H870 for fire-forming .243AI

[reloader243]

I have about 10lbs of H870 powder sealed given to me. I used to load it for 7mm Mag, but as I no longer have that gun,I no longer use the H870. I was thinking of using it to fire-form my .243 cases with 100 Sierra's,about 1500 rnds given to me as well)in a dedicated Savage 111 that I had re-chambered to .243AI std. neck. I found a load for H870 and 107Gr jacked bullets stated at 52C gr. I believe I should be able to use that load for 100gr Sierra's as well for fire-forming. Any thoughts or comments....I do have IMR 4831,H4831,IMR 4350, H4350 but want to use them for load developement in the .243AI good barrel...

 

[Preacher]

Seems like a faster burning power would be better for fire-forming your 243 Ackley cases than that slow burning H-870...
A faster burning powder will usually form the cases better the first time out...

 

[Ackman]

A .243 case is kind of semi-improved as is. The shoulder stays the same diameter, it just blows forward and becomes a lot steeper, body taper becomes very slightly less The .243AI is a step up from the standard cartridge but the difference isn't as large as with some other improved cases. Use the same powder and bullet fireforming that you plan to use with formed brass and work up a fireform load as if it were any other cartridge. Fireform velocity will be close to what it is with formed brass. And with formed brass the load will be very close or a little more. Just find a good fireform load for your particular barrel and you'll be almost there with formed brass. In my rifles the fireform load was 48.3-48.7/760 with a 70TNT. Very accurate and fast.

 

[Chuckhunter]

I agree with Ackman, I know you would like to use up that H-870 but it's extremely dirty powder, and you aren't going to get the velocities that you should. I just formed 300 rounds while on a PD hunt in South Dakota. Took, 243 Lapua brass loaded it up with a load developed for my Ackley and shot them. They formed beautiful and shot extremely well. The Ackley is not easy on barrels so make every shot count.

 

[reloader243]

Thanks guys for the good input...I use a separate rifle/barrel for fire forming,so the Shilen only sees the final fire-formed/necked turned to .268 cases with the Sierra's /Lapua's heavy bullets. I fire-form the cases the 1st time in a std. neck/.275,straight, re-chambered factory Savage barrel. Then I prep the brass as needed and use a K&M neck expander,turn the necks to .2675-.268..load them up for the Shilen barreled rifle to work up a load for that barrel.After the 1st firing and all later firings I do not do anything to the brass except ultrasonic clean,ck the cases, and re-primer, and reload them. Neck run-out has been.0008-.0012 so I think Shilen did me right on the chambering.They don't see a full length or neck die again unless they tighten up when chambering. I use a light neck tension and seat them long and let my chamber seat them to the lands. I know the 870 is dirty, but I can load the case full and with a 100 grain bullet I should be below 45000 cup, so the full case with the lower pressure might be better on the primer pockets I'm thinkin' anyway. I think I'll try some 870 and if the cases don't fire form well, I'll use the 4831, or 4350...
Thanks again,I'll get back with you guys on the results..

 

[reloader243]

As an update on using H870 for fire-forming my 243Ackley brass. I loaded 30 cases with 50gr,full case) of H870,fire-formed them in my dedicated fire-forming rifle,Std neck .243AI chamber) with Sierra 100gr Spitzers,seated touching the lands. All cases came out great, no lost cases,all straight necks,.0014)run-out)well defined shoulders,tight primer pockets. I will say that after the 2nd firing of the case,1st in the Target barrel), the shoulders are now sharp and well defined. So I'm loading up for a ladder test with Sierra 107s and Lapua 105s...IMR 4350, and H4831 to see what this new barrel likes. Thanks for the help guys and yes H870 shot dirty,but the brass cleaned up great in the Ultra-sonic cleaner.