Boolit Diameter

[newton]

Ok, I have a thread going on my NMBH 45colt in the revolver section but have a generic question to pose here.

I am having some doubts to what size my boolits need to be. You always hear the standard ".001" over groove diameter. Sounds good enough. But in my situation, which is not unique by any means, there are some things I am thinking about.

I will have to take measurements again, but I am really wanting to say that my fired cases measure out at .486" after being fired. If I am not mistaken, I believe the case thickness of the 45colt is around .010" give or take a few thous.

So, .010 x 2 = .020" then add boolit diameter which we will call .452"(which is .001" above bore diam, even though I now am using a larger boolit, but my bore is .451") that equals .462", again, give or take a few thous.

Then take what I am measuring my fired cases at which is around .486" or so. Maybe they might be a little less, but regardless, they are above .480". I will measure again tonight.

That gives .018" - .024" of 'space' that is having to be filled. I think, personally, this is what is giving me fits with accuracy. In theory, the boolit or boolit base at least, is being sized up quite a bit before making it through the throat. My throats are right around .4525".

Is this a good thing? I know it cannot be avoided, but would a bigger boolit be a better thing? And if so, how big is too big?

Thanks!

[fredj338]

Your fired case dims really have nothing to do with anything IMO. It is only telling you the approx size of the cahmber. The bullet isn't bumping up in the chamber but as it hits the throats. Match the bullet to the groove dia or cyl throats, if larger, + 0.001". That will yield best results. If the cyl throats are smaller than groove dia, the only sure fix is to open them up.

[newton]

The throats are larger. I am good there.

You do not think there is room for the boolit to get cocked sideways before entering the throats with so much room in the chamber?

Of course, I am not talking a drastic amount here or anything. But I would think a little could happen. Also, I would think that the bases would have more room to either expand or allow gases around them. But I guess that would all be dependent upon whether the boolit had completely entered the throat before the case had completely expanded to the chamber.

I question all of this because my boolits sized at .452" shoot dramatically different than those I leave unsized. And I am wondering if I might do even better with a little larger boolit.

[The Ranger]

oversize chambers could be hurting accuracy (not saying they are), but you cant correct that with the bullet sizeing.

what size are your boolits as cast?

[Suo Gan]

I am having a hard time keeping all the numbers straight.

What is your mean chamber diameter? .452"
What is your slugged bore diameter?

You want that bore diameter smaller than your chamber diameter, I have heard of NMBH's being very mismatched as far as chamber/bore diameters.

What boolit are you using?

Hope some guru's chime in to help you. Take care.

[Suo Gan]

You do not think there is room for the boolit to get cocked sideways before entering the throats with so much room in the chamber?



You want to seat them out as far as possible for good initial launch. This gets them started good and also eliminates gas cutting.

You need to slug it. What is that number?

[Suo Gan]

I question all of this because my boolits sized at .452" shoot dramatically different than those I leave unsized. And I am wondering if I might do even better with a little larger boolit.

You want the boolit with a good snug fit in the throat, as far in as possible. If you are using a boolit with a crimping groove not fitting your gun...then get her one that fits her!

[newton]

oversize chambers could be hurting accuracy (not saying they are), but you cant correct that with the bullet sizeing.

what size are your boolits as cast?

I'm going to have to measure that tonight. In fact, I am going to do a lot of measuring tonight. I would be lying if I tried to say a number right now.

[newton]

I am having a hard time keeping all the numbers straight.

What is your mean chamber diameter? .452"
What is your slugged bore diameter?

You want that bore diameter smaller than your chamber diameter, I have heard of NMBH's being very mismatched as far as chamber/bore diameters.

What boolit are you using?

Hope some guru's chime in to help you. Take care.

Mean chamber diameter is right around .480-.486" I will make a definite note of it tonight. Slugged bore I know is right at .451".

I think maybe you are wondering what the throat diameter is? It is apart of the chamber, but distinct as to its name and purpose.

The throat is .452" give a little on the hundred thousands side.

[newton]

You want to seat them out as far as possible for good initial launch. This gets them started good and also eliminates gas cutting.

You need to slug it. What is that number?

So your saying as close to the throat as possible? Slugged the throats at around .452".

[newton]

You want the boolit with a good snug fit in the chamber, as far in as possible. If you are using a boolit with a crimping groove not fitting your gun...then get her one that fits her!

I guess I am at a loss here. Could you explain what you mean?

[462]

Slug all six chambers. Size the boolits .001" fatter than the largest cylinder throat.

Sizing boolits to .452", for cylinder throats that are .4525", is less than an optimal way to go about it.

Sizing boolits smaller than cylinder throat diameter has never worked, for me.

[375RUGER]

I will have to take measurements again, but I am really wanting to say that my fired cases measure out at .486" after being fired. If I am not mistaken, I believe the case thickness of the 45colt is around .010" give or take a few thous.

So, .010 x 2 = .020" then add boolit diameter which we will call .452"(which is .001" above bore diam, even though I now am using a larger boolit, but my bore is .451") that equals .462", again, give or take a few thous.

That gives .018" - .024" of 'space' that is having to be filled. I think, personally, this is what is giving me fits with accuracy. In theory, the boolit or boolit base at least, is being sized up quite a bit before making it through the throat. My throats are right around .4525".



When I read this it makes me think you don't know the difference between the bore and the chamber or your decimal is in the wrong place.
The bore is the ID of the barrel. Has nothing to do with the chamber where the cartridge case is enchambered during firing. I would not try to fire a .010 over diameter boolit in my guns.
I think .489" is the SAAMI max chamber dim for the .45LC. So you are within spec.
If your bore is .451" you will be fine if you shoot a .453" boolit in it. If you can find a boolit that when seated in the cartridge, just starts into the throat, then the boolit/cartridge will be already aligned/centered in the chamber when you pull the trigger--that would be ideal. According to your measurments you should have a boolit that is sized .453, that is what I would shoot.

[Suo Gan]

Mean chamber diameter is right around .480-.486" I will make a definite note of it tonight. Slugged bore I know is right at .451".

I think maybe you are wondering what the throat diameter is? It is apart of the chamber, but distinct as to its name and purpose.

The throat is .452" give a little on the hundred thousands side.

Yes I meant throat. And you are saying it is .452" What is the bore diameter?

My guess is that you are sizing them too small and using the crimp groove on the boolit and the boolit is skipping down the bore.

[USSR]

My throats are right around .4525".

Forget your barrel's groove diameter. Your throats are .4525", so size your bullets to .453".

Don

[Wolfer]

I like to have to push a little to get a sized boolit to slide thru my cyl.
I like the lead that sticks out of my cartridge to be snug in the throat ( the area just ahead of the chamber ) for about .100. This gets me centered and straight .

I don't know how big your mold casts but if I had better luck unsized then I wouldn't size them. If I remember right your using lee 452-255-RF so I would like the area just ahead of the crimp groove to be .453 or above as long as they will chamber.

My 452-255 drops out of round 452x457, my throats are .452 and I shot these boolits for a long time unsized with very good results.

[Bob Krack]

Sounds to me like we are talking target accuracy being desired - fine and dandy.

Relative accuracy, minimal or non-existent leading, maximum performance with a particular powder, case, primer, boolit says to me........If your throats are .4525 then the appropriate boolit size is .453 as USSR mentions. BUT - if your groove size happens to be something more like .453 or .454 for example, ya better get your throats enlarged for optimal performance.

I've learned a lot here, but learned firsthand over 35 years ago that a lead alloy projectile being at groove size or smaller will "lead" the barrel. Don't matter if it is cast undersize, made undersize by a sizing die, the case "squeeze", or undersized revolver throat(s).

Good luck,

Bob

[44man]

Actually it does no good at all to use a boolit over throat size. Better if they just fit through. You can also shoot bore (groove to groove) size with accuracy even if under throat size.
It does no good at all to use the throats for size dies.
With .4525" throats and a .451" bore, I would use .452" boolits.
I am contrary of course, you need to expect it from me! [smilie=l:
Too many other factors come into play for accuracy. Nose guidance at the cone so the cylinder is pulled into line is one. That tiny side play in the cylinder is SO important. A boolit that does not slump and takes the twist as soon as it can without skidding past the base band is another. A slower start to the boolit without full pressure while it is still in the brass is another.
Velocity match to twist just might be the most important of all. This is my biggest sticking, thorn in the side. Every revolver shooter ignores twist, spin, stability and seems to think anything can be shot but they would never do less in a rifle. Every single boolit needs a certain velocity and spin to be stable. If your boolit needs 1000 fps, do not expect it to shoot way under or over. That is why we work loads and the ONLY reason we do.
Some will say to use a chronograph to find the lowest SD's, etc but that ignores velocity match to twist and just might shoot the largest patterns you ever got with a shotgun.

[felix]

Excellent, JIm! ... felix

[newton]

Thanks for the replies guys. I was a little off in my memory of the measurements. And for the record, I am not wanting to shoot .460" boolits out of my gun. haha.

The bore mics out right around .451" give or take a little. I have a mic, and the last time I slugged it came out right at .4509"-.451".

The throats are right at .4525" for sure and they are all pretty uniform.

The fired cases come out at .478", and sized they are .469".

But I am past that now. My hardheadedness has been softened by those with greater wisdom than me.

I have heard both sides of the great debate on boolit diameter. And honestly, I am to the point of I'll try anything within reason. If my gun will shoot a smaller diameter boolit than the throat, so be it. If it needs a larger one, so be it.

I am just ready to come to a decent load with it. I think I am about there, if I can keep from over analyzing things. I am not looking for one hole groups...I just want groups.

I was just concerned about the large jump in diameter from sized cases to fired cases and wondered if a larger boolit would help. I am thinking now its not that big of a deal. Sure, it might help to shrink a 2" group to a 1 1/2" group or something, but at this point I would love to have a 3" consistent group.

Thanks again.

[newton]

I like to have to push a little to get a sized boolit to slide thru my cyl.
I like the lead that sticks out of my cartridge to be snug in the throat ( the area just ahead of the chamber ) for about .100. This gets me centered and straight .

I don't know how big your mold casts but if I had better luck unsized then I wouldn't size them. If I remember right your using lee 452-255-RF so I would like the area just ahead of the crimp groove to be .453 or above as long as they will chamber.

My 452-255 drops out of round 452x457, my throats are .452 and I shot these boolits for a long time unsized with very good results.


So when you chamber a round do you have to press it in, or does it just drop in?

You remember right. That is the boolit I am using. They do drop out of round, just about like yours. .452x.454 or so.

[44man]

So when you chamber a round do you have to press it in, or does it just drop in?

You remember right. That is the boolit I am using. They do drop out of round, just about like yours. .452x.454 or so.
Rounds can just drop in chambers. If you neck size, after a while you need to push them in. No harm at all and almost no difference.
I load the 45-70 revolver and full length all the time. You can chamber from across the room but you can also hit 1" targets at 100 yards---YES YOU, not just me.
I want all of you to stop going to extremes. The little tiny stuff means nothing. You need to put things together, no one thing is going to help you.