Reloading practices

[Tpb10505]

The problem with using a commercial (i.e., Hornady) "comparitor" to measure CBTO is that the diameter of the comparitor insert is very likely not the same as the diameter of your die's seating stem. Consequently, you will likely not get consistent CBTO measurements after seating. The reason is, in my testing I've found "ogive form" to be very inconsistent, even in what is considered high-quality commercial target bullets. So what I've done to remedy this is to make a comparator insert with a dia. as close as I can to the dia. of my seating stem (neither the original comparitor insert nor the one I made is even close to where the ogive actually meets the rifling). I then use a Sinclair "Seating Depth Gauge" to establish OAL to "touch" (what to "touch" is a different discussion), then using the same bullet, I seat it to the calculated OAL for "touch" and then measure the resulting CBTO, using the modified comparitor insert. That gives me a starting reference point, for seating depth, it also gives me very consistent CBTO measurements.

If you’re using the same comparator to measure both CBTO with the Hornady tool and the CBTO of your loaded round, how would that yield inconsistent CBTO measurements? Ogive form seems to be more of a bullet issue than a tool issue, no?

 

[Chuckhunter]

Well, sounds like I should measure length from cartridge base to ogive as OAL.

Colt, when I log in my data, I have two columns, one is OAL and the other is OALG (#1 is Overall Length and #2 is Overall Length in Gauge). You'll be able to identify best seating depth for accuracy according to your targets and OALG, then the OAL will let you know if that depth will work in your Magazine. Just a suggestion. Good luck.

 

[Bill Norris]

Colt, when I log in my data, I have two columns, one is OAL and the other is OALG (#1 is Overall Length and #2 is Overall Length in Gauge). You'll be able to identify best seating depth for accuracy according to your targets and OALG, then the OAL will let you know if that depth will work in your Magazine. Just a suggestion. Good luck.

Really important to include that data in the log.

 

[COLT45SA]

Really important to include that data in the log.

Good suggestion, but mine is a single shot so there is no consideration of magazine length.
Appreciate you response~!!

 

[wkdickinson]

If you’re using the same comparator to measure both CBTO with the Hornady tool and the CBTO of your loaded round, how would that yield inconsistent CBTO measurements? Ogive form seems to be more of a bullet issue than a tool issue, no?

As I said in my post, the difference comes from the Hornady (or any other) comparitor having a larger diameter than the bullet seating stem. So if the form of the ogives vary the distance between where those two diameters on the bullet are located longitudinally, will also vary. Hence the variance in the CBTO using the Hornady comparitor. Only my opinion, but I've proven to myself many times.

 

[gmr4]

In this video Sam Milliard discusses the methods and differences between the two measurements. He also goes into the issue of length changes between measuring rounds loaded with fired brass and un-fired brass. The one fact that he drives home is the dangers of thinking one might be just touching in the lands BUT in reality jammed completely when flirting with "hot" loads.

Man, I’ve referred many newbys to Sam Millards videos.. 2-3 have followed them and even purchased the same equipment and each is well on there way with reloading. Panhandle Precision rocks.