Best Arrow Setup for the Hoyt Carbon RX-9 Ultra (2025)
Short answer: a 250–300 spine shaft cut to 30" back-of-point, a 100 gr point and a 16 gr insert — about 434.6 gr finished at 11.6% FOC, leaving the Hoyt Carbon RX-9 Ultra near 282 fps. That is at 29" of draw and 70 lb. Six draw-length and draw-weight combinations are tabulated below, all of them inside Hoyt’s published range.
Same cam and same riser material as the standard RX-9, three and a half more inches of axle-to-axle, and two more inches of draw length available at the top. The Ultra is the one to buy if you are tall, and the arrow spec moves accordingly.
The recommended starting build
Every number below came out of the same engine that runs The Forge, at 29" of draw and 70 lb — the middle of this bow's published range. Nothing here is typed by hand.
- Shaft: Easton Axis 4mm Long Range, 250 spine, 9.8 gpi (.166 inside diameter; .229–.244" outside — archers shop by ID, so that is the one listed first)
- Cut length: 30" — draw length plus one inch, measured back-of-point, the Easton BOP convention
- Point: Field Point 100 gr
- Insert: Easton Axis 4mm HIT Insert, 16 gr
- Nock: Easton Axis Nock 4mm (.166), 5 gr
- Fletching: 3 × AAE Hybrid 23, 5.7 gr each, 3° offset
- Adhesive: 1.5 gr insert epoxy + 1 gr fletch glue — counted, because your scale counts it
- Total weight: 434.6 gr
- FOC: 11.6% — inside the Recommended Hunter Range (11–15%)
- Launch speed: 282 fps real-world (294 fps rated)
- Kinetic energy: 77 ft‑lb · momentum: 0.545 slug‑fps
- At 40 yards: 267 fps, 69 ft‑lb retained, 36.2" of drop
The spine is charted. The mass, FOC, speed, energy, momentum and drop are derived. See the note under the next table for what that distinction costs you.
Spine and build at three draw lengths
Three draw lengths inside the Hoyt-published 26"–32" range, at two draw weights, all on the same reference shaft. Arrow length is draw length plus one inch, measured back-of-point, which is the convention the Easton chart's length axis uses.
| Draw length | Draw weight | Arrow length | Effective draw weight | Spine window | Total weight | FOC | Speed: rated / real-world (fps) | KE (ft‑lb) | Momentum (slug‑fps) | 40 yd drop |
|---|---|---|---|---|---|---|---|---|---|---|
| 27" | 60 lb | 28" | 60 lb | 340–400 | 373 gr | 13.5% | 280 / 268 | 59.7 | 0.444 | 40.3" |
| 27" | 70 lb | 28" | 70 lb | 300–340 | 401 gr | 12.6% | 289 / 277 | 68.1 | 0.492 | 37.9" |
| 29" | 60 lb | 30" | 67 lb | 300–340 | 419.6 gr | 12% | 281 / 269 | 67.3 | 0.501 | 40.1" |
| 29" | 70 lb | 30" | 77 lb | 250–300 | 434.6 gr | 11.6% | 294 / 282 | 77 | 0.545 | 36.2" |
| 31" | 60 lb | 32" | 74 lb | 300–340 | 438.2 gr | 11.4% | 293 / 281 | 76.8 | 0.547 | 36.6" |
| 31" | 70 lb | 32" | 84 lb | 250–300 | 454.2 gr | 11% | 306 / 294 | 87.3 | 0.593 | 33.3" |
Charted versus derived, plainly. The spine window is charted: it comes
out of recommendSpineFromInputs, which reproduces Easton's published hunting selection
chart to 98% and Victory's to 89%. Effective draw weight is that chart's own intermediate
term. Everything else — total weight, FOC, speed, kinetic energy, momentum, drop — is
derived from the component sheet and a ballistics model, and derived numbers carry more error than
charted ones. Drop is computed for an arrow released level with no sight elevation, which is a
comparison figure between rows, not a hold-over.
What changes if you go heavier or lighter
One variable, four points, at 29" of draw and 70 lb on the same 250 shaft. Point weight is the lever most people reach for, so it is the one worth seeing whole.
| Point | Total weight | FOC | Effective draw weight | Spine window | Speed (fps) | KE (ft‑lb) | Momentum | 40 yd drop |
|---|---|---|---|---|---|---|---|---|
| 85 gr | 419.6 gr | 10.1% | 75.2 lb | 250–300 | 289 | 77.7 | 0.538 | 34.6" |
| 100 gr | 434.6 gr | 11.6% | 77 lb | 250–300 | 282 | 77 | 0.545 | 36.2" |
| 125 gr | 459.6 gr | 13.8% | 80 lb | 250–300 | 272 | 75.5 | 0.555 | 39" |
| 150 gr | 484.6 gr | 15.7% | 83 lb | 250–300 | 261 | 73.6 | 0.563 | 42.2" |
Read the columns against each other and the trade is obvious. Going from 85 gr to 150 gr moves FOC from 10.1% to 15.7%, costs 28 fps and 4.1 ft‑lb of kinetic energy, and gains 0.025 slug‑fps of momentum. Kinetic energy and momentum disagreeing is not an error — energy scales with the square of speed and momentum scales linearly with mass, so a heavier, slower arrow genuinely has less energy and more momentum. Momentum is the one that predicts penetration.
The direction that catches people out: adding weight at the FRONT weakens dynamic spine and pushes you toward a stiffer shaft — watch the effective-draw-weight column climb by 7.8 lb across that sweep. Adding weight at the BACK does the opposite, and at roughly half the magnitude. Heavier nocks, heavier vanes and a wrap all stiffen dynamic spine. A well-known spine calculator has that backwards; ours does not, and we show the working.
The 11–15% band is our Recommended Hunter Range for FOC. It is not a timid choice and it is not a compromise — it is where broadhead-tipped arrows recover from launch fastest without giving away the trajectory you paid for. Extreme-FOC builds have a place; a general-purpose hunting arrow off this bow is not it.
Speed: the rated number and the real one
Two speed columns run through this page and they are not the same claim. Rated is the IBO formula applied to Hoyt's published figure and adjusted for your draw length, draw weight and arrow mass — a bare bow's number. Real-world is that figure plus the measured gap between what bows of this model actually chronograph and what the formula predicts, which is where a rest, a sight, a stabiliser, a peep and a quiver all live.
| Bow | Offset vs the IBO formula | Tests (n) | Std dev |
|---|---|---|---|
| Carbon RX-9 Ultra (2025) | -12 fps | 3 | 6.3 fps |
That offset is the mean of 3 chronograph tests, with a standard deviation of 6.3 fps. 3 readings spread 6.3 fps wide. That is real evidence, and it is still not your bow. Put yours over a chronograph and the whole page recomputes around the number you measure.
At the reference build the two read 294 fps rated against 282 fps real-world. Every derived number on this page — kinetic energy, momentum, drop — is computed off the real-world figure, because that is the arrow that leaves your bow.
Tuning notes for the HBX Gen 4
HBX Gen 4 again, and again Hoyt publishes the chart. The Ultra's own chart covers a longer span than the standard RX-9's, which is the whole point of the model.
Cam lean is corrected with HBX cam spacers. On a longer axle-to-axle the same amount of lean produces less nock travel error, so the Ultra is measurably easier to get a clean bullet hole out of than its short sibling — that is geometry, not magic. Cams chase the tail; the rest moves 1/8" maximum and then you stop.
What I would actually do
Long-axle-to-axle bows get sold on "forgiveness" and the word is doing a lot of unearned work. What actually happens is that a given cam-lean error translates into a smaller angular error at the nock, and a given amount of hand torque moves the string less. Both are real. Neither of them fixes an under-spined arrow, and both of them will let you ignore one for longer, which is worse.
Draw length and mods on the Hoyt Carbon RX-9 Ultra
Two questions come before arrows: what draw lengths does this bow cover, and which module do I need. The first is published, and it is the one that changes your arrow.
- Draw length range: 26" – 32" (Hoyt published spec)
- Draw weights: 40-50, 50-60, 55-65, 60-70, 65-75, 70-80 lb
Hoyt publishes the chart, so here is the link rather than a retyped copy: Hoyt Carbon RX-9 Ultra draw length chart. Read your existing module number and position off the cam before you change anything, and read the case on the position letter — an uppercase and a lowercase letter are different holes a quarter of an inch apart.
Draw length is not a comfort setting, it is a spine input. One inch is worth roughly 3.5 lb of effective draw weight — about a third of a spine class — and it moves every sight mark you have. Run your real draw length through The Forge and the spine, mass, speed and FOC all move with it; the arrow spine calculator shows the method written out; the sight tape generator reprints the tape.
Bow specifications
| Spec | Hoyt publishes |
|---|---|
| Speed rating | 340 fps (ATA) |
| Axle-to-axle | 33.5" |
| Brace height | 6.375" |
| Let-off | not published by Hoyt on the spec sheet |
| Draw length range | 26" – 32" |
| Draw weight | 40-50, 50-60, 55-65, 60-70, 65-75, 70-80 lb |
| Mass weight | 4.3 lb |
| Cam | HBX Gen 4 |
Every figure above read from hoyt.com — 2025 Hunting Compound Specs (PDF) on 10 September 2026. If Hoyt revises them this page is wrong until we fix it — tell us at sal@sparrowexpeditions.com.
Common questions
What arrow spine do I need for a Hoyt Carbon RX-9 Ultra?
At 29 inches of draw and 70 pounds, with a 100 grain point and a standard insert, the engine's window is 250 to 300 spine on an arrow cut to 30 inches back-of-point. That window is charted against Easton's and Victory's published selection ranges. Change your draw length by an inch or your point by 25 grains and it moves, which is why this page prints six combinations rather than one number.
How fast does a Hoyt Carbon RX-9 Ultra shoot a real hunting arrow?
About 282 feet per second with the 434.6 grain reference build on this page. The rated figure for the same arrow is 294 fps. The difference is a measured chronograph offset of -12 fps for this model, averaged over 3 tests. Your bow will not read exactly this. Nobody's does.
What FOC should I run on a Hoyt Carbon RX-9 Ultra?
Eleven to fifteen percent is our Recommended Hunter Range and the reference build lands at 11.6%. That band is where a broadhead-tipped arrow recovers from launch quickly without giving away trajectory. Chasing 18 or 20 percent buys penetration you can also buy with total arrow weight, and costs you drop at every distance you actually shoot.
Where do these numbers come from?
The spine windows come from the same function that runs The Forge, which reproduces Easton's published hunting selection chart to 98 percent and Victory's to 89 percent. Weight, FOC, speed, kinetic energy, momentum and drop are derived from the component sheet and a ballistics model. The bow specifications come from Hoyt's own published page, linked on this page, read on 10 September 2026. Nothing on this page was typed from memory.
Do I need a different arrow for broadheads on a Hoyt Carbon RX-9 Ultra?
No — you need the same arrow, tuned. Build the shaft on this page with field points, get it flying, then put broadheads on the same arrows and shoot them at 30 and 40 yards. If the broadhead group walks away from the field point group, that is your tune talking, not your spine choice. Fix it at the cam and the rest, in that order, and only then consider a different shaft.
Shop this setup
- Shop all arrows & shafts →
- Inserts, half-outs and collars →
- Vanes and fletching →
- Check this 250-spine build in The Forge →
Not sure the 250 is right for your draw? Put your real numbers into the arrow spine calculator — it runs the same engine as this page and it will tell you when you are between classes rather than guessing for you. Then print the tape with the sight tape generator.
Nearby bows
- Best arrow setup for the Hoyt Carbon RX-9
- Best arrow setup for the Mathews Lift X 33
- Paper tune chart and the cam-lean correction table
Built by archnerds, for archnerds — The Forge by Sparrow Expeditions. Questions, corrections and chronograph data: sal@sparrowexpeditions.com.