large meplat visit velocity

[canuck4570]

after readind some of your topics it seems that the larger the meplat the higher the velocity should be for good accuracy.....My question is if the bullet is a no gaz check tipe to what size meplat should I stick to.

the rifle I shoot is a ruger no 1 in 4570 with 1 in 20 rifle pitch
the mould I want to have made will be around 500 gr. with most of the bearing surface iside the case to limit the powder space
velocity will be between 1200 and 1500 fps
thank you Michel.

[Bass Ackward]

after readind some of your topics it seems that the larger the meplat the higher the velocity should be for good accuracy.....My question is if the bullet is a no gaz check tipe to what size meplat should I stick to.

the rifle I shoot is a ruger no 1 in 4570 with 1 in 20 rifle pitch
the mould I want to have made will be around 500 gr. with most of the bearing surface iside the case to limit the powder space
velocity will be between 1200 and 1500 fps
thank you Michel.


Michel,

Since you are going 500 grains, your bearing length should be long enough to produce a fairly high ballistic coefficient. That means it can support a longer nose .... or a wider meplat. A bullet only needs to be driven harder because it isn't stabilizing. I would guess that 70% would be tops. If it were me, I would hold at 65% just to be safe since you don't have the gas check to push it harder should I be wrong.

But in truth, all my 45s are 60%ers these days. I just don't need anymore.

[felix]

Yes, BA, just about all (real looking) Keith boolits have no more than 61 percent meplat. 60 percent would be my max also, unless bores are smaller, like the 22-28 which would be limited to 55 percent max, 50 preferred, to handle the wind resistance better. ... felix

[Spokerider]

I too have been researching 45-70 525 grain cast bullet designs. I've visited the Shooters Forum, where Beartooth bullets has a non gas checked 525 gr. "piledriver" and Garret bullets has 500gr. [ I think Garret's is a 500 gr. ] cast bullet, both of which look to have a larger meplat than 65%.
I visited Mountain Man mould's website, where he has an online bullet mould program, where you actually design and draw your own bullet for him to manufacture the mould. This is a neat program. I matched up my 525gr. 45-70 design / drawing to copy that of Beartooth's Piledriver design, and it appears that the Beartooth Piledriver has about an 85% meplat.
This is what I'd like to have in my 525 gr non-gas check design, an 85% meplat. I too am wondering how long the nose should be above the crimp in order to best stabilize out of a ballard-rifled Marlin GG, and how wide the grease grooves ought to be. [ grease groove to contact surface ratio, that is ]. I want to drive this bullet to the 40000 pressures the GG is capable of.

I'm discovering that bullet design is a complex thing........
Check out Garret's 45-70 bullet, and Beartooth's Piledriver design. They both come with great reviews.

[Spokerider]

I too have been researching 45-70 525 grain cast bullet designs. I've visited the Shooters Forum, where Beartooth bullets has a non gas checked 525 gr. "piledriver" and Garret bullets has 500gr. [ I think Garret's is a 500 gr. ] cast bullet, both of which look to have a larger meplat than 65%.
I visited Mountain Man mould's website, where he has an online bullet mould program, where you actually design and draw your own bullet for him to manufacture the mould. This is a neat program. I matched up my 525gr. 45-70 design / drawing to copy that of Beartooth's Piledriver design, and it appears that the Beartooth Piledriver has about an 85% meplat.
This is what I'd like to have in my 525 gr non-gas check design, an 85% meplat. I too am wondering how long the nose should be above the crimp in order to best stabilize out of a ballard-rifled Marlin GG, and how wide the grease grooves ought to be. [ grease groove to contact surface ratio, that is ]. I want to drive this bullet to the 40000 pressures the GG is capable of.

I'm discovering that bullet design is a complex thing........
Check out Garret's 45-70 bullet, and Beartooth's Piledriver design. They both come with great reviews.

[Bass Ackward]

I too am wondering how long the nose should be above the crimp in order to best stabilize out of a ballard-rifled Marlin GG, and how wide the grease grooves ought to be.

I'm discovering that bullet design is a complex thing........
Check out Garret's 45-70 bullet, and Beartooth's Piledriver design. They both come with great reviews.

Spokerider,

Post this over on Dan's Forum. (scroll down on the left) He has made enough of these that he should be able to tell ya. The super wide meplats sometimes have to be a little shorter to chamber. And it really depends on the gun. Dan was shooting 80% meplats and couldn't break 5". I told him to cut back to 75% and same loads dropped to 2 1/2". So some guns just don't seem to want to stabilize the heavies unless you drive them hard. And then sometimes you still have issues.

Everything in life is a compromise. Sometimes you win, sometimes you loose.

[The Nyack Kid]

spokerider
the piledriver has a 82% memplat or .376 across and a .450 inch long nose these are suposed to be max for unaltered marlins.

[Blackwater]

I too have been playing with Dan's website, and one of the moulds I want is a 535-545 grainer for my BPCR and black powder. Need to slug the bore & throat and make a chamber cast, but I think I'm nearing a final design. I'm just glad Dan doesn't charge by the minute for use of that program! As noted, I at least THINK I've learned a lot from it.

I mainly have been playing with a bore rider, plain base, probably 3 grease grooves, 535 gr. of WW's (MAN! I want to get rid of that requirement for tin!), @ a .735 nose with .080" front driving band, and @ .240" on the bore riding nose portion. Only real unsettled matter is that meplat. I've tried everything from 60% on down, and I like something about them all, but have "finally" (I think?) settled on either 60% for superior effect on game, and 50% for better long range BC. I ain't totally throwed out 40% either, though.

BC is a GOOD thing, but seems like some reasonable size flat on the nose would make the bullet spin with a little more certainty and "trueness," for lack of a better word, since more of the mass is toward the outer dimension than with a smaller meplat or more pointed nose. Can anyone give any relevant comment, observation, experience, data on these parameters? I love the way Dan makes his AL moulds. Those SS pins on both sides is a VERY neat little feature! Can't wait to get one ... or should I say SEVERAL!

BTW, I DO realize my parameters are completely my responsibility, and accept that. It's just a VERY neat thing to be able to "design" my own bullets, and I thank Dan for that. Knowing me, and from experience, I'll probably design a dud sooner or later, but that won't be Dan's fault. Like that bank robber in the movie "Dirty Harry," I just "gots ta' know!"

[drinks]

I have the Lee 500gr 3R and add a gas check, but if I wanted a 500gr wfn with gas check, I would at least try the Lee C457-500-F, they are less than $15 at Midway.

[felix]

Blackwater, the only time I would even consider a bore rider is when I needed the powder space in a straight walled case; or, when I didn't want to extend too far below the end of the bottled neck, while keeping the throat the same, but wishing for more boolit mass at the same time. You give up too much real guiding force by default with any kind of bore riding design, making it more important to select a bore riding boolit with proven performance. Examples of the latter great ones are fairly well known in the smaller calibers, such as in the 30-35 caliber range. ... felix

[Bullshop]

You give up too much real guiding force by default with any kind of bore riding design,
Felix
Yes that is what I am seeing trying to make little boolits go fast. The designs with full diameter bearing keep on going where the bore riders quit.
BIC/BS

[Blackwater]

Well just HECK! Here I was, thinking I was nearly through, and y'all go and burst my bubble. Actually, though, with that tight chamber in the Browning BPCR, using a bore rider to get more powder room is exactly what I was trying for. Correct me if I'm wrong, but I thought the Postells and Creedmoors were bore riders. I'd figured on going with a .449" specification, since Dan's spec on that part is minuz zero to plus one thou. That should be pretty snug, and if oversize, I ought to be able to change alloy a bit and get a very close fit, or so I'd planned.

Where am I going wrong? I realize there's no greater alignment factor than a long bearing surface. That's the calling card of the old Loverein designs, isn't it? I'm currently shooting 74 gr. by wt. of Goex 2F behind a Saeco #745 with WLRM or Fed 215M primer. Those Saecos have a bore riding section in my gun, or at least have appeared to in that Badger barrel. A couple of freinds have gotten stellar results from the Lee 500 gr. BP design, and will probably try that one, too.

If, and I realize that's a kinda' big "if," I can get it to truly ride the bore, isn't that the only way I can get more powder room in that 2.1" case? I don't want to shoot anything but black in that particular gun, though I don't shoot anything but smokeless in my other two .45/70's.

Obviously I've got a ways to go yet on cast bullets, which isn't a surprise at all. Sure is fun learning.