IGF-1 itself is never "felt", regardless of dose. Only its side effects can potentially be felt. I am referring to its ability to reduce BG levels. If BG levels get low enough the individual will indeed feel it. However, this dose-dependent effect is highly affected by both bodyweight and insulin sensitivity. Secondary factors, such as the individual's current BG levels, as well as any food still undergoing the digestive process, will also play a role.
By saying that everyone who uses 50 mcg of IGF-1 LR3 will "feel" it, you are essentially saying that 50 mcg is a large enough dose to lower anyone's BG level to the point of hypoglycemia. That just isn't true. For one, IGF-1 itself isn't that powerful of a BG lowering agent. Insulin is MUCH more powerful in this regard--a full 10X more powerful. 10 iu of insulin regular human supplies a much more powerful BG lowering affect than 50 mcg of LR3...and MANY people don't feel 10 iu of insulin at all.
In fact, I can name 2 pro bodybuilders that I personally know, whom I have communicated with extensively on the phone and via email, that don't feel a thing when using 40 iu of regular human insulin pre-workout. One of these men downs over 350 grams of carbs during the training window, so it's not that surprising that he doesn't feel it, especially when you consider that he doesn't have the best insulin sensitivity either. On numerous occasions I have used 15-18 iu of Novolin (regular insulin) and didn't feel my BG drop at all because I ate so much food before and after administering it. On at least one occasion my BG levels never even dropped down into the normal range, let alone below normal. They remained elevated the entire time the insulin was active. The fact that I didn't have the best insulin sensitivity at this time also helps explains why I didn't "feel" that dose of insulin.
50 mcg of LR3 doesn't come anywhere close to even 10 iu insulin from a BG lowering standpoint, let alone 20 iu or 40 iu. The point here is that there are lot...a LOT...of people who will absolutely not feel 50 mcg of LR3.
I am not aware of any mechanism, outside of BG reduction, by which an injection of IGF-1 LR3 can be "felt". If you know of any, please let us know.