How much over bore dia. before you must resize a cast boolit?

[Centaur 1]

In low pressure pistol calibers such as a .380 auto and .38 special; how many thousandths over bore diameter can my cast boolits be, before I should start worrying about sizing the boolits.

My situation is that I just started casting the LEE.358-105gr swc, and they measure .3595"/.360". I'm just loading low power plinking loads and all of my guns will chamber rounds made with this boolit. Two of my guns are revolvers, a S&W model 19, and a Colt Police Positive special.

I'm not worried about either one of those two guns, but my concern lies with my Ruger LCP .380 auto. I know that the stock answer is no, the boolits are too big, but people just assume that a .380 acp has a bore diameter of .355". I slugged the barrel on this gun and the bore diameter is .3573". I know that I'll probably get a sizer eventually just to make the boolits rounder, but money's tight and I can't get one right now. I know that they aren't too too expensive but I'm on Social Security Disability and I have two children in college. The little money that I do have is being used for a good cause so I don't mind waiting.

My concern lies with the LCP since it's a semi-auto and I have worry about the gun functioning as well as shooting. It actually surprised me when I slugged the barrel because I didn't expect it to be .0023" over what we consider standard. I have to assume that the guns reputation as a reliable back-up pocket gun, must come in part because of loose tolerances that will help to keep parts sliding instead of jamming.

My boolits as cast are .0022"/.0027" over the bore diameter, which is an average of .00245". Without doing anything special these boolits seat nicely in a .380 casing, and the finished cartridge drop into the chamber easily. I understand that we're supposed to slug the bore and size the boolit to .001" over, but I see some guys recomending a size of .002"-.003", and in some cases like a Marlin with micro-groove rifling I've seen recomendations of up to .004" over. I even do that myself with my 30-30. I reamed out the gc step of a Lee 150grain fn mold with a .3115" reamer and they work great as plinking loads, but it's a rifle that's much stronger than my tiny .380 acp.

I guess that my real question is: is there any cold hard rule about not sizing cast boolits? I understand that with a lot of guns, the round won't chamber if the boolit is .002-.003" oversized. If the gun will let it chamber, what is the maximum tolerance that's never to be exceeded, no matter what? Is it .003" over bore, or maybe .004",.005", .006"?

I'd like to hear opinions on this, what do you all think?

Thanks, Mike

[geargnasher]

Your last paragraph captured the essence of what my basic response is to the rest of your post. There are no rules for sizing cast boolits. There are some guidelines, and I think that almost always a boolit needs to be at least groove diameter, but the rest is determined by the individual gun.

Other considerations are your dies, do they allow the seating of larger boolits without squeezing them undersized? How about chambering? How about reliable function? Only you and your particular gun can answer these.

bottom line, if your boolits will chamber as cast, and if you pull a seated one and it's still a little bit over groove diameter, I would load some up with published starting load data and see how she does.

Gear

[Moonie]

As a rule I don't normally size pistol boolits. But then I don't have a lubrisizer either. I either pan lube or use 45/45/10. I also don't normally try to push the limits of my cartridges either, that is for young men who are indestructible, I do remember those days however...

[Centaur 1]

Thanks gear, sometimes the obvious is hard to see. I pulled a loaded boolit and I recovered one that was shot into a soft target that wasn't damaged. I just used a light taper crimp on these boolits and when I pulled one it measured .356". So it turns out that the seating process "sizes" my boolits for me, and I've been worrying for nothing. I learn something new every day on this site.

[Three-Fifty-Seven]

Thanks gear, sometimes the obvious is hard to see. I pulled a loaded boolit and I recovered one that was shot into a soft target that wasn't damaged. I just used a light taper crimp on these boolits and when I pulled one it measured .356". So it turns out that the seating process "sizes" my boolits for me, and I've been worrying for nothing. I learn something new every day on this site.

Actually you do have something tho worry about . . .


I slugged the barrel on this gun and the bore diameter is .3573".

When you are seating them you are swaging them down too much, as they need to be at a min .358, preferably .3585 - .359 . . .

Does the gun lead up? How is accuracy?

ETA:

Try taking the expander/flare plug out of the 38 spl die, and putting it in your 380 die, or just use the 38 spl die to expand and flare/bell your 380 case, then seat and pull, and measure . . . may fix the problem . . .

[Centaur 1]

As soon as I measured the boolit I thought the same thing, that they were undersized. I'm not getting any leading though. I still have the front band on the boolit that's full sized, the band that's forward of the crimp groove. Also when I measured a boolit that was shot, it measured the full diameter of the bore so I'm assuming that it obturates when I fire it. I air cool these boolits to try and make them as soft as possible. That's a great idea about using the expander plug from my .38 dies. I'm not sure that they'll work because they are different brands, but I might just go ahead and buy a .38 expander plug for the .380. Up till now I've been lining up all of my sized brass and belling the case mouth with a plumb bob and a small plastic mallet. This method works good, but it's an extra step that a larger expander plug might alleviate. Thanks for the suggestion.

[noylj]

Sounds like things are working well.
However, for those not so lucky, I would suggest:
1) Measure the ID of a fired in your gun. Subtract 0.001" from this dimension—this will be the largest bullet you can safely shoot in that case in your barrel.
2) You have slugged your barrel. I shoot bullets from 0.001-0.004" over groove diameter without problems.
3) Get an expander that will expand the case to 0.001" less than your bullet diameter. Lee is quite reasonable for this sort of custom work. This will prevent most swaging of your bullets.

[GP100man]

I shoot the biggest lead boolit I can get in the hole !!!

[Gohon]

Measure the ID of a fired in your gun. Subtract 0.001" from this dimension—this will be the largest bullet you can safely shoot in that case in your barrel.

This doesn't make any sense to me.............what am I missing?

[bgokk]

This doesn't make any sense to me.............what am I missing?
ID of fired case I think??:popcorn:


BG

[chboats]

Gohon - What noylj is saying is take a fired case, preferable a fll power load, and measure the inside of the case. This will give you the largest bullet that can be chambered in that case. I say "that" case because different brands or lots can have different wall thickness.

An over sized boolit that chambers will fire without problems. I have a Ruger 357 that I shoot .359 boolits in that the barrel grove diameter is .352. Before I knew that it was way undersized I had fired factory jacketed loads with no excessive presures.

Happy shooting

Carl

[Gohon]

Okay, now I understand what noylj was getting at. I guess it was the words "safely shoot" instead of properly chamber that through me off.

[mdi]

You wouldn't happen to be using a Lee Factory Crimp Die? The Lee dies size the case after seating the bullet, often swaging down the bullet dia.

[Centaur 1]

You wouldn't happen to be using a Lee Factory Crimp Die? The Lee dies size the case after seating the bullet, often swaging down the bullet dia.

I'm fairly new to cast boolits and reloading so I might be doing something wrong. No factory crimp die, just a regular Lee seating die. I'm trying to be careful and just taper crimp, but I might need to back off a little more. I adjusted the die so that I started to get a visible roll crimp, then I backed it up some. I'm thinking that maybe I need to reverse the procedure and work up on the taper instead of backing away from a roll crimp.

Btw, I like your signiture. It made me think about a guy in Walmart last week. He was insisting to the clerk that he needed "regular 9mm's", not the stuf marked 9mm Luger. He bought a box of ammo that said 9mm hollow points. When another customer told him that it was the same caliber, he got really nasty. He told everyone that he was a reloader so he knows what he's talking about, and that we're all in danger by shooting 9mm luger in a 9mm pistol. We all had a good laughed after he walked away.

[NSP64]

You should have asked him"if your a reloader, why are you buy factory ammmo"?

[geargnasher]

Actually you do have something tho worry about . . .

When you are seating them you are swaging them down too much, as they need to be at a min .358, preferably .3585 - .359 . . .

Does the gun lead up? How is accuracy?

ETA:

Try taking the expander/flare plug out of the 38 spl die, and putting it in your 380 die, or just use the 38 spl die to expand and flare/bell your 380 case, then seat and pull, and measure . . . may fix the problem . . .

Excellent idea on the .38 expander, but it might have to be spaced down to reach the .380 case if it's a Lee brand. The RCBS and Hornady dies might adjust that far.

Centaur, your expander plug should be belling the cases for you if it's adjusted properly, if you're having to do an additional bell with a plumb bob maybe you should try adjusting your expander down some more. Even the .380 expander should have enough bell shoulder to open them WAY up at the mouth. Still won't solve your swaging issue though, gotta get a bigger expander plug. Be cautious though, your pistol might not chamber full .358" boolits if you can get them seated without squashing the boolits.

As for Noylj's recommendation, I have a little bit of an issue with it. First, fired case ID varies widely with brass composition and temper (read: Brand), number of firings, peak average pressure of the load, the dies used to work the brass during reloading, and case thickness. The only way to know exactly how large a loaded round your gun can safely fire is to either do a chamber cast or an impact slug of the chamber. An impact slug is easy for a boolit caster. Take a case that was fired in the gun, clean the outside, and fill it with SOFT lead to just above the level that you would seat a boolit to and just touch the rifling. Cast a few boolits with soft lead, pure is best, and wrinkles/poor fillout don't matter. "Seat" a boolit in your lead-filled case and chamber it, it may take a push to get it to go to battery because your COAL should be a bit longer than normal. Take a brass rod as big as you can reasonably get in the bore, wrap it with masking or electrical tape, stick it down the barrel from the muzzle and pound the boolit/case hard until it forms into a solid mass in the chamber/throat area. Tap the action open and carfully extract the slug, you might want to keep the rod against the "boolit" the whole time to keep it from being pulled out of the case. Now you have a good impression of your chamber and throat and something that will stand a good mic'ing. Your loaded cartridge diameter limit should be about .001" under the chamber neck diameter of your slug. If you're running the ragged edge of too big on your loaded diameter, you should segregate brass by lot and check each time you use different headstamp/lot of brass or change alloys or dies. Case thickness varies greatly.

The little birdie in the back of my head needs to speak here also: Often, if you have something that works for your purposes, no need to go fixing it. You might set your expander deeper to skip the extra belling step and just go with it as long as you understand that what you have isn't "ideal" and you may need to get a bigger expander if you start having problems at some point.

Gear

[Centaur 1]

The little birdie in the back of my head needs to speak here also: Often, if you have something that works for your purposes, no need to go fixing it. You might set your expander deeper to skip the extra belling step and just go with it as long as you understand that what you have isn't "ideal" and you may need to get a bigger expander if you start having problems at some point.

Gear

Thanks Gear, I definately agree with the idea of why fix what's not broken. I'm not worried at all with the load that I'm using, it just gives me something to think about if I were to work up full powered loads. I understand the warning signals of loads that are pushing pressure limits, but the .380 is a low pressure load and I'm not sure that I'll be able to see those signs while keeping within the limitations of the caliber.
I'm trying to understand the firing process logically in my mind and I have a theory. I understand that everything will effect pressure to some extent. I have also read on here that some guys will load a cartridge using only a primer to purposely lodge a boolit in the barrel, then knock the slug out so that they can measure the barrel diameter. Here's what I'm thinking. If the primer alone will propel the boolit forward into the barrel, then isn't the boolit at that point, "sized"? Has anyone ever seen any actual numbers on chamber pressure when the only thing changed was the boolit diameter? I'm not sure that I'm explaining it properly, but say if someone measured the pressure in a .380 with a .359" boolit. Then size another to .358" and use the same load, then one at .357", .356", etc.. Is this a dumb question?

[runfiverun]

nope.
you gain about 300 psi by being a thou over sized, until you hit about 3 thou over, then it goes higher.
remember lead is malleable and slippery.
being oversized isn't that big a deal unless you are jamming a nose in the lands, then it's another type of problem with certain powders.
the lube grooves etc. gives extra lead somewhere to go as it moves along [see barnes banded stuff? thats why they cut those in there, pressure relief].
you can run into other issues with short cases [necks too] and cast in a semi/bolt/whatever, also but it's easily spotted [cause the gun jams after a few shots].
it's all stuff that CAN happen but rarely does.
correct sized oversized don't really matter much does it? cause you work your loads to your gun and 500-1000 psi pressure gain isn't gonna be that big of a thing, unless you are running ragged edge.

[noylj]

I am glad that you corrected the fact that I left out the word "case." Typing and typos are such a problem, particularly with a cruddy keyboard.
If a fully expanded case (full factory load) has an ID at the case mouth of .402, then any bullet that was over .402" in a case with that same wall thickness will, at worst, chamber but leave no room for case expansion to release the bullet.
The nice thing is that you can do things with even the hardest lead that would be a disaster with a jacketed bullet.
The flip side is that a .398" jacketed bullet will probably shoot very well in a 0.401" groove diameter barrel.
What most people find out is that their die set was designed for jacketed bullets, which, being harder, do not swage down in size like a lead bullet will. these die sets generally have an expander that will not expand the case enough (expander diameter is too small) to allow a lead bullet to be seated without being swaged down, unevenly, in diameter. If you are shooting 0.401 lead bullets, your expander diameter should be 0.399-0.400" so the case ID is only 0.001" smaller than bullet diameter.
Then there are people who only bell the case mouth, try lead bullets, and give up because they lead too much, not even realizing that they aren't even loading their jacketed bullets properly. However, since they are generally shooting minute of barn door in some action pistol competition, absolute accuracy is way down in their needs for a load.

[Bret4207]

Lotta good info here. The only thing I would add is that the ID of a fired case idea was to give a ball park of the max size you can usually chamber and that it will often be close to throat size. Note the qualifiers in that sentence. People have rebated the lower portions of boolits to fit oversized throats and undersized chambers. Using words like "as large as you can safely fire" are misleading, but necessary.

[Shiloh]

I also don't normally try to push the limits of my cartridges either, that is for young men who are indestructible, I do remember those days however...

Me too, glad they are over. Wisdom from maturing, and common sense prevailed.

Shiloh

[docone31]

yeah, me too.
I can fire a 30-06 all day long. Those days of Mega hand and shoulder cannons are gladly done. I mean, what was I thinking?
I am a big guy, over 6'6", was a body builder for years. I just plain got hurt back then.
Someone else can do that for me today.
Phooey!
Target shooting with a .460 Weatherby, and an XP-100 in .375 H&H!
I must have lived on Testosterone back then. My shoulder used to hurt for weeks.
Today, I like a nice, easy day at the range. Sometimes I do not even check my target for several sets.
No one at the range has anything like I used to fire either! They are all wimp guns.
Of course I can barely lift my arm today.
Could be connected somehow.

[Jech]

So in theory, does this all mean that I *may* not need to resize my 452-230-TC boolits for use in my SA XD? They normally drop .454-.455...

[Bret4207]

If they chamber without resistance, yes. But- they may be chambering because the seating/crimping die is sizing the boolit within the case. Be advised that if you normally use, say, .452 boolits and substitute a .455 your pressures will be different (higher) if the boolit remains at the larger diameter after loading. Best to back off a bit at first and observe carefully.

[ricksplace]

yeah, me too.
I can fire a 30-06 all day long. Those days of Mega hand and shoulder cannons are gladly done. I mean, what was I thinking?
I am a big guy, over 6'6", was a body builder for years. I just plain got hurt back then.
Someone else can do that for me today.
Phooey!
Target shooting with a .460 Weatherby, and an XP-100 in .375 H&H!
I must have lived on Testosterone back then. My shoulder used to hurt for weeks.
Today, I like a nice, easy day at the range. Sometimes I do not even check my target for several sets.
No one at the range has anything like I used to fire either! They are all wimp guns.
Of course I can barely lift my arm today.
Could be connected somehow.

I'm sure not 6'6", more like 5'10", but the rest of your post fits my history pretty well. I had a hard fall skiing (been a downhiller for 50 years+) and broke both arms and tore my rotator cuff. After the surgery on my rotator cuff, the surgeon told me that I had multiple micro tears in all of my tendons in my right shoulder and wondered what might have caused them. I still like shooting the big guys, but now it's cast boolits, and muzzle breaks in my 458, 416, and 375. My shoulder is back to normal, actually better than what used to be normal, and I intend to keep it that way. Yup, I'm still skiing.

[Centaur 1]

Just a little update after going to the range today. I shot 100 rounds and Elsie fired flawlessly and there weren't any signs of excessive pressure. I don't have a chrono, but when I compared the recoil to factory loads mine had slightly less of a kick. I think that I'm happy right where I'm at, I don't want to beat my gun up with heavy loads. A very close friend of mine is the rangemaster where I shoot and he was surprised with the recoil. He's a .45 auto lover and my little .380 changed his perception of the round. When he walked up I got a lot of "How Cute" remarks about the "Tiny little bullet". When he got done shooting he said "Wow, I did not expect that". The best part is that the mold cost me only $20, and I shot 100 rounds today. The range is the only place locally that has .380 ammo and they charge $24 for a box of 50 rounds. When you factor in primers and powder, I broke even after just 50 rounds.