Can someone please tell me exactly what they do and also, do you use one in your rifles?


I just bought one in .308

The bullet thingy is for measuring to the rifling. I haven't had much luck learning to use it.
The case measuring thingy measures the case brom it"s base to the datum line on the shoulder. If the gage was made exactly to spec, at a "zero" reading your brass is at SAMI chamber mimimum.
If you know the amount of spring back your brass has you can extrapolate the chamber headspace dimention. With a chamber cast you can measure without worrying about spring back.
I use these tools to help setup my resizing dies for what is often refered to as Partial Full Length Resizing. Measure a good sample of fired brass. Take the average, subtract what ever amount of shoulder set back you want(I typically bump .002" or .003".) Screw the die into the press. Backoff one turn from contact with the shell holkder. Size one case , measure it, adjust the die as needed repeat until you are sizing to the dimention you calculated.


muck

Here's a fun test.
Use the RCBS precision Mic to measure the head space length of a bunch of new unfired cases, record the readings and calculate the average head space length of new brass.

Now measure the head space length on a bunch of cases recently fired in your favorite rifle that haven't been resized yet..
Again record and calculate the average length.

Subtract the the two measurements and you will know how much your brass is being worked on the firing/resizing cycle.

For example: my rifle fired cases measured -.006" less than the ANSI specified head space length.
But new brass measures -.010" less than the ANSI specified head space length.

So a full length resize will only work my brass .004" assuming the sizing die returns the cases to exactly the length they were before they were fired.
Now I will be able to adjust my FL sizing die to just set the shoulder back maybe .002" to .003" and save fatiguing the brass too much.

quote:

Originally posted by Buglemintoday:
Can someone please tell me exactly what they do and also, do you use one in your rifles?


I just bought one in .308

I have one for every caliber I own. I use it to measure head space after sizing, then after I finish loading my rounds, I measure each one when bullet is seated, to ensure length to ogive is consistent.

When I full length resize, I push shoulder back .002.

I find that depending on bullet loaded, I am adjusting my Redding micrometer frequently, and checking the finished round in the RCBS mic. It's not too much extra effort and I've gotten quite fast with it.

I adjust it most with bullets other than Nosler ABs, Btips, TSX, and Bergers.

Thanks guys! It sounds like it is a valuable tool in your reloading equipment

They are actually accurate and easy to use if you read the instructions before you try to find the lands, and keep in mind that the "bullet thingy" is made to simulate a bullet of an "average" ogive. The point on the ogive that contacts the lands would be your furthest seating point. You'll want to back your bullet down hundredths of inches from there.

The headspace finder requires that you shoot some cases before using it. What you're doing is expanding the brass and then measuring it to gage the length of your chamber.

If you are planning on using the tool to measure the chamber of a factory gun you might consider casting the chamber instead. One reason a lot of people have trouble with the bullet seating part of the tool is that they are trying to find the lands in factory rifles which have been built purposely with very long throats to prevent inexperienced handloaders from loading into the lands. Many do not realize how much pressure increase they can build this way, so the company lawyers now dictate chamber size, it seems.


http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=462291

To those using Precision Mics or other case body length comparators:

What has been your experience when measuring the "case headspace" or case body length from case head to datum line of shoulder of your fired cases? Are your case sizes consistent after sizing?

I have found that new, unfired cases measure about -.004 on my Precision Mic. Fired cases USUALLY measure about +.001 to .002, so the shoulder of the case expands or moves forward about .005 to .006".

After carefully adjusting the sizing die (Redding type S full length die) to try and set back the neck to a reading of between -.001 and .000 (in other words, bumping the shoulder back .002"), I have found that there is a surprising amount of variation when I measure the resized cases. Most of the cases measure .000 to -.001, but occasionally a case will measure -.002 or as much as +.002. I am carefully lubing each case the same way and sizing with exactly the same technique. I have even tried sizing with a "double bump" at the end. In other words, I bring the ram up, hold a second, lower the ram a very small amount, then raise the ram a second time. This does not seem to change the post-sizing case measurements.

Could there be that much variation in the brass "springback" that such variation in results could occur? Any comments?

FYI, I am using Black Hills Match .223 brass from two separate lots. One lot is from new Black Hills ammo that was fired once in my rifle (Cooper .223 model 21). The other lot is a batch of once-fired brass puchased on Ebay, all with Black Hills Match headstamp. With regard to the second lot, I can understand why there would be variation in the pre-sized brass (fired in different rifles), but I don't understand the variation on the post-sized brass, all using the same Redding sizing die.

Any thoughts?

Infantrytrophy,

I use a different tool to measure head-shoulder dimensions for fired vs sized cases. My goal is to quantify the amount of sizing I do - typically between .001 and .002". I also see variation in how much cases are sized, even with brass from the same lot, fired the same number of times, same die setting etc. I don't get as much variation as you, though. .001" variation is probably typical.

I have always put it down to variation in brass. I know that is not very scientific, but brass does vary for non-obvious reasons. Have you ever tried to trim a bunch of cases to the same length, load all with the same load, fire in the same chamber at the same temperature, and size with the same die setting. After all this, you will find variation in case lengths, and I'm not sure where it comes from?? Brass varies...

- mike

Have I got this right? Your talking about a very accurate gauge, that shows that you are not getting accurate results.

quote:

Originally posted by JAL:
Have I got this right? Your talking about a very accurate gauge, that shows that you are not getting accurate results.

Jal,

Not exactly. I think that the gauge is accurate in that it will measure any given case correctly. I can take a given case and measure it repeatedly over several days with the same result. (This technically would be termed precision.)

What we are talking about is variances in the different samples of brass. If I take several pieces of once-fired brass (same headstamp) and size them with a specific sizing die, a few of the resized brass pieces will vary in case body length (from base to shoulder). Most of the pieces will measure the same, but a few will vary. The precision mic will measure each piece the same repeatedly, but there will be variation between some (not all) of the pieces of brass - even though they have been sized in the same die.

It could be my source of brass, obtained by firing store-bought factory ammo from Black Hills. Could the pieces of brass from this ammo come from different lots?

Perhaps I should buy new brass from the same lot, fire it, resize it and then check with the precision mic. That might show that brass from the same lot has less variability and might suggest that my brass might have come from different lots.

quote:

Originally posted by infantrytrophy:
If I take several pieces of once-fired brass (same headstamp) and size them with a specific sizing die, a few of the resized brass pieces will vary in case body length (from base to shoulder). .

Thanks infantrytrophy, but from the part quote above, what I was wondering is someone on AR suggested the Hotcore method of measureing for PFLS'ing was inaccurate.
I assumed the measurements your talking about was to get every case 2 thou short at the shoulder.
Now people are saying cases vary as proved by the precision measurements.

Therefore I'm thinking I may as well stay with the bolt close feel method? After all I think it's the Jerk on my trigger that is the real problem, but hey, I do love gadgets.

quote:

Originally posted by JAL:
... what I was wondering is someone on AR suggested the Hotcore method of measureing for PFLS'ing was inaccurate.

Hey JAL, I do not think they are meaning to imply that. They are simply wasting their time and their money buying Thingys that allow them to measure something that doesn't need to be measured. If they believe they are gaining something from it though, then more Thingys to them.

quote:

I assumed the measurements your talking about was to get every case 2 thou short at the shoulder.

Nice catch. By them forcing it back 0.002" from a snug Bolt closure, they are creating Excess Headspace. That shortens case life and prevents the very best possible accuracy.

quote:

Therefore I'm thinking I may as well stay with the bolt close feel method?

If you want the best opportunity for accuracy and the longest case life, setting the FL Die for a snug Bolt closing P-FLR is no doubt the best way to go. And no Thingys are needed.

quote:

...but hey, I do love gadgets.

That is reason enough to get one. That helps keep the economy stimulated and provides fodder for threads.

quote:

Originally posted by Hot Core:
That is reason enough to get one. That helps keep the economy stimulated and provides fodder for threads.

I guess I'm not really doing my part. I have one of these that according to the instructions will measure the ...can't call it headspace...GAP BETWEEN THE CASE SHOULDER AND CHAMBER SHOULDER on 44 different listed calibers for the same price!

I'll try to do better.

Hey Woods, I was thinking about this at half-time. What you guys really need is a Thingy for "each and every" Case.

For example, if you have 100 223Rem Cases, you really should have 100 Thingys so the measurements are exactly relevant to each specific Case. Yeah, one Thingy for 44 different Cartridges is no good at all.
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I've pretty much decided Thingys also need their own measurement Base. For example, you measure the Shoulder <-> Case Head distance and instead of 1.500"(Inches) it really should read 1.500T(Thingys). That way you all can discuss it and all the Data collected is relevant to a "Thingy Base". Still totally worthless Data, but at least it would allow you all to compare it.
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Now that Mitt Romney has dropped out of the race, perhaps he would convince his good buddies on the Olympic Committee to create a "Thingy Toss". Similar to a Shot-Put, but it could also be measured in "Thingys". You could create a Texas Team and represent all of us in the next Olympics. You have my full support!