the parent case. (Ackley designed his chambers to fire off the shelf, parent case ammo) I've always gotten excellent accuracy with F/F loads and do further load development after forming. A consistent bullet weight & powder charge will yield the most consistent case forming dimensions. Have fun!
Just some more considerations to ad to gotcha... If you were f/f off the shelf ammo would be good. But, you already have Lapua brass and 75 gr. bullets.
So, now you need 22.250 dies to size and load the new Lapua brass in order to f/f it. You could probably use a mild load, about 35 gr. of your IMR 4350 with the 75 gr. bullets to fire form... Check manuals to verify powder loads...
After you f/f, you will need a set of 22.250 AI dies for the formed brass... Then, you could work up loads with IMR 4350, or consider RL19 or RL22, or other powders.
Good luck... The 22.250 AI is keeper.
Once you are formed you can follow carefully .220 swift load imfo for starting points towards stiffer loads for performance. Start low and work up slowly till you see pressure signs. Do NOT start at the higher loads as pressure has to do with bullet size(pressure ring) to actual bore size and chamber size so be darn careful to have a fun experience. Do not take internet loads and run with them until you can substantiate they are in a book to make sure the other guys chamber wasn't tighter or looser than your own. This is how people make mistakes. I have so many reloading manuals it would make your head spin but use them as a cross reference to double and triple check what you conclude to be safe.
Couldn't agree with Jon more. One of the results of Ackleyizing is to reduce bolt thrust tremendously. This means that pressure signs will come all of a sudden. You'll have virtually no pressure signs........ add .2 or .3 grs more powder and out of nowhere be flattening primers. ( no advanced notice) Your pressures will be well into the red zone when this happens. Just a "word to the wise" :).......... It's a good practice to keep track of case head diameter and throttle back when you reach .001" expansion...........