SPS is great to purchase from. Blems will come boxed or bagged and clearly labeled. If it is a tipped bullet, the tip may be a different color than their color system for caliber or white for accubond, etc. Make sure to weigh every bullet. Once weighed, you are going to partially see why they are blems. This does not mean that they will not shoot well. We as consumers can only test so many things. The factory absolutely knows why they are blems. Otherwise, they would be sold for more as either first quality or "overruns." By weighing each and lining them up according to weight, you should see a Bell curve distribution. For instance, if they are supposed to be 150gr, the majority are going to be 149gr to 151gr, with a few under and over those. The Bell curve may be skewed, but this isn't a statistics class - haha. Now looking at your lined up bullets, you can notice what is missing......the ones that are exactly 150.0gr and the ones that are either 149.9 or 150.1. You may also get a few bullets that are 3.0+ grains or so under or over the advertised weight. They will all shoot... as in, they are able to be loaded into brass and fired. You will not receive "unshootables" from SPS. For most people, after weighing and sorting, this distribution is acceptable.
On spitzer tip bullets, the lead tip may be slightly deformed or shaped differently when compared to firsts.
That said,
If you are really shooting matches, weighing and sorting blems isn't worth it. Just buy firsts (and sort those!) Rifle match loading has so much time and effort in brass prep, charge weights, etc. Weigh a box of match bullets and you should see the difference. Tighter tolerances, less variation and no need to sort out the outliers.
If you are really shooting 500+ yards, just buy firsts. The little differences blems have make significant differences as distance increases.
Quick blem story if you've read this far:
I once bought some 180gr .308 bullets (but not from SPS). They looked as great as first quality. I sorted them by weight, grouped the weights in 0.4gr increments and loaded up some 308 Win. They flat out wouldn't shoot. I'm talking about 3-5moa out of rifle that should be 1.5moa. Ok, maybe I need a different workup for the manufacturer's ogive geometry. A couple different powder and primer workups didn't help. I ended up measuring the length of the bullet and found two distinct groups. Not something that I could see with my eyes, but a quick caliper measurement showed some that were significantly longer than the others. Once I separated them by weight and then length, the accuracy returned. The short story is, blems are cheap, but buyer beware - you don't really know why that lot was rejected.