Bore Sized Boolits

[Super Sneaky Steve]

I've been casting and shooting a long time and I've always cast and shot boolits 0.001 over bore as we all should, but some of my automatic pistols don't like to chamber fat boolits and I've never actually tried to size a powder coated boolit to bore anyway.

I noticed a company called Blue Bullets and they sell bore sized bullets in 9mm and .45 Auto. Their boolits are powder coated. Has anyone tried to shoot bore sized PC boolits?

[jdgabbard]

I haven't, at least not PC'd. But it might work. There's only one way to find out....

[Jack Stanley]

I haven't played with powder coat yet . For the most part I size bullets to .0005" over groove measurement and it works quite well . In some case i may size .002" over .

Jack

[jdgabbard]

I haven't played with powder coat yet . For the most part I size bullets to .0005" over groove measurement and it works quite well . In some case i may size .002" over .

Jack

I have found that in 9mm I have to go .002-3 over to even stand a chance at not leading. So much so I threw away my 0.356 sizer. But most of the time 0.001-2 works for me. Never tried any at exactly bore diameter.

[fredj338]

I load a several calibers in a bunch of did pistols. I always go 0.001" min larger than bore or jacketed size. I size all my PC bullets after baking for uniformity. No issues but in some 9mm brass. I size 0.357" for about 6 diff 9mm, including stock Glock bbls, no issues with leading or accuracy.

[243winxb]

There are two diameters in a barrel. The greater (major) diameter is the groove; the lesser (minor) is the bore.

Of what one do you speak of? Do you mean a "Bore Rider"? :kidding:

[Jack Stanley]

For me , I always start with the major diameter . Perhaps paper patching and powder coat will begin with the minor diameter ... I don't know .

I was going to try paper patching but I never got around to it .

Jack

[missionary5155]

Does appear Super Sneaky is hiding in the shadows.
I cannot imagine a bore size cast slug pushed by smokeless being of good service.

[Silvercreek Farmer]

Maybe be a dumb question but are you seating down to the ogive?

https://www.brazosprecision.com/Overall-Length-OAL_b_9.html

[charlie b]

A major cause of leading (and copper fouling) is when there is 'blow by' when the bullet enters the barrel.

The reason many people use .001 over groove dia is due to the variables of bore measurement. If your bullet is even .0005" under then it does not seal, you get 'blow by' and leading.

Then there is the effect of wear on the throat from the time you measured it that will cause the initial bore/groove/throat dimensions to be slightly larger than measured.

Then there is the option of using softer alloys so the initial pressure spike upsets the bullet into the grooves. If that is happening for you then you can get away with a smaller dia bullet. It is the same principle some of us use when we put slugs in a muzzleloader. The bullets are very close to bore dia, slipping in the barrel easily. A relatively large charge of powder is used that will upset the bullet into the grooves.

Basically, .001 to .002 over groove dia is a 'safe' dia.

[LAGS]

I cast and size my Boolits to .001 larger than the groove size.
Then I PC them and Resize them to the same size.
Now on my Tokarev 7.62x25.
I cast the Boolits size them to groove dimensions.
Then PC the Boolits and again resize them to the groove size.
My barrel is .310 groove diameter.
If I try to load the cases with .311 or.312 cast Boolits , they hang up when chambering on the neck.
But those pistols were designed for FMJ bullets that are the barrel groove diameter.
So the chamber neck area is snug on the loaded casing with the .310 FMJ's.
Sizing the PC Boolits to the groove diameter has not effected my accuracy at all.

[mdi]

For cast boolits the important dimension of the barrel is groove diameter. I slug the barrel of every firearm I get (except 22 rimfire) and always size my cast boolits at least .002" over grove diameter. I have 5, 9mm handguns and size boolits to .356" to .358" depending on which diameter works best in a particular gun. I can get by with .357" but sometimes my "perfectionist" needs exacting dimensions...

[DougGuy]

For cast boolits the important dimension of the barrel is groove diameter. I slug the barrel of every firearm I get (except 22 rimfire) and always size my cast boolits at least .002" over grove diameter. I have 5, 9mm handguns and size boolits to .356" to .358" depending on which diameter works best in a particular gun. I can get by with .357" but sometimes my "perfectionist" needs exacting dimensions...

This is not entirely correct nor accurate.

For starters, it matters not what groove diameter is *IF* the throat is sizing down the boolit as soon as you fire it. What IS most important, is throat diameter.

In a revolver or an autoloader, the boolit still has to pass through the throat before it reaches the rifling. If you have a 9mm pistol, and you size to .358" and seat way down low in the case because the assembled round will not plunk at published COA measurements, and your throat (is there is one) is smaller than the boolit, then the throat is serving as a sizing die every time you pull the trigger.

Same with a revolver. It doesn't matter how much over groove you size the boolit to, it will still exit the front of the cylinder at throat diameter if the throats are smaller than the boolit.

Otoh, if you have an undersize boolit and you touch off a stout enough charge of powder, AND the alloy is soft enough, the boolit will obturate until it is confined by the throat, and again it will leave the front of the cylinder at throat diameter. This is a good way to "trick" a 44-40 into getting away with a larger boolit than the neck of the chamber will allow. Hone the throats to the diameter you want the boolit to be, and let pressure do it since it is a difficult and expensive process to make the neck area of the chamber large enough to seat your assembled ammo.

[Cris T]

Can it be dangerous to make the bullet too big? What if I used a .460" bullet in a 45/70 (16bhn) that slugged at .4575" major diameter? Could that be dangerous? (providing the charge was good)

[LAGS]

Sizing cast Boolits .002" larger than the groove diameter will work , but can raise the chamber pressure a tiny bit.
But if the cast Boolits is too tight , it in theory can increase leading in the barrel due to more drag.
But having a Boolit that is way too big also makes the casing expand when the Boolit is seated in the case.
Now the loaded casing fits tighter in the chamber.
Like it was said by others.
A loaded casing should drop right into the chamber with a little Plunk.

[centershot]

Can it be dangerous to make the bullet too big? What if I used a .460" bullet in a 45/70 (16bhn) that slugged at .4575" major diameter? Could that be dangerous? (providing the charge was good)

In my case, it hasn't been a problem. The bore of my Marlin 1894 .357 Magnum mikes 0.3555", that's a 9mm bore! I load the Lee 158 RNFP as cast, 0.360", tumble-lubed twice with BLL to 1400fps using Blue-Dot powder.. It's a plain base boolit so I don't push any faster to avoid leading. With a 4x scope on it, it will give 1-1/2" groups at 50 yards, no pressure signs.

[rockrat]

I have shot powder coated in my 45 acp and 9mm without any leading. At groove diameter, that is. Seems like the powder coating acts as a thin bullet jacket

[mdi]

Every revolver I own the cylinder throats are larger than the groove diameter. I've only done a few chamber casts of my rifles to get throat diameter, but none have been problematic with cast boolits. All my semi-auto handguns (10) have proper throat diameters, none affecting groove diameter. I size all my revolver bullets to the same diameter at the cylinder throats (I have measured all cylinder throats). My semi-autos are usually sized at least .002" over groove diameter and chamber cleanly. So for me knowing the cylinder throat and groove diameters are more important than the bore diameter. I normally get good accuracy and minimal leading, if any, from my cast bullet sizing...

[Super Sneaky Steve]

https://thebluebullets.com/product-category/9mm-38-super-355/

Here's a link to the bullets I mentioned. I doubt they would be selling them if they didn't work well. All their 9mm is sized .355"

Maybe it's worth trying.

[Johnch]

I powder coat some of the bullets I use

As for what sized bullet to use depends on the gun
As I have a DW 15 in 357 mag that shoots .360 dia bullets great
As I used to us it for IHMSA
With 180 gr cast , to knock over the 200 meter rams
But those loads were not for the faint of heart or will ever be posted ( a LOT of AA #9 and a small rifle primer )

My Glock 17 gets .358 cast normally
But the HP balks at chambering any bullet larger than .356

So I test and see what a gun will feed and chamber
As IMO there is not exact 100% correct answers

John

[jdgabbard]

https://thebluebullets.com/product-category/9mm-38-super-355/

Here's a link to the bullets I mentioned. I doubt they would be selling them if they didn't work well. All their 9mm is sized .355"

Maybe it's worth trying.

Way too high priced in my opinion. For that price you could buy bulk 9mm jacketed bullets from RMR. (https://www.rmrbullets.com/product-category/bullets/) There's zero point in buying undersized bullets that are cast lead for the same price as jacketed bullets that are going to work without issues. I'm sure they're cast of some really hard alloy at size, and then PC'd.

[Castaway]

There’s a bit of confusion here about bore diameter vs groove diameter. In the case of a 357, bore diameter will be 0.347+/- with a groove diameter of 0.356 +/-

[MostlyLeverGuns]

Long, Long, Long ago - P O Ackley did experiments on oversize bullets going into rifle bores. Most were with a 30-06 with the chamber sized and tapered to 8mm and .35 with a throat into the .30 cal bore. He concluded that the pressure required to size the bullet was much below normal pressures encountered in firing and that the bullet was sized to barrel diameter long before peak pressure had been reached. This does NOT mean the wrong cartridge in a rifle is NOT dangerous! Using a .310/.311 bullet in a .308 barrel is common, AS LONG AS the cartridge neck has room to expand to allow the bullet to move, a thou - .001" or so, there are normally no problems.