Disclaimer: My apologies to OP
@frjeff as some of us THR OCD reloaders have totally hijacked the thread but there are some information that is pertinent to those new to reloading and that is there are many reloading variables that can affect chamber pressure build/max average pressures that ultimately will affect accuracy on target. (We may start as
reloaders to save money/hobby but some of us become passionate handloaders)
Fact is, we're shooting .355 bullets in our 9mm barrels that are the same groove diameter range as our 38/357 revolvers, and we didn't even know it. Unless you slugged your barrel. And people shoot .356, .357 bullets through their 9mm pistols, too.
Someone will come along and say all their 9mm barrels measure .355 and their 38/357 barrels measure .357. That's nice, but of the dozen+ 9mm and 38/357 barrels I've measured, they run the gamut from .355 to nearly .358.
This is true. I have slugged barrels and have seen 9mm groove-to-groove diameter at .355" to .356"+, and for this reason why many members report being able to shoot .357" sized bullets in 9mm barrels.
Take away for new reloader is that one should slug their barrels to know the groove-to-groove diameter. If they have .355" barrel, using .356" sized lead bullets may not produce leading. But if they have .356" barrel, using .356" sized lead bullet may produce leading and may need to use larger .357" sized bullet to prevent leading.
For shooting plated and jacketed bullets, it's been my experience that slightly larger sizing of bullet can produce less gas leakage and greater accuracy. So if your barrel is .355", using .355"/.3555"/.356" sized plated/jacketed bullets may produce accuracy but if your barrel is .356"+, using larger .3555" (Speer TMJ/Gold Dot/RMR) and .356" (Berry's/Hornady HAP/Zero) sized bullets may reduce gas leakage and produce greater accuracy. Of course, we can't forget the variable of neck tension and bullet setback that will significantly affect accuracy overshadowing bullet diameter so we should also check for bullet setback as part of our reloading QC.
Take away for new reloader is that while many bullet types and sizing can work, certain barrel/bullet diameter combination can produce greater accuracy. And to further improve accuracy, bullet setback QC check should be incorporated into reloading practice and may consider using larger diameter bullets and/or thicker case wall brass to reduce/eliminate bullet setback as reduction of few thousandths in OAL/bullet seating depth can increase chamber pressure by several thousand PSI -
https://www.thehighroad.org/index.p...-and-discussions.778197/page-11#post-12503881
Don't tell people they can expect the same accuracy and pressures interchanging .355, .356, and .357 bullets between 9mm, 38, and 357! Yes, they can use them, but they must rework loads, and they must understand that they WILL NOT SHOOT THE SAME.
This is also true. 9mm is high pressure small internal case volume cartridge and small changes in reloading variable can affect pressures (Remember reduction in just a few thousandths in OAL can increase pressure by several thousand PSI?).
Take away for new reloader - While 380Auto does not operate at high pressures like 9mm, it is still a small internal case volume cartridge and small changes can affect pressures and why published start/max charges have such narrow range (Because pressure can increase from small increase in powder charge).
longdayjake, who owns/runs RMR bullets, has posted on this forum in 2020 on the issue of shooting oversize bullets.
And here's the quote(s) -
https://www.thehighroad.org/index.p...et-down-for-357-mag-use.872458/#post-11586429
There isn't an issue with shooting a .358 jacketed bullet through a handgun. It won't create any noticeable pressure difference. A friend of mine that has pressure testing equipment tested some .357 9mm bullets out of a 9mm barrel and could not get pressures to show any difference in 9mm between the .357 and the .355 bullets ... It was a test barrel and it measured .355"
If you check Accurate/Ramshot load data (Now bought by Hodgdon), you will notice RMR jacketed bullets listed which means pressure testing was done even to +P (Note that max test pressures can vary and "average" may be used for published load data) -
https://www.hodgdonreloading.com/reloading-data-center
- 9mm 115 gr RMR FMJ No. 5 COL 1.120" Start 5.6 gr (1,036 fps) 30,700 PSI - Max 6.2 gr (1,124 fps) 34,100 PSI
- 9mm 115 gr RMR FMJ True Blue COL 1.120" Start 5.3 gr (1,065 fps) 30,200 PSI - Max 5.9 gr (1,151 fps) 33,600 PSI
- 9mm +P 115 gr RMR FMJ No. 5 COL 1.120" Start 6.2 gr (1,129 fps) 36,100 PSI - Max 6.6 gr (1,186) 38,400 PSI
- 9mm +P 115 gr RMR FMJ True Blue COL 1.120" Start 5.9 gr (1,154 fps) 36,400 PSI - Max 6.2 gr (1,199 fps) 38,400 PSI
So for Jake to make such a statement on a public forum like THR is likely because he has hard data to support such statement. Chances are when .357" bullets were shot in .355" barrel, they were reduced down to .355" sizing to not show "noticeable pressure difference".
Don't let LiveLife see this. He'll have a cow.
Nope, no cow needed. If Jake posts he did the .357" sized bullet in .355" test pressure fixture barrel and got no "noticeable pressure difference" from .355" sized bullet, I would have no problem accepting that test result.
Take away for new reloader - There are many reloading variables which can affect chamber pressure change. Some variables overshadow other variables but focus on variables that have more significant change in pressure. IMHO for me based on my limited experience, those are listed below from more to less affect on accuracy:
- Type/nose profile/brand of bullet (Jacketed vs plated and certain brands are more accurate like HAP/Zero/Montana Gold/RMR(ELEY), etc.)
- FP/HP/SWC over RN (Longer bullet base to engage the rifling and also improve neck tension ... I was also told by my match shooting mentors HP has greater rotational stability in flight than RN due to shifting of center of mass towards base that engages the rifling)
- No bullet setback over erratic setback (Consistency of bullet seating depth produces more consistent pressures affected by barrel bore size, bullet sizing, case wall thickness)
- Fast vs slow burn rate powder depending on power factor of load (Lighter target loads favor faster burning powders)
- Consistency of powder charges
- Consistency of bullet weight
- Etc. Etc.
