Recently I inadvertently got some 270 Win cases mixed up. I was using R-P brass and got one W-W case mixed in. Sure enough, the first 4 shots went into a great little group, and the 5 th one dropped low and ruined it. When I looked at the Chrony, I saw that the velocity was 85 fps lower than the first 4 rounds, and now I knew why the bullet went low. In looking at the fired cases, I saw that a W-W case was there, and sure enough it was the 5 th one. At home, I weighed the R-P cases, and then the one W-W case, and found it to be 11 gr lighter, hence more internal capacity, and lower velocity.

Further weighing of cases gave these results:

So you can see that if one was really to have mixed the extremes, he could have one light W-W case at 189 gr. and one heavy R-P at 202 gr. and have a 13 gr. variation, and that is a bit much.

Just to see what would happen, I did exactly that. I took 2 cases from each group, one the lightest and one the heaviest, and loaded them all with the same load of 55 gr of AA 3100 and 130 gr Hornady Spire Points. I then fired all 8 shells (slowly) with plenty time between shots, and recorded the results as follows:

Lowest velocity was 2914 fps, and highest was 3033 fps.

Ah, but the real interesting thing was that I got what could be described as two groups, looking like a “figure 8”. The group was 1” wide and 2” vertical. Obviously the velocity variation was the cause. The really great part is that no game animal would ever know the difference.

This prompted me to experiment further with 300 Winchester Mag Cases too.

The case weights were as follows:

These were all loaded with 71 gr of AA 3100 and 180 gr Speer Hot Cores. The case weight variation here was a low of 243 gr. to a high of 254 gr for an 11 gr spread. An 11 gr. spread in the 300 Mag is not as big a percentage as a 13 gr. spread is to the 270 Winchester.

I again fired all 8 shots slowly and the results were as follows:

The lowest velocity was 2924 fps and the highest was 2966 fps.

There was no perceptible difference in the group shape, and it went 1¼”.

Does this mean that I can just mix and match to my hearts content? If looking at the numbers is the criteria, yes it does, although common sense still tells me to separate cases at least by manufacturer.

I just could not resist one more test, so decided the 338 Win Mag with its larger bore and less critical bore to bullet diameter relationship, so it might be different.

Case weights were as follows:

As you can see by the above weights, there is considerable variation, and the Federal brass was certainly the most consistent.

So I again took two cases of each kind, one heavy and one light case from each group, and loaded them all with this guns particular favorite recipe a 200 gr Speer Hot Core with 76 gr of Rel 19 and CCI 200 Primers.

The total case weight variation was from a 228 gr. W-W case to 251 gr. Federal Nickel. Whoa, that is a 23 gr spread. Certainly that should produce some interesting results, and “interesting” they were.

Velocities ranged from 2888 fps to 2954 fps. Not as wide as I would have thought. One quirk was that the light W-W case did not give the lowest velocity, but the R-P cases did. Naturally those heavy Federal Nickel cases gave the highest velocity.

The really great part was in the group. All 8 shots went into just over an inch. Golly, this is why I love this gun and Walther Barrels.

It must be that the larger bore is just not as sensitive to volume changes as the smaller calibers are.

As I have stated before, I hate to put numbers down, as the next 10 tests could prove these to be different, or prove them dead right.

One needs to do a lot of shooting to really know for sure, but what better way to have an excuse to go to the range more often.

Feel free to write Terry anytime if you need help with anything at tblauwkamp@superior-sales.com