Rookie Question of the Week...hardness vs GC vs velocity

[Kansas Ed]

I've spent the better part of the last couple of months of free time on this site reading, researching, learning. I'm enjoying this new part of my hobby, but hate to make mistakes which have already been ironed out. I've got a long way to go to get to any level of confidence.

So my rookie question of the week:

Almost all of my molds are GC design. Most of my rifles I'm casting for are in the 1400-1900 fps range. (the 30-30 and 25-20 SS may go 2200). I originally started with Lyman #2 from Buffalo arms, but have since ordered a batch of 1:20. We have a BH difference here of 5. I have no question that the #2 will handle these velocities either PB or GC, but I'm not really sure how the GC on a Brinell of 10 will handle velocity. I've been through this website, LASC, and not really gotten anything to this point which I would call "clear" in form of answer. The article on the LASC website gave a good definition and guidelines on MINIMUM pressures for a bullet alloy, but while listing maximums, didn't cover explanation as well. Furthermore the use of the GC wasn't covered. Any input here?

Thanks to all for your patience with the "Rookie"....

Ed

[runfiverun]

the g/c makes up for some of the alloy's short comings in gripping the rifling and in protecting the base of the boolit.
it doesn't stop the nose from slumping or setting back.
the design of the boolit and the support it get's from the barell,as well as the pressure time curve of the powder, will decide how much of that happens.

[44man]

the g/c makes up for some of the alloy's short comings in gripping the rifling and in protecting the base of the boolit.
it doesn't stop the nose from slumping or setting back.
the design of the boolit and the support it get's from the barell,as well as the pressure time curve of the powder, will decide how much of that happens.
Good answer! :drinks:

[DrCaveman]

I think maybe you are looking for too much of a 'black and white' answer here. The consensus I have found is that each gun/load mating is different and that which worked great for one will often not translate so great to others.

There are so many factors involved in cartridge performance, as well as so many different ways to judge success. Cartridge: boolit shape, boolit weight, boolit hardness, boolit diameter, boolit lube, powder choice, powder charge, seating depth etc. Success: accurate at 50 yds, accurate at 100 yds, accurate at 500 yds, low velocity SD, max velocity, clean bore, clean gun, max penetration, low muzzle flash, etc.

As for GC's, I have found them to fix leading problems in my 30-30 and cz527. Same exact loads, with and without check, were cleaner & more accurate with check. But I try to not add checks unless I decide they are needed. Checks cost as much as a primer to me, since I don't make my own.

[Kansas Ed]

Maybe I am looking for something more "black and white" in my question. Probably not a good thing. As far as GC's are concerned, they add little to the cost of the bullets when considering the cost of their mass produced counterparts (J-word), in my perspective. So I'm OK with that. So, I guess I should rephrase the question instead of looking for a hard and fast rule.

Question Rephrased: If I cast any popular well supported .378 bullet in 1:20 with a GC. Do the odds and experience out there say that the 1:20 (as opposed to #2) will cause problems at 1900 fps, loaded with standard CB powders (5744, 4759,4198, RX7 etc)?

BTW: My current mold casts Accurate 35-250A, and 38-270L

Wheelweight around here is all spoken for, or too high priced to deal with BTW, so I'm ordering pure alloy.

Ed

[btroj]

1/20 a.lly at 1900 with those powders will have some troubles with or without a GC.
The gas check helps, it does NOT make up for a very soft alloy driven hard with high pressures.

Fit throughout the firing sequence and an alloy appropriate for the application are more important in many cases than the GC or lack of same.

You can fire the same bullet to the same velocity wi many different powders. As speed increases it is often easier to get good accuracy froma slower burning powder as it is gentler on the bullet regarding acceleration and the slumping pressure can cause.

Your 1/20 bullet is soft enough that a real firm kickin the shorts is too to make the nose and other parts of the bullet slump and change shape. The GC doesn't prevent or mitigate that. If the throats and chamber are snug enough and cylindrical this slumping may not be an issue, chances are they are not.

Some of this needs to be tested and first hand experience gained. Try bullets with different powders and at different speeds. See what happens. What works and what doesn't. Some things just can't be learned from a book or website.

I have always said we learn most from the casting, loading, and shooting bench. This is a prime example.

[1Shirt]

Range results are all that really count. I like Run's reply!
1Shirt!

[captaint]

As Bill would say - Mr. Rifle will give you the definitive answer. Go shootin..... enjoy Mike

[pdawg_shooter]

You might want to consider paper patching for your high velocity loads. That bit pf paper will take the place of the check, isolate the bore from the lead, and prevent the bullet from distorting under acceleration. More or less one stop shopping for accuracy and velocity.

[runfiverun]

ed 1-20 is a different animal than ww alloy.
it's about the same bhn but constructed differently it's a bit mushier [malleable]
great for expansion,weight retention,and such.
i have never tried to use it at medium rifle velocities.
i know most that use tin/lead alloys in rifles use 1-10.
it's worth a try,and the only answer you'll really get is to try it.
make 20 and see how far along you get.

[Kansas Ed]

Once again, thanks everyone. From what I'm hearing, I'm probably pushing the boundaries. I don't mind pushing the edges a little, but at least now I know where to start if things really don't pan out. I need to pick up a .309 sizing die and top punch to complete my tests, as I have plenty of the .378 bullets cast of #2 and won't be working additionally with that caliber for awhile....so that will be on the way later in the week before I can continue with tests.

Happy Shooting,

Ed

[cobbmtmac]

Ed,

Just my opinion, but I would follow "runfiverun" 's advice and I think you will have an enjoyable answer.

[zuke]

Get both the LEE manual's.He goes to great depth's to explain and help you calculate good lead bullet velocity range and how to calculate hardness use's.

[Larry Gibson]

+1 on "the design of the boolit and the support it get's from the barell,as well as the pressure time curve of the powder, will decide how much of that happens." as runfive run said.

To answer the rephrased question; I shoot some PB'd designs of 1-20 upwards of 1450 fps but they begin to lose accuracy from reasons above sometimes below or above that. A good GC'd design well supported with as low a burning powder as practical can boost that to 1800 fps with a GC'd design. Most often I use a 1-16 alloy for any loads, GC'd or PB'd between 1350 and 1650 fps. Above that velocity I use a harder yet malleable alloy with antimony well balanced with tin in it. I use a softer alloy for hunting applications at 1800 – 2200 fps because I prefer expansion in the terminal performance also.

Some like to use COWWs +50% lead and HT or WQ the bullets as the antimony hardens the alloy. I prefer to add 2% tin to the COWWs and then add the 50% lead. Some say they push this alloy to high velocities with incredible(?) accuracy in the 2400+ velocity range. I use that allow both WQ’d and AC’d for various applications in the 1400 – 2200 fps range. Unless I’m using a slower twist for a cartridge I’ve not been successful maintaining consistent accuracy at such higher claimed velocities. Most others aren’t either.

Harder BHN bullets (still with a balance of tin to antimony for proper solution in lead) similar to #2 are used for general shooting, target shooting and practice in that same velocity ranges. I’ll go to a malleable 18 – 22 BHN alloy for HV with such ternary alloys. Adding Cu is proving good for velocities in the 2600+ fps range with properly designed regular cast bullets in some cartridge/barrel twist combinations.

Finally, a 1-20 alloy is a good alloy to experiment with as it is commonly available and is easy enough to make. How well it performs is dependent on the variables runfiverun mentioned plus perhaps a couple more. It is well worth trying, have fun.......that's what it's about.

Larry Gibson

[mpmarty]

Answer your own questions by just loading and shooting those 20:1 cast boolits.