I have some Red Dot powder and would like to use it with Acme 115 grn coated bullets. My question is how many grains should I start with ... i was thinking of reducing the grains by 10%. Is this a good start????
Welcome to THR.
As other members posted, you should always reference published load data when conducting load development with a new bullet.
But there are reloading variables such as bullet nose profile, bullet base length, bullet diameter, etc. which affect chamber pressures and thus require different amounts of powder charge for particular bullet type/OAL used.
While coated lead bullets can be driven to jacketed velocities without leading, they are often sized larger (.356" like lead bullets) than jacketed bullets (.355") so I reference lead load data (For .356" sized bullets) for start charges with coated bullets.
And if I am using significantly shorter OAL (Deeper bullet seating depth), I will reduce my start/max charges by .2-.3 gr depending on how much shorter the working OAL is.
2004 Alliant load data has lead/jacketed load data for Red Dot and 9mm -
http://www.thehighroad.org/attachment.php?attachmentid=182147&d=1364769070
- 115 gr FMJ 1.120" OAL Red Dot Max 4.5 gr (1,150 fps) 32,600 PSI
- 125 gr Lead 1.150" OAL Red Dot Max 4.5 gr (1,145 fps) 32,000 PSI
- 125 gr FMJ 1.150" OAL Red Dot Max 4.6 gr (1,145 fps) 33,000 PSI
While 2004 Alliant load data doesn't list lead load data for 115 gr bullet, it does list lead load data for 125 gr lead bullet and you can reference load data for slightly heavier bullet load data.
And Lyman #49 lists the following for 120 gr Lead RN:
- 120 gr Lead RN 1.065" OAL Red Dot Start 3.0 gr (919 fps) 25,100 CUP - Max 3.9 gr (1140 fps) 32,000 CUP
115 gr coated lead bullets can come with different nose profile that produces different bullet seating depth. You can calculate bullet seating depth and case powder fill as outlined in this post -
https://www.thehighroad.org/index.php?threads/red-dot-9mm-and-case-fill.848934/#post-11078957
Start charge determination - While 10% reduction of 4.5 gr is about 4.0 gr start charge, if you are using a bullet that requires shorter OAL/deeper bullet seating depth than published, I would consider reducing the start charge.
So for .356" sized coated lead bullet that requires shorter working OAL, I would consider starting at 3.8 gr as start charge but keep in mind, Red Dot is large flake powder that meters with .2+ gr variance for me.
With typical 115 gr FMJ/RN bullets, I will usually load to 1.130" OAL and down to 1.110" to improve accuracy. But with MBC Hi-Tek coated 124 gr RN bullet, due to nose profile, I need to seat the bullet deeper to clear the start of rifling in my barrels. The shorter OAL produces deeper seated bullet base which will increase chamber pressure and I usually decrease start/max charge by .2-.3 gr.
FYI, with 115 gr FMJ and plated RN (sized .355") loaded to 1.130" down to 1.110", I will use 4.1 - 4.2 gr Red Dot/Promo which is typical metering variance. This load produces lighter than Winchester white box felt recoil but will cycle all pistols I have and produce good accuracy. Using 4.4 - 4.5 gr will produce more felt recoil and slightly smaller groups -
https://www.thehighroad.org/index.p...blended-promo-for-more-accurate-loads.841097/
Here's W231/HP-38 reference load group for comparison