Ok I'm not new to reloading but I'm stumped.
I have a dillon sqdeal set up just for .38 special.Last month I reloaded 200 158 grn .38 semi wad cutters in tumbled 38 special brass using 4.4 grns of unique weighed on a Lyman digital scale for my S&W mod 14-3.
The first round fired fine then a squib,cleared that and fired 3 more rnds and a squib then 3 more squibs.
I tried 2 more cylinders of loads and had 4 more squibs.
SO I QUIT.went home and pulled the bullets checking the powder charges,they were all fine maybe a 10th of a grain either way.
The shots sounded like a pop and sizzle.
So last night I loaded up 100 rnds using 3.1 grains of bullseye
Shot today and the same results.
I'm using Winchester small magnum primers.
The powder is dry and new.
I just pulled 15 bullets and the charge is perfect
I also loaded 200 9mm rnds with another sqdeal and they worked perfect.
Any one else had similar issues
By elimination:
1-In the first batch, you had 7 squibs out of 18 rounds (3 cylinders), and all the rounds you pulled (that's a count of 182) had 4.4 +/-0.1 grn of powders. It means it's statistically impossible that you had 7 squibs out of 200 and got them all at random in the first 18 shots;
2-You tried another powder and had the same results, so it's near impossible that both bottles of powders were bad, especially if it's the powder you then used for the 9mm;
3-You don't talk about powder residues, so I'll suppose that all or most of the powder has burned. When it's not the case, the gun gets dirty AF, so you would probably have mentioned it;
4-A bad primer usually just doesn't go bang. Sometimes it's a slow fire instead of a no fire, but not for 7/18 rounds and then primers from the same batch working fine in the 9mm;
So what's left? I would tend to blame a combination of magnum primers with not enough crimp. The magnum primer is probably pushing the bullet out of the case before the powder is completely burned, so there never really is that much pressure being built in the case. The pop you hear is the primer and the sizzle is the gaz escaping between the cylinder and the forcing cone.
The reason revolvers do this but pistols mostly don't is that in a pistol barrel, the bullet hits the rifling and stops there, and the pressure can build behind it. Depending on the gun and bullet, sometimes the bullet will hit the rifling while still being in the case, but even if it's completely left, the pressure doesn't really have anywhere to go, so it keeps pushing the bullet. In a revolver, it can escape in the cylinder gap. So the same phenomenon will make for a crappy shot in a pistol and a stuck bullet in a revolver.
I would really switch to normal primers. I would tell you to crimp more but with lead bullets you can only crimp so much. You might wanna try new or 1Fired cases if your brass is old.