Here is a link to a test report contained in a rather large pdf file. The summary section from the report is extracted below:
Accuracy tests were performed on two brands of electronic target used in high power rifle / fullbore competition: (i) HEXTA-002 Match-Grade target (“HEXTA”), manufactured by HEX Systems Pty Ltd,Australia, and (ii) SMT model G2 (“SMT”), manufactured by Silver Mountain Targets, Canada.
The SMT target sensors were mounted directly to the front face of the HEXTA target. In this way both targets independently reported shot position for the same series of test shots (2 strings of 20 shots each). Both targets were operated in accordance with the manufacturers’ current user instructions. The SMT target was operated by the owners of the system, Bridgeville Gun and Pistol Club. Tests were performed at 1,000 yards using .308 projectiles. All shots were supersonic at the target. Tests were performed at Reade Range, Pennsylvania, USA, on June 1, 2017.
The HEXTA results showed very small errors, with standard deviations in the range 1.5 to 2.2 mm (0.06 to 0.087 in). There was no evidence of horizontal or vertical shifts, or radial bias. The results were consistent with results already published by HEX Systems and by independent parties. The SMT results showed significant errors, with standard deviations in the range 9.2 to 50.1 mm (0.36 to 1.97 in). Significant horizontal and vertical shifts were evident, in the range 10 to 107 mm (0.4 to 4.2 in). Significant radial bias towards the centre of the target was evident: average 47 mm
(1.86 in) in String #1 and 11 mm (0.45 in) in String #2. There is no other publicly available test data with which to compare the SMT results.
A glossary of terms is provided at the end of the document.