Chasing The Sweet Spot

[ET]

One goal of a shooter is to try and find the sweet spot of their firearm for best accuracy. Numerous range visits with load adjustments you eventually find the sweet spot and lock into it. To maintain the sweet spot, you have to reproduce exact bore pressure and velocity. Sounds pretty straight forward.

Now with SML using a sabot the sabot becomes a vital component that regulates pressure and velocity.
Alter the characteristic property of a sabot and good-bye sweet spot.
I’ve seen this happen often when ambient temp and bore temp increases. My first encounter was with bore temp. I would shoot 3 consecutive shots having my first 2-shots close together and the 3rd shot would relocate away from the developing group. This used to drive me nuts because I didn’t understand what was happening. Once I started applying proper cooling time between shots, I started to get good 3-shot groups.
My next encounter with temp variation was during load development. After achieving a nice ¾” group at around 55F I was really pleased with my results. Then my next outing the ambient temp was much warmer and my group opens up. To say this drove me nuts was an understatement.
The aggravations and frustrations were due to not knowing what caused group degradation. I now feel that I have a better understanding of what’s happening and can determine what direction I need for adjustments for better accuracy.

From what I’m experiencing with the 50 and sabots I can see why a lot of shooters have gone to the 45. Sometimes I wonder if I should also make that move. But my bond with the 50 is very strong and it still presents some new challenges to explore. Who knows maybe one day if I find a damaged 10ml-II somebody wants to get rid of because of a damaged barrel I may be motivated to acquire it and begin a 45 build. This does interest me but for now my focus is still on the 50.
If someone were to ask me where they should start with SML I would recommend the 45 over the 50. Not to discourage anyone from shooting the 50 but you need to know the temp/sabot variable requires additional attention. I will admit sabot-less SML is the future but not the only way to skin a deer.

[billc]

Lot of life left in the 50, if one wants to look. I like my 45 sabotless, but wouldn't feel bad it I only had my 50. Either one has to be smokeless though :-)

[jims]

Some of still use sabots in our .45s so what you do with sabots in the .50 still has relevance to us. Barrel heat, outside temperatures etc. Keep up the good work and reporting and experimenting.
Like billc said, if I had to use a stock .50 Savage for the distances I shoot I really would not feel handicapped. Use the .45 for lighter bullets and recoil for the daughters but could load down the .50 if necessary.

[sw]

In addition to sabot sensitivity to heat, is the pressure obtained across temperature spreads. In both the 45 and 50, I’ve found that VV110 has been extremely temperature stable. For 209 ignitions, 250g TEZ lightly knurled, HPH12, wool wad 45g VV110 and for 45, 37g VV110, HLBS, wool wad 200SST, 195 B and 225g AccuMax (resized to 0.400) . Burns cleanly, very accurate, not the fastest but quite good, and stable velocity from very cold to very hot.

[encore50a]

Heat and sabots

[ET]

Jul 9, 2020 7:02:35 GMT -5 jims said:

Some of still use sabots in our .45s so what you do with sabots in the .50 still has relevance to us. Barrel heat, outside temperatures etc. Keep up the good work and reporting and experimenting.
Like billc said, if I had to use a stock .50 Savage for the distances I shoot I really would not feel handicapped. Use the .45 for lighter bullets and recoil for the daughters but could load down the .50 if necessary.

Jims
I will keep digging and collecting data as I still have unanswered questions. As for the 45 sabot I am wondering with it's smaller configuration that temp change may not have as strong an effect. Hypothetical example, say the 50 group opens up 40% with a temp change of 10F but with the 45 the group opens up 30%.
For my future testing I will try and hold the load resistance around 20lbs. and watch for change with temp. With the use of a digital infrared thermometer I can closer monitor bore temp. Hopefully a pattern will emerge of load resistance vs temp.

[ET]

Jul 9, 2020 11:00:49 GMT -5 sw said:

In addition to sabot sensitivity to heat, is the pressure obtained across temperature spreads. In both the 45 and 50, I’ve found that VV110 has been extremely temperature stable. For 209 ignitions, 250g TEZ lightly knurled, HPH12, wool wad 45g VV110 and for 45, 37g VV110, HLBS, wool wad 200SST, 195 B and 225g AccuMax (resized to 0.400) . Burns cleanly, very accurate, not the fastest but quite good, and stable velocity from very cold to very hot.

Your numerous mention of using a wad may very well benefit powder ignition especially with warmer temps.
I definitely want to see some results using a wad.

[ET]

Jul 9, 2020 11:37:01 GMT -5 encore50a said:

Heat and sabots

Wouldn't it be nice to have known the bore temp?

[encore50a]

Yup

[reloader22]

By the looks of the sabot in the picture, it was not indexed to have two lands on each petal.  May or may not help in the heat/failure dept but my experience with the 50 and sabots has shown me more consistency in grouping when sabot are indexed.  Also, some here seem to have great experience using VV110 and sabots.  My experience is exactly opposite and in the beginning, this was one of the only powders I used as it was recommended by the "book", here and by others.  I pulled my hair out trying to eliminate flyers and sabot failures.  It was only after the experience by others with larger doses of slower powders and the revelation of .458 bullets over .451-.452 and settling on H4198 did I find nervana in regards to speed, accuracy, consistency and sabot integrity.  Now, I never tried VV110 with .458 bullets and maybe that would help my gun using that powder.  

[ET]

What I find interesting is that some of us experience negative results where others have positive results.
I’ve never had sabot failures where there is loss of petal/s or shredding with .451-.452 bullets. It makes me wonder if lapping my barrel is a contributing factor. It would definitely remove any machining burrs and take any razor-sharp edges off the lands. The Savage 50 barrel is not noted for quality machining.

What some shooters may experience is that a recommended load doesn’t perform quite as the poster states. That is no surprise to me. In order to reproduce another shooter’s results your load parameters have to pretty well match. If you can chronograph the loads velocity and it is lower than expected then load resistance is lower than what was originally used.

With SML we don’t have a solid standardization because the shooter is in control of some of the variables that defines his load. So, it’s no real surprise why we get different results even using the same bullet/sabot and powder load. But you have a starting point to work with to find out what your SML likes. When adjusting a load, I find a log book is really helpful for referencing what works and what didn’t work.
In the end one’s persistence of pursuing an accurate load will make it happen.