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Old November 26, 2012, 02:31 PM   #1
hhunter318
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.375 Project Questions

I'm wanting to develop a .375 cartridge from either the .416 Rigby case or an improved version of the .378 Weatherby(with the magnum belt turned off by lathe). Is 2900 to 3000 fps plausible with a 330 gr bore rider or VLD with these case capacities?
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Old November 26, 2012, 03:42 PM   #2
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With a long enough barrel? Sure.

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Old November 26, 2012, 06:58 PM   #3
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I'm getting 2850 out of a 300 gr. pill from my 375 RUM and I can squeeze a little more from it.

In a 378 Weatherby you can put about 7-10 more grains of powder; maybe 12-14 grains if you "improve" the round and make it nearly straight walled. You're already at max with the 378 W. and not really going to gain much. You could make 2900 fps maybe a hair more with a 330 gr bullet but that is really stretching it.

To get where you want to go, you are going to need a couple or three tricks to get there. First is the longest action possible so you can seat the bullet out further allowing more powder in the case. Then you need lots of freebore to help with the pressures you are going to encounter. Then you will be talking in terms of 26" minimum barrel length for the powder burn.

When all is said and done you also should be talking a 10 lb.+ rifle sans scope because it's going to kick like a Clydesdale .... trust me on this one.
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Old November 26, 2012, 08:09 PM   #4
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I actually planned on having a barrel in the 32 - 34" range. Weight isn't that big of an issue as I planned on it weighing upwards of 20 lbs. I'm thinking of a Lawton 8000 action, Kreiger or PacNor barrel with a straight taper barrel, McMillan A5 stock, and of course some type of break.
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Old November 26, 2012, 08:30 PM   #5
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With your specified build components, what you are looking for is certainly in the realm of possibility. Your weight range also makes it something that can be shot more than a couple of shots in a sitting.

With that action in mind, you could use a brass like a 505 Gibbs and EASILY reach or exceed your velocity goal while keeping your pressures under 60K. But then again, that is how Chaytac does it.
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Old November 26, 2012, 08:39 PM   #6
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Well I don't want to jump to a Cheytac. The 375 SnipeTac has been very effective, but component price is ridiculous. I want to build this with the .416 Rigby as the parent case. .416 Rigby brass doesn't sting the wallet as severely. I want to see how much performance I can achieve being restricted to this case capacity. Shorten the neck to .350, blow the shoulder to 35 degrees, minimize body taper and the like. Once this project gets rolling I think I might get some hydraulic case forming dies from Hornady for this round. It'll be a fun project. Any input or other ideas are sure welcome though.
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Old November 26, 2012, 09:09 PM   #7
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Hold up...

You are talking about buying hydraulic case forming dies and you are balking at the cost of 375 Snipetac brass? Sounds a little penny wise pound foolish to me.

Why not just go with a 9.53 Saturn? It is basically what you are talking about.

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Old November 26, 2012, 10:18 PM   #8
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I'm going to have to go with Jimro on this one. The 9.53 Saturn makes just under 2900 fps. with a 350 gr. bullet from a 27" barrel. Give it that extra 5"-7" you are talking about and you should easily hit 3000 fps. It is a 375 - 416 Improved....just what you are looking at. That also means dies are already available (no extra cost for custom made one of a kind dies*); RCBS lists them under Group G custom dies and they run $144 for the set.

Lazzeroni Ballistics

* I have an unconventional idea of my own and I know the dies will cost me.
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Old November 27, 2012, 03:01 AM   #9
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If I am not mistaken the .338 Lapua is a necked down 416 Rigby.

Hornady makes some reasonably priced .338 Lapua brass.I am not real fond of necking up,I'd rather neck down,but I have had good luck necking up with the Cream of wheat trick.

I have even made a chamber insert of the desired case using a chambering reamer,and turning the outside of the insert to drop into an old break action single 12 ga for firing the cream of wheat loads.Worked great!
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Old November 27, 2012, 09:11 AM   #10
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The 338 Lapua has a 2.724" case length; the 9.53 Saturn is shorter than the 2.900" of the 416 Rigby if I remember correctly. And on Lazzeroni's website, they only show 2885 fps with a 350 gr. VLD. It's always an option though. I did some research on them earlier on. Note, I said I would go for the hydraulic case forming dies later on. Just to avoid fire forming.

Last edited by hhunter318; November 27, 2012 at 09:29 AM.
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Old November 27, 2012, 04:54 PM   #11
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2885 fps with a 27" barrel and a 350gr bullet.

Add an inch to the barrel and drop the bullet weight to your 330gr bore rider and you are there. Go all the way to a 32" barrel and I'd be surprised if you didn't blow past 3050 fps, assuming 30fps gain per inch, even a base of 2885 gives you 3035, using the 350gr VLD loading.

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Old November 27, 2012, 10:59 PM   #12
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Gotcha. I didn't see the barrel length. That makes the 9.53 Saturn sound a good bit better in hindsight.
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Old November 27, 2012, 11:08 PM   #13
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Case capacity isn't always a good indicator of performance. A lot of the old cases had a high capacity to keep pressures down with fast burning powders (think 375 H&H, 416 Rigby, 404 Jeffrey). With a propellant that is more closely matched to case capacity you can sometimes "do more with less."

The current crop of "Short Magnums" illustrate this point quite well, reduced case capacity does not mean reduced ballistics, at least not with the normal range of projectiles one usually shoots. Once you get to the ultra slow end of the powder spectrum and heavy for caliber bullets, case capacity becomes much more important.

Although unless you have a reason for choosing the 9.5 bore, long range shooting can be done much cheaper with a 338, 300, or 7mm magnum.

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Old November 28, 2012, 05:00 AM   #14
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I noticed Sierra has a long range specialty 350 gr 375 match bullet now
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Old November 28, 2012, 02:35 PM   #15
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The reason i'm going with the .375 bore is for the .941 BC of the 330 ground Lehigh Bore Riders and just want a round that performs well out to 2,000 yds.
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Old November 28, 2012, 11:31 PM   #16
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That is a theoretical G1 BC. A few years back SOCOM did some COTS testing for a new sniper system, the 408 Cheytac was one of the contenders. Even with a high muzzle velocity and high BC they were unable to hit the 2k target, with multiple shots. A standard 408 load should be supersonic past a mile with the published BC's for the projectiles.

Doppler radar tracked projectile flight, and the Cheytac became "wobbly and erratic" around 1400 meters as velocity dropped off, same as the 50 BMG from the McMillan Tac50 already in the inventory.

So don't think you'll be "good to go" with a high BC bore rider design, some of those bullets just do not handle the transonic range very well. The high desert air has a has a slower speed of sound, so you would think that those high BC bullets would fly better longer, but sometimes it just doesn't work out.

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Old November 29, 2012, 11:38 AM   #17
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Thanks for that insight Jimro. Never knew that about the Cheytac testing. Is it an inaccuracy on their part of the published BC or just the design of the bullet. In another post I asked about a ballistic calculator that used only velocity and 3 POA's at different distances to adjust the BC accordingly, therefore seeming more accurate, to me atleast. Would this be a better approach?
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Old November 29, 2012, 07:35 PM   #18
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If you look at Sierra Bullets website, you'll see that they list multiple B.C.'s for their bullets based on velocity ranges. That's because any projectile exhibits a different B.C. at different velocities let alone altitudes, barometric conditions, etc.

A single B.C. (usually highest number) is given based on the optimum velocity of the bullet at STP. Once outside of the sweet zone all bets are off. Also, for real long range shots, B.C. is only one of the factors that one needs to take into account. Another is the rounds inertia.

A 105 Howitzer...105x372R has a muzzle velocity of only 1550 fps. but it has a maximum range of 8300-8500 yards. We are talking almost 5 miles which is on the high side for a man portable weapon of much higher velocities. You may want to look up what a B.C. 1 round "IS". That was established quite a few years ago. As was referenced earlier...you'll want to look at the "G1" round.
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Old December 1, 2012, 03:16 PM   #19
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Quote:
Thanks for that insight Jimro. Never knew that about the Cheytac testing. Is it an inaccuracy on their part of the published BC or just the design of the bullet. In another post I asked about a ballistic calculator that used only velocity and 3 POA's at different distances to adjust the BC accordingly, therefore seeming more accurate, to me atleast. Would this be a better approach?
Ok, sometimes simple questions have complicated answers, I'll try to tell you what I know from my experience, but I'm going to have to draw a lot on some of my friends and co-workers who shoot beyond 1k on a more regular basis (last time I shot beyond 1k was about 4 years ago. 1400 meters with a Barret M107).

You can calculate BC in a number of ways, the "industry standard" is the old G1 reference as it produces the highest number.

The standard G1 projectile originates from the "C" standard reference projectile (a 1 pound (454 g), 1 inch (25.4 mm) diameter projectile with a flat base, a length of 3 inches (76.2 mm), and a 2 inch (50.8 mm) radius tangential curve for the point) defined by the German steel, ammunition and armaments manufacturer Krupp in 1881. By definition, the G1 model standard projectile has a BC of 1. The French Gavre Commission decided to use this projectile as their first reference projectile, giving the G1 name. Pulled from Wikipedia.

Note that the G1 model is good for flat based bullets with a double radius tangent curve profile. This is actually a very good reference for flat base spitzer bullets.

The G7, G7 (long 7.5° boat-tail, 10 calibers tangent ogive, for very-low-drag bullets) was designed to deal with the more modern spitzer boat tail design (which the US adopted in M1 loading of the 30-06 in 1925, 175gr FMJBT with 9 degree boat tail).

The boat tail angle is an interesting topic, the 13 degree boat tail of the 168 SMK "International" bullet (designed for 300 meter free gun) does not handle the transonic range very well at all (bullet destabilization). The older M1/M72 bullets with the 9 degree boat tail handled the transition just fine, as did the older 180gr SMK (which had an 11 degree boat tail, IIRC). The 175gr SMK was developed to replace the M72 bullet, and it did that quite well.

Ok, science aside, some match bullets work better than others. Flat base bullets are going to be the most accurate at short ranges. Boat tail bullets are going to be most accurate at long ranges. Bullets that handle the transonic range smoothly will be most accurate at extreme ranges. The transonic range really starts at about Mach 1.2 for some reason, I don't know why this is, and I don't know why some VLD design match bullets don't handle the transition well.

If you want to shoot long range, look at what other people are shooting long range. A 300 Win Mag will get you to a mile if you are shooting a 220gr SMK (which handles the transonic range nicely). Shoot the same 300 Magnum with the 210 VLDs (which have a higher published BC) and you will get erratic accuracy through the transition range to subsonic, but you will also get a flatter trajectory inside of the supersonic range (well beyond 1000 meters from a magnum).

A 338 Lapua (or any of the comparable 338 magnums, RUM, EDGE, etc) will get out out past a mile with a good bullet (250gr Scenar or lockbase is the "traditional" load). The Lost River 270gr bullet is probably the best compromise between velocity and BC, although there are a number of folks who swear by the 300gr SMK.

Sorry to ramble, but ballistics on paper are a lot different than ballistics in reality once you get beyond a kilometer. One of my snipers, (God rest his soul) had no problem making hits at 1400 meters with M118LR at the Yakima Training Center. The combination of high desert air and a bullet that handled the transonic range let him use the m24 very effectively to provide precision shots 200 meters shy of double the doctrinal range for snipers.

Heck, those old Brits shooting Enfields at Bisley range did amazing things with a cartridge that had a midpoint trajectory height of over 4 story building. Having a bullet that is stable down to subsonic velocities is absolutely key to long range accuracy.

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Old December 1, 2012, 03:43 PM   #20
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Thanks Jimro,

That's probably one of the most helpful bits of info I've read as far as considering calibers or cartridges for extreme long range. I will say that transonic velocity crossover was probably the least of my worries in the brainstorming process. Thank God for people with years of experience such as yours. Explaining the G1 vs G7 models gave me a better understanding of the BC determination. Thanks for all of the knowledge.

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Old December 1, 2012, 06:20 PM   #21
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Just what are you trying to accomplish exactly? There are very few places in the US where you can really stretch the legs of a magnum rifle.

If I had to start it all over again, I'd go with a 260 Rem heavy barrel Savage launching 140gr Nosler Custom Comp bullets. I went the 308 Win to 300 Win Mag, then I sold the magnum as I really couldn't stretch it's legs the way it was meant to be shot. Shooting a magnum at 200 yards because the base commander won't open up the 1000 yard national match range is...frustrating.

Then I PCS'd to a place where the 1000 yard range is open one weekend a month, and I had no magnum to shoot. Can't wait for next years High Power season to start off.

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Old December 1, 2012, 06:38 PM   #22
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One quick add to Jimro's info.

The transonic range is from .8 mach to 1.2 mach. These numbers are not hard numbers due to differences caused by temperature and pressure but they are the numbers aeronautical engineers work with and are a good guideline. Between these numbers you have air flow that is both sub. and supersonic and that causes erratic turbulence around the projectile as well as a traveling shock wave in front of the moving object. Some projectiles (aircraft or bullets) handle this transition better than others.

Match 22 ammunition is usually loaded to leave the barrel at 1050 fps. or less or approximately .95 mach. The shape of these bullets handles the speed well and they drop out of the transonic velocity range quickly; usually about 50 yards out. High velocity 22 ammo. at 50 yards is solidly in the transonic range at this distance.
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Old December 1, 2012, 06:50 PM   #23
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Wow, some amazing info that will do me no good but loved reading it!

My take was 338 Lapua (designed exactly for the purpose of "to go long" accurately.)

And ditto on cost. Worried about a sheckle here or there for what you are putting into this?

Ok to fiddle, it human, its fun, but I am not into a twisted sort of rational, just admit its fiddling (or slicing the onion finer still)

At this point the rifle and pistol spectrum has been sliced and diced so finely there is nothing new under the sun.

Now perpetual motion, thee is a field you can really make in impact in!
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Old December 2, 2012, 12:37 AM   #24
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I have places where I can shoot out to 3000+ yards. I have problems with feral hogs, which poses for good target practice at long range. And I just really want to see how much performance I can squeeze out of this case without jumping to a .375 Snipetac or Cheytac or Allen Magnum. I don't want to do a 375 RUM. I don't want to go above a .590 bolt face. I want to base it off the .416 Rigby, neck it down to .375 having a .350 long neck and a 35 degree shoulder and also minimize body taper. If I can get atleast 2850 or 2900 fps with a 330 or 350 gr match grade .375 bullet, I will be happy.
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Old December 2, 2012, 01:06 AM   #25
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I am of the opinion that there are cheaper ways to do what you want, but in the spirit of firearms as a hobby, never let cost get in the way of a project.

I've seen some wilcats in the 9.5 bore before, and at best they are a "marginal increase" over the standard long range fare. But their creators have fun building them.

Have you shot much long range before?

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