different loads shoot the same

I am working with WST powder and have loaded 20 rounds each of 3.0, 3.3, and 3.5 with a 158 gr lswc bullet. All three of these powder charges shot the same size groups from my Model 19 with 4" barrel. I am not the best shot by any means but all shot a 1 1/2 to 2" groups. No one group was any better than the others. How can that happen with a .5 gr difference in load ? How do I decide which load to load or should I go a little under and a little over to see if the groups get a little smaller ?

What range were you testing?
Sandbagged, machine rest, or free hand?
A few more specifics would help in analyzing.

I am shooting indoors range 50 ft using a sand bag rest.

At 50 feet,all those loads would be ragged holes.
At minimum 25 yards
And best at 50 yds.

As to loads. I'd just load up what a high master is shooting.

A 4 inch Model 19 wouldn't be my first choice for target work.  But that said, first I'd start with a known load like the Federal 158 RN lead load and see what they shoot in your pistol.  This will get you a baseline.  Might even try some factory 148 HBWC too.

LSWC don't seem to shoot as well as RNL bullets.  Many have reported that here.  So try some of those.  Cast or swayed, but there have been good reports on the Hornady RN 158 swaged bullet.  Then I'd change powder.  700X or Bullseye or even Red Dot or Green Dot?  WST is a good powder and should shoot well but the magic may be something else.

this same gun with 2.7 of WST shoots 148 gr zero swagged wad cutters into one ragged hole. But I do not get one ragged hole with 158 gr lswc bullets. What puzzles me is that all three loads shoot the same at 50 ft and there is a powder spread of .5 grns.

rebs, If you looked at a ballistic chart you would find that at 50' your POI would be less then 1/4" difference. If your not shooting one hole groups then they would look just the same.

Len

Using a 158gr RN  bullet BC of 1.71 and a MV between 800 and 1100 fps sighted in at 50 yds the POI at 15 yds is only .501". That's with 300 fps difference.

Len,  How would you go about trying to tighten up the groups ? More or less powder ? Other things ?
Maybe that is the best I can get with LSWC bullets ?

Rebs, My load for the 158gr bullet is 3.6 gr of WST. That may or may not help you. I use a 6" barrel and I am pretty certain the bullet is getting the most push it can out of that load. It would take one of the true powder Guru's on here to tell you how that load would work in your 4" barrel. Yes, it does make a difference. That may be one of the reasons your load change is making so little difference to your POI. Well, and the ballistics of course. You might have to find a faster burning powder or increase your charge (if powder is already fast enough)to get the same MV that I get out of my 6". That 19 can take more load.

len

Thank you for the help Len I appreciate it.
Another thing I was thinking about is I am loading these loads in Starline 38 brass and the gun is a 357 magnum. Perhaps a 357 magnum case might be better because of less jump from the cylinder to the forcing cone ?

No. Use the.38 case,my opinion and experience.

OK Thank you Jim, I'll follow your advice.

Have you tried any factory ammo? That would tell you if it's the gun, the load, or you.

I doubt it is the gun or me because it shoots Zero 148 gr wad cutters beautifully, good tight groups.

Do a search on this forum for
distinguished.38 loads

Plenty of info

With my M19 and a six barrel I can hold close to the ten ring with Wadcutters with SWCs maybe the 9 Ring on a good day on the short line off hand. 

100% of the WC is bearing surface and that is important and I can never reload 38 specials as good as Factory Zero or Remingtons. 

I think many guys use factory ammo for DR for that reason. 

Could be the recoil but I actually think the 105s are more accurate than the 158 SWCs using 3.5 VV320.