Tumbling poor accuracy need help

I have the Lyman 356402 mold, it throws 121 grains with wheel weights, it is a truncated cone boolit. I shoot it mostly in the 9MM sized to .355. these boolits shoot crappy and have shot bad for 20 years. Tumbling is very common and general accuracy is a joke, lube is alox-beeswax.

I've tried Linotype and even dead soft lead with no appreciable change. Can anyone offer some suggestions to get this boolit shooting as it should? I've never slugged the barrel but it shoots jacketed bullets OK and they are .355

First thing to try is sizing .357" I have tried cast in all my 9mm's and they chamber fine at this diameter. A jacketed slug is alot sturdier than any alloy boolit, and will hold to the rifling with minimal contact.

Lead, being much softer, needs a better (deeper) grip on the rifling. A slightly undersized boolit will allow gas leakage past the slug, resulting in leading, and poor accuracy. A bigger slug will help on all counts. Good luck.

Yeppir, you be too small.
Start at .356 min. I use .356, and it does real well in my Star.
.355 is too small.
Jacketeds sizing is just not thick enough. I usually go .002 over. I can go jacketed +.001 with paper jackets.
.355 should do well with jacketeds, lead, too thin.

Yea, What they said.

I like that bullet in a 9. I agree it's sized and or cast too small.

+1 on what they said. Too small. My 9mm gets fed .358s.

It may also be the twist rate of your barrel. According to Bar-Sto barrels the twist rate of American barrels is the same as 38 special barrels that is 1:16 where imports are made as fast as 1:9. The cast bullet is not able to grip the rifling and put enough spin to stablize the bullet causing leading,tumbling and poor accuracy.
A bullet with more bearing surface like the 147 will help, also using slower powders.

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Originally Posted by deltaenterprizes

It may also be the twist rate of your barrel. According to Bar-Sto barrels the twist rate of American barrels is the same as 38 special barrels that is 1:16 where imports are made as fast as 1:9. The cast bullet is not able to grip the rifling and put enough spin to stablize the bullet causing leading,tumbling and poor accuracy.
A bullet with more bearing surface like the 147 will help, also using slower powders.

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I doubt it. The 9mm is usually criticized for having too FAST a twist for the short bullets it shoots. If anything I would think a 1:16 twist would be better for cast boolits because it puts less rotational stress on the boolit.
I agree with the others, .355 is too small for a cast boolit in 9mm. Comparing jacketed and cast dia. is apples and oranges. If you do a search you will find most casters size to .357 or .358 for 9mm.

If you want to know, take the time to slug the barrel!

Hey Ohio, Up here in Mich. when we have that sort of problem we try using a 50/50 mix of ww and soft lead. I use that mix in my Barretta with that same mould you have for the last 10 yrs. I agree with the other advice about sizing with a .357 or even unsized and just tumble lube them with LLA. I stumbled on the larger sizing about 7 yrs. ago when I forgot to change sizers after doing some 158 slugs for my .38, at least I had changed the top punch first. I noticed a difference the next time I went target shooting at my gun club with better scores. :Fire: :castmine: Robert

I guessyou guys know more than a man that has been making match pistol barrels for more than 25 years!

It could have to do with the twist rate,sure enough,but you should slug your barrel.Thats the best way to see whats needed.

I use the same bullet in my Sig. Size them to .356 or .357. Both shoot good. If I shoot them fast I'll get a small amount of leading. That's with wheel weights.

I would try a small batch sized larger ....... and also try Hardcast416taylor's idea on trying a few "as cast" (unsized) and just lube with tumble lube ..........

Could be a real eye opener!

Three 44s

like was said my 9s have allways shot best with 357 bullets. Your on the right path with linotype. Harder lead will do better then soft in them ususally. Also make sure youve got all the jacketed bullet fouling out of the gun. Many 9s are shot ALOT and it can take some work to clean them properly. One more thing is when your loading take the time to carefully seat your bullets. Its real easy to get a 9mm bullet seated lopsided. A couple easy experiments are to shoot your bullets faster then youve been and slower. If the faster one shoots better and doesnt tumble its probably the rifling twist thats giving your problems. If the slower one shoots better its probably rifling dept and your normal load is going to fast for the rifling and striping through. Usually if this is happening you wil be getting alot of leading though and since you didnt mention that i doubt thats your case. If none of this works you will probably want to do what deltaenterprise suggested and move to a 147 grain bullet.

Size of the bullet is a definite factor. If it is too small it gets cockeyed/off center in the bore and you've got the yaw going before it gets much beyond the the end of the barrel. I had probs a long time ago with this bullet and dumped it in favor of the RCBS 9mm that is a truncated cone shape ( the cone is cut off and there is a meplat). The 402 was not favorably commented on either by Dean Grennel. The problem is the long(er) nose that makes the length of the bullet a bit longer than necessary (for a given twist) and that means it has a longer center axis to spin (around) on. Some folks may get it to work alright but that would depend again on the rate of twist; they may have faster ones. Slugging your barrel, measuring the diameter of your castings and changing the sizing diameter to a size larger are all necessary for helping to solve the problem. If no amount of experimenting with these factors improves the situation or gets it right then put the mold on E-Bay...someone will bid it up to double what you paid to start with and you can get a different mold to use successfully. LLs

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Originally Posted by bpost1958

I have the Lyman 356402 mold, it throws 121 grains with wheel weights, it is a truncated cone boolit. I shoot it mostly in the 9MM sized to .355. these boolits shoot crappy and have shot bad for 20 years. Tumbling is very common and general accuracy is a joke, lube is alox-beeswax.

I've tried Linotype and even dead soft lead with no appreciable change. Can anyone offer some suggestions to get this boolit shooting as it should? I've never slugged the barrel but it shoots jacketed bullets OK and they are .355

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I doubt very seriously that you have a 0.354" diameter bore. The 0.001" difference is the ideal differential for cast bullets to function correctly. May I suggest that you obtain a few .38 caliber round balls and push them through the bore. Then mic the diameter, add 0.001" to the diameter and you will have your ideal sized diameter. Make sure that you mic the as-cast diameter of your cast bullets also. This will ensure that they are not going to be undersize to begin with. I am sure that your problem will disappear after you have completed these tasks.