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Silvertip 44 01-29-2010 04:33 AM

Sizing cases for individual rifle headspace
I posted this thread on another forum and haven't received any comments yet.
Maybe I am trying to accomplish something that i can't do anyway but thought that I would see if any of you reloaders might be able to help me.

I got all excited a while back and decided to order a RCBS precision mic headspace gauge and a small base XDIE to reload for my M1A's.
I went to the range today and fired a few rounds through two of my rifles to test some new loads and bullets as well as to have fired cases for measurements.
When I got home, I measured the cases according to instructions and found that both rifles measured and averaged out at +.006 on the guage. I measured 20 cases for the standard rifle and 30 for the NM.
As I read deeper into the instructions it states that RCBS does not recommend using the precision mic in reloading for autoloaders and some lever rifles and or ammo that requires small base dies.
It is basically recommended that ammo for the M14/M1A and the M1 Garand be reloaded using small base dies. Some reloaders do and some don't.
Ol Hook showed me how to measure my fired cases a couple of times and explained to me that if I reloaded to just under rifle headspace accuracy would improve even more. He showed me how to strip the bolt then size the case to where the bolt just closes so the lugs lock with the newly sized case in the chamber.
According to instructions I should size to +.004 for optimum chamber fit but I might have to go to +.003.
Now my question is would loading to meet headspace requirements be safe in my rifles. I certainly don't want to create a dangerous situation or to damage my rifles.
In my closed space thnking, I had planned to also load in such a manner for a couple of my Garand rifles should this method show decided improvement in the M1As.
I will certainly appreciate any comments or advice on the matter.

cpttango30 01-29-2010 10:20 AM

You don't want EXCESSIVE headspace. You say yours is micing at .006 and your wanting to load at .004 leaving .002" slack. That sounds ok to me. I have never did all this either. I just pull handle and shoot. I have one rifle that when you close the bolt the neck of the case rubs on the chamber and is really tight the first time I load them. It changes after I fire them because the case fireforms to the chamber. So you should really only have to do this once then just neck size them from then on. I also don't do much loading for M1a. Robo or one of the other guys will be along shortly I am sure to give some more insite.

masterPsmith 01-29-2010 12:40 PM

This is all great when loading for consistant accuracy in a bolt or single shot rifle. It will increase shot to shot accuracy in semi-autos also, but with a price. All ammo for semi autos should be full length sized using a small base die for reliable feeding and chambering. If you size your cases for minimum headspace in your M1A, you will have occasional FTFs. Any dirt, dust, powder fouling, etc., will cause chambering problems preventing the bolt from fully rotating into battery when closed and subsequent failure to fire. Just the nature of the beast. If you are using these loads only for paper and don't mind having to keep the chamber clean while shooting, then have at it. If you need 100% go bang all the time, then full length size your cases...........................


robocop10mm 01-29-2010 01:15 PM

Trying for the tightest posible fit in any semi-auto will cause the occasional (or perhaps frequent) malfunction. If you want the best possible accuracy and are willing to put up with the malf's, neck size fireformed brass.

Some rifles will operate just fine with full length resizing. Some need small base dies. It is the rare shooter that will ever see the benefits of such fine tuning of ammo.

I full length size everything as reliability is most important to me.

Silvertip 44 01-29-2010 03:21 PM

Thanks fellas. I am beginning to load using the small base XDIE so maybe I should just full length size for a while until I can determine if it shows any enhancements over my small base standard dies.
Due to the fact that both M1A and M1 Garand have free floating firing pins and can have an out of battery detonation I will hold off on loading to just under chamber specs. From what I have seen, an out of battery fire is something that I don't want to gain first hand experience.

Innovative 01-29-2010 06:56 PM

Silvertip 44 ......

I just wanted to say that there is an accurate way to measure the chamber clearance (at the shoulder) that YOUR handloads have in YOUR particular chamber. Check our my website, and you'll see how I do it. I also have over 120 pages of reloading tech tips there.

- Innovative

skullcrusher 01-29-2010 07:01 PM


Originally Posted by Innovative (Post 220848)
Silvertip 44 ......

I just wanted to say that there is an accurate way to measure the chamber clearance (at the shoulder) that YOUR handloads have in YOUR particular chamber. Check our my website, and you'll see how I do it. I also have over 120 pages of reloading tech tips there.

- Innovative

Welcome to the forum. How about stopping by the Introduction section and tell us a little about yourself. :)

Innovative 01-29-2010 09:12 PM

skullcrusher .......

Read my website, and you'll see everything about me .... well almost.

Here's the short story:
  • Christian
  • Semi-retired
  • Former Marine ('70 - "72)
  • NRA Life Member
  • Self Employed inventor w/2 patents

- Innovative

Silvertip 44 01-29-2010 11:48 PM

Thanks for the reply Innovative, however, I was asking more for advice and assistance rathar than an advertisement.

Innovative 01-30-2010 12:11 AM

Silvertip 44 .......

My whole website only has (2) items for sale. The other 124 pages are shooting & reloading tech tips. Measuring your headspace and your case width (above the web) will ensure that your handloads will always fit properly. Chamber clearance (at the shoulder) at .003" is perfect for your Garand.

- Innovative

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