Bumping shoulders

[warnera1102]

So I am working on my load development on a brand-new remage criterion barrel 7mm rem mag.
Originally I shot virgin hornady brass that measured 2.104 from case bottom to the datum point in the shoulder for load development. After firing the case is now 2.114. I always have heard and read to bump the shoulder back 0.002" or use the bolt (without a firing pin) to let you know where the shoulder needs to be. So the case inserts and the bolt handle falls over with a 2.114 shoulder. I thought this was odd as I felt the 2.114 case would have some resistance.So to check my theory,I had an old case ( same 7mm rem mag from an old barrel) that measured 2.118. I continued to bump the shoulder until the bolt closed with no resistance, that measured 2.114. I'm not sure if it matters but I'm using a RCBS full length die and the brass is on its 2nd sizing ( original load development and now reloading for shooting).
So I guess my confusion is if the case is fire formed to a shoulder measurement of 2.114, wouldn't the bolt closed with some resistance? What am I missing here?

 

[TheOfficeT-Rex]

The shoulder won't blow all the way forward in the first firing, but it will get close enough. There is some brass spring back after the firing sequence.

Its a belted magnum, so that sort of growth is expected, and also not critical to headspace. Just bump it back a k or two and press on.

 

[Steel head]

So I am working on my load development on a brand-new remage criterion barrel 7mm rem mag.
Originally I shot virgin hornady brass that measured 2.104 from case bottom to the datum point in the shoulder for load development. After firing the case is now 2.114. I always have heard and read to bump the shoulder back 0.002" or use the bolt (without a firing pin) to let you know where the shoulder needs to be. So the case inserts and the bolt handle falls over with a 2.114 shoulder. I thought this was odd as I felt the 2.114 case would have some resistance.So to check my theory,I had an old case ( same 7mm rem mag from an old barrel) that measured 2.118. I continued to bump the shoulder until the bolt closed with no resistance, that measured 2.114. I'm not sure if it matters but I'm using a RCBS full length die and the brass is on its 2nd sizing ( original load development and now reloading for shooting).
So I guess my confusion is if the case is fire formed to a shoulder measurement of 2.114, wouldn't the bolt closed with some resistance? What am I missing here?

As long as the belt properly held the cartridge head against the bolt face the shoulder blowing forward 10 thou isn’t an issue.
From now on you can just bump the shoulder back 2ish thou and not worry about it.
As for your measurements brass does spring back a bit.
You may want to double check your measurements and make sure your tools are squared away.

 

[warnera1102]

As long as the belt properly held the cartridge head against the bolt face the shoulder blowing forward 10 thou isn’t an issue.
From now on you can just bump the shoulder back 2ish thou and not worry about it.
As for your measurements brass does spring back a bit.
You may want to double check your measurements and make sure your tools are squared away.

I guess my concern or misconception was that if the case measured 2.114 it would be fire formed and harder to chamber at 2.114. Your saying that it is a few thousands larger to be the exact chamber size during firing and the spring back after puts it at 2.114?. The brass chambers (no firing pin) easily with the bolt handle falling on its own at 2.114, should I stick with that measurement of 2.114? I have reset the calipers and checked measurement several times with maybe a 0.0005 difference.

 

[Steel head]

I guess my concern or misconception was that if the case measured 2.114 it would be fire formed and harder to chamber at 2.114. Your saying that it is a few thousands larger to be the exact chamber size during firing and the spring back after puts it at 2.114?. The brass chambers (no firing pin) easily with the bolt handle falling on its own at 2.114, should I stick with that measurement of 2.114? I have reset the calipers and checked measurement several times with maybe a 0.0005 difference.

If it’s fired and 2.114 and fits back in the chamber fine that’s probably because 1-you brass is fairly fresh and not super hard and needed annealed and 2-your pressures are realistic for your rifle.

I neck size a lot for some of my rifles (because it’s awesome if you’re lazy!) and with annealed brass and sane pressures I can load that case 3-4 times without touching the shoulder or body and not get a tight bolt.

Keep you brass annealed and set your die to keep the shoulder at 2.114 or a smidge shorter if it’s for hunting and be happy.

 

[warnera1102]

If it’s fired and 2.114 and fits back in the chamber fine that’s probably because 1-you brass is fairly fresh and not super hard and needed annealed and 2-your pressures are realistic for your rifle.

I neck size a lot for some of my rifles (because it’s awesome if you’re lazy!) and with annealed brass and sane pressures I can load that case 3-4 times without touching the shoulder or body and not get a tight bolt.

Keep you brass annealed and set your die to keep the shoulder at 2.114 or a smidge shorter if it’s for hunting and be happy.

Thank you. Yeah the gun is more for long range target shooting than hunting now. I just have been consentrating on making my reloads more consitant to take any issues of equation.

 

[memtb]

So I am working on my load development on a brand-new remage criterion barrel 7mm rem mag.
Originally I shot virgin hornady brass that measured 2.104 from case bottom to the datum point in the shoulder for load development. After firing the case is now 2.114. I always have heard and read to bump the shoulder back 0.002" or use the bolt (without a firing pin) to let you know where the shoulder needs to be. So the case inserts and the bolt handle falls over with a 2.114 shoulder. I thought this was odd as I felt the 2.114 case would have some resistance.So to check my theory,I had an old case ( same 7mm rem mag from an old barrel) that measured 2.118. I continued to bump the shoulder until the bolt closed with no resistance, that measured 2.114. I'm not sure if it matters but I'm using a RCBS full length die and the brass is on its 2nd sizing ( original load development and now reloading for shooting).
So I guess my confusion is if the case is fire formed to a shoulder measurement of 2.114, wouldn't the bolt closed with some resistance? What am I missing here?

I am willing to accept some bolt closure resistance....not a great deal of resistance. I try to minimize my set-back, as I want to get as many firings from my brass as possible. I set my dies until I barely contact (gently kiss) the shoulder. I then chamber the sized brass. If the bolt closure is greater than I’m comfortable with....I make a slight die adjustment...and recheck for fit! Using this method, I get 10 firings from my brass in my .375 AI, loads are at maximum pressures.....before discarding the brass! memtb