Mac, Ackley Improved cartridges are basically given a 40 degree shoulder and their body taper reduced significantly but not completely.

The most important aspect of an AI cartridge is it's headspace. It must be the same as the parent cartridge so that factory ammo can be fired in it.

There are so called gunsmiths out there that say they can open up a chamber to a AI without shortening the barrel. This is simply not true !!!
A proper and correctly cut chamber includes a set back so that the proper headspace is obtained.

If this is not done issues with case head separation will more than likely follow.

Ominivision1 wrote:

But the best part was case longevity, it seems with the sharper shoulder angle, the cases were not stretching like the parent /06 was, and if any, all I had to do was neck size.

You bring up an interesting point !!!

The design that P.O. Ackley settled on reduced back thrust to the point that case trimming was nearly eliminated.

Slim, you need to look at the .250 and the .250AI and compare them amongst other .25 caliber cartridges.
You'll find they are capable of reaching a given velocity with less powder then their bigger brothers.

The .250AI is said to be capable of nearly 3300fps (I've seen this from a number of sources) with a 100gr bullet and burn about 10grs less of powder in doing so.
That is in 25-06 velocity range !!!

I'll be the first to say I have my doubts but there are some that swear to it.
Hopefully some day soon I'll know !!!


As for BC........... Haven't given it a thought. The bullets I'm considering have already proven themselves worthy enough for me.
The only exception would be the Barnes TTSX, Don't think they'd pose to be a problem though.

I am glad you brought up the barrel setback thingy, I have had to explain that to several people in the past that wag their head back and forth til I draw a picture of the unimproved chamber then by the spec's superimpose the new one on it. The deciding factor ends up being the joint between the neck and shoulder it ends up inside the drawing of the old chamber by a few thousandths and is the determining factor for the headspace. This centers the virgin case and must spring somewhat if the case is any where near saami max. (which they usually are not) I have had only one instance of some brass being max it was a box of factory Winchester .270 Win. it would fit my factory model 70 but not an old M.C.A. with a real nice chamber.

www.gunbroker.com/Auct...=257109664
you got these yet?

Thanks for the link !!!

I've actually been considering custom dies. Most FL re-sizing dies reduce the body more than I care for. The standard .250 is a prime example, the heavy taper tends to shrink the body excessively sending the brass up the neck that in turn needs trimming after re-sizing.
I doubt the AI will have this issue but I still prefer to size as little as possible and not use a neck die.

Here's a sample of 100gr. load data from Sierra !!!

250AI
Barrel Length: 26"
Twist: 1 x 10"
Case: Winchester
Trim-to Length: 1.900"
Primer: Remington 9 1/2

powder---- 2700 2800 2900 3000 3100 3200
varget----- 34.1 35.3 36.5 37.7 38.9 40.1
IMR-4064- 34.7 35.9 37.1 38.3 39.5
RE-15----- 33.5 35.0 36.5 38.0 39.5 41.0
IMR-4350- 39.2 40.4 41.6 42.8 44.0
Energy---- 1619 1741 1867 1998 2134 2274

(sorry got no idea how to make/insert a graph/chart like pumpkin and slim)

Been thinking about the pressure limit Sierra used in this development.
The .250 Savage is only about 45,000 CUP
Do you think they set it the same for the AI ???

The .257 Roberts is also in the 45,000 CUP neighborhood....... anyone who knows anything about the .257 Roberts will probably agree that it's limit was set to low.
I can't help but wonder if the same is true for the .250 Savage.

The reason I'm questioning this is due to reports/articles I've seen and read putting the velocity of the AI on par with the 25-06 while using 22 and 24 inch barrels. (3300+)

Like I said before ....... I have my doubts !!!

Any thoughts or comments .......................

a modern bolt gun will take higher pressure than an old lever, your pressure limits may have been set to include all makes of rifle chambered for the cartridge conserned .I believe many cartridges suffer like this.

Some of the loads listed in your sierra manual puts the 250AI into the 257AI category. www.nosler.com/Reloadi...rains.aspx

While Noslers site does not have any loads for the 250AI, I'll betcha if you call or send an email to a few of the bullets manufacturers, they will send you some load data.

I did visit one site that had load data which used RL-19 instead of RL-15 and the speeds were about 100fps less than the sierra loads. I just checked my 12th edition 1995 speer book and the sierra loads are approaching even the 257 Weatherby Magnum loads which is held at 55,000 psi loads according to the speer book!!

I would say call or email a few bullet and powder people and use that info as its better to have more than one source of data.

The SAAMI specs for the 250 and 257 both have a +P loading:
......................................PSI...........................CUP
250 Savage................................................45000 CUP 50000cup +P
257 Roberts.............54000 / 58000 +P.........45000 CUP

As I understand it most manuals use the more modern +P pressure limits.
Keep in mind there is no coorelation between the CUP and the PSI units - they are sometimes higher and other times lower.


Paul

I guess the early 99's were a little different than those that were chambered in 22-250 Rem, .243 Win, .308 Win, .358 Win, 7mm-08 Rem and .284 Win.
Early models had chamberings that were well under 40,000 CUP.
That's probably why the .250 was kept at 45,000.


OV1.... I see what your saying, I'm beginning to believe that the Sierra data is in the area of 50,000CUP
I know that the .257AI (Roberts) is usually just over 50,000
Planning on giving Sierra a call to confirm...... when I get a chance.
The 257 Weatherby is capable of 3600fps according to Nosler (100gr)


Paul, Never heard of a .250+P loading......definitely aware of the Roberts+P...... Thanks for the info !!!

chambered, would you consider an AR in .25 WSSM? It has the performance of a .25-06.

Absolutely not !!!

The only AR I'd consider is a RRA 9mm or 40cal M4 with the 10.5" barrel......... pure fun and everyone wants to tell ya how illegal it is !!!


If I were to find a 25-06 or a 25WSSM in a Browning A-Bolt (stainless or composite) I'd probably buy it if the price was right.
That doesn't mean I'd give up on the .250AI though.

Finally got around to checking into the pressure issue !!!

Wasn't able to give me any solid numbers but without a doubt they would have ran the AI up to it's limits and backed off that for the published data.
That should put it in the area of 50,000CUP

I think it's safe to say obtaining 3,000+ out of a 22" barrel is feasible/possible.

Heres a good read, www.shootersforum.com/...idges.html