Harder alloy for microgroove rifling?

[brewer12345]

I have had challenges getting consistent accuracy from my 336 with microgroove rifling. I noticed last night that the lyman cast manual specifically mentions alloy of 15 hardness or better. This would be notably harder than the 94 3 3 I usually cast with. Is the hardness really that big a deal? Thinking about using 90 5 5 next time.

[JonB_in_Glencoe]

I edited the microfiber out of your title.

Have you thought about Heat treating your 94-3-3
http://castboolits.gunloads.com/show...eat&highlight=
I got about 24BHN, but with lower oven temps, you'll get less hardness.

[brewer12345]

These will be hollow points from the mihec 35 rem group buy so I don't want them that hard. These will be hunting boolits that I want to deform and hold together.

[popper]

#2 is fine for max loads in the 30/30 MG but you can cut it 50/50 and heat treat (WD). Fit is still KING. I've gotten decent results with 1% Sb/1% Cu/1% Zn, H.T GC'd with 2400 powder. More testing tomorrow, weather permitting.

[Harry O]

My experience has been that harder (to Bhn 12-15) is better than softer with microgroove. Personally, I think Bhn is too low for just about anything in a rifle.

[osteodoc08]

My experience is the fatter, the better. Cast and size as large as will chamber. Use an M die to expand the case neck and try not to size the boolit down during the crimp stage. I’ve got a few great shooting Marlin MG barrels.

[lotech]

I had good results with ww alloy in a .45-70 Marlin Micro-Groove, but I only loaded to about 1,300 fps with Lyman #457193, about 420 grs. The advice to use as fat a bullet as will chamber is good advice. I think my bullets were about .460",maybe .461".

[mattw]

In my 41 mag and 357 mag Marlins I have been using 94/3/3 for years. The key has always been proper fit with these rifles. My hunting loads are not hardened, but my general shooting loads are water dropped. Over the last year or so, I have been learning to PC and I think I will try that as well. May not need to water drop any after this, but fit will still be key!

I do not think I have ever fired a jacketed bullet from either rifle and both are pre-safety Marlins.

[largom]

I use a 50/50 +2% tin alloy in my Marlins and all rifles. I load for top velocity and lube with FWFL. Boolits are shot "as cast" if they will chamber and allow room for neck expansion. Have Marlins in 30-30, 35 Rem., and 45-70. Have killed many, many deer with them, all one shot kills. As others have said shoot the fatest boolit your gun will handle.
Larry

[Outpost75]

Fit is IT!

I use 1:30 tin-lead alloy from Roto Metals for full-charge hunting loads in all of my .35, .44-40, .44 Magnum and .30-30 rifles.

Microgroove barrels DO require fat bullets in all calibers.

Advice given by those above is correct. Harder alloy than 10-12 BHN is neither required nor desired.

[CPC24]

I inherited a Marlin .30-30 with microgroove rifling. It works well with .308 diameter, but I tried .310 and it seemed to shoot even better. I normally load them in 7.62x54R or even 300 BLK.

[Lloyd Smale]

Ive found through the years its a rare gun that doesn't shoot better groups with harder alloys. Micro grooved barrels especially because of there shallow rifling. Big difference though like was said in micro grove barrels you want to run as big of a bullet that will run reliably. My micro grooved 444 shoots its best with 433 bullets. My 444 outfitter with conventional rifling does just as good with 430s as it does with 433s. Big and hard are the way to accuracy with a micro grooved gun.