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how to find/know the correct diameter for a bullet

3K views 13 replies 8 participants last post by  prescut 
#1 ·
I am a new reloader, (am still studying) and, so far have at least two matters of concern/confusion.
1. in the reloading data given in various handbooks, the cartridge case is specified. Does this really make a difference? (other than military brass) (i.e. remington vs winchester, vs hornady)
2. more importantly, how is the correct diameter of the bullet determined? one of the instances of concern is the .45 acp bullet. in one manual, it specifies .452, and in most others it specifies .451. what to do? wrong diameter in barrel seems to be a sure recipe for "bad things".

have learned and continued to learn tremendous amounts here. any thing to help clear up confusion is appreciated.
 
#3 ·
Brass depends on what you're loading for.

If you just want to shoot, and you're happy with 1 1/2 to 2" groups at 100 yards, and less than max loads, then no, it don't matter.

If you're trying to put them all in the same hole, or push them as fast as you can, then yes you need to not only stay with one BRAND, but if possible, stay with the same LOT. The more consistant you are in your components, the more consistant your loads will be.

In your 45 example, I'm betting the smaller bullet was jacketed and the larger was lead.

In store-bought bullets, the lead ones are usually .001 larger than the jacketed. .355/.356, .357/.358 .429/.430, .451/.452.
 
#4 ·
A while back I read a report from a notable gun scribe about the proper sized bullet for the .45 ACP. The gun he used was a match grade Colt put up in a Ransom Rest, and several different loads were put through the gun with both .451" and .452" cast bullets. In every one of the loads, the .451" bullet shot the smaller groups. This doesn't mean you gun will perform the same, but that's how I'd bet on it.
 
#5 · (Edited)
Jacketed bullets, use groove diameter. Cast bullet, .001 to .002 above groove diameter however.....ain't there always a "however" or a ""but"....sometimes in rifles best accuracy is achieved by sizing slightly below throat diameter. As you've no doubt already learned, handloading is a journey, not a destination.

Sometimes you're also at the mercy of what is available. Case in point being my 9.3 X 57. The jacketed bullets I was willing to pay for were .001 to .002 below groove diameter. It is evident there is enough diameter there for the rifling to get a grip on the bullet as it still shoots more than accurate enough.
 
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#6 ·
Reread gmoody's post. Basic reloading 101. It's probably noted in your reloading manuals the OD of the bullets used for each load listed, for instance I happen to have a Hodgdon manual on my desk and in the 45 ACP section, jacketed bullets used are listed at .451" and lead bullets at .452"...
 
#7 ·
I use mixed brass for .30-06, .30-30, and 7mm TCU. For the .30-06, I get 0.75-1.25" groups at 100 yards. For the .30-30, I get 1.25-2.25" groups. For 7mm TCU, I get 0.5-1.0" groups. MAYBE I could shrink the groups with matched cases, but it simply isn't worth it.
For pistols, I can say after a lot of testing that it makes no difference. In fact, when I compile all the loads using mixed and matched head stamps of the same load (loaded at the same time and sorted after loading), the mixed produced a slightly smaller average group size and std. dev.
Bullets:
If you were selecting bullets to meet SAAMi requirements for .45 Auto, you would use 0.449-0.452" jacketed bullets or 0.450-0.453" lead bullets for use in all guns chambered for .45 Auto. As a reloader, you are better off slugging your barrel and using jacketed bullets that are the same as actual groove diameter (which can range from 0.450-0.454") and lead/plated bullets that are 0.001-0.002" larger than actual groove diameter.
 
#8 ·
Where does one find the "odd size" jacketed bullets?

You say 45 auto should use jacketed .449 to .452, depending on actual groove diameter.

So supposing I slug my Springfield 1911 and it comes out .449. Where do I find .449 jacketed bullets?

Because I've never seen them.
 
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#9 ·
>So supposing I slug my Springfield 1911 and it comes out .449. Where do I find .449 jacketed bullets?

Make you own? Get a Corbin swage die and swage the 0.451" bullets? Remember that SAAMI says you can use up to a 0.452" jacketed for ANY .45 Auto. Write the manufacturer and complain about your barrel?
 
#10 ·
I agree with noylj in that using jacketed bullets that correspond to ones actual groove diameter is best and his means of acquiring them. I also agree with the others that in more modern firearms the recommended bullet diameters is more than acceptable, adequate.

Only time I've had to swage jacketed bullets is for a few really old rifles from before SAAMI or CIP existed and dimensions were all over the place. For instance, I have Sauer & Sohn, 9 X 57 Mauser that has a groove diameter of .352 so I made a die and punch to swage .358 jacketed bullets to .353-.354. Reason being .355 jacketed rifle bullets are rather scarce in these parts. In the opposite direction 9.3 is supposed to be .366 but a lot of old German 9.3's have a groove diameter of .358. Only way to actually know is to slug your bore as noylj mentioned. I am convinced that a necessity, a prerequisite in old firearms but not needed with newer firearms.
 
#13 ·
To expand a little on what you wrote. Years back I read a piece in a large gun journal about what to do when odd sized bullets couldn't be readily found. The guy that wrote the piece had a European bolt action in 9.3 caliber (.366") when it was relatively unheard of here. He had 300 grain Hornady .375" bullets, and found a machine shop with a centerless grinder that could reduce the diameter of the .375" bullets to the needed .366" for his gun. After getting these done he took them home and sample weighed a few, and somehow they were at the standard 286 grain weight that the 9.3 usually calls for.
 
#11 ·
I believe SAAMI is the "recommended manufacturing tolerance". So, if a barrel slugs out to .449" it is still a "legal" 45 ACP barrel. Manufacturing tolerances are present in everything made in a shop, factory or garage, and there is a "range" of acceptable sizes. Not practical to have every product/piece an exact dimension. Most gun manufacturers can keep really tight tolerances, but three is some "lee way".My 1911 slugs out to .451"+ (mebbe .0005" more). And my P90 runs about .4505".
 
#14 ·
Hey OP,
You might want to learn to read the signs of leading in the barrel. That will tell you quickly, without slugging or measuring, if your bullets are too small. Too small and the hot gases will escape around the bullet and melt the lead, leaving it in the barrel. Yuk !

There's size, hardness, gas checks, velocity, and a few other issues to diagnosing.
 
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