There have been some discussions about seating depth and I thought this might be useful for the newer reloaders here.
Overall length (OAL) measurements are usually given in the reloading manuals, and these refer to the measurement from the tip of the bullet used in the manual to the base of the case. As time goes on, a new reloader may refer to the data, for example, in his Hornady book for a 130 grain .270 Win but has Sierra bullets on hand. If you had both bullets on hand you may well find seating them to the same book-recommended depth gives you competely different results; here's a reason why:
In other discussions on this site advice was given on how to seat bullets for accuracy so that the ogive is some distance (0.01", 0.015", 0.02" etc.)from the "leade."
Here are measurements from 4 different bullets for my 25-06, made from the ogive of each using a Stoney Point Comparator rather than just the tip to the base of the case: (this may not come out as a table so just connect the dots)
Bullet...To the "Leade"...0.015" from the Leade...Tip to base
Hornady 117gr spire... 2.722"... 2.707" ... 3.172"
Hornady 117gr SST...2.713"... 2.698"... 3.191"
Sierra 120gr HP...2.770"...2.755"... 3.175"
Hornady 120gr HP...2.729"...2.714"...3.197"
Notice how the measurement from the ogive to the base differs among these bullets, all due to difference in shape and style of manufacture. If you start with a Hornady 117gr spire and use the OAL measurement of 3.172" as a guide for the other three, the following differences will occur:
The 117gr SST seated to an OAL of 3.172" will actually have your bullet seated 0.19" deeper, or a total of 0.034" away from the leade.
The Sierra 120gr HP will be 0.018" rather than 0.015" away frorm the leade.
The Hornady 120gr HP will end up 0.040" away from the leade.
If you happened to use the Hornade 120gr HP measuement of 3.197", tip to base of case, as your guide, the reverse would be true - all of the other 3 would be longer and some would actually jam into the rifling.
So for best accuracy, might I suggest you learn how to seat your dummy rounds at the leade and then seat the bullet whatever depth you find is most accurate. But you must do the procedure for every different bullet you play with for your rifle.
Any expert comments are welcomed
Overall length (OAL) measurements are usually given in the reloading manuals, and these refer to the measurement from the tip of the bullet used in the manual to the base of the case. As time goes on, a new reloader may refer to the data, for example, in his Hornady book for a 130 grain .270 Win but has Sierra bullets on hand. If you had both bullets on hand you may well find seating them to the same book-recommended depth gives you competely different results; here's a reason why:
In other discussions on this site advice was given on how to seat bullets for accuracy so that the ogive is some distance (0.01", 0.015", 0.02" etc.)from the "leade."
Here are measurements from 4 different bullets for my 25-06, made from the ogive of each using a Stoney Point Comparator rather than just the tip to the base of the case: (this may not come out as a table so just connect the dots)
Bullet...To the "Leade"...0.015" from the Leade...Tip to base
Hornady 117gr spire... 2.722"... 2.707" ... 3.172"
Hornady 117gr SST...2.713"... 2.698"... 3.191"
Sierra 120gr HP...2.770"...2.755"... 3.175"
Hornady 120gr HP...2.729"...2.714"...3.197"
Notice how the measurement from the ogive to the base differs among these bullets, all due to difference in shape and style of manufacture. If you start with a Hornady 117gr spire and use the OAL measurement of 3.172" as a guide for the other three, the following differences will occur:
The 117gr SST seated to an OAL of 3.172" will actually have your bullet seated 0.19" deeper, or a total of 0.034" away from the leade.
The Sierra 120gr HP will be 0.018" rather than 0.015" away frorm the leade.
The Hornady 120gr HP will end up 0.040" away from the leade.
If you happened to use the Hornade 120gr HP measuement of 3.197", tip to base of case, as your guide, the reverse would be true - all of the other 3 would be longer and some would actually jam into the rifling.
So for best accuracy, might I suggest you learn how to seat your dummy rounds at the leade and then seat the bullet whatever depth you find is most accurate. But you must do the procedure for every different bullet you play with for your rifle.
Any expert comments are welcomed