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Posted: 12/13/2008 5:09:48 AM EDT
| By using the Hornady headspacing bushings with a case fired from your weapon,and then measuring a non-fired factory round in the Hornady bushing set,would it be safe to say that your rifles headspace is relatively inbetween those two measurements? With a fired case,is the optimum shoulder setback .002 ? |
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I've measured a ton of Q3131A and the headspace was far shorter than I would ever recommend anyone set a resizing die.
You're on the right track. Measure a few fired cases, then set the sizer die to push the shoulder back about 0.0015 to 0.002 inches. If you get 0.003 or 0.004, that's okay, too. The maximum should be held to 0.008 inches. I stay on the end toward 0.002 for a serious target rifle with custom barrel and chamber. Cartridges sized that way function in my other rifles, too. |
| Thanks for the reply! I had one more question. Could you use this same practice for once fired brass not used in your weapon. I mean,once you make the adjustment on the resizing die with fired cases from your rifle,can this method still be used with cases not fired from your rifle? |
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Quoted:
Thanks for the reply! I had one more question. Could you use this same practice for once fired brass not used in your weapon. I mean,once you make the adjustment on the resizing die with fired cases from your rifle,can this method still be used with cases not fired from your rifle? Sir, FWIW I resize brass not fired in my rifle that way all the time. As AeroE mentioned as long as the resized brass is within the range specified for that cartridge everything is OK. Just don't expect the resultant reloads to be as consistant. JMHO, 7zero1. |
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Hey guys, is there any way someone could explain what headspacing EXACTLY is and why/how you adjust it? Headspace Definitions and Thoughts, for re-loading........ http://www.nationmaster.com/encyclopedia/Headspace http://www.gswagner.com/headspace/headspace.html That last one is what some people like to use. Then, some people (me) like to use a cheap and simple gauge like the Foster, Dillion or Wilson type. There are a lot of choices........... http://www.sinclairintl.com/cgi-bin/category.cgi?category=REMTHT&type=store ___________________________________ BTW.........for a gunsmith, the tools used to check headspace on a rifle differs from the tools used to check the ammunition. Here is an example of the tool a gunsmith would use to check a rifle's chamber for headspace. http://www.policeone.com/police-products/firearms/accessories/ammunition/press-releases/1670747/ HTH. Aloha, Mark |
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Quoted: Hey guys, is there any way someone could explain what head spacing EXACTLY is and why/how you adjust it? I'll explain it as I understand it at the risk of being ridiculed  A cartridge has two ends: the mouth and head. The head end is the primer end. Head space is the space between the bolt face and the head of the cartridge when the round is chambered. When a cartridge is fired it expands in all directions. The chamber of the gun keeps most of the expansion of the cartridge in check. That leaves only the mouth end of the case and the head end of the case as directions to expand. Nothing bad will happen if the mouth end expands, it already has a hole for gases to escape, the hole the bullet is seated in. Bad things will happen on the head end if the brass expands too much. The brass will thin to the point of rupture and gases will escape into the action of the gun, maybe causing a KABOOM. How to avoid the case expanding too much at the head end? Size the case so it doesn't have room to expand to much on the head end. Brass like taffy, can only be stretched so much before it breaks. |
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Quoted:
Quoted:
Hey guys, is there any way someone could explain what head spacing EXACTLY is and why/how you adjust it? I'll explain it as I understand it at the risk of being ridiculed
A cartridge has two ends: the mouth and head. The head end is the primer end. Head space is the space between the bolt face and the head of the cartridge when the round is chambered. When a cartridge is fired it expands in all directions. The chamber of the gun keeps most of the expansion of the cartridge in check. That leaves only the mouth end of the case and the head end of the case as directions to expand. Nothing bad will happen if the mouth end expands, it already has a hole for gases to escape, the hole the bullet is seated in. Bad things will happen on the head end if the brass expands too much. The brass will thin to the point of rupture and gases will escape into the action of the gun, maybe causing a KABOOM. How to avoid the case expanding too much at the head end? Size the case so it doesn't have room to expand to much on the head end. Brass like taffy, can only be stretched so much before it breaks. Assault Rifler is correct. Now, the question is, how do you avoid the problems and set the case headspace correctly? When reloading, you need to use a set of calipers and a Hornady Stoney Point case headspace gauge. Take a case that's been fired in your rifle. Measure the cartridge using the gauge. Set your Full Length sizing die so that the shoulder of the case is bumped back around .002 or .003 inches. If not, adjust and try it again with another fired case. When you get that amount of bump-back, then lock your die down and measure one more case just to make sure. If it still bumps back around 2 or 3 thousandths, then size your batch. The method insures that your cases are resized enough to fit into your chamber, but not so much as would cause excessive headspace. Bolt action guys can get away with fire-forming and neck-sizing only. Semi auto shooters must use the case headspace gauge method and full length resizing dies. |
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Or..........
You could just do it this way with a cheap and simple gauge. This is how I do mine.
6) I use a single station press (RCBS Rock Chucker). You could use a progressive Dillon IF you wanted to. It's a personal choice. But, with whatever press you choose, consider shell plate/shell holder and/or press "flex.” I use a regular FL size/de-capper die, NOT the small base dies. To begin, lube your cases. Then, FL size and de-cap, 1 or 2 cases for a test. Gauge the re-sized case(s), to confirm that the "correct size" has been achieved. I use a Forster Products case gauge (the Wilson or Dillon case gauges are also popular choices). Insert a case into the case gauge. The headstamped end of the case, needs to be at or between the high and low cuts on the gauge, to pass. This checks the headspace. While the other end, is used to check if the case will need to be trimmed (a job for later on). IF, it’s not the “correct size,” your die setting will need adjustment. Lower the ram and simply screw the die in or out a little. Don’t forget about the lock nut. Then, re-size another couple of test cases and check your work again. Repeat the test and adjustments, as needed. When you're satisfied that your test cases are properly re-sized, do the entire lot (remember to test some cases throughout the run). HTH. Aloha, Mark |
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Thanks guys. I always wondered what was the difference between nato ammo and it's commercial versions. I knew it had something to do with headspacing. The difference in the NATO chamber and the SAAMI chamber is mostly the free bore at the chamber throat. The NATO chamber has a long freebore that requires the bullet to jump a small distance before it engages the rifling, and this helps mitigate the higher operating pressure. If the bullet of a 5.56X45 round was jammed into the lands before firing, the chamber pressure would be much higher than spec. Think of cartridge headspace in this way; it's a description of the volume available for the case to expand into upon firing. If there is too much space around the case, when it expands the brass is stretched (strained) so much that it fails or the life is reduced. The idea is to provide just enough space so the cartridge chambers easily and the empty case extracts easily after it shrinks back closer to the starting dimensions. One rifle might have a 5.56 chamber for good reliable operation with a wide variety of ammunition in rough conditions. The only expectation from the brass is that it works correctly one time, so if it gets stretched and expanded short of failure, that's all that is required. The most obvious trade off is potential accuracy. Another rifle has a tight chamber with just enough room to let the cartridge operate (it's useless if the cartridge can't be chambered) and release the bullet, while holding everything in alignment with the bore. Accuracy is foremost. Brass life is probably good, but hot loads might still trash the primer pockets before the necks and shoulders give up, and that is generally accepted as part of the cost. This is likely not a SAAMI chamber, by the way, the neck diameter is probably too small and requires neck turning of the brass for safe operation. A SAAMI or Wylde chamber is somewhere in between; sensible compromises for safe and reliable operation with good accuracy. |
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