250 AI vs 25 Creedmoor case capacities

[20 TAC]

I have read where case capacities between the 250 Ackley and 25 Creedmoor are almost identical, and I’ve read where the 250 AI has about 5% more case capacity than the 25 Creedmoor. Can anyone offer their findings on this? I’m in the middle of developing a light bullet load for a 25 Creedmoor and find that by using 250AI load data I’m running into pressure signs much earlier than the max loads listed for the 250 AI. I do not have a chrony set up to verify velocities yet.
Any help is appreciated. Thanks!

 

[20 TAC]

I just measured water volume on a pice of new Alpha 25 Creedmoor brass. 48.5 grains water to bottom of the neck and 50.5 grains of water to top of the neck.so according to this data, they are nearly identical. Standard 250 Savage is around 43 grains if I read correctly. Even more puzzling why I’m getting hard bolt lift with the loads I’m running. Would trying a different brass other than Alpha be advisable? I have researched and found the hard bolt lift on Alpha brass to be an issue with a few other chamberings??

 

[358WCF]

I just measured water volume on a pice of new Alpha 25 Creedmoor brass. 48.5 grains water to bottom of the neck and 50.5 grains of water to top of the neck.so according to this data, they are nearly identical. Standard 250 Savage is around 43 grains if I read correctly. Even more puzzling why I’m getting hard bolt lift with the loads I’m running. Would trying a different brass other than Alpha be advisable? I have researched and found the hard bolt lift on Alpha brass to be an issue with a few other chamberings??

Horseshoes & hand grenades maybe, but my 22-250 Ackley using '90s era WW 22-250 brass fully formed holds 50.9 gns of H20 full to meniscus. Unsure if it's as fired or re-sized volume. WW brass from back then was kinda known to be more spacious inside than other brands.

 

[jghoghunter]

Horseshoes & hand grenades maybe, but my 22-250 Ackley using '90s era WW 22-250 brass fully formed holds 50.9 gns of H20 full to meniscus. Unsure if it's as fired or re-sized volume. WW brass from back then was kinda known to be more spacious inside than other brands.

20 TAC said:
I just measured water volume on a pice of new Alpha 25 Creedmoor brass. 48.5 grains water to bottom of the neck and 50.5 grains of water to top of the neck.so according to this data, they are nearly identical. Standard 250 Savage is around 43 grains if I read correctly. Even more puzzling why I’m getting hard bolt lift with the loads I’m running. Would trying a different brass other than Alpha be advisable? I have researched and found the hard bolt lift on Alpha brass to be an issue with a few other chamberings??

358
I'm not quite sure what you are saying. Are you saying that 50.5 to your 50.9 that your 90's brass has that you would look for that brass so you can gain .4's of capacity over just buying the creedmoor brass. Trust me I'm not a creedmoor fan but this is a no brainer in my book.

 

[358WCF]

20 TAC said:
I just measured water volume on a pice of new Alpha 25 Creedmoor brass. 48.5 grains water to bottom of the neck and 50.5 grains of water to top of the neck.so according to this data, they are nearly identical. Standard 250 Savage is around 43 grains if I read correctly. Even more puzzling why I’m getting hard bolt lift with the loads I’m running. Would trying a different brass other than Alpha be advisable? I have researched and found the hard bolt lift on Alpha brass to be an issue with a few other chamberings??

358
I'm not quite sure what you are saying. Are you saying that 50.5 to your 50.9 that your 90's brass has that you would look for that brass so you can gain .4's of capacity over just buying the creedmoor brass. Trust me I'm not a creedmoor fan but this is a no brainer in my book.

jg,

Commenting on the similarity in capacity of my 22-250 Imp. brass to 20 TACs Creedmoor brass & noting that WW brass is likely more spacious than Alpha. Thinking the 22-250 Imp should be very similar to 250 Imp. brass, thus the horseshoes & hand grenades comment (comparing dissimilar things?). No recommendation except maybe to stop where there's pressure sign because it's likely, well, a pressure sign regardless of "the data says it's in the middle".

Note: If he's using Sierra's data they used WW brass, not Alpha.

 

[just_jon]

My 8X W-W 250AI sized brass holds 50.5 grains.

 

[20 TAC]

My 8X W-W 250AI sized brass holds 50.5 grains.

Thank you for this. Seems like there isn’t much difference at all. I’ll have to keep working on this project. I would say this Alpha brass has provided some learning opportunities for me so far.

 

[Frankm]

They s/b nearly identical just like a 22-250 AI vs a 22 Creedmoor. Shoulder angles and about .005 “ different shoulder diameters is pretty much it.

 

[Frankm]

They s/b nearly identical just like a 22-250 AI vs a 22 Creedmoor. Shoulder angles and about .005 “ different shoulder diameters is pretty much it.

 

[AlNyhus]

My fired 250AI cases (Lapua 22-250 brass) holds 50.8 of water to the top of the neck.

 

[p-man]

The 25CM compares identically with the 250 Sav Imp (30deg); the 250 Sav Ackley Imp (40deg) averages 1.0 grains more.

 

[20 TAC]

Thanks to all for the replies. Finally shot some loads through the chrony. I have yet to find a suitable accuracy load with the 75 v max out of the 9 twist barrel. 85 Nosler BT shoot acceptably for rifle’s intended use. And at about 3,400 fps it should be a hammer on coyotes. 110 Accubond shot exceptionally well with impressive velocities and N-150.

 

[CacheCropp]

I’m considering the same cartridges, 250 AI and 25 Creed (and 25x47). If using Lapua 22-250 brass, what is the max PSI? I’ve seen 3 different numbers listed from 58k PSI up to 65k PSI.

 

[JLT]

I’m considering the same cartridges, 250 AI and 25 Creed (and 25x47). If using Lapua 22-250 brass, what is the max PSI? I’ve seen 3 different numbers listed from 58k PSI up to 65k PSI.

Lapua brass will take pressure, quite a bit of it. In fact, an AI configuration will mask pressure signs you would see ordinarily with parent case brass. I don't have a .25 caliber, but I do have a couple of .22-.250 AIs and I do have some combinations that I consider on the warm side, but you wouldn't know it looking at the brass (Lapua). I don't have a Pressure Trace and cannot measure chamber pressure accurately, so I use muzzle velocities in the context of the powder I'm using.

One of my barrels is a 1:8 twist, and it likes 75 gr. ELD-Ms pushed hard with RL-23. My work-ups helped me establish 3,500 fps as a practical safe limit, since I started to experience intermittent sticky bolt lift above that number. Not regularly, just once in a while, and no extraction irregularities at or below that number. Hard(er) bolt lift on every round with an AI configuration is WAAAY over pressure IMO, and it's asking for trouble.

 

[CacheCropp]

JLT, Much appreciated. Makes perfect sense.