Bumping the shoulder back.

[Kingrich09]

I'm still new to all this and understand what it means (kinda) but unsure how to accomplish it. What is the process for "just bumping the shoulder back" on fire formed cases that will be used in the same rifle? Does this require a certain type of die or can it be done with a FL or SB die? I'm assuming it is done by not screwing the die all the way so it is not touching the shell plate? How do you know where to stop?

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[Greg]

What are you shooting? Auto loader or bolt?

[cynjon]

In order to know where the shoulder is before and after "bumping", you'll need a headspace comparator gauge such as the one from Hornady. Here's a good video that describes the process and how to use the comparator, as well as full-length sizing vs. neck sizing vs. bump sizing: https://www.youtube.com/watch?v=V2Wt8-VqeAE

[Kingrich09]

Currently I reload for 223 ans 300 blackout both in the AR platform. I'm not currently having any issues I'm just trying to get a better understanding of this.

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[cynjon]

I typically bump the shoulder back .001"-.002" for most of my bolt guns, but I do neck size for a couple of them as well. For all my AR platform rounds, I full-length size to get back to standard dimensions for better feeding and reliability.

[Kingrich09]

In order to know where the shoulder is before and after "bumping", you'll need a headspace comparator gauge such as the one from Hornady. Here's a good video that describes the process and how to use the comparator, as well as full-length sizing vs. neck sizing vs. bump sizing: https://www.youtube.com/watch?v=V2Wt8-VqeAE

Thank you for that link that answered a lot of questions and things are starting to make some sense. Is shoulder bumping something that is commonly done for semi autos or is it strictly for bolt action? Obviously those cases would only be good for the rifle they were previously fired from.

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[cynjon]

Every rifle is different, but I would think that if you are keeping the brass specific to a particular firearm, whether it's semiauto or bolt, then bumping the shoulder would probably provide reasonable reliability and would work fine for 99% of people. If you're talking about life or death "every round needs to chamber 100% of the time" reliability, then I'd be using ammo that leaves more tolerance for fitting in the chamber. When starting with unknown brass, I always full-length size for the first reloading. Load some up with a shoulder bump and see if you have any reliability issues...if not, load 'em and shoot.

[Big Eddy]

Bumping the shoulder back is only recommended for bolt action rifles. Even then it is not necessary, it is a trick used to prolong case life and some say increase accuracy. If it is used for ammunition in auto, lever or even pump actions it can lead to feed issues.