Optimum bullet diameter; jacketed bullets

[mdi]

I'll put this in the swaging section 'cause I figger those of youz guys that make jacketed bullets will know, so...

I've been reloading for quite a while and about 12-15 years ago started casting. Prior to this I didn't give the dimensions of the bullets much though, .44 caliber is .44 caliber, right? I haven't loaded any jacketed bullets since. By casting I learned to measure barrels, cylinder throats and chambers. Now, shooting lead bullets I learned the proper size for a lead bullet is .002" or so over groove diameter or the same size as the cylinder throats, but I haven't given jacketed bullets a second thought as to diameter vs groove/bore diameter.

So, what is the optimum jacketed bullet diameter? Same size as groove diameter? Smaller than groove dia.? Or larger than groove diameter? Bullet diameter vs bore diameter?

I've been doing some reloading for my 2, 9mms, lead and jacketed, and enquiring minds wanna know...:veryconfu

[Reload3006]

I go with groove dia. works well for me the larger the more pressure but that is something you already know. I dont like to swage my bullets down in my bore anymore than I have to also because I dont want to facilitate core separation.

[DukeInFlorida]

Your reloading data book gives you the SAAMI standard bullet diameter for each caliber.

Use that info for jacketed bullets.

[mdi]

I slugged the barrel of my new 9mm, and got .357". A lot of the jacketed bullets sold as 9mm are .355". Is .002" under groove diameter good for accuracy, fouling? I was thinkin' 'bout some .38 bullets @ .357".

[mortre]

I've been using .356 plated bullets in a 9mm that slugged .356. I haven't had issues either way so I couldn't say if it was better or worse. But I would say it is worth a try. Start low though, I hit max published velocity well before I hit max published load. I have thought about trying to load the Speer .357 135gr Gold Dot's in the 9mm to replicate their 38 Special Short Barrel loading.

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[runfiverun]

you have different accuracy with different brands of jaxketed because of the jaxket and core.
an undersized soft core/jaxket combo [like the sierra target bullets] will bump up and fill the grooves like cast will.
there's a compatability factor with jaxketed and your bbl,sometimes diameter influences this and sometimes it's all about the jaxket/core/land interface.

marlins big claim to the microgroove was increased accuracy, because they had more lands [to grip] and they were rounded [to not muss up the jaxket]
when in reality it was because they were cheaper to make [but hey that's business]

[DukeInFlorida]

I'll repeat, for the sake of clarity:

Your reloading data book gives you the SAAMI standard bullet diameter for each caliber.

Use that info for jacketed bullets.

[mac1911]

I'll repeat, for the sake of clarity:

Your reloading data book gives you the SAAMI standard bullet diameter for each caliber.

Use that info for jacketed bullets.

Duke, I know what your saying is a good thing and safe of course. I do have a few questions though.
My mosin nagant 9130 has a bore dia. Of. 301 or the inpression on the slug (lands) the bore measures. .313
hodgdon web sight gives load data for. 308 bullets. .005 under size. Would this not be good?
Wouldn't a bullet of say 311 or 312 be better suited....
I will be casting some 314s for it soon.

[DukeInFlorida]

The question wasn't about cast boolits.......

It was specifically asked regarding jacketed bullets.

BIG difference when it comes to bullet diameters.

[Wayne Smith]

Unless you are ordering a die it is very expensive to have multiple dies per caliber. I would go with the nominal bullet size simply because that size has been successful for years in that caliber. Precise fit is way cheaper for cast and probably more necessary. Cast is more forgiving, too.

I have a Hawk die that is swaging bullets .459". I am using 40S&W cases for half jackets and pure lead inside, but I will be loading these at the bottom of the 45-70 data and working up. That is because my Encore barrel measures .4575". Soft lead and thin brass is likely to swage down but I have no idea how much pressure will be generated by this process. Thus I start at Trapdoor levels and watch carefully.

[mdi]

I'll repeat, for the sake of clarity:

Your reloading data book gives you the SAAMI standard bullet diameter for each caliber.

Use that info for jacketed bullets.

Your post was clear the first time, but not applicable. No need to repeat.
Yep, for a beginning reloader your post has some validity. As I stated in my original post I've been reloading for quite a while. I have been reading/using reloading manuals since 1980, or there abouts (actually I did some reloading with a Lee Loader in the 70s (a few thou. .38 Specials), and yep, I read the instructions/load data). But SAAMI specs are what manufacturers voluntarily follow ("voluntary industry standards..."); no hard and fast "laws". For example I have a .44 magnun that SAAMI says should have a .431" groove diameter (rifle), but I have slugged a rifle several times and get .433"-.4335". My Hornady manual, 7th Edition, say I should use bullets of .430", by your suggestion .003" undersize. My 9mm slugs .357", .002" over SAAMI suggestions?

My question was not what size bullets to use, but what is the optimum (best) bullet to bore fit for jacketed bullets...:?:

[Reload3006]

a jacketed bullet of bore size is optimal or .001 - .002 undersize is ok too and the jacket is what prevents leading that would occur in cast or lead bullets. I would prefer bore size but i would not go oversize because of pressures and the spring back effect of copper-brass jackets. the lead will squeeze down and stay and the jacket will spring back adversely affecting accuracy.

[DukeInFlorida]

Think, for a moment, about what happens to the bullet material displaced by the LANDS of the barrel.
And, then consider that UNLIKE a cast boolit, a jacketed bullet is a constrained envelope. A cast boolit can stretch and extrude a bunch with not much ill effect. A jacketed bullet can't do that.

You run the risk of exaggerated pressure if you choose too large a jacketed bullet for a given caliber. The .002 rule doesn't apply to jacketed boolits like it might to cast boolits.

If you want to stray past SAAMI specs for bullet selection, or powder amount, proceed at your own risk. You came asking for advice. As a professional teacher of the reloading science, I can't advise you to do anything other than follow the SAAMI specs, for safety reasons.

[mdi]

Think, for a moment, about what happens to the bullet material displaced by the LANDS of the barrel.
And, then consider that UNLIKE a cast boolit, a jacketed bullet is a constrained envelope. A cast boolit can stretch and extrude a bunch with not much ill effect. A jacketed bullet can't do that.

You run the risk of exaggerated pressure if you choose too large a jacketed bullet for a given caliber. The .002 rule doesn't apply to jacketed boolits like it might to cast boolits.

If you want to stray past SAAMI specs for bullet selection, or powder amount, proceed at your own risk. You came asking for advice. As a professional teacher of the reloading science, I can't advise you to do anything other than follow the SAAMI specs, for safety reasons.
So, just follow what the books say, no matter what the actual dimensions of your gun happen to be?

Thank you for your input, but I guess I asked a difficult question. Meebe I'm not accustomed to "oh, give or take .003" here or there is good enough", but I would think someone would know the best fit of bullet to gun for jacketed bullets, specifically.

Back to cast bullet section...

[mac1911]

Ok, leave out the stance on safety for just a secound.
If my barrel slugs out at 301 lands and 313 on grooves if there where no data would a fmj bullet of 312( only common size I found so far) or 313 dia. Be a good choice.

It just might be that so many mosins shoot poorly as so far the commercial ammo I have tried is loaded with fmj. 308 dia bullets?

I have searched high and low and can not find anything on sami specs for 762x54r other than preasure?
my hornady manual shows only 308 and 310 dia load data.
Just as confused as some.

[MIBULLETS]

Duke, I know what your saying is a good thing and safe of course. I do have a few questions though.
My mosin nagant 9130 has a bore dia. Of. 301 or the inpression on the slug (lands) the bore measures. .313
hodgdon web sight gives load data for. 308 bullets. .005 under size. Would this not be good?
Wouldn't a bullet of say 311 or 312 be better suited....
I will be casting some 314s for it soon.

Yes. If your groove diameter is .313, a bullet that fits it would be best. There is nothing unsafe about this case. The spec for that cartridge is not a .308 but something like .311 or .312. Check the link below for Sierra bullets. At the bottom of the list, they show .311 bullets just for this purpose.

http://www.sierrabullets.com/index.cfm?section=bullets&page=rifle&caliberID=9

[MIBULLETS]

I slugged the barrel of my new 9mm, and got .357". A lot of the jacketed bullets sold as 9mm are .355". Is .002" under groove diameter good for accuracy, fouling? I was thinkin' 'bout some .38 bullets @ .357".

As far as the barrel goes it would probably be just fine, but there are other things that come into play here. By putting a larger bullet into the case you will increase that diameter as well. It could affect pressure and functioning of the gun. If you try this, just be sure that the loaded rounds fully enter the chamber and easily eject by hand.

[mdi]

Gosh fellers, I'm no rookie when it comes to reloading and I have been fitting lead bullets, safely, in several different guns for mebbe 12+ years. I came here hoping someone had some insight in optimum (best) bullet to barrel fit for jacketed bullets. I'm aquainted with safe reloading methods and have used hand tools, single stage, turret, and for a very short time progressive presses. I have been using precision measuring tools for 50 years (give or take 3 or 4) and know how to use these on revolvers and semi-auto handguns. I am well aware of safety issues concerning "fat" cartridges in chambers, and have been fitting bullets and cartridges to guns for a while now. Sorry to have caused such a stir; it was/is a simple question.

[Wayne Smith]

Like many simple questions, however, it does not appear to have a simple answer. In the past I have found the Sierra bulletsmiths to be very helpful in answering questions. I'll bet they have the data to actually answer this one factually.

[BT Sniper]

Hello to fellow Oregonian.

IMOP you should look for bullets that will match your "groove" diameter of the barrel within +/- a half thousandth.

Example- 30 cal = .3075-.3085

or a sluged barrel of .3130 = .3125-.3135

Good shooting

BT

p.s. as far as what might be the optimum or "magic bullet" diameter for given barrel??????? I don't know?

[g-1]

hello everybody,
I have no experience in swaging, but I tried a couple of times to make solid bullets with a precision CNC machine.
I have some experience in reloading , and looking thist thread regarding the right size of the bullets reminds me of a big issue I had with my dies.
Especially with Bench rest dies ( I'm referring to rifle BR dies, but I assume that there are BR dies also for pistols calibers ) some strange behaviour can happens.
I made solid bullets with the exact size of .308" and with my great suprise I discover that they got stuck in the die! ( Redding competition seater )
looking at my Lapua scenar bullets I found that they were .307" and not .308"
SAAMI specs and bore diameter are important , but I suggest to take a look also at the reloading seater die before swage a larger bullet to avoid the same trouble that I had.
my 2 cent.
ciao