Welcome to the Cove, Errol!
Yes, they are basically the same. The whole exercise of MSA helps you quantify the two types of variation (position variation - bias, linearity and width variation-GRR) for measuring a particular characteristic.
Various indexes can be computed.
A. Based on a Bias/Repeatability Study
(Ref: My old notes based on the booklet "Capability of Measuring Instruments": Robert Bosch)
Take repeated measurements (25-50) on a production master, calculate average and Repeatability StDev.
The two indexes calculated are:
1. Cgm = (0.2 * Tolerance) / (6 * Rpt_Stdev)
2. Cgmk = Least of
( RefValue + (0.1 * Tolerance) - XBar) / (3 * Rpt_StDev)
-OR-
( XBar - (RefValue - (0.1 * Tolerance)) ) / (3 * Rpt_StDev)
Both should be >= 1.33; and bias (XBar-RefValue) not significant.
B. Based on GRR, typically two indexes are recommended:
1. Measurement Capability Index (MCI_I) based on Process Variation is defined as:
MCI_I = 100 (Sigma_GRR/Sigma_process)
Sigma_Process is calculated from ongoing SPC studies: RBar/d2
2. The other index, (MCI_II) is based on tolerance:
MCI_II = 100 (5.15 * Sigma_GRR/ Tolerance )
In place of 5.15 you can also use 6 to cover 99.73% spread.
Acceptance criteria for both these are:
<=20% :Good
>20 - <=30% :Marginal
>30% :Unacceptable