Shoulder Bump: 1.556" feels perfect – still size to 1.554"?

[CreedTrigger]

Hey folks,
I’m setting up to reload 6.5 Creedmoor for a bolt gun and wanted to double-check my shoulder bump strategy.

Using a Hornady Headspace Comparator (.375" insert), I measured:

Group	Average Shoulder (in)
Fired brass (my rifle, no primer)	1.556375
Hornady ELD Match (new)	1.5561875
Hornady American Gunner (new)	1.5559

So my fired brass is slightly longer than both factory rounds (by ~0.0002"–0.0005"). Everything chambers and shoots fine.

I also did the “feel method” from Erik Cortina’s video (with a stripped bolt), and my brass starts to close tight at 1.5575″. 1.557 was the outcome... of this method.

My question:​

Should I size to:

• 1.556″ → almost no bump,
• or
• 1.554″ → 0.002″ bump like everyone advises?

My goal is precision, and good brass life. I’m leaning toward 1.556″ – but curious what others here would do in this case.

Thanks for your input!

 

[KnowNothing256]

It somewhat depends on your use case.

First, in my experience, primer pockets are what give out on Hornady brass, so I wouldn’t worry as much about shoulder bump.

The other aspect is, how sure are you that your brass and chamber will always be clean? If you’re doing any field shooting, then I recommend 1.554” to leave room for foreign material taking up room.

 

[spife7980]

My question:
Should I size to:

• 1.556″ → almost no bump,
• or
• 1.554″ → 0.002″ bump like everyone advises?

My goal is precision, and good brass life. I’m leaning toward 1.556″ – but curious what others here would do in this case.

Thanks for your input!

Make it 1.555 and split the difference. It may or may not have fully grown. If 1.556 feels fine then leave it there, not really a critical decision.

 

[Supersubes]

As long as you have enough clearance to account for the tolerances your working in (sizing variations, etc)plus some fouling or dirt/debris, you're good.

 

[memilanuk]

You've got an awful lot of decimal places going on there... what are you measuring with that you think you're actually reading to the tenths or below?

 

[DHDeal]

Everyone has given good advice.

Normally I would ask what does the target look like, but it seems you haven't gotten that far with your handloads.

I have gone to the effort of pulling my firing pin and ejector (when able to) and I have moved on from that. I just measure 5 fired cases now, and go from there. My measurements from incrementally sizing a case to get my bolt drop freely to just measuring 5 cases and subtracting. 002", is close enough for me.

I enjoy tinkering and did not consider it a waste of my time, but the target was never going to show a difference in my experience. Not that it matters, but I dabbled in some 600 yard benchrest, have some very nice accurate rifles built for benchrest, and unknown amounts of expensive reloading equipment. I just haven't found shoulder bump to be one of the deciding factors in extreme accuracy as long as you don't try to get silly.

That doesn't mean I over size my cases, I just don't consider .002" to .003" shoulder bump to matter to me. What matters to me is whether all cases chamber without any drama. Everyone one of my rifles has a FL sizing die set up for it because I hate money and am probably OCD where guns are involved....

 

[Entropicitis]

There is no way you are measuring down to the micron. How did you measure bolt close on a case longer than your fired brass?

 

[memilanuk]

I'm guessing someone ran an average in a spreadsheet, and copy-pasta'd all the digits, rather than truncating back to the thousandth like they should. Then they're trying to read something significant from what are basically rounding errors.

At that point, he's probably better off just going with sizing til the bolt closes easily... cuz numbers aren't his strong suit.

 

[Kaldor]

Bump 2 thou. 1.554. Leave a little room. That little bit of case expansion isnt going to hurt the brass. You always need to leave a little room or Mr Murphy will bite you in the ass eventually.

 

[kentuckyMarksman]

Go ahead and bump it back. A little dirt gets in your chamber and your ammo may not chamber.