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.40 Caliber BPCR Accuracy (Read 7800 times)

texasmac Frequent Elocutionist Offline Posts: 2153 Location: Central Texas Joined: Aug 16^th, 2004	.40 Caliber BPCR Accuracy Jun 18^th, 2019 at 11:29am	Print Post
	Those of you that shoot a .40 caliber BPCR may be interested in the article I just posted titled, “.40 Caliber BPCR Accuracy – Twist Rate vs. Bullet Length vs. Velocity”. It can be accessed at the following link: (You need to *Login* or *Register* to view media files and links) Wayne

	NRA Life (Benefactor & President's Council) Member, TSRA Life Member, NSSF Member, Author & Publisher of the Browning BPCR book
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art_ruggiero Frequent Elocutionist Offline Posts: 1222 Location: CT Joined: Dec 14^th, 2008	Re: .40 Caliber BPCR Accuracy Reply #1 - Jun 18^th, 2019 at 1:25pm	Print Post
	thanks wayne, great article art ruggiero


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GrumpyBear Full Member Offline Posts: 139 Location: Western,Pa. Joined: Sep 30^th, 2017	Re: .40 Caliber BPCR Accuracy Reply #2 - Jun 19^th, 2019 at 10:19am	Print Post
	Good article Wayne, Thanks.

	Μολὼν λαβέ Don't pick a fight with an old man. If he is too old to fight, he'll just kill you. Shash-yazhi -bear-cub Brian
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beltfed Frequent Elocutionist Offline Posts: 1826 Location: Central Wi Joined: Dec 20^th, 2007	Re: .40 Caliber BPCR Accuracy Reply #3 - Jun 19^th, 2019 at 9:34pm	Print Post
	Schuetzendave, Here is an example of my 369 gr Elliptical Ogive/Minigroove bullet from a 16 twist 40-65 can do at 800yards. The bullet has a 70% of length ogive and Minigrooves. Overall length is 1.325". Over 70 gr Swiss 1.5, for 1375fps. Holes thru target even out to 1000yds were Round. Oh: score at 1000yds in that match was 88/100. Fourth overall match for the day for this Oldster just behind younger guys shooting 45 cals beltfed/arnie

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Skalkaho Oldtimer Offline Posts: 863 Location: Montana Joined: Sep 29^th, 2006	Re: .40 Caliber BPCR Accuracy Reply #4 - Jun 19^th, 2019 at 9:36pm	Print Post
	A 17 twist Kreiger shot the $ Bullet very well. Sold that gun and rebarreled my other Shiloh Sharps with a RKS 17 Gain Twist. Same reamer long throat two grease grooves out for A 45-80 in a sense, cheaper than a 45-90 ! Well the same load in the RKS did not stabilize the $ bullet. Damn....So had to hustle and now cast another 600 bullets to do testing before leaving for Quigley. The old Saeco 745 for a 530 gr. bullet 20-1. Shot lights out. A under 2" group average at 300 yds. Will play more with the $ down the way since there are 600+ bullets sitting here! Possible the gain twist throws A quicker spin than a regular twist barrel? Inquiring minds want to know......Yes I'm shooting a 45-70 and this post is on 40-65.Just thought I'd throw it in .

	May the Bullet Gods be with you.......
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beltfed Frequent Elocutionist Offline Posts: 1826 Location: Central Wi Joined: Dec 20^th, 2007	Re: .40 Caliber BPCR Accuracy Reply #5 - Jun 19^th, 2019 at 11:51pm	Print Post
	SDave, I do understand the narrow limits of 400+grain "money" bullet designs in Wayne's study. My added point, about my shorter bullet and stability in the 16 twist rifles blended into Wayne's mention of the shorter bullets like mine. As mentioned in the great article I had in fact corresponded with him, even offering some of the 369 gr E-Mini bullets to include as another "point on the curve" But I understand his concern at knocking over rams and wanting 400+ grain bullets for greater momentum on them critters. And had suggested he order that Shiloh with the 14 twist for better stability in the heavier 40 cal bullets. Oh, and the minigrooves are intended to reduce body drag so as to increase b.c. as shown by reduced come-ups signifying greater retained velocity. Best Regards, beltfed/arnie


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texasmac Frequent Elocutionist Offline Posts: 2153 Location: Central Texas Joined: Aug 16^th, 2004	Re: .40 Caliber BPCR Accuracy Reply #6 - Jun 21^st, 2019 at 12:44pm	Print Post
	Due to Schuetzendave's comments I thought I'd post the following bullet specs. The Buffalo Arms (BACO) JIM410410M3 is my design for the Browning BPCR chamber using a "money bullet" nose. As Sdave noted both the CP & CG of the PJ 40001 (Creedmoor) are located a little more forward than the BACO bullet. For what it's worth, at 500 meters I had more stability problems with the Creedmoor bullet than with the BACO, but the max Creedmoor bullet velocity was limited due to the nose design and 1st driving band affecting COAL & case capacity. Right or wrong, I believe the lower BC of the Creedmoor bullet due to the nose design contributed to the problem due to loss of velocity at the long distance, which I was not able to compensate for by sufficiently increasing the velocity with Swiss 1.5Fg unless I used a lot of powder compression. Wayne
	« Last Edit: Jun 21^st, 2019 at 1:10pm by texasmac »
	NRA Life (Benefactor & President's Council) Member, TSRA Life Member, NSSF Member, Author & Publisher of the Browning BPCR book
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MartiniBelgian Frequent Elocutionist Offline Posts: 1734 Location: Aarschot Joined: Jun 7^th, 2004	Re: .40 Caliber BPCR Accuracy Reply #7 - Jun 22^nd, 2019 at 2:27am	Print Post
	If you want to get stability by increasing speed with a BPCR, you're fighting a losing battle - it just won't happen. You will never be able to get enough velocity increase to get there.


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beltfed Frequent Elocutionist Offline Posts: 1826 Location: Central Wi Joined: Dec 20^th, 2007	Re: .40 Caliber BPCR Accuracy Reply #8 - Jun 29^th, 2019 at 4:26pm	Print Post
	Schuetzendave, Interesting. I am confused: Your photo of the "original Doc Lay money" bullet as designed by Dan T. sure looks like "a 40 cal version of the Lyman 457132 " --the Postell. ??? beltfed/arnie


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marlinguy Frequent Elocutionist Offline Ballards may be weaker, but they sure are neater! Posts: 18055 Location: Oregon Joined: Feb 2^nd, 2009	Re: .40 Caliber BPCR Accuracy Reply #9 - Jun 29^th, 2019 at 5:48pm	Print Post
	beltfed wrote on Jun 29^th, 2019 at 4:26pm: Schuetzendave, Interesting. I am confused: Your photo of the "original Doc Lay money" bullet as designed by Dan T. sure looks like "a 40 cal version of the Lyman 457132 " --the Postell. ??? beltfed/arnie Looks like my Lyman Snover 410663.

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beltfed Frequent Elocutionist Offline Posts: 1826 Location: Central Wi Joined: Dec 20^th, 2007	Re: .40 Caliber BPCR Accuracy Reply #10 - Jun 29^th, 2019 at 6:17pm	Print Post
	Indeed, in Dan T's opinion, the Dr Richard Gunn designed for Ron Snover"-Lyman 410663 is one of the best of over the counter bullets out there for BPCR. And, I feel this bullet is really a "pre-money money bullet" The best improvement on the 410663 basic profile is to have shallower grooves as well as have the top two or three drive bands at bore ride diameter so as to allow seating it out for more powder capacity, particularly in the 40-65. And then , best in a 14 twist barrel. beltfed/arnie


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Old-Win Frequent Elocutionist Offline Posts: 1827 Location: Minnesota Joined: Nov 24^th, 2005	Re: .40 Caliber BPCR Accuracy Reply #11 - Jun 30^th, 2019 at 7:25am	Print Post
	IIRC as told to me by a well known mould maker, Dan came to him with two bullets and wanted to have him grind cutters for each bullet shape. One was a Metford bullet and one was a Sharps paper patch bullet. He then wanted moulds made with small shallow grooves rather than deeper ones. The mould maker created two new shapes of which one became the money bullet because of a win at the Quigley. A while later, Dan returned and wanted the Metford bullet's nose changed so he reground the cutter to the new specs. Dan returned a third time and wanted to go back to the original Metford nose shape and he was told by the mould maker that he wouldn't do it because it took too much time to grind the cutter. There are many iterations of the money bullet out there now but this is a picture of an early one with the later one. From L to R, early Postell, Sharps paper patch, money bullet as done by Baco, first money bullet. All .45 cal.


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Old-Win Frequent Elocutionist Offline Posts: 1827 Location: Minnesota Joined: Nov 24^th, 2005	Re: .40 Caliber BPCR Accuracy Reply #12 - Jun 30^th, 2019 at 7:40am	Print Post
	From reading Nennstiel, as the velocity of the bullet drops to subsonic velocities, the flow field around the bullet changes. The center of pressure moves forward and when it passes the center of gravity, the bullet will lose dynamic stability. As Dave says, a bullets stability is probably a combination of bullet shape, length and placement and depth of lube grooves. All I know, is that I shoot the one that works best for me. Bob


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GrumpyBear Full Member Offline Posts: 139 Location: Western,Pa. Joined: Sep 30^th, 2017	Re: .40 Caliber BPCR Accuracy Reply #13 - Jun 30^th, 2019 at 8:24am	Print Post
	Old-Win wrote on Jun 30^th, 2019 at 7:40am: From reading Nennstiel, as the velocity of the bullet drops to subsonic velocities, the flow field around the bullet changes. The center of pressure moves forward and when it passes the center of gravity, the bullet will lose dynamic stability. As Dave says, a bullets stability is probably a combination of bullet shape, length and placement and depth of lube grooves. All I know, is that I shoot the one that works best for me. Bob And of course Bob,inquiring minds would like to know which one that is ?

	Μολὼν λαβέ Don't pick a fight with an old man. If he is too old to fight, he'll just kill you. Shash-yazhi -bear-cub Brian
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MartiniBelgian Frequent Elocutionist Offline Posts: 1734 Location: Aarschot Joined: Jun 7^th, 2004	Re: .40 Caliber BPCR Accuracy Reply #14 - Jun 30^th, 2019 at 8:50am	Print Post
	No, it doesn't require 'overspinning' - it just requires a faster twist. There is no 'right' twist for a caliber. You adapt the twist to the bullet you want to shoot - either that, or you go the other way round. By your reasoning, all modern jacketed bullets require 'overspinning' and will yaw, so are basically flawed, as their CG is pretty far back.


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