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This is for a rifle, not handguns. With all the suppliers being back ordered on the popular molds I am looking at one that mimics the double grease groove design, but only uses one larger grease groove instead. I can lube these with White Label 2500+ or Powder Coat them. Either way, is there a problem with one large grease groove at 2,000 fps?
Caliber, weight, design?
I have no doubt Tom at Accurate molds can and will make what you want, as can others.
I have a 480 gr., .460, NEI bullet mold that looks a lot like a KTSWC with a very long nose and one large lube groove. I've never tried it with smokeless but it is excellent with BP.
195 grains, .360 WFN, PB and GC. Just got off the phone with the gentleman in Utah with NOE asking about back order times. He was very helpful, and when I also asked about the grease groove designs he said the large single grease groove was for old BP designs (as you just mentioned), but that it will lube a modern rifle bore as sufficiently as the double groove design, as long as good lube is employed.
If anyone has experiences and antidotes on the subject I'm all ears.
Thanks.
There were some who preferred one large groove vs multiple smaller grooves with smokeless. I never used one so cannot comment one way or the other. As long as the groove is filled then I don't think it matters much.
PC might be another issue since it will not completely fill the groove. Only one way to see. Load some up and see how they do.
My opinion, and I have no targets to back this up, is that with one big grease groove, you have a huge unsupported area of the bullet. For the most part it will not matter, as you have support on either side of it. The harder the alloy, and the lower the pressure, the less this will matter. I base this on recovered bullets that show collapsing grease grooves or other deformities from high pressure rounds. I have one bullet that shoots fantastic in a handgun with soft alloy, but recovered bullets show no trace of a crimp groove.
I then started playing with different bullet designs for higher pressure. Most people know you need the nose supported as much as possible, which is important. What I've also found works great with grease grooves is a shallower angle, less deep, and multiple of them. For example, I have a 220 grain .360" bullet that has two grease grooves that are fairly shallow, and cut with 35 degree angles, as well as the gas check. I also made the grooves as small as possible, both to maximize bearing surface, as well as minimize unsupported area that can deform. These work great, and show no deformation even from the hottest loads. Compare that to a Keith bullet, which has a fairly deep groove and very steep sides, I think my NOE version used 65 degree sides. The bullet still shoots good in a handgun, but recovered bullets usually show the lube groove collapsing with hot loads. In 30 caliber, a lot of designs go with both a bunch of lube grooves, and with steep angles. I'm not exactly sure why. The Saeco #315 for example has 5 lube grooves, plus the area above the gas check, yet all the grooves are fairly deep. It holds so much lube, I only fill two grooves with lube. Some people only fill one. The design shoots great, but can be a bit fussy on mold temp to get it to release easily.
The flip side of that is a shallow lube groove will not work as good with low pressure rounds. A steeper angle will allow the lower pressure to pump that lube onto the outside of the bullet during firing. In a blackpowder or low pressure round, I would want a steep angle. The H&G #68 will often still have a tacky lube stuck to it after being fired, indicating not much is used during firing. That bullet has a rounded groove near the front end. A softer or more crumbly lube will eject after it leaves the barrel, Canaruba Red will not. If I were to modify that design, I would put a single small groove, with steep sides, close to the base of the bullet. Then you could look at something like a TC Maxiball for a muzzleloader that has one huge, and one gigantic lube groove. I think there is more at play on why that bullet is the way it is, but one thing the design does do, is that it deforms when firing. This is a good thing, otherwise it would not be accurate. By being designed this way, they load easy, yet expand to fill the rifling when fired.
Short version for your case, I will take two lube grooves, you don't want the bullet to deform at all. I might even consider 3 if it is a plain base. The less distance you leave unsupported, the better.
Thank you, Megasupermagnum, that was helpful information. I have enough experience with the types you are addressing to understand your point. Also, as a long time traditional muzzleloader, the Maxiball reference fit in here well.