Rimfire Central Firearm Forum banner

Win 760 Powder

664 Views 10 Replies 6 Participants Last post by  Squeezer
I have been doing some load experimentation on my .243 consisting of the following : Lapua cases, Fed. #210 primers & Sierra 70 gn. HPBT Matchking bullets. I have a large qty. of new IMR-4064, so I have been concentrating on using that. Kind of settled on using 36 gns. as it produces 100 yd. 5-shot groups in the .3's with a velocity just over 3,000 fps. On a whim I decided to try some 40 yr. old Win. 760 powder that I had on hand. A load of 41.5 gns. gave 5-shot groups in the high .2's at an avg. vel. of 3,010 fps. All good except the powder is very dirty burning! The cases are showing carbon deposits all along the sides of the cases, whereas with the 4064 I would only get carbon fouling on the ctg. necks. Question is: is this common for 760, or could the powder have somehow changed characteristics with age? It looks OK, flows well & doesn't smell strange. I am even seeing carbon buildup on the face of the bolt edge, which shows me that I am getting a good amount of blow-by around the case.
1 - 11 of 11 Posts
On a whim I decided to try some 40 yr. old Win. 760 powder that I had on hand. A load of 41.5 gns. gave 5-shot groups in the high .2's at an avg. vel. of 3,010 fps. All good except the powder is very dirty burning! The cases are showing carbon deposits all along the sides of the cases, whereas with the 4064 I would only get carbon fouling on the ctg. necks. Question is: is this common for 760, or could the powder have somehow changed characteristics with age? It looks OK, flows well & doesn't smell strange. I am even seeing carbon buildup on the face of the bolt edge, which shows me that I am getting a good amount of blow-by around the case.
Win 760 is a double-base (nitrocellulose + nitroglycerine) spherical powder. It's not the fastest or the most accurate for any bullet I have used, but it has a wide range of applications. Jack-of-all-trades, master of none. My experience has shown me that ball / double-base powders generally burn dirtier than extruded single-base propellants, and that they ignite best using a Magnum primer.;)
4064 and W760/h414 I won't say old but are "legacy standards". For a cleaner burn I'd go for 8208 which replaces blc2/748. For heavier projectiles go for any of the 4350 flavors. H414 is weaker in extreme cold so build the powder load in the summer to avoid hot loads.
  • Like
Reactions: 2
i always used h380 in my 243. as to 40 tears old should be ok as long it was stored properly. it will have a heavy solvent smell if it's gone bad. by the way h414 and w760 are the same powders.
All good except the powder is very dirty burning! The cases are showing carbon deposits all along the sides of the cases, whereas with the 4064 I would only get carbon fouling on the ctg. necks. Question is: is this common for 760, or could the powder have somehow changed characteristics with age? It looks OK, flows well & doesn't smell strange. I am even seeing carbon buildup on the face of the bolt edge, which shows me that I am getting a good amount of blow-by around the case.
I suggest your excessive carbon fouling might be caused by cases that are not squeaky-clean when fired. The brass is supposed to expand to fit the chamber upon firing, and to cling for a brief moment to the chamber walls creating a tight seal. Just a thought...
I suggest your excessive carbon fouling might be caused by cases that are not squeaky-clean when fired. The brass is supposed to expand to fit the chamber upon firing, and to cling for a brief moment to the chamber walls creating a tight seal. Just a thought...
I believe you hit upon it! I have 3 brands of brass that I measured for expansion in the same location on the cases - about .100" from the extraction groove towards the case neck. Results were: Lapua = .4716"; Winchester = .4721"; Dogtown = .4739". This was an average of 10 readings for each brand. In their advertising literature Lapua states that their brass formula is "harder" that other brands in the case body area, and this could be why their cases did not expand as easily to provide a good case seal & allow some blow-by of gases. This was with twice fired cases, I will monitor subsequent firings to see if the cases continue to expand.
  • Like
Reactions: 1
Many years ago 760 proved to be my most accurate power in both my .243 and my 22-250. Crazy part it was the same powder load! 38.6 gr with any good 52-53 grain bullet with Fed 210M primers in the 22-250. 38.6 gr under the Sierra 100 gr Boat Tail Spitzer with the same fed 210M primer! Neither was quite a max load but plenty for hunting any animal I cared to hunt.

Hogdon 414 is the same powder in a different can.:)(y)
I suggest your excessive carbon fouling might be caused by cases that are not squeaky-clean when fired. The brass is supposed to expand to fit the chamber upon firing, and to cling for a brief moment to the chamber walls creating a tight seal. Just a thought...
Excessive carbon fouling and/or pitting of the bolt face can also be signs of over-pressure. Please check your primers for pitting etc.
Excessive carbon fouling and/or pitting of the bolt face can also be signs of over-pressure. Please check your primers for pitting etc.
Squeezer, no signs of over pressure, in fact quite the opposite as cases are not expanded to full chamber size.
Hey there! I'm new to this forum and I stumbled upon this thread about Win 760 powder.
Hey there! I'm new to this forum and I stumbled upon this thread about Win 760 powder. I had a similar experience with some powder that I found in my grandpa's old reloading stash.
Welcome! I suggest you review the "Stickies" at the top of each forum as a good starting place from which to dive into your topic of choice.
1 - 11 of 11 Posts
Top