COAL using Hornady Comparator

[pv107]

I recently purchased a Hornady bullet comparator to give me more consistent COAL measurements with my reloads. If anyone else has used this, do you have a COAL recommendation for a 223 Rem in a semi-auto rifle (AR15/556 chamber)?

For my 308 bolt action it's fairly simple. Using a dummy round I gently close the bolt then measure where the ogive touches the lands/groove and backing off .010". I imagine doing this with the slamming action of the semi-auto will affect the bullet seating and affect accurate measurements.

[maxx03]

You can go as far as the magazine will allow. I load 69 grain SMK to magazine length with excellent results.

[pv107]

You can go as far as the magazine will allow. I load 69 grain SMK to magazine length with excellent results.

Thanks. How about for 55gr FMJ?

[maxx03]

You can load those to 2.200 per Hornady 9th edition. Or try seating them as far out as your magazine will allow, you don't necessarily need to seat them to the cannelure. I usually seat these to 2.200. But I load 308 150 grain Hornady fmj to magazine length in M1A and AR10

[popeye4]

You can go as far as the magazine will allow. I load 69 grain SMK to magazine length with excellent results.

In most AR chambers, the magazine will be the limiting factor. However, if you are loading the 80 gr. SMK, for instance, you will be loading past this limit (single shot only) and identifying where the lands are can be useful. To measure that, get one of these: http://www.hornady.com/store/Lock-N-...Curved-1-Each/

[bubbapug1]

The dummy round method is far superior IMHO to the comparator method. I've never need able to get a truly accurate measurement off the lands with the "system" for whatever reason. I think the camming forces of the bolt on the dummy round push it forward a fair amount which you can't replicate with the hornandy. It's a nifty idea, but in practice it falls short....literally.

I know a few folks who also have tried both methods and go with the dummy round.

[pacrat]

The dummy round method is far superior IMHO to the comparator method. I've never need able to get a truly accurate measurement off the lands with the "system" for whatever reason. I think the camming forces of the bolt on the dummy round push it forward a fair amount which you can't replicate with the hornandy. It's a nifty idea, but in practice it falls short....literally.

I know a few folks who also have tried both methods and go with the dummy round.

+1

Your individual rifle is the best way to tell you the best seating depth. Actual COAL means nothing as long as it fits the mag and doesn't bind into the lands.

All copper bullets are a different kinda duck. They need more jump to leade to lower "start pressure".

JM2c

[Mr Blu]

The dummy round method is far superior IMHO to the comparator method. I've never need able to get a truly accurate measurement off the lands with the "system" for whatever reason. I think the camming forces of the bolt on the dummy round push it forward a fair amount which you can't replicate with the hornandy. It's a nifty idea, but in practice it falls short....literally.

I know a few folks who also have tried both methods and go with the dummy round.

How does the dummy round method work???

I'm asking because I have never heard of it before, which isn't saying much because I have only been reloading for about 1 year.

[jh4db536]

Hornady sells modified brass that are proper headspace and threaded in the primer pocket to accept a hornady threaded COAL rod. The neck is expanded to zero neck tension so a bullet of your choice can slide in and out more easily. You remove the bolt and jam the dummy round into the chamber which pushes the bullet forward into the lands since it can slide freely. You lock this setting and pull the dummy round out and measure the dummy round with your bullet comparator which gives you the exact coal to hit your lands. You can use this measurement to set your bullet seating die and zero out the micrometer.


Sinclair tool works using same principal except it doesn't use a special brass.

Problem with these method is the bolt is removed and the brass is inserted by hand into chamber which doesn't replicate the force of a bolt. The modified brass from hornady also is generically headspaced. Sinclair tool allows you to use your own form formed shoulder bumped brass (brand).

The dummy method is to take your fresh fire formed brass, dent the neck for fiction, and barely seat a bullet in there. You will remove the ejector spring and maybe claw from your bolt and chamber this dummy then actually close the bolt. The bullet hitting lands will push the bullet into the brass further to get you the right length theoretically. Then you have to carefully remove the bolt and dummy for measurement. Inaccuracy comes from movement of the bullet between bolt opening, extracting, and measurement of the dummy since it night not be held tight enough by the dented neck.

I personally use the Sinclair tool and I get repeatable results. I tried the bump method without success for the reasons above.

[Mr Blu]

I personally use the Sinclair tool and I get repeatable results.

Is this what you're talking about???

http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx