Your chart is familiar: one of our members here developed that load
and did the graphs, etc. In fact, he's one of the reloaders I communicated with, and worked in conjunction with, on these Speer 8 loads. He even sent that load off to brassfetcher and paid the fees for testing it. I wasn't that interested in that particular bullet, so I chased the lead stuff. IIRC, he eventually blew up his 642--or stretched it, or whatever. He may even check into this thread to give us some more information.
FWIW,
here is a link to a brief discussion of the "Speer #8" SR-4756 / 38 Special loads I started at Handloads.com.
My post was just to my S&W forum link--but fortunately, Paul5388 COPYed in that post. Here's the relevant data:
* 4.8 gr: 551 fps, 9.8 SD RR158 (nom. 10% below current Hodgdon 38 Special MAX of 5.5 gr.)
* 5.0 gr: 583 fps, 16.0 SD RR158
* 5.2 gr: 635 fps, 15.9 SD RR158
* 5.4 gr: 665 fps, 28.2 SD RR158
* 5.6 gr: 709 fps, 30.0 SD Sp158 (one-tenth gr. above Hodgdon 38 Spl. MAX.)
* 5.8 gr: 744 fps, 32.8 SD Sp158
* 6.0 gr: 750 fps, 25.4 SD Sp158
* 6.2 gr: 780 fps, 19.5 SD Sp158 (probably about CIP 38 Spl. MAX)
* 6.4 gr: 801 fps, 12.0 SD RR158
* 6.6 gr: 807 fps, 35.9 SD Sp158 (one-tenth gr. above Hodgdon 357 M / 27,600 PSI--their MAX)
* 6.8 gr: 833 fps, 23.5 SD Sp158
* 7.0 gr: 927 fps, 28.7 SD Sp158
* 7.2 gr: 932 fps, 30.9 SD Sp158
* 7.4 gr: 951 fps, 21.5 SD Sp158
* 7.6 gr: 978 fps, 28.5 SD Sp158
* 7.8 gr: 985 fps, 18.4 SD Sp158
* 8.0 gr: 1018 fps, 19.5 SD Sp158
* 8.2 gr: 1043 fps, 28.6 SD
and, here is the text related to these loads, edited a bit:
chrono results: Spring 2008--38 Spl, 4756, 158-gr., 2" barrel
I finally edited the chrono results I've gotten on a complete set of 4756 reloads.
All results are from a S&W 640 (2&1/8" barrel). All cases used were Starline; all primers were WSPs. The two bullets used were 1) Red River 158LSWC-358s, and 2) Speer 158LSWC-HPs (357+?). LOAs though 6.4 gr. are 1.460; 6.6 gr. and up are at 1.455+....
Each data set represents a minimum of ten rounds fired, although a couple of results are based on 9 rounds due to the random chrono error. Most rounds were chrono'd off an older Pact Mark IV; when that broke down, it was replaced with a Chrony Beta. (comparison with reference ammo suggested a non-identifiable variation of less than 1%.)
...NO unusual indicators of high pressure ever showed up--no sticky extraction. Primers did show increasing flattening and, at the 7.8-8.2 range, were beginning to crater--but there was no piercing or leakage.
It should be noted that, at the time I built these rounds--last winter--I was still learning how to crimp well / properly. Some of the (implied ES) and SD higher numbers show this, but my impression is that 4756 is position-sensitive, and no unusual attempts (tilting up or down) were made to compensate for that.
about pressure: [for their 38 Special loads] Hodgdon's 5.5-gr max is at 17,900 PSI with a 158-gr. XTP, LOA 1.455." For their 357 Magnum 4756 loads, they show a 6.5 gr max at 27,600 PSI with a 158-gr "MEI CASET LSWC .357" LOA 1.620.
Earlier posts in these 4756 threads have identified the nominal FBI load of 6.3 gr. at plus-p levels, and the 6.8 gr. load at 'barely' plus-p-plus levels. Some analysis of the 8.0-gr. load has suggested that it may have pressure peaks well above 35,000 PSI / 43,000 CUP--perhaps into 50,000+ PSI. IMO--In light of the data, any load above 6.3 gr. should be shot in 357-magnum frames.
Given the 6.3 and 6.8 gr. loads generated up to about 870 fps from 2&1/2" barrels, the data above generally fits, I think.
Some entirely subjective observations from me include the fact that SR-4756 (and WSF) has a very soft perceived recoil. That is, it starts out slow / soft, with a very short fast / hard jab at the end. The end is so quick as to be at times unnoticable. Maybe that's the result of a later / 2nd / whatever pressure spike--I dunno. This is one reason, I think, why people want to push this powder--that, and the fabled Speer #8 data.
Paul5388 has shot this 8.0 load for years--mostly from a carbine, if I remember right, and Erich and Paul and others have shot it with no unusual pressure signs in large frame (38-44, N frame) handguns.
It's too bad that the original topics--there were three, with literally hundreds of comments and posts, and eventually some hard data--at the S&W forum can't be linked to since the forum move. There was, for example, a couple of very salient comments about the original FBI loads that could have only come from one of the knowledgable reloading journalists active in the Seventies.
The upshot I think is this: better technology has now allowed us to better identify pressures, and do it more accurately than we could nominally thirty (or even fifteen) years ago. Secondly, modern business considerations of liability has severely limited the upper end of recipes published by the powder companies. (I suspect Hodgdon changed / truncated their 4756 / 357 data just because of the S&W Speer 8 discussions.)
Reloaders are free to load however they want--but none of us want to blow up guns (except for Clark). And, since there are equally good / pragmatic reasons to use 357 cases for these kind of ballistics, I prefer to do it that way.
Jim H.
