How do you know when the crimp is good enough?
When they don't move under recoil.......
Sorry I cannot shed light on the initial question (powder burn on the outside of the case), but I feel compelled to mention that crimp only provides part of the bullet retention.
Friction between the case wall and side(s) of the bullet is (I am told by sources I trust) provides the bulk of the bullet retention.
If your bullets are undersized, squished by a post-sizing die or your case was oversized (due to over-belling or insufficient re-sizing) or your case walls are thin or the brass is not elastic enough to provide a good grip, you may not have a lot of bullet retention.
Lost Sheep
As LS says, neck tension has as much to do with bullet retention as crimp. But in the big bores, proper crimp is a necessary evil.
I load for the .454's big sister. I bell the case just enough to get the bullet to sit on the case to seat it. I've found that by chamfering your cases well after trimming reduces the amout of bell needed and thus improves neck tension. I crimp so that I can see a definite roll into the cannelure. I seat and crimp in two steps. I have never had a bullet jump crimp, and it's a B*#*% to pull 'em with a puller.
Hrnady's 300 Gr XTP-MAGS are quality bullets with a very thick jacket. Hard to deform them with a crimp, you would feel heavy resistance from the press before you would deform the bullet. It is also a .452" bullet and not undersized. I would not use something like the Lee FCD to post size the round, not because of fear of resizing the bullet, but because it would do nothing positive. Unlike a pistol, there is no feeding issues in your revolver. Cases sized and roll crimped properly will drop into your chambers easily.
Again, really big bores are a different animal than pistol loads. This is why folks that have never reloaded for them don't have a clue. As I said before, the residue on my .460 cases are more burns, than powder residue and I get them even on rounds that have sticky extraction......in other words it's not because I don't have enough pressure to expand the brass. I'm surprised with the charge levels Hornady gives for .454. Generally they are always on the anemic side compared to other sources. Again, one reason I use at least three sources of info when developing loads. I've found most times, the extremes at either end can be just that....extremes. When more than one source agrees with each other(and have done their
own load testing), that's generally where I will start.
One thing to look for is sticky extraction. Many load manuals and factory ammo are kept below SAAMI specs in .454 and .460 to aid in ease of extraction. You get sticky extraction, you need to back down. Sometimes it takes only small amounts of increases in powder charges in the big bores to go from easy extraction to sticky extraction. Keep your increases small as you go up the ladder. Do a volume test on your cases, I've found that Starline and Hornady cases in .460 have different volumes and need different recipes to achieve similar performance.
