Ruger SP101 sticky extraction. Any ideas?

[45&30-30]

I have used 17.5gr 300MP/CCI 500 primers in all of my 357 pistols and rifles for the last six years with a NOE 182FPGC. Ejection from two model 27's and rifles are easy. The 101's I get a black residue on the outside of the virgin Starline brass. I've honed the cylinders, 300 grit and 600 grit, cleaned the loaded cartridges with alcohol and the cylinders, dropped powder charges of 300MP to 16grains all to no avail, I still get what appears to be blow back around the case.
With 38 Special wadcutters I get lead spitting in all five 101's that tie up cylinders in 15-20 rounds. Has anyone run into this and found the fix? The boolits are 22 bhn lubed with LBT blue lube.
Just some thoughts/questions, are the thinner walls on the 101 expanding to much with the brass and the brass doesn't have a chance to shrink back down when pressure drops?
Can the forcing cones take a slight chamfer and polish to reduce lead build up on them?

[megasupermagnum]

I've noticed quite a bit of soot with 300MP, and was not impressed with the powder at all. My suggestion is to switch to a better powder like H110.

As for your SP101 problems, the fix is to send it to Ruger. They will fix it free of charge, usually in under 2 weeks.

[farmbif]

I use the 300mp 17.5 gr w/ 358156 cast of straight clip on wheel weights with just a bit of tin added its super accurate in Rossi 92 but have only shot a few through a security six with no sticking problems or excessive soot. I like 300mp, much cleaner than 4227 but not quite as clean as h110 and no mag primer needed. it could be variation from lot to lot

[Neverhome]

Only time I get sooted cases is if I’m working with light loads and the case isn’t sealing the chamber well. Admittedly, I don’t shoot revolvers though. That being said, the load you’re using doesn’t seem low pressure. Hmm
Did 22 bhn refer to the wadcutters? Seems very high if shooting at 38 special pressures. Too hard to seal maybe.
I don’t have an answer for the extraction issues.

[megasupermagnum]

I tried all kinds of combo's with 300mp in 357 magnum, 327 federal, and 44 magnum. It is not a good powder in any of them. Velocity extreme spreads are often 100-175 fps, which is the worst of any powder I have tried. The very best I ever found was the 175 gr Keith in 357 magum with a magnum primer got it down to 65-70 fps ES. Not good. Cases were very often sooty with this powder.

I very much recommend a magnum primer if you use this powder, it does not perform well with a standard primer. The best thing is to choose a better powder. H110, Lil gun, 2400, 4227 are all similar powders that work better.

[onelight]

I have loaded 300mp in 327 , 357 , and 44 mag and had no sticky extraction or any other problems.
But I have not finished my work ups . I hope to work with it more soon.

[shooting on a shoestring]

I’ve had sticky extraction on 2 Rugers and 1 Colt when there should not have been.
All three turned out to be mis cut chambers. Colt had no taper. The Rugers had larger diameters at the front than at the rear. Sounds like your SP101 could have the same thing going on.

Sooty cases means low pressure. Spitting sounds like a large barrel cylinder gap. Could be they are related.

[Petrol & Powder]

As much as I like Rugers, including the SP101, they occasionally make a bad one.

That SP101 may need to go back to Ruger.

As for the OP's loading, I can't speak to 300MP, it's not a powder I'm familiar with.
When it comes to magnum loads for straight walled revolver cartridges (32, 357, 44,..) there's only one powder you need on your shelf - H110.

I don't think one needs to shoot a magnum cartridge every single time you pull the trigger of a magnum revolver. But, when you want to extract all of the performance possible out of that platform, H110 (and its twin ww296) will get the job done. The rest of the time a non-magnum cartridge and a faster burning powder is the ticket.

[onelight]

Shoot a few factory loaded hot 357 rounds through it and see if they have the problem. If they do it needs a trip to Ruger.

[45&30-30]

Thank you all for the possible fixes and personal experiences. I admit I never checked the throats on one of these because accuracy was always good to great until yesterday. A 9mm bullet passed through four of the chambers but sticky on two. I did a casting on the smallest chamber and it mic'd out at .3562" I'm going to open everything to .358" and chamfer the forcing cone and see how that helps. I'll report back.

[megasupermagnum]

Thank you all for the possible fixes and personal experiences. I admit I never checked the throats on one of these because accuracy was always good to great until yesterday. A 9mm bullet passed through four of the chambers but sticky on two. I did a casting on the smallest chamber and it mic'd out at .3562" I'm going to open everything to .358" and chamfer the forcing cone and see how that helps. I'll report back.

I would not do anything to it. If it spits lead, it has problems. Send it to Ruger. It's free, and they will have it back in 2-3 weeks.