For decades, the phrase “No. 1 with a bullet” has referred to a song or album that zooms to the top of the Billboard charts. Given current music industry practices, “No. 1 with a T-shirt” may be more accurate.

Lately, many artists — and their record companies — have been trying to game the system of ranking musical hits by including free downloads of new albums with sales of concert tickets, clothing and other merchandise. It’s a widespread practice, and the result is some confusion about what, exactly, the weekly charts are measuring.

Now some of the very people who have taken advantage of this strategy are complaining about it, and Billboard is under pressure to change the rules governing its charts.

The use of so-called album bundles — tacking a download or CD to another purchase — is an age-old sales gimmick in the music industry, but now it’s everywhere. Of the 39 titles that went to No. 1 last year, at least 18 were sold as part of ticket or merchandise deals. One of the most prolific bundlers has been the Houston rapper Travis Scott, who last year claimed the top spot by selling key chains, hats and access to concert tickets.