I was at the range today with my son. We were shooting my M700 VS in .223. Easily kept 50 rounds of Blackhills 52 gr. match in an inch at 100 yards. This is about all we can hold with the makeshift bench rests we were using. Then started shooting my handloaded Hornady vmax loads and each ten shot string would group into two groups about 4" apart. There was no "stringing". The rounds would randomly go into one group or the other. I don't think it's the scope (Nikon). I did not clean for 100 rounds and I think that may be it.

How often do you folks clean while shooting?

Is there a procedure you use to keep fouling down as you shoot long strings?

I'm getting lots of carbon fouling out now but surprisingly little copper. I'm alternating Hoppes and Wipe Out foam.

BTW this bore is smooth, It's been fire lapped with a Tubb bullets kit.

Two distinct groups 4 inches apart...

It has nothing to do with a dirty barrel but with inconsistent primer ignition in my opinion. When the ignition is good the bullets go into one group and when the primer fizzles the bullets go into the other group. I would try a different primer; preferable hotter. Or maybe your primers are old or have been exposed to moisture?

As for cleaning frequency, I think shooting 100 rounds without cleaning is stretching it. A dirty barrel though would make a bigger more ugly group rather than two distinct groups.

I'll agree with Grumulkin, I had a friend who achieved the same problem, his problem was seating primers inconsistently.

Back at the range last weekend with my oldest son. 30 rounds, we kept them all in 3/4" 5 shot groups. Whatever was wrong is fixed.