With regard to disc thickness. We use 1\2" AR500 for distances of 100M and beyond (no steel on centerfire rifle ranges under 100M). At 100M, the disc remains serviceable (338 LM template) for a couple of years before we switch it out to greater distance if it is showing minor divots or chips. Keep in mind, that there is a fairly high volume of shooting at 100M and steel core is permitted at that distance. It is possible the lighter weight (1/2"), coupled with the deflect angle and pivot swing add to servicibility as opposed to heavier, fixed unit set-ups. I will do a pic of the back bracket weld we use to make change over/repairs easier.
At 100M, we are probably changing out discs once a month because of breaks between the weld and the bracket. It is the shock that seems to be the issue. This shortcoming does not result in damage to the unit other than the need for a reweld. We keep spares on hand which makes changeover quick. The reweld cost is just part of "maintenance". At 200M, the welds last 3-4 months, and at 300M for a minimum of a year or sometimes two.
For RimFire and Handgun, we use 1/4" AR 500 with a direct weld to the hanger. We want to keep these units as light as possible to make sure they react/swing. For RimFire, we have no steel under 50M, and for HG none under 26M. Again, there will be breakage at the welds, but no damage to the disc. The biggest issue with the close-up is that on two occassions in the past couple of years, some idiot snuck steel core onto the RF range and pierced two discs. They had to be pulled and now serve as props at Orientation. Wish the cameras could have picked it up.
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