Overall Length Gauge and Bullet Comparator

Overboost44 · Nov 1, 2014

I did a search and couldn't find anything newer than 2008. I want to check my new builds and existing rifles for proper reloading of .223 and other calibers. I guess the Hornady OAL Gauge and bullet comparator set is the best way to go.

Should I spend the $60, or does someone have one sitting around? I imagine this is the kind of thing you only use once per gun and then it collects dust. Am I right with that line of thinking?

I like having all of my own tools, but sometimes it just doesn't make sense.
http://www.amazon.com/gp/product/B000PD5VLA/ref=ox_sc_sfl_title_2?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
http://www.amazon.com/gp/product/B000PD6SD0/ref=ox_sc_sfl_title_3?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Klunatic · Nov 1, 2014

I have one and would let you use it but I don't think you in my area. It is a tool you don't use often (OAL length gauge) just when you get a new barrel. The comparator is something I use all the time when reloading. This is the only way to correctly measure the Ogive as OAL can vary on the boolits. The Ogive is what counts. I reload my rounds .020 off the lands if I can (and still get them to feed in the magazine).

Overboost44 · Nov 1, 2014

Thanks for the offer. That is a good start for me. I am buying stuff from amazon and wanted to add these to my order. I may as well just get them both and then I will have one to lend out.

BigDaddy · Nov 1, 2014

The overall length gauge is used in conjunction with a modified case to determine where the the bullet contacts the lands. People who have machining skills and a lathe have made their own gauges. The threads for the case are an uncommon type. If you make your own, you can choose a more common thread and die. I have not seen the curved gauge needed for an AR, so I don't know how difficult that would be to make.

Sinclair International used to sell a lead flat topped slug to determine where the threads start. I cannot find it in their online catalog.

Anyone inclined to make their own gauge should google "what threads does a Hornady OAL gauge use?" If a fired case grips the bullet too tight, a dremel cutoff disk and a slice parallel to the case through the neck should solve the problem.

You still need a gauge to measure the OAL of your loaded round. Sinclair sells a "nut" with different sized holes to measure off the ogive of various calibers. I found it had too much wobble to be useful.

fa18hooker · Nov 2, 2014

Make your own from some scrap aluminum and a drill index...they're not the most technically advanced tool out there, and it'll cost you nothing...

Sticky · Nov 2, 2014

You can get away without the oal gage, just neck size a case a tad loose, partially seat your boolit of choice, chamber it, seat it with the bolt (be sure it is 'loosely' neck sized, so it doesn't drive into the rifling). CAREFULLY remove the now chambered round (I don't prime or charge this round, take it apart when I am done) and measure it.

You really need an accurate way to measure off the ogive of the bullet. That is critical. With this measurement, you now have a 'to the lands' value to work from. Simple, effective..

Overboost44 · Nov 3, 2014

I went ahead and bought it. Next time I will give a little more notice for all of the great responses. Oh well, it won't be the first time I spent $30 unnecessarily. The next time someone needs one, just let me know.

IndispensableDestiny · Nov 9, 2014

BigDaddy said:
The overall length gauge is used in conjunction with a modified case to determine where the the bullet contacts the lands. People who have machining skills and a lathe have made their own gauges. The threads for the case are an uncommon type. If you make your own, you can choose a more common thread and die. I have not seen the curved gauge needed for an AR, so I don't know how difficult that would be to make.

It's a 5/16-36 tap. You use a 9/32 drill. You don't need a lathe, a drill press works fine for the hole. The tricky part is to keep the case from turning. With trial and error, you can drill out the case with a hand drill -- I've done it.

Make your modified cases from once fired brass, from that gun, not resized.

The tap is available from MSC Supply online.

You use a straight gauge for an AR. You remove the charging handle and bolt. You only need the curved gauge when you can't easily remove the bolt, like on a lever gun.

I use mine whenever I try a new bullet style. It's not a one time check on a gun's chamber.

K31 · Nov 10, 2014

If you're going to use it, you are going to use the bullet comparator on your calipers each time you set up your seating die. You're also going to use the OAL guage when you change bullets even of the same general shape and weight because as already stated, it's the ogive that counts.

I also would characterize making your own case as "machining". If you find the post by the guy who did it, it takes a drill press, vice, and tap.

Overall Length Gauge and Bullet Comparator

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