I posted this a few days ago in the deer hunting form, and was advised should post in the reloading software.....have a question about the 308 load data in the Hornady Reloading manual. This is in the 9th and 10th edition manuals and as far back as the 7th edition. On the 308 page of 165 grain bullets, it shows the # 30459 Interbond as a 2.750 C.O.L. for this bullet. I reload this bullet and I know if using a full load, like 44 grains for example, and Varget is listed as MAX at 44 grains, but I do not go that far. I use IMR 4064 at 43.5 grains and you cannot seat that bullet to 2.750 C.O.L. I seat at 2.800 C.O.L. and have got excellent results, but no way 2.750 C.O.L. Contacted Hornady this afternoon and they wasn't very helpful. Said they did not list IMR 4064 for that bullet and 2.750 C.O.L. was correct. I do not believe it. Right below thiis bullet is the #3040 and the #3045 and they are much shorter and listed at 2.750 C.O.L. which in a M70 my gun is correct....reload these at this C.O.L. Look how much shorter these are compared to the # 30459 Interbond. Would appreciate it if some with some experience loading this bullet would chime in as what they think. Thanks.

Listing a shorter than normal OAL is more than likely a safety factor that powder and bullet manufactures build into their load data. When you increase the OAL of a cartridge the speed goes down but the pressure goes down at a higher rate. If they gave the max load at the longer OAL and you loaded to a shorter OAL the pressure would be over the max for the cartridge. If you look at Allient Powder load data they only list a max load of powder and a "min." OAL. It can only be assumed(???) the listed Max is the max pressure for the cartridge and any increase in OAL will give a lower (SAFER) pressure.

😆 just what the hell are you talking about. If he would just read in the Hornady manual (Or on the web site) internal ballistics section his answer is there. But even this doesn’t explain why he can’t seat to the recommended depth with that bullet powder combination even though Hodgdon lists 46.3C max of 4064, 165 Horny @ 2.750. He’s either doing something wrong, or his brass is lacking in case capacity. Please don’t confuse the guy.

https://www.hornady.com/team-hornady/ballistic-calculators/ballistic-resources/internal-ballistics

To illustrate the effects of variations in bullet travel before the bullet enters the rifling, we'll compare a standard load with adjustments made only in the bullet's seating depth.

In a "normal" load with the bullet seated to allow about 1/32nd of an inch gap [Fig. 29] between the bullet and the initial contact with the rifling, pressure builds very smoothly and steadily even as the bullet takes the rifling. Pressure remains safe throughout the powder burning period [Fig. 30], and the velocity obtained—3,500 feet per second (fps)—is "normal" for this load in this rifle.

Seating the bullet deeper to allow more travel before it takes the rifling, as in these next two illustrations, permits the bullet to get a good running start [Fig. 31]. Powder gasses quickly have more room in which to expand without resistance, and their pressure thus never reaches the "normal" level. Nor does the velocity; with the same powder charge, it only comes to 3,400 fps [Fig. 32].

When the bullet is seated to touch the rifling, as in the accompanying illustrations, it does not move when the pressure is low [Fig. 33], and not having a good run at the rifling as did the other bullets, it takes greatly increased pressure to force it into the rifling. As the rapidly expanding gasses now find less room than they should have at this time in their burning, the pressure rise under these conditions is both rapid and excessive [Fig. 34]. Velocity is high at 3,650 fps—but at the expense of rather dangerous pressure. Many rifles deliver their best groups when bullets are seated just touching the rifling. Seating bullets thus can be done quite safely if the reloader will reduce his charge by a few grains. The lighter load will still produce the "normal" velocity without excessive pressure.

Swifty52: I will stick with what I said . And as far as you quoting Hornady, these are the people that are not listing barrel lengths and pressure. If they were using SAMMI test equipment why don't they. give pressure in PSI or CUP. I treat their data and any others that don't list pressures as "We shot it in a gun, over a cromo, and it didn't blow up"