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Old 12-09-2016, 07:51 PM
HuntinGuy HuntinGuy is offline
 
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Default 7mm rem mag head space.

I am new to reloading and i am attempting to set my head space on my once fired cases. I am aware that belted magnums head space off the belt, but should not the cases stretch when fired and head space off the shoulder? I want to just bump the shoulder back. I tried the Sharpie method and show no marks on the shoulder, also i pulled the pin and spring on my bolt and tried to feel for resistance on my bolt but felt nothing. Should i just bump the shoulders 2-3 thousandths from where they are not knowing how far they sit from the shoulder in the barrel?
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Old 12-09-2016, 07:58 PM
elkhunter11 elkhunter11 is offline
 
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If the cases chamber easily, don't bother bumping back the shoulder, just neck size. If the cases provide more resistance than you like to chamber, bump the should back just enough so that the cases chamber easily.
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Old 12-09-2016, 08:02 PM
fish_e_o fish_e_o is offline
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Use a gauge please
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Old 12-09-2016, 08:13 PM
HuntinGuy HuntinGuy is offline
 
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I like the idea of always bumping the shoulder to ensure a consistent and reliable feed every time. Also correct me if I'm wrong but a gauge will not set me to my chamber but to SAMMI spec and off the belt.


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Old 12-09-2016, 08:19 PM
fish_e_o fish_e_o is offline
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Quote:
Originally Posted by HuntinGuy View Post
I like the idea of always bumping the shoulder to ensure a consistent and reliable feed every time. Also correct me if I'm wrong but a gauge will not set me to my chamber but to SAMMI spec and off the belt
Then get a different rifle or chamber it for something else
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Old 12-09-2016, 08:21 PM
HuntinGuy HuntinGuy is offline
 
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Quote:
Originally Posted by fish_e_o View Post
Then get a different rifle or chamber it for something else


Sorry you didn't know how belts work.


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Old 12-09-2016, 08:25 PM
fish_e_o fish_e_o is offline
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Originally Posted by HuntinGuy View Post
Sorry you didn't know how belts work.


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I know how trying to determine headspace works and I'm telling you that you're doing it wrong.

You should try to actually measure something. your random piece of brass that is probably not even close to spec isn't a way to set headspace.
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Old 12-09-2016, 09:04 PM
prarie_boy1 prarie_boy1 is offline
 
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I load .338 win mag for a friend and use my calipers and an insert that measures the particular shoulder angle of that cartridge. Take an average of 5-6 fired cases and set the die up so it pushes the shoulder back about .002-.003 in hunting rifles.
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Old 12-09-2016, 10:03 PM
Pathfinder76 Pathfinder76 is offline
 
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Pretend that the belt is not there.
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Old 12-10-2016, 12:57 AM
HuntinGuy HuntinGuy is offline
 
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Quote:
Originally Posted by chuck View Post
Pretend that the belt is not there.


Yes I'm just not sure why the shoulder is not hitting the chamber, maybe if I fire form the shells for the second time the case shoulders should be touching the camber?


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Old 12-10-2016, 04:50 AM
averagejoe averagejoe is offline
 
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Quote:
Originally Posted by HuntinGuy View Post
Sorry you didn't know how belts work.


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Quote:
Originally Posted by HuntinGuy View Post
Yes I'm just not sure why the shoulder is not hitting the chamber, maybe if I fire form the shells for the second time the case shoulders should be touching the camber?


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So you ridicule one person giving you good advice and then can't figure out what your problem is?

During firing the brass expands and grips the chamber walls filling the chamber. It then cools and shrinks a tiny amount. This allows extraction. This is why your once fired brass is smaller than your chamber and you aren't getting marks on the shoulder. Since it headspaces off the belt, the belt holds it back from going far enough into the chamber to touch the shoulder. (As I understand it anyways)

Fireforming them a second time will not solve your problem. But please feel free to ignore the advice that people are giving you because you as a new reloader obviously know so much better than them.
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Old 12-10-2016, 07:27 AM
Pathfinder76 Pathfinder76 is offline
 
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It is likely not touching the belt either.

Once fireformed the brass fits the chamber and until it won't chamber don't bump the shoulder or be doing it very minimally. This is why guages are nice to have.

And, yes, a second firing may make a difference.
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Old 12-10-2016, 11:12 AM
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Hunt4Ever Hunt4Ever is offline
 
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Quote:
Originally Posted by fish_e_o View Post
Use a gauge please
Take note of all the above advice, if you don't use a gauge to measure-how do you know how far you've bumped the shoulders back? I'm new to reloading too, 2 years in. The attached picture is just after 2 reloads of full length resizing (7mm RM/68gr H1000/168gr ABLR), I thought...I was doing this right...extremely dangerous! So I bought Hornadys Head Space Kit - http://www.hornady.com/store/Lock-N-...h-Body-1-Each/
Very easy to use and available, no issues to date.

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Old 12-10-2016, 11:17 AM
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dogslayer403 dogslayer403 is offline
 
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I neck size only on my 300wm and brass is wore out before i ever see any chambering issues try it out before you overthink this one

Like Chuck said forget it has a belt
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Old 12-10-2016, 12:02 PM
lclund1946 lclund1946 is offline
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Quote:
Originally Posted by HuntinGuy View Post
Yes I'm just not sure why the shoulder is not hitting the chamber, maybe if I fire form the shells for the second time the case shoulders should be touching the camber?


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You are asking the right question and I will attempt to explain what is happening and how you can confirm that. There was a good thread asking why manufacturers are going to Non Belted cartridges where I tried to answer the question you are asking. If you did not get a chance to see that thread before it got blocked perhaps you can go back and find it.

This Saami drawing illustrates where the Minimum/Max HS is measured at 0.420" (shoulder datum). The Maximum Cartridge length, to the datum, is 2.1162" and the Minimum is supposed to be -.0070" or 2.1092". However manufacturers have been notorious for manufacturing belted and rimmed cases to minimum shoulder HS and in a maximum chamber, which should measure no more than 2.1353", this leaves a possible 0.0261". This is not uncommon and can be determined by measuring a new case and a fully fire-formed case and getting the difference.

However, as you found out, a low pressure load will not necessarily fire-form0.026" head-space out of a new case. I am assuming that you are using a fired brass in your measurements. If you have full Length sized your brass, with a minimum spec die perhaps you have already bumped the shoulder too far.
[IMG][/IMG]

The best way to determine what is going on is to get this Hornady Cartridge Headspace Gauge Bushing set and use your calipers to measure a new and once fired brass and compare these measurements against the Saami Drawings. The .420 bushing will get you close enough to determine if your brass is fireforming to your chamber. If it is not fireforming then back your die out a turn and FL the brass and them measure where you are at. The shoulder will likely move forward, at the datum, as you size the brass and if it does not touch the shoulder then load and fire again. The next time you FL the brass you may have to turn the die in to "bump" the shoulder.

This problem has been virtually eliminated in the 'Non belted" magnums as tolerance have been tightened up to where HS problems are virtually non existant. In fact they are so tight that some Factory Ammunition will not chamber,but that is another story.

Good luck and if you are able to come to Rimbey I can help you get started.
http://http://www.hornady.com/store/...h-Body-1-Each/
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Old 12-10-2016, 04:36 PM
HuntinGuy HuntinGuy is offline
 
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Iclund1946,

Thanks for the info and thanks for understanding my question, i probably did not explain it that well. I will try your recommendations, sadly Rimbey is a bit far..
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  #17  
Old 12-11-2016, 07:20 AM
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DaleJ DaleJ is offline
 
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Would recommend expanding neck on 7 Rem Mag to 308 then adjust die a bit at a time until you can feel bolt close on chambered cartridge. Set lock ring on the sizer die where you feel the shoulder contact. I've seen a lot of undersize cartridges these last few years.
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