Boolits Sizing for 9mm Question

[RobS]

It's a Glock. A Glock factory chamber is typically generous so you would likely be fine with a sized .358 boolit. A thought - go with a .357" size die and if you need more lap it out to .358 with a strip of 320 or 400 grit sand paper wrapped around a split rod dowl with a bit of oil and a cordless drill.

[Motor]

When I used lube I used to size them .358" and never had any issues. It also worked out well because I actually shoot some of the 9mm boolits in 38spl/.357

I also used to use 15BHN alloy for them. Since I switched to powder coating I'm finding no problems with sizing .356" and using 12BHN alloy. This doesn't mean that I always use .356" though but I know it works. The boolits that I use for both 9mm and .357 I simply just size .358" and use them.

Motor

[Cowboy_Dan]

Short version, I PC and size .356" in an aftermarket Glock barrel.

Long version:

I built my Glock 17 from an 80% frame (using only hand tools, but that's beside the point), and a Combat Armory slide and "match" barrel. It slugs at .3547", but will chamber a .358" bullet. Initial load testing found a most accurate load for the powder used and the Lee 120 TC. Initial tests also suggested that due to the vaugeries in my process, some rounds would resist entering battery until cycled in 2-3 times and showed light rifling marks. All rounds fired fine once in battery.

The next test was to make three test groups: .356" seated with the original seating die settings and .356" and .358" seated slightly deeper. Result was that none of the three groups had the out of battery problem, and all rounds shot into the same group. So I load them sized .356" seated to the shorter OAL confident that even if I short stroke a bit on the press, it will still chamber and fire into the same group. Usual caveats, do your own tests and your mileage likely will vary.

[Lloyd Smale]

I do them all 357. 358 runs in some guns but not others and ive never had leading problems at 357 in any of my 9s

[Shingle]

With a plain base boolit you would be safe with .357, i use several sizes .355-.358 depending on the gun and boolit design.

[trapper9260]

For me some of my 9mm I size them to .356 and one to .358

[Drew P]

My glock barrel, and most of them to my knowledge, are not polygonal inside. They are better described as rounded groove rifling.

Mr fortune cookie has some thoughts about it that make sense.

https://www.youtube.com/watch?v=j1fI0iYeGps

[Sailormilan2]

Two barrels need boolits sized to .358, 4 barrels need boolits sized to .357. 2 barrels need boolits sized to .356. So, I use two sizes, .357 and .358.

[marek313]

I dont want to generalize here but largest boolit that freely chambers will be the most accurate one. I dont really concentrate on the barrel rifling as much as throat diam and freebore size. If your bullet freely chambers then your barrel wont have a problem swaging it whether its .001 or .005 oversized. I dont think it will spike pressure much neither.

Problem is not all guns have generous throats with large freebore areas which is what we as casters look for. I can shoot .3575 from my Sig p320 but my Taurus PT111G2 only chambers .356. Anything larger sticks and you can tell right away when you try to hand cycle couple rounds. I had few live rounds stuck in my Taurus when I ran into couple light primer strikes with boolits that were little large. Slide was stuck as if it was welded shut. Good thing this gun has restrike feature so couple restrikes and i finally got that round to go off and eject.

[DougGuy]

I dont want to generalize here but largest boolit that freely chambers will be the most accurate one. I dont really concentrate on the barrel rifling as much as throat diam and freebore size. If your bullet freely chambers then your barrel wont have a problem swaging it whether its .001 or .005 oversized.

Problem is not all guns have generous throats with large freebore areas which is what we as casters look for.

^^^^THIS... +1

Freebore is the critical part of the barrel just in front of the chamber for casters. It is pretty much industry wide that the manufacturers put very little or NONE at all in a factory barrel and send it out because it shoots factory ammo, usually truncated hollowpoints sold as defense ammo, this is the market they are targeting and these will function .001" or .002" SMALLER than groove diameter, and they will feed and plunk in 99.995% of all 9mm barrels ever made.

Now.. Let's bring this up to speed for handloaders and casters. MOST barrels have little to no freebore, and the freebore they do have is less in diameter than we would want for optimum performance with cast. So.. In a *perfect world* the boolit would be .001" to .002" over groove diameter of the barrel, and the throats (for a revolver) or the freebore (for an autoloader) would be .0005" to .001" over boolit diameter so that you don't have to size smaller or seat deeper to get ammo to feed and plunk reliably.

It is a simple, inexpensive, one-time fix to have the barrel throated to use .358" cast which is the most common size cast boolit in use by shooters of the 9mm. WE, as casters and aficionados of cast boolits simply need to have the throat in the barrel "dimensionally corrected" for the best performance!

Here is a pic of a *properly* throated barrel that is correctly dimensioned for use with cast boolits.



For a 9mm, the freebore is .3585" in diameter, the freebore is roughly .100" in length, and it is on a 1 degree 30min angle which is the gentlest leade in to the rifling that you would want. Almost any 9mm barrel with a throat like this will shoot lights out with .358" boolits.

For the sake of accuracy with the photo, I believe this is a 40 caliber aftermarket barrel for a Glock, but the principle is the same regardless of caliber, only the dimensions are different.

[lwknight]

This variable depends on your specific barrel.
Example: I had 1 barrel that slugged at .356 and a .357 bullet would not chamber. The solution was to get another barrel. The replacement slugged at .3455 and will shoot .355 bullets all day with no leading.
Some guns have looser chambers so a larger bullet will do just fine. Every one is unique.

[Pooka]

Update: I followed bboque1's suggestion and created a slug out of some pure lead melted into a 9mm case. The slug mic'd out at .3556 and an average of 10 powder coated boolits came it at .36464 which gives us a difference of .00904.

So as these are meant to be cheap training rounds should I call it good enough for government work...or should I add another layer of pc to fatten them up a touch?

[EMR]

Update: I followed bboque1's suggestion and created a slug out of some pure lead melted into a 9mm case. The slug mic'd out at .3556 and an average of 10 powder coated boolits came it at .36464 which gives us a difference of .00904.

So as these are meant to be cheap training rounds should I call it good enough for government work...or should I add another layer of pc to fatten them up a touch?

No need to go fatter as that’s plenty thick. Really you only want .001-.002 thicker. You’re at .009. Load a dummy round and see if it plunks (which I kind of doubt). If it plunks then it’s probably good to go. If not, get a sizer to .357 or .358 then recheck for plunking and go from there.

If you’re really that thick at .36464 then you should dust off the extra powder before sticking in the oven.

[gwpercle]

.356 sized boolits gave me problems , going to .357 solved all those problems , the only thing to watch for is the lack of throat in new 9mm pistols. The boolit needs to be seated deep enough to pass plunk test....after that it's all good.
The COL listed in a book may not work, load some dummies to work out seating depth.
Gary

[Pooka]

EMR, thanks for the reply and clarifying things for me. For some reason I was thinking the difference desired was .01 to .02 (YIKES!) hence the question in my last post. I'm ordering a .357 sizer

[DougGuy]

.356 sized boolits gave me problems , going to .357 solved all those problems , the only thing to watch for is the lack of throat in new 9mm pistols. The boolit needs to be seated deep enough to pass plunk test....after that it's all good.
The COL listed in a book may not work, load some dummies to work out seating depth.
Gary

Why do people look at a barrel and assume it's bible and then load for that barrel until it feeds and plunks, REGARDLESS of whether the barrel is anywhwere near SAAMI specs or not?

If you cannot assemble and use ammo loaded to the dimensions given in published loading data, wouldn't that tell you something may be wrong?

The barrel (or a cylinder) is a TOOL. It is a machined GUIDE. Somebody machined it when they made it. If it does not work as manufactured, then RE MACHINE IT. I throw my hands up.

NOBODY makes a barrel that is cast friendly. NOBODY. NOT ONE MAKER that I am aware of throats a barrel properly for cast boolits.

SAAMI specs for a 9mm call for a throat with freebore with leade ins tapered, even if the barrel was EXACT SAAMI specs it would shoot cast albeit sized to .356" and no larger.

Jerry Keefer notes that the 9mm pistol that KEEPS winning these national matches has .100" of freebore and a 1 degree leade angle. If throating had any negative aspects, these guys certainly wouldn't bother.

[Drew P]

Slugging a 5 groove barrel is an interesting process, which takes a few special tools. I believe a 30° machinist V block if I remember right.

[Burnt Fingers]

Slugging a 5 groove barrel is an interesting process, which takes a few special tools. I believe a 30° machinist V block if I remember right.

I wrapped a strip of copy paper around the boolit, measured, then subtracted 2x the thickness of the copy paper.

[Burnt Fingers]

Why do people look at a barrel and assume it's bible and then load for that barrel until it feeds and plunks, REGARDLESS of whether the barrel is anywhwere near SAAMI specs or not?

If you cannot assemble and use ammo loaded to the dimensions given in published loading data, wouldn't that tell you something may be wrong?

The barrel (or a cylinder) is a TOOL. It is a machined GUIDE. Somebody machined it when they made it. If it does not work as manufactured, then RE MACHINE IT. I throw my hands up.

NOBODY makes a barrel that is cast friendly. NOBODY. NOT ONE MAKER that I am aware of throats a barrel properly for cast boolits.

SAAMI specs for a 9mm call for a throat with freebore with leade ins tapered, even if the barrel was EXACT SAAMI specs it would shoot cast albeit sized to .356" and no larger.

Jerry Keefer notes that the 9mm pistol that KEEPS winning these national matches has .100" of freebore and a 1 degree leade angle. If throating had any negative aspects, these guys certainly wouldn't bother.

DougGuy,

I haven't had a chance to take my Canik barrel to the range yet as it's been really wet. But! I'm now able to seat the MP 146 gr RN bullets out to 1.10 and have them chamber! That's a win in my book.

[nueces5]

^^^^THIS... +1

Freebore is the critical part of the barrel just in front of the chamber for casters. It is pretty much industry wide that the manufacturers put very little or NONE at all in a factory barrel and send it out because it shoots factory ammo, usually truncated hollowpoints sold as defense ammo, this is the market they are targeting and these will function .001" or .002" SMALLER than groove diameter, and they will feed and plunk in 99.995% of all 9mm barrels ever made.



For the sake of accuracy with the photo, I believe this is a 40 caliber aftermarket barrel for a Glock, but the principle is the same regardless of caliber, only the dimensions are different.

Your explanation is very good. Unfortunately in Argentina there are no barrels of lone wolf for sale. But I do not quite understand why some IPSC colleagues use their glocks with pc boolits and original barrel.