Subsonic .357 MAXIMUM loads to suggest as a starting point?

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bp78
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Subsonic .357 MAXIMUM loads to suggest as a starting point?

Post by bp78 »

My latest NFA project is slowly coming together. . . .
T/C Encore arrived.
MGM 12" 1-14" 357 MAX barrel arrived along with MatchDot II sight.
Stamp arrived for SWR Octane 9HD.
Smith threaded the barrel.
Paperwork for Form 1 SBR stamp sent off.

The first load I tried, using on-hand .355 125gr LRN in 38 spl cases produced horrible groups. Seriously 15 MOA ballpark. Not sure if it's the short case or under-sized 9mm bullets.

I have 357 Magnum and 100 357 Maximum cases ready to go as well as 190gr and 247gr 358 bullets to try next. Unique & Titegroup both on hand (as well as Clays which is likely way too fast).

Anyone have some guidance on where to start load wise? Looking for just under 1100 fps with either those bullets.
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Bendersquint
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by Bendersquint »

bp78 wrote:My latest NFA project is slowly coming together. . . .
T/C Encore arrived.
MGM 12" 1-14" 357 MAX barrel arrived along with MatchDot II sight.
Stamp arrived for SWR Octane 9HD.
Smith threaded the barrel.
Paperwork for Form 1 SBR stamp sent off.

The first load I tried, using on-hand .355 125gr LRN in 38 spl cases produced horrible groups. Seriously 15 MOA ballpark. Not sure if it's the short case or under-sized 9mm bullets.

I have 357 Magnum and 100 357 Maximum cases ready to go as well as 190gr and 247gr 358 bullets to try next. Unique & Titegroup both on hand (as well as Clays which is likely way too fast).

Anyone have some guidance on where to start load wise? Looking for just under 1100 fps with either those bullets.
Talk to JohnInNH(username).

He is a user of that round if i recall right. He can give you enough loads to make you puke!
bp78
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by bp78 »

Bendersquint wrote: Talk to JohnInNH
He is a user of that round if i recall right. He can give you enough loads to make you puke!
Thanks. Just sent him a PM to chime in on this thread.
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JohnInNH
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by JohnInNH »

My MGM barrel is a 1:12 NOT a 1:14.

The TC factory barrel is a 1:14. I find the 10" 1:14 factory barrel is a problem, the 14" is ok but marginal with 300 gr... the 1:12 MGM shoots heavy bullets well.. 248 gr hunter cast with GC in the 1:14 14" are ok. I got a baffle strike with the 1:14 10" with a 300 gr (pretty sure this was the offender)

Loads below.. Rem 357 MAXIMUM brass, Subs are Win Small Pistol primers, Supers are Win Small RIFLE primers

230 gr thunderhead over 5.1 gr American select = 960 fps in a 16" barrel
230 gr thunderhead over 6.6 gr win 231 in a 16" = 1120 fps (super), in a 10" = 1009 fps, in a 14" = 1037 fps


300 gr lead in 16" 1:12 over 9.1 gr LilGun = 1060 fps, 1020 in a 14" (my current loading for the 300 Hunter cast GC bullet)

248 gr hunter over 6.8 gr win 231 = 1050 fps in a 14"
248 gr hunter over 6.2 gr American Select = 995 fps in a 16" quiet! LOW ES and SD
248 gr hunter over 6.7 gr win 231 = 1043 fps in a 14" (es 14 fps, sd 5)

My supers.. PM me for.. use Win 680 with a 180 hornady single shot bullet, or the 200 gr hornady flex tip.

A1680 is supposed to be the same. Lol.. i get a huge difference.. as did hornady with a large difference back in 1975. Now you can't get W680 as far as i know.. but I get 1875 fps in a 16" with the 200 gr, 1561 FPS in the 14". With the 180 gr I get 1950 fps in the 16"

I would limit the 1:14 twist to the hunter 248 gr bullets.. the 1:12 the 300 gr hunter bullet works very well.

Use at a minimum .357"for jacketed bullets, .358" work well in LEAD. I also use .358" Jacketed bullets.

My MGM 1:12 twist 16" barrel is a .358", my 14" is a .357" 1:14 twist. it JUST works with heavy bullets. My 10" is a fail. I may order a 12" 1:12 .358" MGM barrel. The Factory 357 MAX chamber is CRAP! It will lead horribly.

I sent MGM a dummy loaded round using the bullets I wanted to shoot. It was chambered for the Hunter 300 Gr lead bullet at 1.95" OAL
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bp78
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by bp78 »

Thanks John. Shot you a PM yesterday with my email address in it for those loads.

I was hoping to use up some odd-ball 9mm projectiles I had around. I assume that was the source of my very poor groups.

Do you find a severe accuracy difference between short 38 spl cases and full length 357 max cases?

I do think I will also experiment with Clays & .38spl case plus 158gr bullet. We have an IDPA shooter whose 147gr 9mm loads with Clays sound darn near suppressed without anything on the barrel.
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JohnInNH
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by JohnInNH »

38 spl in a factory chamber will have a massive jump. I used mag brass for a bit, but find the max brass is the way to go, at least if you seat the bullet way out in mag brass the jump is not as bad as short 38 spl factory loads.

It will ring the chamber and will mark the Max brass at that spot ... lots of cleaning to remove the ring in the chamber reduces it, but over time can be permanent.

Get a mag barrel to shoot sol and mag brass and use max in the max barrel.
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Emilio
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by Emilio »

JohnInNH wrote:38 spl in a factory chamber will have a massive jump. I used mag brass for a bit, but find the max brass is the way to go, at least if you seat the bullet way out in mag brass the jump is not as bad as short 38 spl factory loads.

It will ring the chamber and will mark the Max brass at that spot ... lots of cleaning to remove the ring in the chamber reduces it, but over time can be permanent.

Get a mag barrel to shoot sol and mag brass and use max in the max barrel.
John, I need to work a sub 357mag load for my handi, the 38's working fine but want to avoid jump and fill the case, I have some 180gr cast. What would be a good load and have you ever try trail boss? Thanks.
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bp78
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by bp78 »

Ever tried a really fast powder like Clays inside the big 357Max case? Concerned that detonation might be possible given the low charge and much bigger case capacity than 38spl.
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JohnInNH
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by JohnInNH »

I do not have any subsonic 180 cast loads. Its mostly speculation, but trail boss st 10% less than the base of the bullet as a start. Then work down. Or 5-6 gr of Unique. No published subsonic 180 loads that I could find. I use 180 for super. 210-248 gr for subs... or in the 1:12 the 300 gr.

American Select is fast yet takes up lots of space. Still will have lots of empty space. This is why i use a longer heavier bullet for subs. If you only want to shoot 158-200 gr subs get a 357 mag barrel. A 210 gr lead cast over 6.2 gr of Unique in MAG brass wouks OK in my 10+14" max barrels.

The only reason to go with the Max is if you want to shoot the 210+ gr bullets and or shoot rifle ft/lb energy supers.. The max will do both well.
Emilio wrote:
JohnInNH wrote:38 spl in a factory chamber will have a massive jump. I used mag brass for a bit, but find the max brass is the way to go, at least if you seat the bullet way out in mag brass the jump is not as bad as short 38 spl factory loads.

It will ring the chamber and will mark the Max brass at that spot ... lots of cleaning to remove the ring in the chamber reduces it, but over time can be permanent.

Get a mag barrel to shoot sol and mag brass and use max in the max barrel.
John, I need to work a sub 357mag load for my handi, the 38's working fine but want to avoid jump and fill the case, I have some 180gr cast. What would be a good load and have you ever try trail boss? Thanks.
Long distance, the next best thing to being there!
bp78
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by bp78 »

Thanks. I'll see if I can work up a load that groups decently with my Hunter 247gr cast in the mgm 1:14 I already have as a first choice then the Hunter 190's if those don't workout. Thanks.
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JohnInNH
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by JohnInNH »

bp78 wrote:Thanks. I'll see if I can work up a load that groups decently with my Hunter 247gr cast in the mgm 1:14 I already have as a first choice then the Hunter 190's if those don't workout. Thanks.

Make sure you check for stability after working up the load to the 950-975 fps target. The 190 gr could be fun too. Win 231, American Select, Unique all being suitable powders for this.
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peytont
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by peytont »

Not sure it this will help or not. 247gr hunters cast bullet out of a 11" ruger 77/357 barrel clocks an average of 998fps with 5.2gr of W231.
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Emilio
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by Emilio »

Thanks.
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JohnInNH
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by JohnInNH »

Looks like you have a good starting point. You will love playing with round.... A big thumper.

Keep us posted on your results.
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by r »

emilio,
i'm doing 357 mag Hornady 180 XTPs in a handi rifle with 5.6 Unique with fullsize MK9. getting excellent results.
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Emilio
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Re: Subsonic .357 MAXIMUM loads to suggest as a starting poi

Post by Emilio »

r wrote:emilio,
i'm doing 357 mag Hornady 180 XTPs in a handi rifle with 5.6 Unique with fullsize MK9. getting excellent results.
Thank you!
Member of the LSU, SWR, and RUGGED underground. Shame Silencerco!
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