I have one decent load for the .505 Gibbs:
24"-barreled CZ 550 Magnum
S&H 558-grain Brass FN "SHARRC"
H4831 140.0 grains
Federal GM215M primer
C.O.L.: longest crimped load that would fit in the CZ box
5-yard chronograph velocity: 2307 fps

The 500 A-Square does much better with much less fuss. I got bored with the .505 Gibbs after that,
having tried 120 to 140 grains of H4831 in 2.5-grain increments.
137.5 grains shot most accurately, about 1 MOA for 3 shots, but only gave about 2250 fps with the 558-grainer.
Your mileage may vary as do powder lots.
My powder was H4831 "Long Cut," not SC.

A .510-caliber on the .505 Gibbs case would be much more interesting and useful,
or the .408 Chey-Tac, if merely an uncommon bullet diameter is desired.

Does anyone know of any manufacturers that make heavier than 600 grain bullets for the 505? I would like to try some 700 grainers with all of the case capacity of the Gibbs.

Second range session with my Gibbs. I worked up incrementally 2 grains at a time with IMR 4350. Best velocity I obtained was 2641fps with no signs of pressure. I feel that I could have gone at least 2-4 more grains. However, I do not intend to go any higher with velocity. Rather, I will now sight in with an accuracy load somewhere in the range of 2500fps with Woodleigh fmj's and 2250fps with the Woodleigh pp's. Great cartridge that has more versatility than any of the other 50's in my opinion. Very enjoyable Saturday morning at the range on Memorial Day weekend with my 6yr old son and 70 year old Dad, a Vietnam Vet -- 1st Marines 1968 Tet Offensive Phu Bai/Hue. He didn't shoot the Gibbs but enjoyed watching me shoot it God bless America!

Nice! I love the 50s. Happy Memorial Day to your family and a big thanks to your Dad!

Chuck375 -- Happy Memorial Day to you and yours too!

quote:

Originally posted by 505Gibbs2600:
Second range session with my Gibbs. I worked up incrementally 2 grains at a time with IMR 4350. Best velocity I obtained was 2641fps with no signs of pressure. I feel that I could have gone at least 2-4 more grains. However, I do not intend to go any higher with velocity. Rather, I will now sight in with an accuracy load somewhere in the range of 2500fps with Woodleigh fmj's and 2250fps with the Woodleigh pp's. Great cartridge that has more versatility than any of the other 50's in my opinion. Very enjoyable Saturday morning at the range on Memorial Day weekend with my 6yr old son and 70 year old Dad, a Vietnam Vet -- 1st Marines 1968 Tet Offensive Phu Bai/Hue. He didn't shoot the Gibbs but enjoyed watching me shoot it God bless America!

Salute to your Dad for his Service, and to my Pop who got a Bronze Star in Vietnam ('66-'67) and never talked about it before he died at age 75.

You have shown that the 4350 must be THE POWDER for the .505 Gibbs.
I'll skip the H4831 and use H4350 instead next time.

But really now, the .505 Gibbs is the most versatile of the fifty/500-cals???
No way does that make sense. I'll chalk that up to infatuation with a new rifle, a well understood phenomenon among riflecranks.
Happy Memorial Day.

Congrats on your load dev. 2600 fps must rap the hell out of you!! 2400 with a 525 gets my attention...2150 with a 600 grain is about right for me.

Ed

RIP -- My dad and I stopped at a local grocery store on the way home to get some things for a cook out. There were VFW guys taking donations. One of the old timers, looked like Korean War vet, saw my dads hat that had his unit insignia, time in country and Vietnam vet on it. He saluted my dad and said "That a boy." My dad didn't know what to say. In my opinion, Vietnam vets got screwed by this country and they will never completely recover from it. I'm sure you are as proud of your dad as I am of mine. I hope your dad knew it too. God Bless him for his service!

505 puts a smile on my face for sure. Until I can try a T-rex, 585HE or 600 Overkill that will have to suffice! have a great weekend.

505ED -- 2641fps with the 600 grainer gets your attention. But it was manageable. My dad said the gun looked liked it recoiled up about 18 inches though. No fast follow ups!

quote:

You have shown that the 4350 must be THE POWDER for the .505 Gibbs.
I'll skip the H4831 and use H4350 instead next time.

R-17 would be worth a look, too.

I wanted to try RL17 but I wasn't able to find any starting load data. I found some for IMR4350 and went with that. I think you could fit more RL17 into that big case and might get higher velocities.

quote:

Originally posted by RIP:
But really now, the .505 Gibbs is the most versatile of the fifty/500-cals???

Hey 416, 135 grs of H-4831 will give ya around 2250/2300 fps with either 600 gr Woodleigh soft or solid, no fillers needed, I use the 600 gr. Protected Points softs in my 505 Gibbs, they will expand a bit slower than the round nose design and penetrate better.

JM