correct size for a 480 Ruger

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mtngun
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correct size for a 480 Ruger

Postby mtngun » Thu Feb 14, 2008 5:58 pm

from the old forum:

Hi all,

I'm just getting into casting and have several questions on bullet design. I will eventually be casting for my 450 Marlin GG and 480 Ruger SRH. I currently use both Cast Performance and J.B. Young gas checked hard cast. The 45 caliber bullets are 0.459" and the 475 caliber are 0.475".

I have slugged both guns and here's what I found;

450 Marlin: 0.4585"

480 Ruger: 0.4751" (barrel)
0.4791" (all cylinder throats)

I\'ve played around with the bullet design software and settled on 45 cal. bullet that's a 420 gr WFNGC design. The 475 cal. will probably be a 380 gr WFNGC. I will be using WW and 1-2% tin for alloy and be heat treating my hunting bullets.

From what I've gleened from here, and other forums, I'm thinking my 45 cal. slug should drop out of the mould at 0.460". They could be shot as cast or sized just a half a thousandths under to 0.4595.

Now the revolver bullet has me confused. Should it be cast to drop at 0.479 for the throat diameter, or 0.476 for the bore? Does the addition of a gas check negate casting to the throat diameter?

Finally, I haven't bought a lube/sizer yet. I've heard the Star is the best, fastest, and most expensive. Die costs are also higher. The Saeco is robust and priced midrange. The RCBS and Lyman are less rugged but serviceable. They are more or less identical, but the RCBS can handle larger dies. I plan to cast, size, lube, and GC around 1000 to 2000 bullets a year in a couple of calibers. What would be the best one? Ease of changeover is also a consideration. Also, can you seat gas checks with the Star? I've noted in catalogs that only certain size dies are available. Saeco offers a 0.460" die, but RCBS/Lyman don't. Are customs sizing dies available for all of the above mentioned sizers? I have also heard that the Lee push through can be opened up easily for custom sizing. Since it doesn't lube (hard Lube) is it even a consideration?

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Re: correct size for a 480 Ruger

Postby mtngun » Thu Feb 14, 2008 6:00 pm

The 480 -- size to fit the throats. You may want to make the front band two or three thou smaller, or better yet, put a step on the nose so that the nose will not interfere with chambering. Be aware that not all guns will chamber a throat diameter bullet because the case mouth OD may be too large. For example, I had a S&W 44 with 0.4336" throats that would not chamber bullets larger than 0.432" unless the necks were turned.

A gas check does indeed make the bullet less sensitive to diameter. The 44 that I mentioned was happy shooting 0.432" bullets as long as they had a gas check. Plain base was a different story.

The 450 -- your plans sounds reasonable, my only suggestion is to measure the length of the throat -- the distance between the case mouth and the start of the rifling. Make sure that your bullet design will fit in that space, as not all will. As with the wheelgun bullet, it may not hurt to put a step on the nose where the rifling starts.

Sizers -- You summed it up pretty well. I think custom Saeco dies are available from Stillwell. Factory dies can be honed out 0.001" using an electric drill and emory cloth. Personally, I am quite fond of my homemade push-thru dies for sizing, because they size faster, easier, and more concentrically than the lubrisizer. Even though they don't lube, they are still handy for sizing the bullet and crimping the gas check prior to oven-treating.

Alloy -- Your bullets will cast and shoot just as well, or maybe better, without the tin.

Seating checks --Normally I seat gas checks with my thumb, and the sizer merely crimps them on. If the fit is a little too tight, then a seater saves wear and tear on your thumb. I don't think the Star provides for a seperate seating operation.

Be aware that the Hornady 45 check will not be crimped by a 0.459" die. Once the pressure kicks in and obturates the shank, the loose check will be made a tight fit, so it probably doesn't affect the way it shoots, but if you are one of those people who loose sleep over how the gas check fits, you may want to spend a little more for Gator 45 rifle checks.

You are off to a good start by measuring your guns. I wish everyone would do that.

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Re: correct size for a 480 Ruger

Postby mtngun » Thu Feb 14, 2008 6:03 pm

My 450 has been doing real well with JB's Crater Lites with a 0.400 nose to crimp. Groups in the 1" to 1 1/4 range at 100 yards. I recently tried his 420 gr Crater Lite-2's. I believe they're more of a bore rider type as they have a 0.459 dia. band, 0.080 long above the crimp groove. These bullets didn't shoot worth a darn.

My 480 has been digesting a lot of CPB 410 gr WFNGC bullets with 1 1/2" 50 yard accuracy. Now knowing my bore is 0.4751 and the bullets are 0.475, I kind of suspected the checks were doing something good. When I first worked up loads, I tried the CPB 370 gr PB and 375 gr GC versions. The plain base version grouped 2-3 times larger than the gas checked.

If I were to get a 480 cal. GC mould, sized for my 0.4791 throat, are there any corrective actions that can be done if I have problems. I guess what I mean is that you mention it may not chamber because of the case O.D. being to large. Ok, can I simply measure the cylinder and brass wall thickness stackup prior to, or is it more involved? Also being that the bullet is 0.004 over bore diameter, does this create any problems or does it just get swaged down? I know many of these questions may sound stupid, but being new, green, wet-behind-the-ears, to this, it kind of make me kind of nervous to order a $75-$100 mould. For my first revolver mould, would I be better served getting a WFNGC design a couple thou. over bore, or go fit it with a throat sized diameter? I'm not trying to argue, being a newbie, just cautious. You are the expert here. I'm just trying to picture it logically in my mind. Is there that much accuracy advantage going from my current undersized GC bullets (1-1 1/2" groups), to a GC bullet a couple over, or to a GC bullet sized to the throat? I are an Enguneer by profession so I tend to overanalyis and cost justify everything.

As a side note I recently shot a cow buffalo with a CPB 410 gr WFNGC at 1,230 fps. The bullet nose fractured at the cannelure after glancing off of the far side rib. After several conversations with Kelly at CPB, it all seems to point to my Hornady crimp die. The 454, 480/475, and 500 S&W dies all come as a 4-die set. The crimp die performs the normal roll crimp, but resizes/contains the case at the same time. Its impossible to buckle the case with too heavy of a crimp. It sounds like my extra heavy crimp pinched the cannelure so hard it started to fracture the nose. The rib finished what I started. This was not the first case recieved by CPB and the common denominator was the Hornady die

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Re: correct size for a 480 Ruger

Postby mtngun » Thu Feb 14, 2008 6:22 pm

I got a lot of measuring done on my 450 and 480 Ruger, here goes.

450 Marlin

Bore Dia: 0.4585"
Throat Length: 0.206" (measured with bullet seated backwards)

480 Ruger (SRH)

Cylinder Length: 1.740"
Case Length: 1.275 min to 1.285 max
Rim Thickness: 0.070"
Cylinder Length Available: 0.525 max
Chamber Dia.: 0.5072" (avg of 10 readings, just above case mouth)
Throat Dia.: 0.4791:
Throat Length: 0.4535"
Dist. from end of case to start of throat: 0.0715 min to 0.0815 max

Sized Case OD: 0.4985"
Sized Case ID: 0.4685"
Expanded Case OD: 0.4985" ???
Loaded Case OD: 0.5026"
Fired Case OD: 0.5050

Purchased Bullet Dia: 0.4751" (CPB 410 gr WFNGC)
Pulled Bullet Dia: 0.4735" (front band)
0.4745" (middle two bands)
0.4750 (bottom band)

It sure looks like my Hornady sizing die is swaging my bullet. The ID of the die is 0.4982". The loaded round, before crimping should be 0.5050. I was also puzzled at the case OD after a pass through the expander die. I expected to see a bump up. The expander plug is part of the die body. It can't be removed or measured easily.

Note: I had to edit the 480 throat length. Originally measured with caliper. Didn't seem right so I remeasured with depth gauge.

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Re: correct size for a 480 Ruger

Postby mtngun » Thu Feb 14, 2008 6:24 pm

Good Job !

Looks like the 450 has a good throat. That will make life easier on you and on the bullet. A full diameter ogive would probably work, or else you could step down to 0.451" after a 0.190" long front band. Hint: at the bottom of the design page there is a number called "rifle throat length". This is the estimated throat length required for that particular bullet design. Understand, this is an output, not an input. Anyway, when designing the 450 bullet, you'll be OK as long as you keep an eye on what the "rifle throat length" says. That number is just a crude estimate, that does not take into account the exact dimensions of your barrel, but it will get you in the ball park. It does not apply to revolvers, however.

If your 480 rounds are 0.5026" OD with a bullet that is approximately 0.474", then a 0.479" bullet would increase the OD to 0.5076", and that wouldn't fit in your 0.5072" chambers. :x 0.477" might work, but there would be no margin for error. Looks like 0.476" is the best you can do. I'd chuck the Hornady crimp die, or else hone it out so that it doesn't damage your bullets.

If you are going to be shooting 0.476" bullets in a 0.479" throat, then you are free to make a 0.476" diameter front band as long as you like without worrying about chambering problems. Whatever tickles your fancy.

It's just amazing that our guns shoot as well as they do, considering all the funky dimensional imperfections.


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