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# 9mm bullets vs. 38 bullets in 38 special cartridges

1. ### kopsy

21
0
Sep 23, 2009
I have tons of 9mm lead bullets since that was all I was reloading. When I started reloading 38 special cartridges, I wondered if I could use the 9mm bullets that I already had or if I should go out and buy 38 bullets. I found several blogs discussing the merits mostly saying that 9mm bullets would not be as accurate coming out of my S&W Model 10 as 38 bullets would be. But what is "not as accurate"?

To answer this question, I loaded up some 38 special cartridges with both 125gn RN 9mm bullets sizing in at .356 and 125gn RN 38 bullets at .358.

Off to the range I went. I shot three groups of six each (18 per group, 36 in total) at six different targets from a distance of seven yards.

Back at home I took each of the six targets and calculated the Average Group Radius (find the group center, measure the distance from center of group to center of each shot, then average the distances). Then I averaged the three 9mm (.356) groups and the three 38 special (.358) groups and found the difference.

And presto! I now know how much more accurate the 38 bullets (.358) are over the 9mm bullets (.356) - less than a quarter of an inch (<0.25").

That should be less than an inch at 15 yards which is plenty accurate for IDPA. Not anywhere accurate enough if I was trying to shoot 100 yards, but I'm not.

From what I read in the other blogs is that gas escaping around the bullet because the bullet does not fill the barrel completely is what causes the smaller .356 bullet to wobble a bit as it comes out making it less accurate. But gas escaping around the bullet also means that some back pressure is lost and the bullet is flying slower, right? IDPA has some strict power floors that must be met, so the next question is, how much slower is the 9mm .356 bullet traveling vs. the 38 .358 bullet??? That's the next thing to find out - back to the range.

Disclaimer: I'm not a mathematician or a gun smith.

2. ### ilgunguygtEnslaved in IL

Accuracy wouldnt bother me. The gas blowby and ensuing leading of the barrel would bother me more than anything.

3. ### shotgunredlocal trouble maker

8,869
1,081
Mar 1, 2008
Washington (the state)
Hers is what you should try next. go buy one of those \$15. lee sizing dies in .358. Take your lead bullet and put it on a hard surface and give it a light to medium tap with a hammer. then run it through the sizing die. Presto you should have the correct size bullet. You just have to figure out how hard to hit it with the hammer.

4. ### Patrick GrahamFootlong Jr.

Sep 7, 2001
Kokomo Indiana
If you put enough roll crimp on those .356 9mm bullets to make sure they stay in I don't see a problem.

You should chronograph them to make sure you are still making Minor Power Factor.

I'm guessing that leading could be a bit of a problem but probably not enough to interfere with an IDPA match though.

5. ### 1006

873
0
Aug 12, 2007
Newnan, Georgia
When I bought my Press, the seller threw in 8000, 158 grain, lead 9mm bullets, sized at .355. Almost all of them went out the barrel of my 357 revolvers without issue. I kept the velocity down under 900 to reduce leading. They would lead up the barrel if loaded hot.

6. ### GioaJackConifer Jack

Apr 14, 2009
Conifer, CO
Kopsey:

You're on the right track with determining your group size and in NRA bullseye shooting is referred to as 'string measurement' As an example, if two competitors have four shots in the X and one each in the ten ring but the away shot can not be determined visually an appropriate caliber plug is placed in the hole of the away shot and with the use of a string the distance is measured to the exact center of the X. Works pretty nifty... cuts down on a lot of fist fights. Group sizes are determined in the same manner.

For they style shooting you're engaged in, 'accuracy', other than having the muzzle pointed in approximately the correct direction is not really an issue, you can hit a 15 yard target with a slingshot and a rock. Extend your distance to real handgun ranges and incorrectly sized bullets will have you packing your truck during the awards ceremony.

By all means load and shoot the bullets you have on hand, as others have pointed out you may experience leading in the barrel, also be aware of excessive leading of the forcing cone. Next time you order bullets simply get the correct size.

Shotgunred may have been a bit tongue in cheek but he's actually describing a viable way of increasing the size of a cast bullet... kind of.

It's called 'beagling' (sp) and is generally accomplished with the Lyman style sizer. An undersized bullet is placed in the desired sized die, (there are limitations as to how much you can enlarge it) and pressure from the ram compresses the bullet subsequently increasing its diameter to the size of the die.

If you want to be a proficient loader you have to be imaginative.

Jack

7. ### fredj338

22,630
1,430
Dec 22, 2004
so.cal.
Interesting that you don't post your actual group size & at what distance? IMO, 7yd accuracy testing is moot. Undersized lead bullets, if soft enough, may shoot fine @ 7yds, but double that & they groups may be 4x larger @ 15yds. It's not always linear, as the bullet can become unstable the further it gets from the bbl. Leading is also an issue, but again, your individual bbl will determine that. If it works for you great! For close range shooting, accuracy may not be affected much.

Last edited: Oct 22, 2010
8. ### WiskyTMalcontent

Jun 12, 2002
North Carolina
I tried some 0.356" bullets years ago, just a dozen or so, and they wouldn't stay put in the case. Thin R-P brass and an undersized bulet just didn't cut it. The thick IMI brass I have probably would have worked, but I don't know how they would have shot.

The best groups I've ever shot were with my Lee 120TC 9mm bullet that weighs 125 and comes out of the mold at 0.357" loaded with 4.0 Bullseye. They shoot great in my 442, GP100 and Python. The group size at 25 yards was under 3", I don't remember and it's upstairs. It was good enough that Jack showered me with all kinds of hate when I posted a pic of the target. The extra thousandth of an inch could make all the difference though, you'll just have to try and see.

9. ### GioaJackConifer Jack

Apr 14, 2009
Conifer, CO
Wisky if I've told you once I've told you a million times... don't exaggerate. That target wasn't a group, it was a pattern.

Jack

10. ### WiskyTMalcontent

Jun 12, 2002
North Carolina
11. ### GioaJackConifer Jack

Apr 14, 2009
Conifer, CO

You're so easy... it's almost criminal to screw with ya.

Jack

12. ### shotgunredlocal trouble maker

8,869
1,081
Mar 1, 2008
Washington (the state)
While I was being tongue in cheek and would never suggest anyone else do that it certianly would work for for three thousands of an inch. You just need a hammer with a flat face and an anvil. I will do it for the fun of it this weekend. You would have to use a sizing die because you would take it out of round and you couldn't control the exact width. Lead is soft.

13. ### kopsy

21
0
Sep 23, 2009
Yes, I'm sure this would work - lead is soft - but I can't imagine hammering every single bullet so I can run it through a sizing die. That sounds like "work" to me.

14. ### kopsy

21
0
Sep 23, 2009
Honestly, I haven't shot enough of the 9mm in my 38 to see if leading is a problem. And when do you consider leading to be a problem? After a day at the range both my glock and 38 have enough lead that at least half of the barrel rifling (sp?) is obscured. It takes a little extra cleaning, but they are good as new when I get done.

15. ### fredj338

22,630
1,430
Dec 22, 2004
so.cal.
IMO, that is too much leading. A proper fitting bullet w/ the right alloy & powder produces almost no leading for 100s of rounds. Accuracy must be pretty bad at the end of your dhooting session.

16. ### kopsy

21
0
Sep 23, 2009
Well, the test wasn't all about loading what I have as much as it was to see if I really needed two different sizes. The RN bullet I have has a small lip around the edge. I seat the lip flush with the top of the brass in the 9mm, but in the 38 it sits just below so the crimp can go over it. It seems to work fine. So do I need two sizes? Maybe not. I may be able to use .358 which will work fine in the 38 and get squished a little when squeezed into the 9mm.

17. ### kopsy

21
0
Sep 23, 2009
I didn't really consider the group size to be that important. What was important was the difference between the groups using .356 and .358 bullets.

But the second part of what you say makes perfect sense. I should retry the test at 15 yards and then again at 25-30 yards. Of course, the more testing I do the more accurate the results will become.

18. ### kopsy

21
0
Sep 23, 2009
Well, like I said earlier, I'm a newb at this at only 3000 cartridges. So how do I arrive at the right allow and powder? The 125gn RN .356 bullets I have are moly coated and should be the right size for my Glock 17. I use 3.5gr Unique with CCI small pistol primers. They crono at 900fps. A little slow for IDPA, but I'm working on that. I have not ordered a spec sheet on the lead but see that it is using the industry standard (I think that is 92/6/2?).

Given that, what should I change to come up with a cartridge that doesn't lead?

19. ### kopsy

21
0
Sep 23, 2009
BTW: thanks to everyone that has replied. I appreciate the insightful answers.

I haven't done any searching for answers on the last question so if it's already been answered a 100 times just point me in the right direction.

I think I'll work up another test batch and try at 15 yards to see what the difference is.

I'm also going to chrono the .356 and .358 bullets. I don't expect any difference, but I won't know until I try.

I also ordered some 158gr bullets to see if that makes any difference.

And another test I see worth doing is using .356 vs. .358 in 9mm to see what the difference is there. maybe instead of trying to get the .356 to come out of the 38 straight I can squeeze the .358's down to work in the 9mm. I've got to order some more .358 since I used them all in the 38 cartridges.

20. ### WiskyTMalcontent

Jun 12, 2002
North Carolina
My Glock will shoot 0.358" no problem. Bullet shape can be an issue though, so choose wisely or be prepared to shoot them out of a revolver if they don't feed.