Sabot's in F-open?

There is nothing in the rule book explicitly prohibiting them.

Any - Ammunition of any description that may be fired without danger to competitors or range personnel. Tracer or incendiary ammunition is prohibited. The use of armor piercing or any other type ammunition may be prohibited by local range or match regulations. Any ammunition that repeatedly blows primers or splits cases will be ruled defective or unsafe, and will be removed from the firing line.

This is Rule 3.17b here: https://rulebooks.nra.org/documents/pdf/compete/RuleBooks/HPR/hpr-book.pdf

Sabotted bullets aren't accurate enough for any kind of match shooting. Really poor accuracy was the primary reason Remington discontinued the Accelerator line years ago. They didn't shoot worth beans. Picture a 55 grain .223" bullet out of a .30-06 at ~4,080 FPS. Came in .30-30(~3,400 FPS) and .308(~3,770 FPS) too. The idea was for the one gun hunter to be able to use his deer rifle for varmints. Like a varmint would care that it was killed with a 180 or a 55.
F-Class is a Canadian invention. One of our "old guys" who got too old to shoot 'Target Rifle' invented it. A fact conveniently ignored by our Southern cousins. snicker. Any rifle, any sights, any ammo(including reloads), depending on the subdivision with scopes and bipods allowed. The ammo being subject to "Range Rules", but trace, incendiary and AP are not allowed on most civilian ranges anyway.

The M1 Abrams fires a drag stabilized 12lb Tungsten "fletchette" from a smooth bore barrel with discarding sabot.
Twist rate is going to be the problem. A 143gr ELD-M requires at least a 1/9" twist, 1/7 or 1/8 being better.
The .375Ruger has a 1/12"twist. Too slow.

Two problems with the Remington "Accelerator" sabot loads. Marginal quality sabots, and marginal bullets. I still have part of a box I bought on clearance about 40yrs ago. (.30/06) They were 3-4" at 100yds, IIRC.
Would do a number on a coyote or feral dog at close range.

I have some vague notion, perhaps entirely mistaken, that many fin-stabilized discarding sabot rounds intended to be fired from rifled cannon barrels (e.g., 105mm L7 tank cannon) have slip rings or bearings on the sabot intended to reduce or eliminate the rifling spin applied to the flechette/dart/projectile itself.

unless your friend has access to an amazingly good 3d Printer, you will probably be much better off machining the sabots.

Think of the difficulties getting concentric alignment with the bore. High-precision rifle shooters take all kinds of steps to get concentricity in the bullet/brass/bore interface... adding one more link in the chain is surely going to pose some big challenges. I would think the sabot has to be made to VERY exact measurements.

DLrocket89 said:

we're engineers and we're bored

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That falls right up there with "hold my beer..."

On the barrel FEW. Take a hard look at using an annular recoil lug, in a tube gun type setup. I think the symmetry will help.

When one re-invents the wheel, it's nice to know that it came out round. Or, great minds think alike.

Works on an M1 Abrams.

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But where are you going to get DU to cast bullets.

Bored engineers, that's a new one on me. I'm familiar with the "engineers with too much time on their hands" paradigm, but never bored.

Way better results will come from necking the 375R case down instead of fooling with sabots. No way I'd believe a 3D printer will produce as clean of sabot as could be turned anyway, but the entire project is a non-starter for me - if you're buying a barrel, just neck it down.

Personally, I'd run Quickload profiles to determine the appropriate caliber for this job. Guys have been doing a 300-375 Ruger for a handful of years, even improved versions, and I'm sure someone has necked it down to 7mm or 6.5 by now.

You can test your ideas a lot cheaper in a .30-06 and see if you can improve on the Accelerator. If you can't beat Remington, why spend money on a new barrel and all supplies?

taliv said:

i'd start by calling the bullet mfg and inquiring about max velocity. if you push some of the long skinny bullets too fast, they are prone to disintegrating mid-flight due to the rotational stress

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I've read compelling analysis that suggests the disintegrations in flight are related to stresses and heat imparted by friction in the barrel combined with rotational stress. The rotational stress alone might not be a problem without the jacket weakening and core melting that occur without a sabot.

We're also not looking at barrels with terribly fast twists. If he's plugging a 375 Ruger with baby pigs in a blanket, he'll be playing with a 1:12" twist, far too slow to cause catastrophic destruction of these bullets - I might even be concerned they aren't spinning fast enough.

I've always wondered about the accelerators - there's really nothing which stops the bullet from "slipping" inside the sabot, and far less surface area for the sabot to grip, plus the sabot being about twice as thick as those used in front stuffers... I'd be interested to see any kind of math, or any kind of testing done to see if the rotational inertia of the bullet is enough to overcome the friction against the sabot... I suppose the extreme pressure against the base of the bullet in the acceleration might be another "gripping" factor to prohibit slip between the two... Interesting thought experiment I've never gone through before... Might be something you'll need to consider as you design your sabot...