Backcountry_IDN
Well-Known Member
Ok, need some help. School me on "improved" rounds...
Improved casing
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MudRunner2005
Well-Known Member
What specifics would you like to know?
dok7mm
Well-Known Member
Shoulders pushed forward, less case taper and sharper shoulder angle to increase powder capacity.
LoneTraveler
Well-Known Member
IMPROVED rounds have been on the scene for many year.
Most of the improved cartridges was developed by, MR. Parker O. Ackley.
By blowing out shoulders and taking a lot of the taper out of many cartridges he developed many improved versions of standard cartridges. One of the most popular is the 280 Rem. AI. When he got done with the development of this cartridge it became one of the most popular. It comes very close the 7mm RM velocity out of a standard length .470 bolt face action.
This cartridge allows a lighter rifle to be built with near same power of 7mm RM.
Most of the improved cartridges was developed by, MR. Parker O. Ackley.
By blowing out shoulders and taking a lot of the taper out of many cartridges he developed many improved versions of standard cartridges. One of the most popular is the 280 Rem. AI. When he got done with the development of this cartridge it became one of the most popular. It comes very close the 7mm RM velocity out of a standard length .470 bolt face action.
This cartridge allows a lighter rifle to be built with near same power of 7mm RM.
Backcountry_IDN
Well-Known Member
Thank you guys. Just curious on what i should do to my next build. Thinking about between a 7mm-300norma or a .338 lapua improved. Seen guys get 3500fps out of their 338 lapua improved. Since I'm a newer reloader I might have to watch some videos on annealing.
BallisticsGuy
Well-Known Member
I run a .243AI with 115's at 3200 with a good bit of room left over. I could hit 3300fps if I pushed it. I've got 5-6 loadings on my brass and have only ever neck sized (I also run zero head space and a super tight chamber). Never had to bump shoulders or trim necks or body size and they still chamber and extract without a bunch of effort on the bolt. You can fire form the way I did by shooting normal non-ackley loads in an ackley chamber or use the malt-o-meal method. Either works just fine. You can also just use non-ackley loads if that's all that you have and it won't hurt anything.
You gain a few grains of case capacity which translates to a little velocity or to lower pressures. Also, the cases look really cool. I know we all care about that, don't deny it.
Shoulder bumping will require a special die if you end up needing or choosing to do that. My chamber is nuts tight and I run zero head space so with the 40deg shoulder and no case taper in the mix, I've never had to bother. My barrel is nearly done for now on round count. That's been really nice... neck size and go. The brass isn't even near its life expectancy either. I figure I should be able to get >10 loadings per case at this rate which means 2 barrels for one lot of brass. It's not a big savings but it's a savings.
Zero case taper and sharp shoulders mean for much less forgiveness in feeding and extraction which presents itself as decreased reliability. For me what that's actually amounted to is nothing at all. YMMV.
If you mag feed, note: my 10 round mags became 8 round mags because the case taper had been eliminated.
You gain a few grains of case capacity which translates to a little velocity or to lower pressures. Also, the cases look really cool. I know we all care about that, don't deny it.
Shoulder bumping will require a special die if you end up needing or choosing to do that. My chamber is nuts tight and I run zero head space so with the 40deg shoulder and no case taper in the mix, I've never had to bother. My barrel is nearly done for now on round count. That's been really nice... neck size and go. The brass isn't even near its life expectancy either. I figure I should be able to get >10 loadings per case at this rate which means 2 barrels for one lot of brass. It's not a big savings but it's a savings.
Zero case taper and sharp shoulders mean for much less forgiveness in feeding and extraction which presents itself as decreased reliability. For me what that's actually amounted to is nothing at all. YMMV.
If you mag feed, note: my 10 round mags became 8 round mags because the case taper had been eliminated.
Backcountry_IDN
Well-Known Member
Awesome! Thank you for this input. Didnt know i could run non ackley rounds in an ackley chamber. Good to know.
This build is still a bit out, I'm still debating and need to research more.
BallisticsGuy
Well-Known Member
Yup... Fire a non-ackley in an ackley chamber and the case becomes an ackley case. That's how the fire forming works. My .243AI shot the heck out of regular .243 ammo. the only difference was the resulting velocity.
Backcountry_IDN
Well-Known Member
Thank you! Stupud question, but I am going to have to trim after firing? Correct?
Depending on your reamer, typically AI reamers are set up a little short because the length shortens after you fireform. It will say on the print max. Length I usually trim .005 short on max length on AI cartridges and .010 on non 30 deg. or less shoulder angles
BallisticsGuy
Well-Known Member
I've never had to trim after fireforming. Like Sherm mentioned, they're more likely to shorten a tad on fireforming.
MNbogboy
Well-Known Member
I have a couple of 257 Bob A.I. 40 deg and a couple of 6.5/257 Bob A.I. 40s.
I form brass from 25-06 & 270. I leave the necks about .008-.010 long before fireforming. They always shrink for me
After the second firing they are perfect for trimming to spec.
I form brass from 25-06 & 270. I leave the necks about .008-.010 long before fireforming. They always shrink for me
After the second firing they are perfect for trimming to spec.
