Silly little .000.4 does it matter ?

[gray wolf]

I tried some .358 B H N 12 bullets through the cylinder throats
of a 357 revolver.

They don't fall through under there own weight, but push through easily. Throats measure with a Mic. at .358.4
So the bullets are .000.4 under.
The groove is .355.5

Should I anticipate any leading problems in the cylinders or the F/cone ? I hate to open up a sizing die for 3 or 4 tenths.

Slugs from a barrel slugging fall through the cylinder throats very easily.

[tazman]

Shouldn't be any problem at all. I would shoot them and not worry about it.

[GhostHawk]

I would say it would depend on the variables.

With the right variables they could be no problem at all.
With the wrong ones you might see some leading.

Alloy? Hardness? Air cooled or water drop?
Load? Powder? Pushing them hard or light loads or somewhere in the middle?

Lube?

Bullet fit is king, and IMO you want it right first.

But you really won't know until you shoot it.

Follow the evidence, let the gun tell you what it wants.

[str8wal]

I hate to open up a sizing die for 3 or 4 tenths.

3 or 4 tenths is a lot, 3 or 4 ten-thousandths not so much.

Why the second decimal?

As long as the bullets leave the throats larger than the groove you should be okay. I'd say give them a shot and see.

[John Ross]

3 or 4 tenths is a lot, 3 or 4 ten-thousandths not so much.

I wholeheartedly agree. A bullet that is .658" or .758" would be a real problem...

[NSB]

There is no second decimal point when measuring anything. It appears you're referencing a diameter at .3584" . If that is so, disregard the fourth number on that measurement. Unless you're using a gage that measures to five decimal places, the fourth one is what is called the descriminating decimal place. What that means is that you use the last decimal place to round up or round down the preceding decimal place to make a decision with. In other words, in your case just call it .358". Had you measured .3586, .3587, .3588, or .3589 you would have rounded it up to the next .000" and called it .359". Don't even worry about that last decimal, and remember this.....in order to count the last decimal place you're concerned with you need a gage that reads one place beyond. In other words, if the third decimal place is important you need a gage that reads in four decimal places. Hey, I don't know everything but I stayed in a Holiday Inn Express last night.

[Bigslug]

Sounds like you're close enough to ideal dimensions that the only way to know is to load them up and light them up.

My only question: was that .3555" groove measurement taken from a slug that was all the way through a barrel that might have some frame crush at the threads? If that condition exists in your revolver, and it gets lapped out, you may find that your true groove diameter is in the .356"-.357" range, which would be totally ideal for your .358" bullets and .358+" throats. I've found that using a set of pin gauges in a range that (a.) slip fit the bore, and (b.) slip fit past the frame constriction is quite illuminating. Just make sure you have some kind of flexible plastic rod or wire handled brush to push them back out from the frame end if they stick.

[upnorthwis]

In the nomenclature of machining, if we say a tolerance is held to one tenth, we are talking about .0001 not .1 It means a tenth of a thousands. But definitely get rid of that second decimal point.