Load Development (Part 2 of 2)

In part 1 of our two part series on load development, we were presented with an approach which we believe is objective and fact based, and corroborates some of the things that we have observed during our own load development. In part 2 we leveraged this methodology to evaluate the following loads:

• 123 Lapua Scenar with H4350 powder. This is our practice load and given our familiarity with it, we worked up loads in .2 grain increments above and below our regular load of 42 grains.
• 123 Lapua Scenar with Varget powder. Another shooter was reporting excellent results with 38 grains so we had a good idea of where to start. However, his rifle was from a different gunsmith using a different barrel so we decided to explore a wider area in .3 grain increments.
• 139 Scenar with H4350 powder. We didn’t have any data to start with, but our gunsmith reported that 39.6 grains with Berger 140 Hybrids worked well. We decided to explore loads above and below 39.6 grains in .2 grain increments.

It’s important to note than when we were exploring loads toward the higher end, we were constantly monitoring for pressure signs. As soon as pressure signs are encountered it is best to stop and not fire loads with a higher charge weight. You are better off pulling those rounds and reusing the components.

Hornady O.A.L. tool in use

The first step (Phase 1 / Step 1) involved determining the cartridge overall length for the chamber. We used the Hornady OAL Gauge with a cartridge case provided by our gunsmith R-Bros rifles. Hornady provides cartridge cases in various calibers but not the 6.5×47 Lapua. Even in situations where Hornady provides a cartridge case for use with the tool, it is highly recommended that you get a case from your gunsmith that has been fired in a chamber using the same reamer. If you are handy, you could make your own using a fired case – you just need to thread the case so it will screw onto the tool. Be sure to watch the video for tips about using the tool that are best conveyed visually. Long story short, you want to use the tool gently as it’s easy to jam the bullets into the lands resulting in inconsistent readings.

If you don’t have the Hornady OAL Gauge you can accomplish the same thing by loading a number of cartridges in .0025 – .005″ increments and coloring the bullets with a marker. You can then chamber the bullets and determine which length engages the lands. While this method works, we highly recommend getting the Hornady OAL Gauge as you will find many uses for it. For example, this tool really helps when you chase the lands as the barrel erodes.

Since we are using VLD bullets, we like the bullets to just touch the lands, but we don’t want them jammed into the lands where a bullet will be left in the barrel if a live round has to be ejected. The Scenars can be jumped, but they also work great touching the lands so that’s how we load them. If you like to jump your bullets, start .020″ from the lands.

Next came shooting the groups (Phase 2 / Step 1) and gathering chronograph data (Phase 2 / Step 2). It is very helpful to have a partner record the chronograph results and note any anomalies. As shown in the video, we shoot all rounds of a particular charge weight at one target being careful not to break position. However, we do randomize the shooting order of the charge weights. This is different than the round robin method advocated in the OCW method – the round robin method can introduce a lot of human error since it’s essentially a slow motion dot drill. Few people can shoot a perfect dot drill even with unlimited time. There is nothing wrong with shooting in a round robin fashion provided you are confident in your abilities and can completely rebuild your position between each target.

In our testing, there was one group that was much larger than the others due to some rear bag issues we were having. Had we been utilizing the round robin method this error would have been spread out across multiple groups. I could see arguments going both ways – some saying it’s better to spread the error out while others would advocate containing the error and re-shooting a group if it was an anomaly. We be interested in the opinions of our audience on this.

The next step (Phase 3 / Step 1) was the analysis of our groups and chronograph data. The worst group was still under 1 MOA and most groups were well under .5 MOA. In other words, there were no “bad” loads with the 6.5×47 as far as group size is concerned and we can see why this is such an attractive cartridge. However, some loads clearly have lower velocity spreads than other loads and these differences will show up at the longer ranges that we shoot at. As such, it makes sense to use the loads with the lowest velocity spreads. Here’s what we found out (please open up the  Load Analysis Spreadsheet as you read along):

• 123 Lapua Scenar with H4350 powder. We confirmed that 42 grains of H4350 is the optimal load for our rifles. We saw similar results across two different rifles using different lots of powder.
• 123 Lapua Scenar with Varget powder. While we were hoping for an optimal load at 3000 fps, we noticed the slightest amount of bolt stickiness at that velocity. The next step down (37.7 grains) turned out to be the optimal load as far as the chronograph data was concerned so that’s what we’ll roll with when using Varget and 123 Scenars. One thing that really stood out was the consistency of the Varget / 123 Scenar combination across charge weights. We also like the fact that loads using Varget are not compressed. Varget might be the ticket for lighter bullets in the 6.5×47 Lapua.
• 139 Scenar with H4350 powder. The optimal load yielded the lowest SD (1.6 fps) and ES (4 fps) of the day. 39.8 grains of H4350 will yield a velocity of 2788 – pretty respectable. However there is a pronounced flat spot in the velocity curve so 39.7 grains might be a good choice as it sits in the middle of the flat spot.

Here are some additional thoughts and we welcome opinions from the audience on this:

• It’s easy to look at the results and agonize whether you should add or subtract .1 grain from the load (as was the case with the 139 Scenar). To provide some context, lot to lot variations in powder can be pretty significant so even if you dial in a load with that level of precision, you’re going to start over again with each lot of powder.
• With experience, and in consultation with your gunsmith, we believe you can identify a load that is an all around performer day in and day out in your rifle. We have such a load that was recommended by our gunsmith (see below). Ed ran into one lot of powder that was a little hot (he was getting a sticky bolt) so he backed down half a grain so he would get the same velocity as the previous lot of powder. It still shot lights out. The next lot of powder was cooler so he went back to the original load to maintain the same velocity. Again, it shot bugholes. It appears as if the optimal loads for a given combination of components fall into certain velocity ranges – you hear this talked about in the context of optimal barrel time. From our load development, it appears that 123 Scenars going at 2950 – 3000 fps shoot really well. The results from the 139 Scenar suggest that bullets in the 139-142 grain weight class like to cruise along at or near 2,800 fps. It’s really interesting to see patterns like this emerge as it adds a degree of predictability to load development.

Some of viewers may have noticed two very small 5 shot groups labelled 130 VLD. These were our two control groups – one shot before the start of the session and one shot after. As you can see from those groups, our 6.5×47 Lapua match load consisting of Berger 130 VLDs with 42.2 grains of H4350 and CCI 450 primers shoots lights out.

In conclusion, we will adopt the approach outlined in part 1 going forward. It seems to combine the best elements of the OCW method while recognizing the need to minimize velocity variations. There might be a machine rest in our future in which case we can minimize the human element and stop guessing whether a flyer was caused by the shooter or the load.

Finally, a number of you have asked for the spreadsheet we used to track the data. Here it is: Load Analysis Spreadsheet We will be working on instructions that will be provided with a template spreadsheet so you can modify for your particular situation.

Thanks again to the members of our audience who provide encouragement and feedback.