Setting the resize die correctly for 30-06 Ackley????

msinc

New member
How do you know you are setting the resize die correctly to size the case to.001"-.002" under chamber headspace size??? I know the chamber headspace, it is minimum...SAAMI minimum -.004" for the Ackley. How do I know the brass I am resizing is correct for that chamber and not too small??? Too large is easy, it wont want to chamber. I know the signs of being fired too small but I don't want to have to get to that point. I would like to know I am adjusting the die correctly before I load rounds and fire them. Thanks in advance for any info.
 
I use trial and error. Use several fired casings that won't chamber. Start with the die backed out a little, resize one and try to chamber it. Probably won't chamber but if it does you are down too far, back out a little. If it won't chamber screw the die down a touch and try another case. Repeat till one chambers with as little or as much resistance as you want. Now resize a couple more to verify and you should be good.
 
Thanks for the replies fellas...I will answer all three of the last posts in order...

I am not using bushings. I really thought I could just use a fired case but the problem with the Ackley is that it doesn't headspace off a datum line like most rimless cartridges, it uses the junction between the neck and shoulder. So, when you cut the chamber you simply headspace the rifle to a go gauge minus .004" {actually one that has had .004" ground off the big end.} The problem this causes is that the fired case will press or "bump" or move in very easily at that spot when I close the stripped bolt. I am trying to get within .001"-.002" and closing the bolt feels about the same from .001"-.005"...those Sinclair bump gauges really are the answer but unfortunately they don't make the size I need since the Ackley headspaces on the shoulder/neck juncture...I will have to make the tool on my lathe. I have the Stoney Point set which are exactly the same thing, there just is no gauge piece that is the correct diameter for the Ackley. The good thing about all this is that I have the reamer to measure this size. Thanks again guys.
 
An AI only headspaces off the neck shoulder junction during fireforming. After that it headspaces off the shoulder.

A bump gage doesn't need to measure precisely on the datum to give you a useful measurement. Pretty much anywhere near the middle of the shoulder will do. A pistol case would work just fine. Anything that fits over the neck and rests on the shoulder to give you a repeatable measurement with your calipers will work just fine.

- DAA
 
Originally Posted By: DAAAn AI only headspaces off the neck shoulder junction during fireforming. After that it headspaces off the shoulder.

A bump gage doesn't need to measure precisely on the datum to give you a useful measurement. Pretty much anywhere near the middle of the shoulder will do. A pistol case would work just fine. Anything that fits over the neck and rests on the shoulder to give you a repeatable measurement with your calipers will work just fine.

- DAA

I understand, but what am I measuring this against??? How do I know what to set the die to so it sizes the brass to .001-.002 less than my chamber????
 
Originally Posted By: fw707Sinclair makes two different bump gauges for the 40 degree Ackley.

Thanks, I will check this out!!!!
 
They make a 40A and a 40B bump gauge. The shoulder angle is the same 40 degrees on both, but the A fits up to 6mm cases and the B fits the ones over that.
Just attach the bump gauge to your calipers, zero them out, and measure a couple of pieces of fired brass. Then slowly adjust your sizing die down until you see the shoulder length decrease by about .002 or maybe a little less.
 
Originally Posted By: DAAAn AI only headspaces off the neck shoulder junction during fireforming. After that it headspaces off the shoulder.

A bump gage doesn't need to measure precisely on the datum to give you a useful measurement. Pretty much anywhere near the middle of the shoulder will do. A pistol case would work just fine. Anything that fits over the neck and rests on the shoulder to give you a repeatable measurement with your calipers will work just fine.- DAA


I just use my hornady bullet comparator with an insert that fist over the neck and lands on the shoulder. I take a measurement of several fired cases while using the same insert and then resize one piece of brass, measure the case again, and screw in the die until I get the desired amount of bump. Might not be quite as precise as other methods but it has worked well for me. Then I just write down the measurements of a fired case, sized case and which insert was used to measure and I can always go back and verify numbers in case the die setting gets moved.
 
Originally Posted By: midwestpredatorOriginally Posted By: DAAAn AI only headspaces off the neck shoulder junction during fireforming. After that it headspaces off the shoulder.

A bump gage doesn't need to measure precisely on the datum to give you a useful measurement. Pretty much anywhere near the middle of the shoulder will do. A pistol case would work just fine. Anything that fits over the neck and rests on the shoulder to give you a repeatable measurement with your calipers will work just fine.- DAA



I just use my hornady bullet comparator with an insert that fist over the neck and lands on the shoulder. I take a measurement of several fired cases while using the same insert and then resize one piece of brass, measure the case again, and screw in the die until I get the desired amount of bump. Might not be quite as precise as other methods but it has worked well for me. Then I just write down the measurements of a fired case, sized case and which insert was used to measure and I can always go back and verify numbers in case the die setting gets moved.


I think it would be every bit as precise to use the comparator method. All you need is a precise measurement from a given point, and then a precise measurement on the change from that point.
The numbers themselves aren't necessarily important, just the change between the numbers.
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