Fired Brass & Resizing measurement

[ABL_ZA]

Can anyone help me with the best next steps for resizing?

I measured 5 virgin brass at 1.534 - 1.535 for my baseline

I Fired 21 shots.

• 1.5345 (5 shots)
• 1.535 (2 shots)
• 1.5355 (8 shots)
• 1.5375 (6 shots)

So what is going on here and what do I resize this brass to?

Additional Context​

Disclaimer:

• I am relatively new to reloading
• I have never resized

Rifle + Load

I have a Tikka T3x 6.5CM

Around 200 rounds of 143gr ELDX through it. It was cleaned before shooting.

• Lapua Brass (virgin)
• 1.910 case length
• Mandrel .262 lubed with Imperial dry neck lube
• Deburred
• 41.4 H4350

Equipment

• Area 419 Headspace & Ogive Gauge (0.400" Bushing)
• Forster Ultra Micrometer Seating die

 

[wvfarrier]

I always TRIM to saami specifications and its never failed me. However, I do not FULL LENGTH resize my bolt action brass. I keep brass separated based on the rifle it was fired from. Annealing the brass will reduce neck stretching.

 

[ABL_ZA]

I always TRIM to saami specifications and its never failed me. However, I do not FULL LENGTH resize my bolt action brass. I keep brass separated based on the rifle it was fired from. Annealing the brass will reduce neck stretching.

I trim to 1.910

This is regarding headspace and resizing.

 

[Rio Precision Gunworks]

First thing, if you're using calipers to measure brass, just forget the 4 decimal. Calipers aren't accurate enough. Even the third decimal is going to have +/- .001 if you use them perfectly.

That out of the way.....since some of your brass is come out longer after firing, that indicates that some (possibly all) of your brass is not fulling formed.

So, you may only need to bump the longest brass back....if even those. You need to check the brass fitment in the chamber. You can use a method like stripping your bolt and if the bolt doesn't fall free on your longest brass, bump it back until it falls freely. Then more to the brass with the next shortest and do the same until all your brass lets the bolt fall freely (you may not have to bump some or all of your shoulders).

The brass that doesn't need bumping, you will still run through your F/L die so it will size the body, you just won't have the die screwed down enough to bump shoulders.

 

[MarkyMark007]

• 1.5345 (5 shots)
• 1.535 (2 shots)
• 1.5355 (8 shots)
• 1.5375 (6 shots)

So what is going on here and what do I resize this brass to?

small pressure so brass cant fully expand to chamber
primer is blocking your measurement
...