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 IMR 4320 in 223 for AR
thekidb  [Member]
1/21/2009 3:08:59 PM
I cannot find my normal AA2230 powder to push a 55 gr bullet. In fact, I can hardly find any powder at all around here (VA). So, I am going to get creative and work up some loads from existing stock.

I have a sh**load of IMR 4320. Sierra data shows a 2800 fps load that is in the same range of my AA2230 loads, so I going to give it a shot.

Anyone ever used 4320 for bulk AR loading, and, if so, what are your thoughts??

I'm thinking around 26 gr behind a 55 gr bullet.

Thanks.
AeroE  [Moderator]
1/21/2009 5:59:02 PM
That's a maximum load in the 50 ksi class, so you might want to back down to start.
dryflash3  [Team Member]
1/21/2009 10:16:25 PM
I use IMR-4320 in my 7-30 Waters Contender loads.

Never tried it in any other cartridge.

I would imagine it will work, and you will probably need a drop tube.

Cases will be full, work up carefully, Good luck.
TimpAR  [Member]
1/21/2009 11:15:04 PM
I use IMR4320 in my precision .223 77 gr. OTM loads with great results. It gives me about the same size groups as Varget (.5" to .75" 5 shot groups @ 100 yards) in my varmint AR. I have not tried it with lighter bullets yet.

Give it a try, and let us know how you do.
thekidb  [Member]
1/22/2009 4:43:35 PM
Aero, can you tell me which load data you used?? Sierra shows 27 as the max. After I posted, I looked at the online IMR data, and they have reduced their max to 26.1. I chose 26 because it was in the middle of the data set I was looking at. Looks like I need to collect some more info.....

Thanks for the heads up, Aero.

On a side note, Accurate has lowered their max for AA2230 over the past few years. Any idea why the numbers are coming down?? They also lowered the max for AA9 in 44 mag.
AeroE  [Moderator]
1/22/2009 5:39:19 PM
I don't recall which manual I checked, probably IMR's.

Loads are coming down because piezo gages are more common now and the measurements are more accurate. But they are still dependent on all the details of the test.

Rocket2Mars  [Member]
1/22/2009 5:42:53 PM
I have had good loads using IMR4320 in .223 and .308. The bad part about IMR4320 is it is not consistent from lot to lot.
curiomatic  [Member]
1/22/2009 9:26:56 PM
The LYMAN #48 Reloading manual shows a starting charge of 24gr and a max of 27.5gr
(compressed). No pressure given. The velocity of the max load is 3144fps so it looks like this powder slower than optimum for .223 but should work if nothing else is available.
thekidb  [Member]
1/23/2009 8:54:19 AM
Sierra shows separate data for 223 and AR. I assume this is because of the gas operating system??? Anyway, I'm going to call Sierra today and talk to them. The IMR data was probably taken from a test barrel.

Here's where I'm at for IMR 4320:
Sierra: max for AR 26.7 gr @ 2900 fps
IMR: max for 223 26.1 @ 3146

I trust the powder manufacturer's data first, but I think Sierra's may be more accurate for the AR (assuming it was taken from an AR). I post Sierra's answer later.


thekidb  [Member]
1/23/2009 9:30:55 AM
Sierra said they used a Colt AR to work up the data, and that the max didn't show signs of excessive pressure in that particular rifle, but your results may vary .....blah.....blah.......blah.....blah. Same old stuff.

So, we have to assume that the IMR data is lower because they used a pressure barrel and Sierra used an actual AR.

Bottom line: I'll start as one should. Looks like I'm going start low and work up to the velocity of my AA2230 load. I don't anticipate any pressure problems, but we'll see.

Wish me luck.
AeroE  [Moderator]
1/23/2009 11:56:49 AM
I ran into a man last night with exactly the same issue about the Sierra manual (#4, I think). I told him to use .223 Rem data and work the load up as always, and that the only substantial difference in the two sections was probably the measured speed anyway. I didn't compare the two sections, because I don't care.
thekidb  [Member]
1/26/2009 1:48:03 PM
UPDATE:

Tried 24.5 and 25gr of 4320 over the weekend.

25gr of 4320 is only about 30fps slower than 23.6gr of AA2230 and groups are comparable. Good plinking load that's not too hard on brass or action. Since I still can't find 2230, I will commence bulk loading with the boatload of 4320 I have on hand.