View Full Version : Homemade COAL guage question
T-Rex
03-23-2010, 08:49 PM
I have been reloading for awhile now but never tried this before. I just made my own COAL gauge by cutting the neck and drilling out the flash hole. I use a section of cleaning rod to push the bullet forward. For my 10fcp-hs I got these 5 results: 2.686, 2.685, 2.688, 2.686, 2.687. That is just touchings the lands. Sound right???
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Balljoint
03-23-2010, 09:18 PM
If your case is all the way in your chamber and there is some tension on the bullet to hold it in place when you pull the case out then sounds about right
It is hard to say that your numbers seem right or not, as it depends on the bullet you are using.
What we are doing is measuring the distance between the bolt face and the point of contact between the ogive of the bullet and the beginning of the lands. This distance will vary depending on the shape of the bullet. What we are reporting, though, is not this measurement, but rather the overall length of a cartridge (with seated bullet) that results in the ogive just touching the lands, and the difference between the measured phenomenon and the reported surrogate will also vary depending on bullet shape.
That said, in my Savage .308, using 168-grain SMKs, I get a consistent 2.8052 +/- .0003 to touch the lands.
trappst
03-24-2010, 09:57 PM
T-Rex,
No need to drill out the flash hole and use the rod. Cut the neck like you did or less....I just cut one slit in the neck with a dremel. Start a bullet in the neck by hand and rub some gun oil on the bullet.
Throw that bad boy in the chamber and close the bolt. Open and remove slowly....the gun oil should help keep the bullet from sticking in the rifling. Measure.......presto, free OAL gauge.
T-Rex
03-25-2010, 01:43 AM
RKG
Thank you. I do understand why and what I was measuring, I was just wondering if my method was sound since I haven't tried it before.
Those numbers listed were w/ hornady equiv of 168 smk's. Actual 168 smk's were 2.680 avg and hornady 220 sp's were 2.760.
The weird thing when comparing the hornady 168's and sierra 168's was the hornady seem to be better made. The tip of the sierra's was not square but sort of cut off on an angle and the hornadys where perfectly square....
2.680 for a COAL using 168 SMKs touching the lands strikes me as short. The "nominal" COAL for that bullet is 2.800 (per Sierra 5th ed.). As noted, my Savage measured at 2.8052 +/- .0003 to the lands, and my best rounds so far are seated 2.791, which is believed to be about 15 thou off.
Just a guess, but did you resize the case that you're using for measurement? (Since using a StoneyPoint gauge, or your home made one, you can't actually close the bolt, we are actually referencing off the point of shoulder contact. For that reason, you do not want to resize the case (or, possibly, half neck size only), since that will push the shoulder of the case back and result in shorter measurements.)
T-Rex
03-27-2010, 12:16 AM
RKG
Thank you I hadn't thought of that. I had only neck sized the fire formed case used for the piece. In thinking of your idea, I loaded the case (w/o bullet) into the chamber w/ the bolt. I slid my cleaning rod down the bore until it touched the bottom of the inside of the case. I marked it w/ a piece of masking tape and pen. I then reinserted the case w/o the bolt. I held it in place w/ my finger and slid the rod down once more to the inside bottom of the case. It was the same spot on the masking tape as marked earlier. So I tried a previous mention of leaving the bullet long and using the bolt to seat to the lands. 2.806" +/- repeated 3 times. There we go. Thanks for the motivation.
Loaded up some 2.790" rounds at varying charges to test saturday.
RKG
Thank you I hadn't thought of that. I had only neck sized the fire formed case used for the piece. In thinking of your idea, I loaded the case (w/o bullet) into the chamber w/ the bolt. I slid my cleaning rod down the bore until it touched the bottom of the inside of the case. I marked it w/ a piece of masking tape and pen. I then reinserted the case w/o the bolt. I held it in place w/ my finger and slid the rod down once more to the inside bottom of the case. It was the same spot on the masking tape as marked earlier. So I tried a previous mention of leaving the bullet long and using the bolt to seat to the lands. 2.806" +/- repeated 3 times. There we go. Thanks for the motivation.
Loaded up some 2.790" rounds at varying charges to test saturday.
That sounds more like it.
The tip of the sierra's was not square but sort of cut off on an angle and the hornadys where perfectly square....
The 168 gr SMKs I just purchased have the exact same problem. They are cut off at a pretty decent angle. WTF is up with that? I have never purchased these before. I was expecting the most exact tolerances of any bullet I've ever bought, and then I open up the box to find that the tips are all wonky.
P.S. Holy crap. Did the whole closing the bolt on a long bullet thing with my Model 10 .308 and came up with a much longer OAL than you guys are talking about.
T-Rex
03-31-2010, 07:06 PM
Did you cut the neck and put some lube on the bullet?
Did you cut the neck and put some lube on the bullet?
Aha.
P.S. Holy crap. Did the whole closing the bolt on a long bullet thing with my Model 10 .308 and came up with a much longer OAL than you guys are talking about.
Remember, COAL as a surrogate for leade is dependent on the shape of the particular bullet used. Our numbers are for the Sierra 168-gr. MatchKing. They do not relate to any other bullet (including, interestingly enough, the 165-gr. GameKing).
P.S. Holy crap. Did the whole closing the bolt on a long bullet thing with my Model 10 .308 and came up with a much longer OAL than you guys are talking about.
Remember, COAL as a surrogate for leade is dependent on the shape of the particular bullet used. Our numbers are for the Sierra 168-gr. MatchKing. They do not relate to any other bullet (including, interestingly enough, the 165-gr. GameKing).
Yeah, I'm talking 168-gr. SMK. I think that I have some other issue clouding my understanding here.
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