is there a universal pet load so to speak for M1A?
It's been posted a few times on this thread, and I'll post it again. If there's a universal load for M14 type rifles, it's one of the 4895's (IMR or H) under a 168 Sierra Matchking lit by a Fed 210M. During the heyday of the M14 in Service Rifle Competition, this was the load to beat. M852 Standardized it. If I were to pick a second and third choice of powders, I'd look at IMR4064, it's what FGMM most often used, then RE15 which is what was loaded in the later iterations of M118LR. (FYI, 4064 caused the most case stretch in my experience). The arsenals loaded to match the pressure spec making universal charge weights not very useful. Powder lot burn rates varied so charge weights varied to match. Between 40.5 and 41.5 is generally where you should be for IMR4895. You have the luxury of loading to accuracy for your rifle.
Second choice of projectile? 175 MatchKing. Some were playing with the 155 Palma MatchKing. I didn't have luck with that one. My theory was the bearing surface was too short for the 22" barrel. Hornady 168, I didn't have luck back in the day...but I did have great results with a prototype A-max. Hornady upped their game in recent years, so your luck might be better than mine with the Red boxes.
You also mention you like to experiment; you can look at VV N540, N135, N140 and Varget in addition to what's already been mentioned. You can go lighter on bullets, but you don't want to go much heavier than 175, unless you have a good supply of parts. Some folk I know played with WW748, but they complained about inconsistency when the temps rose.
