40-65 Bore/Nose Dimension for Custom Mold

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nlb34
Posts: 15
Joined: Tue May 29, 2018 3:39 pm

40-65 Bore/Nose Dimension for Custom Mold

Post by nlb34 »

I am looking at a second mold to test for hunting and came across a 370 grain mold from Accurate Molds: http://www.accuratemolds.com/bullet_det ... et=41-370D. The one mold I have is a 400 grain Lyman 410655 with the nose measuring .395". On a past post TexasMac referenced his 40-65 had a bore (land) diameter of 0.4005”. Now "assuming" my 40-65 is the same how close would you have the bore ride diameter cut? Accurate Molds allow this to be specified. I could stick with .395" which I know chambers in my rifle or I could creep up somewhere close to .4005".

Thoughts, thanks Brad.
77 sharps
Posts: 330
Joined: Thu Nov 11, 2010 9:45 pm
Location: N. CA

Re: 40-65 Bore/Nose Dimension for Custom Mold

Post by 77 sharps »

In my experience, I would not go over.396” on the nose diameter. You also might want to try a 1/8” soft lube wad under the bullet.
Bulseyetom
Posts: 34
Joined: Fri Apr 24, 2020 1:55 pm

Re: 40-65 Bore/Nose Dimension for Custom Mold

Post by Bulseyetom »

Brad, I went with the Accurate 365G bullet to get one more grease groove. I had him shorten the nose to get a 0.25 meplat and then lengthen the nose riding section to make the overall bullet 1.25 overall length. The great thing about Tom at Accurate is that you can modify any of his designs to fit your bore and groove dimensions. I went with a bore diameter of 0.400 (+0.000/-0.002) and the body 0.410 (+ 0.001/-0.001) to fit my freebore diameter. I have not had any problem with this bullet chambering in my rifle. I would highly suggest doing a chamber cast before ordering a mould so that you can see how much freebore you have and what diameter it is. I play heck trying to measure the bore diameter from a cast so I usually patch a bullet until it is a slip fit in the bore and measure that. I also shoot duplex loads for hunting and that keeps the bore clean as a whistle for many shots. The bullet that I ordered for my 38/56 has the nose riding section 0.001 bigger than bore and it shoots lights out with smokeless but is harder to chamber in my Rolling Block with no camming action. In retrospect I should have ordered bore diameter. Tom
77 sharps
Posts: 330
Joined: Thu Nov 11, 2010 9:45 pm
Location: N. CA

Re: 40-65 Bore/Nose Dimension for Custom Mold

Post by 77 sharps »

Brad
If you are hunting , there’s no reason to use a bore rider bullet. It will only promote leading and make it difficult or impossible to fire multiple shots if you are using BP. That bullet cast 20/1 will be an excellent killer. Just for information, the original.40/65 WCF load used a 260 grain bullet and was considered to be adequate for elk. Personally I use a 350 grain bullet in my.40 hunting rifle.
nlb34
Posts: 15
Joined: Tue May 29, 2018 3:39 pm

Re: 40-65 Bore/Nose Dimension for Custom Mold

Post by nlb34 »

Guys thank you for the advice and pointing out the similar 4 grease groove design. Is there a rough "rule of thumb" on when more grease is needed? At bullet lengths above X, or weights above X, or speeds above X?

As I look at these two bullets the length and weights are similar, I suspect I could get more power under the 3 groove design. Now as for performance & accuracy I don't know if the longer nose & shorter body on the 3 groove design is inferior to the 4 groove with longer body & shorter nose.
Kurt
Posts: 8428
Joined: Wed Oct 12, 2005 10:28 pm
Location: Not Far enough NW in Illinois

Re: 40-65 Bore/Nose Dimension for Custom Mold

Post by Kurt »

Brad,

For a hunting bullet I would keep the ogive short for a follow up shot.
My choice for a hunting bullet would be one like this upscaled to the .40. http://www.accuratemolds.com/bullet_det ... et=38-290R This is a bullet like the Lyman 457-121 PH I use in the .45-70 Lever rifle. I can empty the tube using black powder without a fouling problem. It is an original Pope design that works very good for just about any purpose.

Tom might already have one for the .40 in his signup. I had him make a clone of the 121 PH that is the proper diameter for the .45 and it is also listed in his catalog.

Kurt
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77 sharps
Posts: 330
Joined: Thu Nov 11, 2010 9:45 pm
Location: N. CA

Re: 40-65 Bore/Nose Dimension for Custom Mold

Post by 77 sharps »

Kurt
The base of that bullet is going to extend about 1/4” below the case neck. Is that going to promote gas cutting problems? When I first saw the 3 groove bullet the first thing I thought was it needs another grease groove but then I though about the bullet base being exposed to the gases if it were longer.

For follow up shots, if the bullet nose is kept 0.004” under bore diameter, it will allow many shots to be fired without fouling control. I believe that the Lyman 457125 was originally designed that way.

Brad. If you are going to be a serious BPCR hunter, you should give PP bullets a lot of thought. PP bullets have a few advantages over GG bullets. I know PP can seem intimidating, but they are quite easy once you understand the basics.
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