338 NM to 338 NMI. 338 LM to 338 LMI

[Bubba Boomstick]

Manson has a page dedicated to Ackley Improved cartridges that has been posted on their site for years.

If you read it, You will see that the Ackley improved cartridges are about 0.004 shorter than the standard chambering. So what they told you is what has been the case for a long time, P.O. Ackley designed these cartridges so that you could still shoot factory rounds if needed or if that was going to be your method for fireforming.

This is why you must turn off one thread in most cases to be able to chamber the Ackley properly. You can use the standard cartridges go gauge as a no-go gauge if you stop chambering when the bolt will close about half way on a go gauge, After tightening the barrel, It will only close a little above half way. The case will have slight resistance when it's chambered.

Now on the 338 Imp. I do not know how many thous shorter it is, If it even is, Their are lots of improved cartridges and many of them have their own designs and specs.

Thank you for that information. I am by no means an expert on wildcats or Ackley cartridges I am just a bubba.

If you are referring to this article:

Understanding Ackley Improved: A Detailed Guide to Wildcat Cartridges and Custom Rifle Performance | Manson Reamers

mansonreamers.com

It doesn't mention those details. I am not sure where the article you are referring to is.

 

[Sniperhandle]

Thank you for that information. I am by no means an expert on wildcats or Ackley cartridges I am just a bubba.

If you are referring to this article:

Understanding Ackley Improved: A Detailed Guide to Wildcat Cartridges and Custom Rifle Performance | Manson Reamers

mansonreamers.com

It doesn't mention those details. I am not sure where the article you are referring to is.

How Ackley Improved Chambers are Headspaced

“Ackley Improved” versions of standard calibers have been popular for many years. Increased velocity, reduced brass stretch and the desire for something unique are all reasons for customers requesting these chamberings.

mansonreamers.com

It's been years since I read it and it took me a bit to find it, Hope this helps.

I am not an expert either, But I have chambered quite a few Ackleys and a couple hundred standard calibers at least. I still am a hobbyist, But I have a very good understanding of headspacing and Ackley headspacing.