Hornady Bullet Camparator Gauge and HOMEMADE modified case

nevanevan

nevanevan

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I ordered the appropriate case off EBAY so that I could make my own modified case gauge as everybody is sold out of 300 WIN MAG modified gauges. My question is, Would I wan't this case to be FL sized first which I assume the hornady one is, or a once fired chamber matching piece of brass from the rifle I am reloading for. The reason I'm confused is because the hornady comparator tool requires you to push the brass tight to the chamber so it rests against the shoulder of the brass. If it is FL sized I presume that the shoulder will be 0.020-0.005 or shorter as it is bumped back in the FL die compared to a one fired neck sized piece of brass. What method should I use? By the way the die was a 5/16-36 UNF HSS Plug Right Hand Tap which costs about $10 to my door from CHINA, sure beats the $8 per case locally if you can even find one.

Evan
 
A once-fired case from your rifle would certainly be most accurate, especially if you can easily drill and tap one for each gun, but ONLY if you plan to neck size exclusively for that rifle. If you're going to FL resize your rounds, use a FL sized case.

The neck should not be resized or you won't get a bullet in it without a seating die.
 
A once fired case will almost certainly have enough spring in the neck to make getting a bullet in without a die very tricky. Try using it with the gauge in your rifle, and I'm pretty sure it will jam in your lands and give you funky measurements. I think you'll have to somehow expand the neck enough to get the bullet in easily, but still have the slightest grip.

Also, the shoulder of a once fired case won't correspond exactly with shoulder in your chamber. It takes a few firings to get the brass to expand fully.
 
No, FL sized is unnecessary. The shoulder thing is really not important, only the length from the head to the ogive of the bullet matters.
Try using fired brass a few reloads old. The biggest issue is the neck being too tight.

I'm surprised you couldn't find one online. Where did you look?
 
I have made many dozens of calibers (especially for sizes like 257 Newton and the 8x56 mannlicher schoenauer type stuff).

I full length resize the brass But try not to aggressively set back the shoulder). Then use a dremel (you can use a round file) to open up the inside of the neck so the bullet slides in and out -snug but moves without pounding.

Then measure away.

I found that if I use neck size or partial size, the shell can get stuck without being all the way into the chamber. Remember that you are just pushing it in with your hand and not a bolt.

I never measured a standard from Hornady brass that has been modified, but I do not stress the slight difference that are possible between brass - once you find your lengths, you can adjust from there in your reloads.

Good luck. I can make one in about 2 minutes now.
 
Alpheus, the reason im asking about FL sizing is that when the shoulder grows after firing, it expands and since the gauge uses force from your hand to the shoulder, the case base will be a greater distance from the ogive of the bullet throwing off what should be a very accurate measurement.

Evan
 
No, that's incorrect. You want the dimensions of the modified case to be as close the those of the chamber. If the shoulder of the case is bumped back, the length from ogive to head will be smaller then what it should be. The shoulders don't fully expand after the first firing. Using a case that has been fired a few times but still chambers easily will mean the shoulders will be more expanded and closer to the shoulder of your chamber.
 
I agree with Alpheus in theory - but in practice you will need to resize the fired brass somewhat (more or less depending on how it fits un-sized) to get it into the chamber easily with the gauge screwed into the modified casing. You dont want to force the gauge into the chamber.

It will need to be resized.

The ones you buy from Hornady are generic in size and not custom made to your chamber of your rifle. They are (I would assume) to SAMI specs to fit every rifle - autoloader, pump, bolt etc. The measurement you get are for your particular rifle - then you adjust your bullet depth in any event to get your best loads - for your rifle.

The measurements are always going to be somewhat relative and not an absolute value.
 
I have made several dozen of these modified cases for my AI chamberings etc.

A case fired in YOUR rifle works perfectly. DO NOT resize the case!!

Use the proper Tap drill [7.2mm] and the 5/16 - 36 tap [make sure you are straight]

You can feel the shoulder of the case contact the shoulder in the chamber if you do this correctly.

If you feel that your brass has shrunk during the first firing, then neck size a case and fire it again.
Then make your modified case [remember, do not FL or neck size the case you are modifying.]

Regards, Eagleye.
 
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The cases from hornady are all unfired cases that have been drilled and tapped.
And also the necks have been expanded. Thats pretty much it.

I have made many of my own as well. Full length/ neck sized ( and dremeled up to a loose fit), what ever allows the case a dependable repeatable return to battery position.

I really like this tool and it has also aided me in tracking throat erosion (roughly mind you).
For each barrel, I take a single bullet and take 4-5 measurements for over all length to the rifling. (Take the average) I then mark the measurement on the bullet. Put the bullet in the die box for that rifle.
After that, i can periodiclly clean the bore, and remeasure with that original bullet. The change in measurement can give you an idea of the throat erosion that is occurring.

This has worked fine for me over the years, but has its limits as all proceedures do.
Hope that can help someone.
 
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