I am not so sure.
IMHO,
leading is reduced when the bullet base deforms to seal with the barrel (with the help from
liquefied lube providing gasketing seal) from the high pressure powder ignition gas.
Normally, lead bullets used are sized slightly larger than the groove diameter of the barrel (.001" larger) and the rifling digs into the side of the bullet. If your barrel has "true"
polygonal rifling (see comparison picture below), the bullet base must deform at 40S&W chamber pressures (around 22,000-33,000 PSI for lead load data) to match the polygonal shape of the rifling to fill the voids between the bullet and the barrel. If not, high pressure gas will escape through the voids and cause gas cutting/increased leading.
I am doubtful, but your challenge is finding a 40S&W lead bullet soft enough to deform/bump to match the polygonal rifling of the barrel and hard enough to stay intact with the working pressures of your test loads. And that may not ensure that your test loads will not lead in your barrel (see comments on leade length below). My Taurus PT145 barrel is oversized at .455"-.456"+ and with 12 BHN Missouri 200 gr SWC (Bullseye #1) bullet sized at .452", the bullet base deforms/bumps enough to not cause leading BUT I am using lower 45ACP lead load pressures (15,000-19,000 PSI).
BTW,
Missouri Bullet supplies 40S&W lead bullets at 18 BHN and
ZCast Bulletz at 14-16 BHN and I believe most other commercial bullet casters offer 40S&W lead bullets at 20-24 BHN. One thought is Missouri Bullet has foundry certified lead alloys at 10/12/15/18 BHN so you COULD ask if Brad would cast some 40S&W bullets at 15 BHN (Never know, he MIGHT find some "spare" time to cast some 40S&W bullets in 15 BHN
... BTW,
9mm 147 gr FP bullet are 15 BHN). Perhaps you could order some 15 BHN bullets and ask a reloader who casts to pour you some 40S&W bullets? (What are friendly THR members for? You may find a volunteer just for curiosity sake)
As to Glock rifling, it is truly not a polygonal rifling as the barrel is round with six "hexagonal" rounded rifling.
Another thing you'll need to check is the leade length of the steyr barrel. Leade is the space the bullet jumps from the chamber/case neck to the start of rifling. If the leade is on the longer side, gas cutting and leading will increase.
When shooting lead bullets, longer the leade, more high pressure powder ignition gas leaks around the bullet. For this reason, many match shooters will use the longest OAL that will work in their pistol/barrel/magazine so the bullet's bearing surface will engage the start of rifling as soon as the primer is hit, but when using lead bullets in semi-autos, using the Max OAL is limited by your pistol's ramp/barrel/magazine so your working Ideal OAL may need to be shorter, resulting in gas leakage, gas cutting and more leading!
Below is a comparison picture of 40S&W Lone Wolf barrel on the left with typical leade length and 45ACP Sig 1911 barrel on the right showing very short leade (almost no leade) - Can you say chamber pressure build up PRONTO!.
