.475/.505 Gibbs

31 January 2010, 20:37

Bwanawannabee

.475/.505 Gibbs

I am interested in duplicating or improving .470 NE power in a bottleneck rimless cartridge suitable for a bolt action of the same caliber. Velocity goals are 2350 to 2400 fps with 500 gr. bullets

Has anyone on this forum any experience in working with the Gibbs case necked to .475 with no other changes.

I know that this case is overbore even for the .505 cal but am hoping that with the use of very slow powders such as R22 and R25 I can achieve suitable loading densities without using fillers.

I am considering using the .408 Chey Tac as a parent case but do not know if it been improved with blown out shoulders etc., plus I think it would be better to neck down rather than up.

I expect that I will need to move the shoulders back on the Gibbs case to acheive a more practical case capacity.

If anyone has some advice and experience to share, it would be greatly appreciated.

Sandy

31 January 2010, 21:19

boom stick

Called the 475 Royale. Should be a le to find a reamer for it.
The 470 AR is something to consider.

31 January 2010, 21:47

jeffeosso

The 470 royale is the case, and it can do FAR more than what you are wanting. slow powders require LONG barrels to achieve peak velocity and high percentage burns.

My little 470 AccRel can easily get 2300 with a 22" barrel, and push in on 2400, if you want.. and 2150 is a piece of cake, all with 500gr bullets. If you like 25" barrels, you can get there from here.

my signature has several links to cases and ammoguide for load data (its INTERNET loads, so proceed with caution) and stuff.

The gibbs case, is HUGE, requiring an enfield, or cz, or much more expensive actions. The ARs only require a run of the mill standard length action, like a 7rem mag or 300 win, but can also be done on 270 oe 30-06 actions.

So, enough infomercial on the AccRel -- the case you are discussing the 470 royale, and is a rather expensive way to get where you started goals point you

01 February 2010, 00:08

Bwanawannabee

quote:
Originally posted by jeffeosso:
The 470 royale is the case, and it can do FAR more than what you are wanting. slow powders require LONG barrels to achieve peak velocity and high percentage burns.

My little 470 AccRel can easily get 2300 with a 22" barrel, and push in on 2400, if you want.. and 2150 is a piece of cake, all with 500gr bullets. If you like 25" barrels, you can get there from here.

my signature has several links to cases and ammoguide for load data (its INTERNET loads, so proceed with caution) and stuff.

The gibbs case, is HUGE, requiring an enfield, or cz, or much more expensive actions. The ARs only require a run of the mill standard length action, like a 7rem mag or 300 win, but can also be done on 270 oe 30-06 actions.

So, enough infomercial on the AccRel -- the case you are discussing the 470 royale, and is a rather expensive way to get where you started goals point you

Thank you Boomstick and Jeffeosso

I will investigate the 470 AR.

Also looking at the .475/416 Rigby that Saeed worked on and in addition the 470 Mbogo looks promising.

If Saeed sees this could you give an indication if the shoulder gave an adequate surface to headspace on an was this cartridge loaded to Rigby pressures or higher.

Thanks again.

Sandy

01 February 2010, 00:26

Idaho Sharpshooter

I just happen to have a set of .475 Gibbs reamers setting on a bookshelf about four feet behind my head. PM me and we can chat about it.

Rich
550 Gibbs

01 February 2010, 03:55

jeffeosso

Sandy,
another, perhaps better, 470x416rigby is www.470mbogo.com ..

01 February 2010, 06:19

Bwanawannabee

quote:
Originally posted by Idaho Sharpshooter:
I just happen to have a set of .475 Gibbs reamers setting on a bookshelf about four feet behind my head. PM me and we can chat about it.

Rich
550 Gibbs

Thank you Rich

I am going to check out the 475/416 rigby and the 470 Mbogo.
Sandy