@copaup - Nope, I didn't take any photos of the muzzle flash - believe me though, it was there! It was visible (knowing that I was focusing on the front sight) against the background (wooden bench, grass, gelatin block) that was in full sunshine.
@XDKingslayer - Thank you for the offer. There are two other people looking to participate in the testing right now... I will let everyone know once I have heard back from them (or not).
Hmmm. The idea of 'walking up' the load is a great idea. But this test is being paid for by someone else, and they have two factory loads that they would like to see tested in gelatin. So, I'm on a budget for time in order to do this test... but a load development may be the only solution in the future. Thank you for the advice.
Basically ... there are two things that can usually be said for my website - it's run on a shoestring budget (the necessity of buying gelatin powder and new refrigerators for when the heat load breaks them) and the time that I can spend on it is usually short in supply.