.223 versus .223 AI question.

[amlevin]

I understand that the .223 AI has greater powder capacity and the different shoulder angle pretty much does away with the need to trim cases after the initial run.

My question is what else does the AI case configuration do other than provide more room for powder?

I have a rifle chambered and throated for long bullets, seated with the pressure ring at the neck/shoulder junction. With bullets seated in this manner I have room for almost 2 grains more powder. When loading at max loads with powders like CFE223, H-4895, 2000MR, IMR 8208 XBR, and 77 gr bullets I can't seem to get enough pressure to keep the case necks from getting covered with soot. If I start at loads less than Max I get soot back beyond the case/shoulder junction and primers are just as rounded at the edge as when un-fired.

I've taken some "excursions" into the "over-max" range with no pressure sign whatever. Primers still have well rounded edges, no cratering, no heavy bolt lift, no ejector marks, and still lots of soot on the case necks. Speeds, with the 77 gr HPBT's (SMK and Nos C/C's) are nothing special and certainly don't follow the extra powder that's pushing them.

The barrel is a brand new Benchmark

My question is, "since I seem to have the extra case capacity, could I treat this combination more like a .223 AI than a straight .223? Go ahead and move (carefully) into the .223 AI load range?

Like I said, no pressure with standard max loads.

Anyone else been down this road?

 

[jpretle]

Curious as to what your chamber neck diameter is, as opposed to a loaded round.

 

[amlevin]

Measures .2540".

 

[jpretle]

and the loaded round, neck measurement???

 

[bheadboy]

with the chamber for longer bullets, and the powder not getting pressure up enough for a clean burn, I am curious why you have not tried sligltly faster powder 322 would be a start, h335 or benchmark also? I think the powders you are using are to slow.

Bob

 

[searcher]

I have a 6PPC barrel that was perhaps "over lapped" or something, creating a slightly larger I.D. than normal for the caliber to obtain the pressure one would normally get with a particular load. In any event, that tube requires fairly stiff loads of anything - even the faster powders, but is very accurate. I use loads of LT-32 that are "way beyond" published max loads with absolutely no signs of pressure and my velocities are not that much higher than normal. No way I could use that load in my other barrels.

 

[amlevin]

with the chamber for longer bullets, and the powder not getting pressure up enough for a clean burn, I am curious why you have not tried sligltly faster powder 322 would be a start, h335 or benchmark also? I think the powders you are using are to slow.

Bob

Perhaps, but those are what I have at the moment. I may get something faster but so far I haven't filled the case to anywhere near 100% and have no 'flame' at the muzzle, again with the 77 gr bullets.

 

[amlevin]

and the loaded round, neck measurement???

.248"

 

[amlevin]

I have a 6PPC barrel that was perhaps "over lapped" or something, creating a slightly larger I.D. than normal for the caliber to obtain the pressure one would normally get with a particular load. In any event, that tube requires fairly stiff loads of anything - even the faster powders, but is very accurate. I use loads of LT-32 that are "way beyond" published max loads with absolutely no signs of pressure and my velocities are not that much higher than normal. No way I could use that load in my other barrels.

I'm thinking this is what I have as well although the bore measurements don't indicate that it's oversized. It's only a 3 groove barrel, canted rifling and when looking down the bore it looks like I'm getting a pretty full contact with the "grooves" so not much gas leakage.

There is far less bullet seated into the case body than with most 77 gr + bullets when loaded to "suggested" OAL's. Lots of throat so as I said earlier, I can seat the pressure ring above the neck/shoulder junction with little or no jump.

I'll keep "sneaking up' on max pressures. Sooner or later I'll start flattening primers, then I'll back off a little.

 

[jpretle]

I guess I don't see that sooted necks cause much of a problem, but I wonder if using brass w/ thicker necks would make some of that sooting go away. A .248 loaded neck leaves plenty of room in your chamber neck for over working that brass, loosing a bit more elasticity each time it is fired then re-sized.

 

[CatShooter]

I've taken some "excursions" into the "over-max" range with no pressure sign whatever. Primers still have well rounded edges, no cratering, no heavy bolt lift, no ejector marks, and still lots of soot on the case necks. Speeds, with the 77 gr HPBT's (SMK and Nos C/C's) are nothing special and certainly don't follow the extra powder that's pushing them.

The barrel is a brand new Benchmark

My question is, "since I seem to have the extra case capacity, could I treat this combination more like a .223 AI than a straight .223? Go ahead and move (carefully) into the .223 AI load range?

Like I said, no pressure with standard max loads.

Anyone else been down this road?

If you have more room, and no pressure, then add more powder.

I don't say this lightly - there is no hard max load in a book - all rifles are different. Some will lock up the bolt before max is reached, others will gladly eat more powder well oer max Ine of my ^mm's will tak 5 grains over max and still show no pressure signs.

Consider the book as a starting point - increase the load and watch for the usual suspects.

 

[varmintshooter]

CFE 223 is temp sensitive, if you work up a load in cold weather you may find that it is to hot in warm weather. Your soot may go away when the weather warms up.

 

[MrMajestic]

Somebody needs QuickLoad and plug in his numbers.

 

[amlevin]

CFE 223 is temp sensitive, if you work up a load in cold weather you may find that it is to hot in warm weather. Your soot may go away when the weather warms up.

Aware of CFE's temp sensitivity. That said, my shooting days have an average temp of 55 degrees. Rare excursions to the 20's and summer mornings are usually in the 60's.

I'd be far more concerned if I was shooting in one of those areas where winter meant shooting at zero or less and Summer's are 100+. Here we are more moderate.

 

[amlevin]

Somebody needs QuickLoad and plug in his numbers.

I did use my "numbers" in "Load from a Disk" which has been a good tool for me and it shows I can use as much as 26.4gr of Varget or 25 gr of H-4895, obtaining ~2850 fps with the 77 gr Bullet. Pressures are calculated in the 50,000 CUP range which should be at or near max.

My fired case holds 30.3 gr of H2O, is 1.750" long. Bullets are measuring .940" in length and COAL in my Rifle is 2.435"

I would definitely be interested in whether QL yields similar numbers.

 

[amlevin]

[
If you have more room, and no pressure, then add more powder.

I don't say this lightly - there is no hard max load in a book - all rifles are different. Some will lock up the bolt before max is reached, others will gladly eat more powder well oer max Ine of my ^mm's will tak 5 grains over max and still show no pressure signs.

Consider the book as a starting point - increase the load and watch for the usual suspects.

Took your advice and added some more powder. Alliant published 25.2 gr of 2000 MR as their "only load" and say don't exceed.

I started out yesterday at 26 gr and ended at 27 gr. Here are the results:

The load of 26.2 gr sure looks "promising" 8). Speed of 2850 fps.

The "hole" with a bullet for comparison:

Here are the cases fired and no pressure sign at all until I got to 26.8 gr when the slightest bit of a ridge started to form around the firing pin. The bolt is a stock Remington bolt that has merely been faced when the action was trued. The 27 gr load had only a slight bit more but primer edges remain radiused. No heavy bolt lift or extraction issues. Cases starting second from the left match the target groups. Cases on left were from a previous "low pressure" load.

27 grains is about 99% of the available space under the bullet based on weight of powder that fills the case to the case wall/shoulder junction versus the actual charge weight. Don't think there is anything to be gained by stuffing more powder into this case. As the target shows, the groups just opened up as I added powder. 26.2 gr looks more than "workable". Also, case necks were much cleaner. The loads from 26.2 and up showed what is supposed to be the optimal "sine wave" powder residue pattern.

Still working on my CFE 223 load. It has more "speed potential" according to the Mfr's data.