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CPM M4 has more abrasive edge retention than MagnaCut, but MagnaCut has a much higher corrosion-resistance rating. Their toughness scores are close. The main ownership decision is whether M4’s wear advantage is useful enough to accept the extra rust care.
Performance Ratings
For the science, we turn to Dr. Larrin Thomas of Knife Steel Nerds, who has kindly allowed us to share his ratings here.
The toughness score of 7 is for original Crucible MagnaCut. In written feedback to KnifeInformer, Dr. Thomas provided a toughness rating of 8.5 for Erasteel MagnaCut; his January 2026 testing explains the differences between the two versions. This table uses the original version.
| Property | CPM M4 | CPM MagnaCut |
|---|---|---|
| Abrasive edge retention | ||
| Toughness | ||
| Corrosion resistance |
Heat treatment, hardness and geometry affect actual knives.
CPM M4 Has a Wear Advantage
CPM M4 rates 6 for abrasive edge retention against MagnaCut at 5. We would favor it when abrasive cutting is frequent and the blade can be maintained appropriately.
This comparison uses CPM M4. Do not assume an unspecified conventional M4 blade shares the same rated performance merely because the chemistry name is similar.
Our CPM M4 steel profile explains its properties and care in more detail.
The Toughness Scores Are Close
Original MagnaCut rates 7 for toughness and CPM M4 6.5. That half-point difference is small; we would avoid making it the deciding factor without considering the actual knife.
The Erasteel MagnaCut update is separated in the rating note. Claims about one production version should not be silently attached to another.
Our MagnaCut steel profile explains its properties and care in more detail.
MagnaCut Is Much More Corrosion Resistant
The corrosion ratings are 9.5 for MagnaCut and 4 for CPM M4. For wet carry or a knife that sees frequent food and moisture exposure, MagnaCut has the clearer advantage.
CPM M4 is not stainless. Clean and dry it after use and protect it during storage as appropriate; the cutting edge remains exposed even on a coated blade.
Is the Extra Wear Resistance Worth the Care?
We would choose CPM M4 when abrasive wear is a specific limitation and regular maintenance fits the routine. For a versatile everyday knife with fewer rust concerns, we would lean toward MagnaCut.
If two models differ substantially in grind or handle, evaluate those first. A modest wear advantage is not a reason to buy a knife poorly suited to your work.
Composition
Our steel composition guide explains the elements and the differences between reported values, ranges and limits.
CPM M4: Niagara supplier typical CPM M4 chemistry; not an individual knife assay. Niagara Specialty Metals: CPM M4.
CPM MagnaCut: Niagara typical composition, mass %; selected elements, not a batch analysis. Niagara Specialty Metals: CPM MagnaCut.
| Element | CPM M4 | CPM MagnaCut |
|---|---|---|
| Carbon (C) | 1.3% | 1.15% |
| Chromium (Cr) | 4.3% | 10.7% |
| Molybdenum (Mo) | 4.5% | 2% |
| Vanadium (V) | 4% | 4% |
| Tungsten (W) | 5.6% | Not listed |
| Manganese (Mn) | 0.3% | Not listed |
| Silicon (Si) | 0.3% | Not listed |
| Niobium (Nb) | Not listed | 2% |
| Nitrogen (N) | Not listed | 0.2% |
Compare Two Knife Steels
Sources and Update Notes
- Dr. Larrin Thomas: knife steel ratings · Property ratings; the scores describe steels rather than individual finished knives.
- Niagara Specialty Metals: CPM M4
- Niagara Specialty Metals: CPM MagnaCut
