Diy COAL Gauges and AR15's

[Wolfdog91]

Quick question for those that use DIY coal gauges (I'm referring to the ones where you take a once if brass fire formed in the rifle oval out the case mouth a little or make a cut in the neck so you can add or take off tension from the bullet) . When your using them in an AR or other semi auto rifle do you chamber them like any other round, ride the bolt forward in them or press fit them in the chamber then extract them with the bolt?
Thanks!

[Rick Hodges]

My experience with AR's has been the magazine was the limiting factor of overall length of cartridge with bullet not the chamber throating.
If I was trying to determine distance to lands I would place the dummy round in the chamber by hand and then ride the bolt home and extract it.

[NC_JEFF]

Rick has given good advice but after you find your COAL, go back and see if the round still fits in your magazine. My Bushmaster Varminter runs out of COAL before it gets anywhere near not fitting the magazine.

[sigep1764]

I echo the above. I load to as long as the magazine will let me with a 70 grain lead boolit and still don't get into the lands.

[Dimner]

This is a great question, one I was wondering a while back.

For my application, which is CMP Highpower format shooting... A shooter single loads at two different stages. Meaning, you load the rifle one at a time and not from the magazine (I use the bob sled).

So I made up two different loads for this format of shooting. First, a load that had the absolute best accuracy, regardless of the cartridge being too long for a magazine. The second load was one that would feed reliably from the magazine. It bears mentioning that I really only gained about 1/3 MOA accuracy by making a single loading handload. But it was a fun project to work on.

Anyways, how I did the OAL.... First, I removed the lower from my upper. This takes the buffer and spring out of the equation and makes moving the bolt easier and less likely to trap my fat fingers. Then with my preferred bullet in the modified case (with the split neck) I inserted it loosely into the chamber and manually slid the bolt into position. Then I use the charge handle to slowly slide it out and help gently eject the dummy round. I did this about a dozen times. Threw out the 2 or 3 odd ball readings, and used the average of the rest.

[Wolfdog91]

Ok another question. What donyallnuse for a dummy round ? Like I've always used a piece of fire formed brass for my bolt guns but with a semi auto would you do the same or use a pice that's just been sized as you would eveything else?

[Lloyd Smale]

My experience with AR's has been the magazine was the limiting factor of overall length of cartridge with bullet not the chamber throating.
If I was trying to determine distance to lands I would place the dummy round in the chamber by hand and then ride the bolt home and extract it.

yup for sure with 556 guns. A couple of my BO's are fussy about some bullets seated out to far though. I doubt your going to seat a bullet out far enough that will still fit in a mag and kiss the start of the rifling in the chamber. Most ars are built to run and run dirty not for bench rest shooters. Its why most guys who shoot the 80s and up in 556 guns single load them.

[jsizemore]

Ok another question. What donyallnuse for a dummy round ? Like I've always used a piece of fire formed brass for my bolt guns but with a semi auto would you do the same or use a pice that's just been sized as you would eveything else?

I bump the shoulder a thousandth or 2 and make sure it chambers without issue. Then I shapie a seated bullet and look for interference marks or lack there of when the bolt goes to battery. This will work on most any bottleneck cartridge.