Thread: 357 mag subsonic reloading data

Good morning all.
First time starting a Thread so please be gentle.
Does anyone here have experience or data they are willing to share regarding 158gr subsonic loads using powders other than Trailboss as I have that sorted but I’m running low on Trailboss and Hornady’ s SWCHP’s.

I’m not looking for 38spl data as I have heaps of 357 brass and am not keen to buy more brass.

I have some AP70 but find it very inconsistent with velocity with lead projectiles. I have tried both the Hornady and Speer 158gr SWC HP’s. I haven’t tried it on jacketed projectiles yet. I have 1000 Noslers JHP’s coming.

Using mixed brass, small pistol primers, seated out to what I have found works best with a light crimp. I have a Lee die set but also have a Hornady but haven’t used it yet.

Very happy with the Hornady SWCHP’s/Trailboss combo as it is what I think, very accurate and my ES is roughly 10fps, 1020-1030ish, the Speer aren’t accurate or consistent no matter what i seem to do with them.

I run them in a Bergara single shot 16 1/2” topped with a AR Bushnell 3-12 with BT and BCD zeroed at 50yrds.

Good for 1 n a bit Moa running the Hornady at sub speed (have found the sweet spot) and bang on moa with XTP’s, 125-158’s. 125 remingtons run at about 2-1/2.

Strelok sorts the Rabbits, Magpies n Plovers to 150with subs without disturbing the stock or the Fallow where I shoot. Also good on the Fallow.

I am pretty impressed with the combo and it is getting a heap of use but I am running out of components for my current loads.


Anyway, keen for some ideas.
Cheers

Just use .38 Special loading data. It will work fine in a .357 case.

other than AP70N and trail boss...what powder do you have or can actually get???? once you work that out....data will be more relevant....as Gundoc says...use .38 special data...pretty sure guys without reloading set up just use .38special factory stuff as a subsonic.

38 spl data seems to be based on pistol length barrels and to 38spl OAL’s.
If i use this charge data with a larger case capacity, how will this translate? If I load to 38spl OAL from what i understand the jump to the lands becomes an issue.
I look at the recommended charge of AP70 and in my head it looks tiny. I’m wondering if that may be the cause of the ES increase and maybe I’m using the wrong primer?
I’m not scared of doing the work up but more wondering if anyone else has been here before. Also the shortage of the Powder/projectile choices forces 1 to short the process and not waste the items to come to similar conclusions others have crossed off.
I have Titegroup and 296.

so longer barrel length will SLOW load down,after a point...X amount of inches the powder burning and pressure good,then acceleration stops and slowing begins...this is why some fellas have issues with subsonic .22lr giving out sonic crack when they have really short barrels......a long barrel .22lr very very very seldom has the same issue.
I havent loaded .357 but did tootoo with 7.62x39mm and subsonic loads but used trail boss which you have used....it is still around to purchase..you sound like its working BETTER for you than most other people...so grab some more.
forget OAL of .38 special...my recomendation is to use the load you already have with X projectile...the load that shoots best and set up your seating die using that length.... your data for .38 Vs 357 will be different only in % of case filled
back of my head there is warning bells re 296......pretty sure its the one that is use ONLY at full capacity.....could be wrong but please check before trying lighter load using it.

ADI site has shite ton of load data in pistol section for the .38 special.....compare it to the .357 data if concerned.....looks like a heck of a lot of bangs per pound of powder....3-4-5grns a pop most of the loads in that range.
might be some load there that helps the inconsistancy you had with AP70.....

I hear you @Micky Duck.
I have tried to find Trailboss but can’t find any locally and no-one freights powder.
I can’t help but thinking I’m missing something with the AP70n that might make the load more consistent.

Originally Posted by Muddyundy

I hear you @Micky Duck.
I have tried to find Trailboss but can’t find any locally and no-one freights powder.
I can’t help but thinking I’m missing something with the AP70n that might make the load more consistent.

I shoot a lot of cast in a Rossi Puma 92, but not subsonic,.well, not deliberately. When I got it I had a small bunch of 38 sp Pistol loads that had been given to me that I decided to shoot off rather than deconstruct. There was a variety including wadcutters with what turned out to be very small amounts of powder behind them. I finished up knocking several projectiles out of my barrel with a rod. Fortunately I was watching for problems. So first thing, whatever low load you use, have a rod on hand and make sure the bullet actually left the muzzle.

Second. I developed a bunch of goat loads using both 357 and 38sp data. I used AP70N to good effect in both. But I was going for max hitting power not subs. I was loading 38sp cases to strong +P levels which occasionally in older multi fired brass gave me split cases. But they were deadly and accurate and pre-Aunty I did so to get more rounds in the tube. I have used other shotgun/Pistol powders and found they all worked. I think you could persist with AP70N and do a finer increment test of .2gn steps downwards. I suggest a Balance Beam measure as .2gn is about the margin of error on most sub $125 digital scales. Your Balance Beam will be precise. 296 is a great powder but not for reduced loads.and I don't see it published for 38sp Do not go below stated minimum with this powder. It truly is a minimum as Micky warns. It is a 357mag load not for 38sp. Titegroup is a very fine precision powder and will produce 920fps with 3.8gn under a 158gn projectile in 38sp. Folk are wary of it because it is not bulky and is real easy to double or even triple charge cases..not fun at all. But you should find this a very accurate powder. Was loved by paper punchers with Wadcutters for its accuracy.

Finally I would be wary of putting 38sp loads into 357mag cases. The different case volume will give you different pressure performance and it may not always be to your liking. There are plenty of powders and published loads specifically for 357mag that are subsonic. I shoot them in 357mag Pistol and if I want to shoot 38sp loads in the Pistol I use 38sp brass, not 357mag - there is no need to mix them up. Good luck!

Use a fast powder like ADI AS30 Red dot WW231 N320 Bullseye start with .38 Special maximum loads in .357 Mag cases
Try these for projectiles, https://www.trademe.co.nz/a/marketpl...2&bof=dHi5Yiha
I have a 166 grain cast bullet it is a Truncated FP works ok in lever guns PM if interested.

I am no help on subs. But just like to say those Hornady xtp158 like to be driven into a pigs head or flank and the tail gate if nothing else presents its self. Alliant 2400 seems to work for me. I have some 158 lyman? leads to an interested forum member.
Hopefully that's gentle enough.
KH

Thanks Guys.
Yeah beam scale all my loads and have had a bit of a play around with Titegroup and also looked at the minimum load as being too light. I guess i will be doing a bit more exploring of the AP70 route as its the easiest to get. The data looks a little better using jacketed bullets using AP70 as the loads for lead versus jacketed is different . No doubt friction related.

Originally Posted by Muddyundy

Thanks Guys.
Yeah beam scale all my loads and have had a bit of a play around with Titegroup and also looked at the minimum load as being too light. I guess i will be doing a bit more exploring of the AP70 route as its the easiest to get. The data looks a little better using jacketed bullets using AP70 as the loads for lead versus jacketed is different . No doubt friction related.

AP70 could be too slow burning for Sub loads my best accuracy is between 6,5 grs and 7.3 grs with the 166 grain cast bullet it does over 1000 fps in a 6" pistol barrel
you are correct it is a friction thing cast bullets go faster than jacketed with the same powder charge due to less friction be careful with powder coated bullets they
are less slippery than lead, Always work down with sub loads not up specially with jacketed they are bastards to get out when stuck ,
A powder to try for subs is 700X shot gunners use it a lot so it is easy to find if there is a Gun club in your area.

so correct me if Im wrong here...if you getting best accuracy between 6.5-7.3 grns in 6" barrel.....in rifle barrel you will be using more powder for same velocity??? because it possibly slowing down again.......

Definitely I always work down.
A glance at X700 data has a start of 3.4gr for LSWC for 867fps in a 10” barrel. Could be a contender.
ADI shows 6.5gr AP70 in 18” barrel using LSWC at 1350fps and 5.8gr behind a 158xtp for 1059fps is minimum load. I have tried 5.8gr behind SWCHP and found it to be faster than speed of sound. Worked back from there and ended up at 5.5gr. Here is where the ES opened up and I’m below 45% case capacity. Shock horror I know but was rolling between 950-1100fps. I stopped there.
I have read stuff in the past about flash hole opening or changing primers.

As I say, just checking to see if anyone else has been here and done that and whether they had some good results.
After a quick ph around today, no-one seems to have any Trailboss and don’t know when it will be around again.

Originally Posted by Muddyundy

Definitely I always work down.
A glance at X700 data has a start of 3.4gr for LSWC for 867fps in a 10” barrel. Could be a contender.
ADI shows 6.5gr AP70 in 18” barrel using LSWC at 1350fps and 5.8gr behind a 158xtp for 1059fps is minimum load. I have tried 5.8gr behind SWCHP and found it to be faster than speed of sound. Worked back from there and ended up at 5.5gr. Here is where the ES opened up and I’m below 45% case capacity. Shock horror I know but was rolling between 950-1100fps. I stopped there.
I have read stuff in the past about flash hole opening or changing primers.


As I say, just checking to see if anyone else has been here and done that and whether they had some good results.
After a quick ph around today, no-one seems to have any Trailboss and don’t know when it will be around again.

You are not going to get flash over or S.E.E in a pistol cartridge; do not open flash holes in any case all it does is stuff the case,
The reason your ES open up is the pressure drop below its optimal level go to a faster powder 700X is still a good choice velocity
wil be higher as there is no cylinder gape to bleed off pressure,
Trail Boss is probably not that much use in the .357 Mag any of the fast pistol and shotgun powders will do and are easier to find,
Hornady list 7 powders with start load velocities of 1000fps with their 180 grain XTP in a Rossi 92 16" barrel
If you are interested there is One box left in stock at Steve Wholesale.