A Warburton trumpet or cornet top identifies a rim-and-cup component. The complete configuration also needs a backbore, receiver-specific shank and any custom bore information. This reference focuses on the standard size-4 tops and the documented modular system.
Sources checked: . Next scheduled review: . These are access dates, not manufacturer revision dates.
Size 4: retain the maker’s original units
Warburton’s size-4 chart publishes an internal diameter of .660 in / 16.75 mm and an outside diameter of 1.075 in / 27.3 mm. Calculating .660 × 25.4 gives 16.764 mm (16.76 mm rounded); that is a conversion, not a replacement measurement or proof that the chart is wrong.
The checked Warburton pages do not specify a numerical depth below the rim for this diameter. A measuring convention from a different maker must not be presented as Warburton’s own.
| Top | Published internal diameter | Cup label from the maker | Backbore identity |
|---|---|---|---|
| 4SV | .660 in / 16.75 mm | Shallow V | Separately selected |
| 4M | .660 in / 16.75 mm | Medium | Separately selected |
| 4MC | .660 in / 16.75 mm | Medium Cup | Separately selected |
Original sources: Warburton: approximate comparison charts · Warburton: trumpet and cornet tops
Record the top and backbore separately
Warburton describes a two-piece system of interchangeable tops and backbores. The top selector distinguishes material, rim style, diameter, cup and standard/wide versions. Preserve these options rather than treating every top with the same code as one immutable configuration.
The FAQ gives #27 (.144 in) as the standard trumpet bore and discusses custom enlargement. This is a factory default, not a measurement of every used or customized piece. We therefore document the default here without assigning an unconfirmed bore to an individual catalog record.
The maker suggests backbore 6 or 7 as an initial fitting trial; that does not mean every 4M is supplied with No. 7. A top’s name also cannot establish trumpet, cornet or piccolo receiver fit on its own.
Original sources: Warburton: trumpet and cornet tops · Warburton: standard bore and configuration FAQ
Backbore numbers and suffixes
The current backbore selector lists sizes 1–12. The maker groups them by relative size/resistance as below; these are fitting descriptions, not numerical bore diameters or a linear prediction of response.
Star (*) versions change the upper cylindrical section to a taper rather than simply enlarging the standard throat. B and D describe external-shank variants; the standard external size is C and is not stamped as a C suffix. A number, star and shank letter convey different parts of the configuration.
The product page and FAQ disagree about whether B is made to order. Confirm current availability rather than inferring it. Cross-brand thread compatibility and numerical thread dimensions are not certified by this guide.
| Numbers | Maker’s relative grouping |
|---|---|
| 1–3 | Tightest group |
| 4–6 | Tight to medium |
| 7–9 | Medium-large |
| 10–12 | Largest / symphonic group |
Original sources: Warburton: trumpet and cornet backbores · Warburton: standard bore and configuration FAQ
Approximate comparisons are not interchangeable geometry
Warburton places 4SV near Bach 3E, 4M near Bach 3D and 4MC near Mt. Vernon Bach 3C in its approximate chart. Preserve that chart’s scope: it does not prove identical rim contour, volume, throat, backbore or playing feel. The Mt. Vernon qualifier must not be dropped.
Material choices, mass and cup codes alone do not prove greater endurance, range or projection. Signature designs and low-brass products need their own source checks; this guide does not certify the entire Warburton catalog.
Original sources: Warburton: approximate comparison charts · Warburton: trumpet and cornet tops
Independent reference, not a performance promise
This is a selected source-checked reference, not an exhaustive stock list or a laboratory measurement database. Unknown specifications remain unknown. Manufacturer fitting advice, player reports and measured geometry are different kinds of evidence.
Commercial arrangements do not determine specifications. These are ordinary reference links; BrassFit has not activated a commission agreement with Warburton. Product prices are left to sellers’ websites.
Original source register
- Warburton: trumpet and cornet tops · accessed 2026-09-30
- Warburton: approximate comparison charts · accessed 2026-09-30
- Warburton: trumpet and cornet backbores · accessed 2026-09-30
- Warburton: standard bore and configuration FAQ · accessed 2026-09-30