Brass issues Why? Why? Why?

[Ggmac]

Your results should be a bell shaped curve . Your testing only weeds out the tight ones . I don't think its you , unless your lube is not equally coated .
More likely brass dif , they all have a + or - in dimension tolerances

 

[jcampbellsmith]

Bin the cases that don't meet your requirements or mark them up for use as foulers. Regards JCS

 

[jlow]

Let's say, I have 50 pieces of 308 brass. All are from the same lot. All have been fired equal times from the same rifle, using the same bullet and same powder charge. All 50 are full length sized, trimmed, chamfered and deburred. Before loading, I chamber checked them. 45 chamber as expected. 3 will be slightly tighter and 2 will be tight-tight. I can still close the bolt but, it's tighter than I'd like it to be.

What am I doing? What's causing the brass to be different?

The problem here is you think you use the same lot of case, same bullet, and same powder charge, the pressure will be the same. This is certainly a fallacy. Because if this is really true, then all our rounds loaded with only these restrictions would shoot exactly the same and we know for sure this is not true. So many things about case conditions such as case volume, neck tension, neck length, bullet seating depth, bullet base too give and many more all can affect pressure and in return case expansion. Unless you have all of these totally under control, you cannot expact what you are expecting.

 

[CH Luke]

1) Measure what your base to shoulder needs to be and adjust your die to get it there. Method is to strip the bolt and adjust to where the stripped bolt has the slightest resistance. Video out there easy to find.
Why? New brass grows with each additional firing. If you let it grow too far beyond determining then you face having to bump the shoulder much more than .001" and face other complications mentioned above.

2) Neck tension. It is possible to cause hard or even impossible bolt closing by not reducing the size of the very top of your brass enough when sizing.
Easy to determine. One of the things mentioned above is to take comparative measurements of everything. One thing to compare is the top edge of rounds that will chamber snug but easy and compare to the ones that won't. Only takes .001" to not even chamber (learned the hard way). If you were using neck bushings just go one a .001" smaller.

Had a similar problem recently. Finding the right base to shoulder dimension for your chamber and always bumping to that keeps things closing nice and smooth. Measure the shoulder on every one after sizing.

Continue to monitor your loaded neck diameter after additional firings. Neck bushings simplify that (or might cause it if you have too big of a size). If you don't have them then follow the advice from multiple sources above on how to get consistent results.

 

[savagedasher]

Let's say, I have 50 pieces of 308 brass. All are from the same lot. All have been fired equal times from the same rifle, using the same bullet and same powder charge. All 50 are full length sized, trimmed, chamfered and deburred. Before loading, I chamber checked them. 45 chamber as expected. 3 will be slightly tighter and 2 will be tight-tight. I can still close the bolt but, it's tighter than I'd like it to be.

What am I doing? What's causing the brass to be different?

From what I see the brass is peeped only.
If it was done with a full body die. The resistance in the brass is the problem so anneal. If the die has a expander ball remove it and re size . The few that had resistance could be the size of your chamber. That being the case size the tightest and rest will be fine.
Without tools to check we all are guessing . Larry