Re-creating Berger’s AMAZING 77 OTM 223 Load

The 223 trainer build we completed here on Ultimate Reloader is a one hole shooter with the factory loads from Berger: The Berger Match Grade 77gr OTM Tactical loads that is! In this story we’ll try and duplicate this load from some reverse-engineering and with some shooting. This will be fun!

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Results with Factory Ammunition

Break-in was conducted using Berger 77 grain OTM 223 Remington Match ammunition, the first 5-shot group measured just 0.222″ – WOW!

And here’s some chrono data from this factory ammunition for 10 shots:

Avg 2810.55 fps
ES 67.06 fps
SD 19.93 fps

Breaking-Down Factory Rounds

Using an RCBS collet bullet puller, bullets were pulled from Berger factory cartridges. The powder was then weighed on our EJ-54D2 scale from Cambridge Environmental: (see my story covering that scale HERE)

24.6 grains, or 24.7 if you round up!

After close examination with some powders we had on hand (focusing on Vihtavuori) we speculated it was Vihtavuori N140.

Testing Handloads

We loaded two loads and shot 10 shot strings over the chronograph. Here’s the load data we used:

These loads were shot suppressed this time:

These loads shot really well! With 10 shot groups ranging from 0.372″ on up to about 1/2 MOA. For “fast fire”, mirage off the hot suppressor/barrel in freezing temperatures was an issue for some of the groups.

Above- first 10 shot tests with 24.6 grains (left) and 24.7 grains (right) N140 powder (suppressed).

Here’s the complete set of chronograph data:

Factory Berger Ammunition:

Avg 2810.55 fps
ES 67.06 fps
SD 19.93 fps

Hanloads: 24.6gr N140:

Avg 2724.86 fps
ES 30.29 fps
SD 10.82 fps

Hanloads: 24.7gr N140:

Avg 2736.67 fps
ES 36.76 fps
SD 11.37 fps

Conclusion

Results were excellent and I consider this a success. Group size was statistically the same as the factory load. Due to careful powder handling/measuring the hand loading we are able to reduce the velocity ES/SD.

Why was our load a different velocity than the factory? Could be several things, powder lot, difference of powders, neck tension, primer. Or maybe another factor of the powder due to powder humidity during the loading.

Articles describing this factor here for reference:

https://chronoplotter.com/2021/08/19/how-does-humidity-affect-powder/

https://www.vihtavuori.com/know-powder-moist-content/

A video from Mr Bryan Litz about the subject:

https://www.youtube.com/watch?v=OIvVBPCwXAw

Bolt Action Reloading:

https://www.youtube.com/watch?v=OIvVBPCwXAw

Tests of the reloading room on this day shows humidity level to be at 34%.

Success! We were able to replicate this with an even better SD/ES. I chalk the velocity difference up to powder lot or a combo of temperature and humidity differences. We should be able to reproduce the factory ammunition velocity with some lot to lot testing, and some experimentation with powder charge.

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Thanks,
Gavin