Pressure forming vs formed Ackley cases?

[Clark]

I am having trouble getting 25 Krag Ackley to feed with a 25 ackley chamber.
But the 25 Krag ammo feeds just fine.
I would like to give them the same load, with a formed case in the chamber and unformed cases in the magazine.

 

[mongo chicago]

Full length resize the case if you are not already doing so. If you are, then I can't think of anything else.

 

[Nick LaFave]

He is having trouble getting them to feed from the magazine, it sounds like they chamber when single loading fine.

 

[Uncle Ed]

Are your cases that are failing to feed stopping at the case shoulder?

The case that you are forming have more body taper and a two step shoulder.

Where is the case stopping when failing to feed?

 

[Clark]

It jams when the case has the shoulder 0.25" into the chamber when the rear of the case needs to rise 0.25". That would work in a tapered case, but not a straight case. If I gently lift the rear of the case slightly, the bolt can push the case in.

 

[Twicepop]

What kind of a rifle are you shooting them in? From what I've seen over the years, Ackley improved cartridges don't feed well from controlled feed rifles, unless the feed rails have been modified to accept them. As an example, Mauser rifles (at least the M98) are designed to have the cartridges stacked in the magazine at a 30 degree angle. When the cartridges are fired in an A.I. chamber and stacked in the magazine, because of the increased diameter at the shoulder, they are now larger than the front of the feed rails and won't feed properly if at all.

 

[Clark]

It is in a Mosin Nagant
I got to feed yesterday by running the fireformed 25 Krag Ackley dummies a little into a 30-40 Krag sizer with decapping stem removed.
This reduced the shoulder width from 0.45" to 0.43" and now it feeds.

Earlier I had to:
1) make extractor relief cut closer to center of the barrel as case base is smaller.
2) file out the receiver feed lips for the shoulder being 0.3" further forward.
3) mill out the sides of the magazine for the shoulder being further forward.

Why waste time with a Mosin Nagant?
Compare google search volume (2004 - present) of:
1) "Mosin Nagant"
2) "Remington 700"
3) "Mauser"
https://trends.google.com/trends/?geo=US

 

[Clark]

Forming at full pressure while sighting in got shoulder splits.
No damage to chamber shoulder as seen with borescope.
46 gr IMR4451 115 gr NBT 3.05" OAL = ~ 65kpsi

But shooting a buck at 4 degrees F got no split and a formed shoulder.

 

[jplahr]

When I form Ackley cases I lube the cases with a small amount of oil to help the case slip in the chamber. I don't put the oil on the shoulder. I'v never had one split like yours.