Shoulder bump questions

[lav2323]

Hello, have a question about shoulder bumping, this is for my 6.5 cm. I bought new hornady brass, this brass band new and full sized, the shoulder is 1.580 ish. After shooting a few rounds to get my fire formed measurements, so I could bump the shoulder the recommended .001-.003. My fire formed brass is around 1.625 to 1.630. Playing around with the new brass at 1.580 and bumping the fire formed brass. The brand new brass sized at 1.580 shot way better ground than doing a bump. My question is if I size that shoulder from 1.630 down to 1.580 is that too much, and am I overworking the brass going down that far. Thanks.

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[Local Loader]

It's not 6.5cm but I do that with my 223/5.56 and 308/7.62x51 brass and it all runs just fine with no issues. If sizing it works better for your shots than I'd say size them.

 

[lav2323]

It's not 6.5cm but I do that with be 223/5.56 and 308/7.62x51 brass and it all runs just fine with no issues. If sizing it works better for your shots than I'd say size them.

Sounds good thanks. So at worst, I just probably won't get as much life with the brass I'm assuming? Since it's working the brass down that far?

 

[Mikej]

I presume this is a bolt gun?

Do you have the Hornady headspace comparator?

With the comparator you measure a new unfired round and compare it to your fired round. The difference is the amount you bump the shoulder back.

BUT, you can also see if your fired brass will chamber in the gun without bumping the shoulder. If your fired brass will allow the bolt to close with very light pressure all you need to do is size the neck and check trim length. Trim accordingly.

What are you measuring that is 1.580"?

 

[lav2323]

I presume this is a bolt gun?

Do you have the Hornady headspace comparator?

With the comparator you measure a new unfired round and compare it to your fired round. The difference is the amount you bump the shoulder back.

BUT, you can also see if your fired brass will chamber in the gun without bumping the shoulder. If your fired brass will allow the bolt to close with very light pressure all you need to do is size the neck and check trim length. Trim accordingly.

What are you measuring that is 1.580"?

Mike,

Yes to both of those. I just shot some loads with fire formed brass. So I didn't bump the shoulder. Just left the shoulder as it was fire formed, resized only. approx 1.630 with comparator. The bolt did require some extra force to close. When I backed it to 1.620 no problem with closing The 1.580 measurement is the hornady brass brand new out of the bag. So there is, I think, a good amount of distance there. And my best groups where with the 1.580 shoulder. Just wondering if it wise or smart to bump the shoulder all the way back to the 1.580.

 

[Mikej]

Mike,

Yes to both of those. I just shot some loads with fire formed brass. So I didn't bump the shoulder. Just left the shoulder as it was fire formed, resized only. approx 1.630 with comparator. The bolt did require some extra force to close. When I backed it to 1.620 no problem with closing The 1.580 measurement is the hornady brass brand new out of the bag. So there is, I think, a good amount of distance there. And my best groups where with the 1.580 shoulder. Just wondering if it wise or smart to bump the shoulder all the way back to the 1.580.

This is my way of thinking....If that bolt closes on fired brass with just a hint of resistance as you drop the bolt handle, your right where you want to be. Not bumping the shoulder should add longevity to the brass.

 

[lav2323]

This is my way of thinking....If that bolt closes on fired brass with just a hint of resistance as you drop the bolt handle, your right where you want to be. Not bumping the shoulder should add longevity to the brass.

Mike,

Yeah makes sense to me. Thanks for the help!

 

[503_Hunter]

New to reloading and have 6.5cm as well. Have some fired brass ready to have shoulder bumped. What type and brand of die are you using to bump the shoulder?

Thanks!

 

[Hooyah DeepSea]

If you are gauranteed to only use that brass or completed cartridges in only one gun, then just neck resizing is acceptable. But, if you are possibly going to put those in any other gun, I recommend full length resizing always, including the slight 'cam-over' at the end of the stroke.

 

[Mikej]

New to reloading and have 6.5cm as well. Have some fired brass ready to have shoulder bumped. What type and brand of die are you using to bump the shoulder?

Thanks!

I like Hornady myself. Though you'll have to get a shell shell holder.

And RE the above. I just back my die out so it doesn't contact the shoulder. It's only .005" ish. I don't see that affecting neck tension area.

edit. I should add. In the/"MY" Swede Mauser the chamber is virtually the same as shell dimensions. My fired cases rechamber with no resistance.

 

[osprey]

In a hunting rifle I would definitely bump shoulders back at least .002-003" from fire formed length. .005" is just fine. If it is a bench gun, you can get cute and experiment with less bump. Just remember that you can gall your lugs pretty easily if they are not kept properly lubed. Many competitive shooters are coming around to the benefits of slightly bumping the shoulder back and getting away from neck sizing only. Benefits include longer bolt lug life and less rifle upset between shots when working the action.

 

[osprey]

Another thing to note is after a few firings I noticed my shoulder bump readings would become inconsistent after sizing. The solution has been to anneal the brass prior to sizing. My results are now much more consistent. Welcome to the rabbit hole!