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375 SuperMag problems with handloads etc.
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February 29, 2020
5:11 am
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SuperMagger
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Bought an almost unfired 375 SM large-frame DW some time ago. After making some brass from 375 Winchester cases, I went to the range to see how my revolver will shoot. The load was 21 grains of H110 with Sierra 200-grain flatnose bullet, the one and only jacketed bullet there is for 375 SM. According to books I have (Shooting Steel and Gun Digest Book of Metallic Silhouette Shooting), this should be quite mild load? Velocity should have been about 1200 fps from the 8-inch DW barrel, but it wasn´t…I fired three shots and the cases were stucked in the cylinder, and I had to hammer them out. My chronograph showed the velocity being 1510 fps (ten ft. from the muzzle)!

After making some further loading experiments, I found out that it is impossible to make sensible loads for my gun with H110. I tried AA-9, with similar results: stucked cases and wild pressures even under starting loads from those overmentioned books. What to do? The only powder which does not give pressure signs, is VihtaVuori N120 (as I live here in Europe, not very many U.S. powders are available). Starline 375 Winchester brass is available, would it be better than those Winchester cases? How on earth my gun gives so erratic pressures even with under-minimum loads?

And further, does anyone know about how many 375 SuperMags were ever produced? My gun is originally imported here (to Finland) about 35 years ago from IHMSA and its serial number is 286. I guess there weren´t so many 375 SMs produced?

February 29, 2020
8:48 am
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Andrew1220
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I would definitely recommend buying new 375 brass to rule out your 375 Win cases being the issue. 

Does the gun have rough chambers? 

February 29, 2020
9:22 am
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SCORPIO
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I’ve not had any issues with H110 in any of my SM gund including the 375.  That is a yempetmental cartridge though.  It’s most accurate at the top end of the load range and the difference between starting loads and max loads isn’t very much.  You may want to be sure your case volume is not too small, that would cause higher pressures for a given load. Try some of different brass and see.  

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February 29, 2020
1:27 pm
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justbill77
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I have shot with h110 ,h4227 and ww296 with no issues with stock cases and I use cut down 3030 cases.

When I bought it there were no cases for it so that was what was recommended.

you said you loaded h110 my data has 23.5 grains for 220 grain bullet as starting loads you have to be careful with light loads they will give you pressure issues.

It was found that light loads can blowup guns, it was due to the powder laying flat in the case which exposed more of the powder to the primer at once than if the case is full or has more in it.

I have also shot 270 gas check cast bullets out of it no issue with pressure. Now people will tell you the 3030 cases are not as strong for this gun but I have had no issues with them. They say the shoulders are not strong enough can blow out the back I guess. I have looked at my cases all the time no issues have shown up.

People like to light loads rounds the bullet is the most cost in the round then powder and primer around 3.5 cents, I use to buy primers for 11 dollar per 1000 I was shocked the last time I purchase primers.

Powder is not that expense why light load rounds with the chance of blowing up your gun. I saw a picture of the rifle that blew up the pieces of that gun were not very big and I talked to the shooter and he didn’t get hurt but scared the stuffing out of him very lucky

March 1, 2020
9:18 am
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SuperMagger
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Thanks for the responses. Yes, the chambers were rough when I bought the gun, but I polished them and they seem to be okay now. As I wrote, no problems with VihtaVuori N120, but lots of problems with H110 or AA-9. I can´t imagine putting 23 grains or more H110 into cases, I´m pretty sure the revolver would be damaged – velocity would supposedly be something like 1700-1800 fps, maybe.

I have tried cases made from Remington 32 Win. Special brass (almost identical to 30-30) and their volume is much more bigger than 375 Win brass, but the situation is nevertheless the same: stuck cases with H110 or AA-9, even with minimum or mediocre loads. Can this be somehow related to primers? As I read from the book “Shooting steel”, there were some diffrence in opinions about what primers to use. Some said that magnum pistol primers should be used, some other said that the cartridge needs rifle primers. I tried CCI large pistol magnum primers and then moved to CCI Large Rifle and that is what I have lately tried to use.

Some of you said that “the gun shoots well” or “groups tight”. What kind of accuracy you have got from your DW 375 SMs? My 744 10-inch 44 mag shot 5 shots into 1,5″ at 50 yards with Sierra 250 grs FPJ and my brother´s 740 8-inch 357 SuperMag about 2″ at the same distance with Speer 200 grs FMJ. The best I have got from my 375 SM is about 3-4-inch groups at 50 yards, and I´m not satisfied. It should shoot about 2″/five shots to be useful at competition, but there´s always flyer or two which ruins the group. They do not always come from the same chamber, so that´s not the explanation.

March 1, 2020
7:25 pm
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SCORPIO
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I’ll second what was mentioned about the light loads and pressure issues.  I’m not familiar with AA9 or the VV powders.  Is it possible they are bulkier than H110, W296?  I find my 375s group tighter when the bullet is driven fast.  I’m not a competition shooter so a lot of the inaccuracies are probably me not the load or the gun.  

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March 5, 2020
10:33 am
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SuperMagger
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Yes, VihtaVuori N120 is much bulkier than H110 or AA-9. Could this be the reason why it does not raise the pressure to the stars? I can put about 25-26 grains of N120 to the cases and pressures are still ok, even though the velocity is higher than with H110. It is hard to believe that putting more H110 (for example 23-24 grains) to the case would lower the pressure…? Or does it? I don´t have Hornady 220-grain-bullets, only those Sierra´s 200-grainers and some Winchester-marked 250-grain FPJ`s which I haven´t tried yet (they are quite heavy,not sure if it is wise to use them?)

Now I´m getting the idea what you guys mean: too small amount of “thin” ball powder burns too fast along the case before hitting the base of the bullet, so the pressure spike occurs, am I right? If there were more powder in a case, the base section of the powder would ignite first and after that the flame enters the mouth part of the case and starts the bullet with “easier” pressure…or something like that. That makes some sense, but I´m still a little shy to making heavier loads, as the pressure signs were so heavy even with 21 grs of H110.

Hope you understand the expressions I use, they may not be always correct as I write foreign language to me…

March 5, 2020
5:03 pm
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SCORPIO
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I think you’ve got the idea.  It’s always a good idea to be cautious when working up loads, be methodical, be precise and make notes.  You seem to be well aware of this and are doing the right things.  If you are getting good results with the VV N120, I think I would be concentrating on developing loads based on that powder.  I’m going to look at some of my loads and data for the 375.  I’ll post some of my loads for reference.

Anything worth doing is worth doing well.

My father

If a man designed it, and a man built it, then a man can fix it.

My grandfather

March 5, 2020
5:43 pm
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SCORPIO
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Here are a few of my loads:

21.6 gn H110 with a 200 gn LFP Sierra bullet.  No signs of pressure problems.  

18.4 gn 2400 with a 200gn LFP Sierra bullet, a bit of an inaccurate load.  No signs of pressure problems.

22.0 gn 4227 with a 220gn FNSP  seated to a depth of 2.070 these ran 1300 fps on my 8″  These were given to me by a friend who chronographed them on his gun at 1300 fps.  

All my loads are from my Hornady manual Fourth edition.  All  oads based on a 220 gn bullet.

They list the minimum load for H110 at 19.2 gn  and maximum at 22.6gn

For Win296 they list minimum at 20.4gn and maximum at 22.9 gn.

 

Various manuals state slightly different min and max loads for a given powder and bullet weight.  

I see no warnings about low volumes causing pressure issues.  

I’d still be interested in knowing the internal volume of your cases.  I somewhat suspect that they are somehow smaller volume and thus are causing a higher pressure for a given powder charge than other brass for same cartridge.

It would be easy to measure case volume with water and a small graduated cylinder.

Anything worth doing is worth doing well.

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If a man designed it, and a man built it, then a man can fix it.

My grandfather

March 12, 2020
11:30 pm
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Gary J
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SCORPIO said
I think you’ve got the idea.  It’s always a good idea to be cautious when working up loads, be methodical, be precise and make notes.  You seem to be well aware of this and are doing the right things.  If you are getting good results with the VV N120, I think I would be concentrating on developing loads based on that powder.  I’m going to look at some of my loads and data for the 375.  I’ll post some of my loads for reference.  

Thanks for sharing those hand loads. That gives me sime ideas for mine.

March 18, 2020
3:06 am
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SuperMagger
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Okay,

So I went and fired a few test shots on Saturday. The weather was horrible, 5 below zero (Celsius) and freezing crosswind, so the results may not be statistically valid…I used VihtaVuori N120 powder, 26,2 grains (case almost full), CCI rifle primer, Winchester 375 brass. It was so cold that I didn´t get velocities, but the gun worked fine, no sticky cases and no pressure signs on primer. Grouping seemed better, about 3″ at 50 Yards, but I got one wild flyer 5 inches over the rest of the group (might be due to my frozen trigger finger). So, the theory of “more powder-better results” might have some truth in it.

I loaded another test series of cartridges, 26,5 grains of VV N120 (I think that´s the absolute maximum). Now I´m waiting for better weather to test them. I´ll report what happens then. Maybe I´ll try H110 also, but carefully…

Thanks for your responses!

SuperMagger

March 20, 2020
8:22 am
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SuperMagger
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Now the weather was fine, so I fired some  groups at 100 yards with 26,5 grs of VVN120. Seemed a little better, about 6 inch grouping was the norm, but still some wild flyers. Maybe one chamber shoots wide? Still no pressure signs, cases came out from the cylinder without pushing the ejector rod and primers did not flatten. Maybe a little bit more still?

Today I was not sure if the mediocre grouping was due to the gun or my tired eyes…Sun shined bright, and somehow the rear sight cut seemed too tight, so I couldn´t get sharp vision of the front blade. I have a BoMar rear sight somewhere, think I´m gonna install it to the gun.

If the weather is fine on Sunday, think I´ll go and shoot some loads with H110 and maybe 26,7 grs of VVN120.

March 24, 2020
1:13 pm
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SuperMagger
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New results: 26,8 grs of VVN120 shot three bullets into one inch at 100 yards, but twice about 6″ above the rest…don´t know if it was me or the gun, as I had  problems with vision this time also. Still no pressures signs, but the recoil starts to get unpleasant…the gun recoils about 80-90 degrees upwards, even though I have Hogue rubber grip on. But I think there may be some potential on this load, hope my eyes are not so tired next time I go to the range…

Tried also load of 22 grs/H110. No deal, the pressure went to the skies – primers severely flattenend and cratered, all signs of overloading very visible! The load was VERY hot, recoil also very sharp and unpleasant! It is clearly impossible to use H110 in this particular revolver, but why? Loading handbooks are full of hotter loads for 375 SM, but my gun does not tolerate them. What can be the reason??

And one thing still: mounting the BoMar Silhouette sight did not work. The package says “For Dan wesson Large Frame revolvers” and the sight fits fine on my brother´s stainless 357 SuperMag. My gun´s rear sight is different – the sight frame is about 3/8″ longer! Do all 375 SuperMags have different kind of rear sight compared to other Large Frame DW´s? The elevation screw hole is positoned differently on my revolver, and that´s why the BoMar sight doesn´t fit. I didn´t know there are more than one version of the rear sight.

There are two nice stainless 357 SuperMags for sale on my neighborhood, the other being almost unfired, with second barrel still on its sealed paper wrapping. Think I´m gonna buy one of them…or both.

SuperMagger

March 24, 2020
1:21 pm
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snake-eye
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Sounds like you have been infected with dwas and there is no cure! big-grin

March 25, 2020
4:04 am
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SuperMagger
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Better that than COVID-19!

But seriously, I`ve owned and been shooting DW revolvers for decades…the first one was 8-inch VH stainless .22LR, and to be honest that was one crappy gun. I didn´t shoot well, chambers were rough and the mechanism was not working well. I sold the gun, but I didn´t give up: couple of years later I bought a 10-inch 744 large frame revolver, and what a beautiful gun it was! It shot better than any 44 magnum I´ve seen, five shots into one inch at 50 yards! I won some silhouette matches with it, getting scores like 57/60 or 38/40 many times. But after years of heavy use (maybe 20 000 shots fired) it began to shoot loose, so I let it go…and my brother had bought a 357 SuperMag, which we both used.

Then came a pause of about ten years (house, kids, divorce, remarriage) and I began again to gain interest on SuperMags. When I saw the 375 for sale, I had to buy it, even though I didn´t know then where to get loading dies, cases and bullets…My gun may be the only DW 375 on the continent…So now I try to get it shoot accurately, and seeing those 357 SuperMags made me think that maybe….

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