Gunnut, I even used standard Federal primers for silhouette with 296. I get sub one inch groups at 50 yds with cast boolits and with the 240 XTP's for competition I had scores of 1/2" groups at the same distance. Case neck tension is important for good ignition as is a heavy bullet.
I size my cases to just below where the base of the bullet will be. I want the back of the case to be close to chamber size to hold the bullet close in line with the bore and it also is easier on the brass extending case life.
296 is not that hard to ignite. I have played with it by putting paper wads over the primer before loading the powder and never noticed the difference. Darn hard to get the paper residue out of the cases though, have to flush it out with water.
If you get good neck tension and still like the magnum primers, keep using them. I am not trying to change you, I just say what I have found works for me. I won Ohio state silhouette with 79 out of 80 with standard primers using my .44 Super Blackhawk. I have done more experimenting with revolver brass then you could ever think of. Every kind and method of sizing and expanding, opening primer pockets to take rifle primers, bushing flashholes, installing flash tubes to get the fire in the front of the powder charge, every crimp from none to the extreme and I could go on and on. All of it was too much work to be practicle but I wanted to know what would happen. My SB has over 55,000 rounds through it alone. I can't count the different revolvers and calibers I have had besides what I now have. All has been a work of love and I only try to pass on some things I learned.
Everyone has their favorite way of doing things and I just would like them to try something else to see the effect. If it doesn't work for them, it's OK, I'm not pushing. But what if it does help? I would feel better having helped a little.
All that is over now and I just shoot for fun and hunt with them. I do know what works best for deer. Want to know? Just ask!
OH hell, not entirely true, I do enjoy scuffling with you guys a little.

Raf, even though I use heavy hard cast boolits, the 300 XTP should work fine. I would not go lighter because the .44 240 gr XTP's never made it all the way through my deer. I know a quartering shot might not make it to the boiler room so I quit using them. I never hit a big bone with them but I am sure it would be bad.
The XTP is the most accurate bullet made, just use the heavy for caliber ones.

I have found neck tension to hold bullets better than a crimp. I use the expander die from my .44 Mag dies to bell the case mouths on .45 Colt and .454 Casull rounds. This gives me extremely good neck tension. Rounds loaded this way tend to be more consistent over the chrony and on paper.

MS, you are absolutely right. Neck tension is the secret to accuracy. This is why I scrapped the old RCBS dies in favor of Hornady titanium nitride dies. I had a rig made up to measure the seating pressure so I could sort the loads according to how tight the bullet was held in the case. The difference between a tight case and a loose one can be as much as 12" in point of impact at 50 yds. RCBS gave me the very worst variation. I know they have since corrected the .45 Colt dies but I am unsure of their .44 dies.
Crimp has absolutely no effect on accuracy and it's only function is to hold the bullet under recoil or in the case of tubular magazines, to hold the bullet out where it belongs.
If you can feel a difference in the force needed to seat a bullet, you are not going to get any kind of groups.
What you are doing with the .44 expander is very good. I shoot cast boolits though and have to be careful that too tight of a case may size down my boolit when seating. Although if you look at the neck area on my loads, you can actually see the grease grooves, they are tight!
I am glad you jumped in here with that, good job!

Jim, boolit weight and shape is more important then velocity. I have the same arguments on the bowhunting forum with guys using super light arrows at high velocity. A slow heavy arrow will go all the way through a deer and kill fast. A light fast arrow will stop quick, sometimes less then half way through. A bone really stops them. No way to talk to these guys! All they think about is how fast they can get an arrow launched. I have NEVER said to shoot as fast as possible, only to use the proper boolit and go for the most accurate load you can find. We do have a lot of speed freaks though. I am sure all of your loads are adequate for hunting if you can hit what you shoot at.