My Thoughts On Written Loading Data and Testing

[BigBolt]

Many of us have had issues with loading data not just in semi autos but just about every type of gun. For example, my Big Horn Armory carbine chambered in .500 S&W magnum and the MFG states not to exceed the COL of 2.15". Some books call for COL of 2.290 and Hornady factory 325gr FTX will not fit as the COL is 2.290. When reloading I have had to trim the cases below 1.615 which is below the SAAMI minimum standard. When using Berrys 300 gr, 350gr and 375 HCGC all is well and 99% of the listed loads do not exceed 2.15" COL.

My Henry 45/70 is also fussy SAAMI calls for a case trim length 2.1.05 to 2.085". Again, Hornady factory loads cases are 2.045" for their 325 gr FTX loads with a COL of 2.590" which is different from SAAMI standards. My typical case trimming for 350 gr Berrys and HCGC is 2.050" with a COL of 2.500"

Manufacturers typically make their ammo somewhere in the middle of SAAMI specifications. I have used different MFGs with both good and bad results. I usually start a dummy test for fit and then make adjustments from there. Straight walled cartridges are more forgiving than bottleneck cartridges. At one time I use to trim 9mm and 40 S&W cases. I do not trim the cases anymore just adjust the COL for fit and finish which works the best. Also, I have learned some of the minimum loads listed do not work well. I typically start in the middle of the minimum and max loading data. This has reduced the majority of malfunctions to 0% for ejection and operation of any gun.

A bud has two Marlin 45/70 lever actions one was his dads which is about 30 years old and his is about 3 years old. Rounds made for his dads work in both rifles. However, rounds made just for his rifle do not fit well in his dad's rifle as the breach will not close. Off the shelf ammo works in both of them and when measured they are also different than some posted loads. He has also found loads made for his rifle are more accurate than off the shelf ammo and the ones mad for his dad's rifle.

 

[K22]

I've always considered published data as a reference and starting point. The most reliable, in my experience is the data published by the bullet manufacturer. However, the data is not absolute and that is why most of us engage in the process of load development, slightly adjusting this load data to find the optimum combination that produces the best performance.

When embarking on load development it's important to be able to detect and read pressure signs. With that said, I start with published data and work my way up. For most standard cartridges, there are well established powders / bullet combinations that have worked successfully for decades. The accuracy loads stated in some loading manuals is a good place to begin in my experience.

With regards to trimming, I've cut my trimming down about 50 to 75% by measuring the chamber length with a Sinclair chamber length gauge. But just wholesale suspension of trimming without regards to the chamber length is not a good idea in my opinion since you do not want to jam the case into the lands which could create a high-pressure condition.

For me personally, I never seat the bullets closer than .010" to the lands and in most cases, about .020" off the lands. I've never found in necessary to jam the bullet into the lands to obtain excellent serviceable accuracy. Since functionality and reliably are just as important to me as accuracy, my reloading is also geared towards achieving such.

I don' believe reloading is all that complicated if you adhere to the basic principles outlined in a good reloading manual such as Lyman's Reloading Handbook. I think where a lot of problems arise in reloading bottle neck rifle cartridges is using fired cases from unknown sources.