9mm COL

[ArchAngelCD]

in Hornady 8th, 124gr HP-XTP - c.o.l. : 1.060". However titegroup is not listed in the powders.

The brand new Hornady 9th Edition manual lists the same data as the 8th Edition posted above.

BUT, all the other advice in this thread is good too...

 

[engineermike]

I've loaded 9mm anywhere from 1.060 to 1.135, I think the SAAMI max COL is 1.169 for 9mm. (Just going off memory here) As shone above different bullets have different shapes and different over all dimensions. (Some bullets are longer than others even though they are 9mm) You can use the published load data and start out at the lower end and work your way up. But as you shorten you COL, using the same powder charge, the pressures go up. (That's assuming you are using the same bullet each time) Look over at the Hodgdon's web site and they have load data for Titegroup.

 

[greybeard57]

I read a page the other day that explains the difference very well about OAL per different shape of bullet and how those different shapes work inside the magazine and how it affects bullet jump from crimp to rifling. For semi-auto it gives as an example a SWC v RN bullet. Obviously if the SWC was loaded at the same OAL as the RN there would be no way it would A) enter the magazine and B) chamber correctly even if it somehow where forced into the magazine. And it showed that even two different brands of RN may have different ogives causing different headspace problems. The easy solution is to take a known factory or handloaded bullet that works well in the gun and eyeball the two side by side. The standard that every other bullet design needs to stay inside of is the one that works. Clear as mud? If not visit the page for more info. It makes it a lot clearer.

http://38super.net/Pages/Overall%20Length.html

FWIW- my first conservitive reloads where at 1.148-1.155 oal. loaded with Winchester 115 RNHB with 4.3gr win231 and federal primers. They worked, but more powder was needed because I had a lot of sooting. The second batch was increased to 4.5gr. at the same depths. I made a few at each depth within that range up above. The shortest length suggested was 1.100 for my load. This was from Ron (Don?) at Hodgdon's whom I called to find out what recipe I could use since there wasn't one published for this combination. One question I asked was how the OAL influenced this combination with this powder. He said that since w231 is such a fluffy powder it's not a problem. The bullet depth will not affect the pressures to a violent degree unless the OAL is seriously short or the bullet has no jump space. This jump space is relative the to the speed of burn which influences the pressure spike essentially at the moment of detonation (wrong word but ya know what I mean). This jump allows the bullet to gain momentum before it engages the rifling which slows it down (or, more correctly, prevents it from accelerating) which causes an immediate secondary rise in pressures. The two spikes are so close together they are actually measured as one pressure spike. The biggest variable in pressure is how tight the bullet is inside the rifling. Slight variations in bullet diameter are inevitable in mass production. Keeping the powder charge at reasonable levels will take the stacked tolerances and keep them within acceptable parameters.

Those guys at the powder companies are pretty sharp.

 

[ranger335v]

"Does SAAMI not specify dimensions for barrel throats? "

Only the minimum.

 

[engineermike]

Well graybeard;
I'd say you have a pretty good understanding of the variables with C.O.L. and bullet shape/s. I believe I will save your source and read it a little closer but I did find it interesting and useful.

Thanks;
Mike