Yes, that's the usage I woudl recognise, and the spelling. But it seems like two separate meanings may have become conflated at some point...

blag,n.

slang.

[Etym. unknown.]
Robbery (with violence); theft.

1885 Session Paper 30 July 471 There has been another blag down round here. 1936 J. Curtis Gilt Kid 22, I don't want to say ‘O.K.’ and then find out that I've let myself in for+doing a blag on the crown jewels. 1960 Observer 24 Jan. 5/1 The top screwing teams, the ones who went in for the really big blags, violent robberies.

Hence blag v., to rob (with violence); to steal. So "blagger, one who blags.
1933 C. E. Leach On Top of Underworld x. 137 Blag, snatch a watch chain right off. 1938 F. D. Sharpe S. of Flying Squad i. 15 Blaggers, screwsmen, [etc.]+abound in the Underworld of London. Ibid. 329 ‘Johnny blagged the till’—Johnny took the till. 1945 J. Henry What Price Crime? 93 Another is known as the ‘blagger’ or ‘snatcher’. These are usually young louts who specialize in snatching ladies' handbags and bolting off.


Compare this to the entry for blague:

[Fr.]

Pretentious falsehood, ‘humbug.’

1837 Carlyle Fr. Rev. (1857) II. iii. v. vi. 313 The largest, most inspiring piece of blague manufactured, for some centuries. 1865 Day of Rest Oct. 580 That is all blague. 1886 Huxley in Pall Mall G. 13 Apr. 13/2 It believes in shibboleths and sentimental blague.

OED2