Partially undersized bullet.

[Bazoo]

I have a lee 429-240-2r that casts out of round. Most of the bullet is .430+. But there is a small section, about a 1/8 that is undersized. It is more like .4285. My bore is .4292. After sizing, the slight undersized section is still there.

I’ve never seen where others have tried bullets that had a slight undersized portion and I’m interested in what will happen here. Some of the bullets will hit the undersized portion on the land, and they would be fine I’d think. But what about the bullets that hit with the undersized portion on the groove? Will it just lead a bit and be shot out with the next shot? Will it lead severely? Will it not lead because of a thin layer of lube?

I’d love to hear from folks that have shot bullets like this.




Please don’t turn this into a “send your cylinder to Doug” / “if you’re not sizing to cylinder throat dimensions you’re wasting your time” / “powder coating will solve your problem” thread. And for the record I’m pro having Doug work his magic on my cylinder throats, but it’s not in the scope of my question.

[DougGuy]

You are not taking into consideration obturation. If your alloy is malleable enough and your load is stout enough it will only have that flat spot until you touch off the load. Once pressure bumps it up to fill the cylinder throats, it will exit the front of the cylinder at throat diameter, with no flat spot.

[Bazoo]

I appreciate the reply Doug. So it’s a non issue if obturation happens. What about with a harder bullet than what will obturate at the pressure?

[gwpercle]

Swamp People say ... CHOOT EM' !
What the sizing die didn't fix ... the firing and bump-up will .
Don't use Super Hard cast boolits ... a 1/16 or 1/20 (Tin / Lead) mix should do the trick .
Gary

[deltaenterprizes]

Lap the mold if you are worried about it!

[beagle]

Wouldn't worry too much about obturation. When that pressure hits the base, they'll bump. Shoot 'em and see or you might try beagling them up a bit all around and see what you come up with after sizing./beagle

[Bazoo]

I’m surprised at the replies that say it won’t be an issue. I have 18 loaded to test so I’ll see and report back.

I appreciate everyone’s thoughts.

[DougGuy]

Let me offer this.. Way back when I first started addressing cylinder throats, my two Rugers were the guinea pigs. The 45 Colt Vaquero had a REALLY bad thread choke, .449" or less. The point I am wanting to make is this.

Shooting 300gr XTP over 22.5gr W296 shot to the sights and a tad low. Shooting 320gr SSK TC boolits that were mostly lino over the same 22.5gr W296 put those high and to the left, about 6" higher and 3-4" to the left of the XTP group.

After I Taylor throated the choke out of the barrel, the SSK shot to same centerline, just a bit above the XTP so it shifted the POI of those a LOT since this was only about 20 yards or so, but it did NOT CHANGE the POI of the XTP loads. Now the SSK loads printed just on top of the XTP group.

This tells me that the XTP bullets were swaging their way through the badly choked barrel, and then bumping up to seal in the bore after they cleared the choke. Otherwise, they too would have shifted POI. The SSK was not obturating after clearing the choke. These bad boys went through over 3 FEET of seasoned oak firewood, and when recovered could dang near be loaded again and shot, nose flattened out a little and lands engraved in the sides, 99% weight retention.

Unless you are shooting some BHN22 or harder boolits, you should experience obturation as well over a magnum charge of slow burning powder. I can see no practical reason for shooting any harder boolit than ACWW, and best results will be noted with Elmer's suggestions of 20:1 for everyday general shooting, and 16:1 for a special purpose, big hog, cape buffalo, BIG Alaska brown, moose, elk, griz, etc.

That flat spot would be the least of my concern, and I wouldn't have that mold long before I got curious and added one or two more molds and began experimenting with those boolits.

[Bazoo]

This certainly isn’t my only mould. But it’s my first experience using it. I rarely use anything harder than wws and sometimes 50:50/ww: pb.

[DougGuy]

I’m surprised at the replies that say it won’t be an issue. I have 18 loaded to test so I’ll see and report back.

I appreciate everyone’s thoughts.

Shoot one in the deep end of a swimming pool. Bet the flat spot is long gone nothing but rifling engraved on the boolit.

[megasupermagnum]

Is the undersized section along a mold parting line? If so, it is almost certainly a case of the mold not aligned. This can often be caused by the tiniest bit of lead on the mold somewhere, but can also be the pins.

[Bazoo]

Shame I don’t have a pool.

The section is at the parting line, but to the side of it slightly and not directly on it. It didn’t occurr to me maybe a piece of lead is offending. I’ll have to give it another look. I’ve cast with the mould a couple times with the same result. I got it used. But I went over it some and lubed it with my pencil. Thanks.

[megasupermagnum]

Yes, that is exactly how a mis-aligned mold will cast. Look for problems there. Hold the mold up to the light, you should see very little light. If you do, try closing it with your fingers, not the handle.

[Bazoo]

Been my experience, it’s the norm for lee moulds to be this way, but often it’s not so bad to cause an issue.


I shot the sample bullets today and they leaded moderately. They were from ww alloy. Accuracy was okay at 15yards. From a fouled but not leaded bore.

For comparison, some RCBS 44-250-k sized .430, but of 50/50 ww/pb alloy shot clean this afternoon. I cleaned the leading from the bore between with a cylinder full of gas checked bullets, RCBS 44-240-SWC.

Both were 4.4 bullseye.

[megasupermagnum]

It's definitely not normal. Unlike others, I don't believe you will get these to work as they are. You need to get them round, or at least big enough to where the sizer hits it. Obturation wont fix it.