.300 Remington Ultra Magnum (300 RUM) Once-Fired Brass for Reloading
Our .300 Remington Ultra Magnum (300 RUM) once-fired brass is washed and polished for reloaders looking for reusable .300 RUM cartridge cases. Steel and aluminum cases are removed, and this product is supplied as Boxer primer pocket brass unless otherwise stated.
This brass is Washed & Polished rather than fully processed. Cases normally retain their spent primers, so reloaders should complete their normal inspection and case-preparation procedures before loading.
Product Summary
| Specification | Details |
|---|
| Cartridge | .300 Remington Ultra Magnum (300 RUM) |
| Brass Type | Once-fired brass |
| Condition | Washed & Polished |
| Case Material | Brass; steel and aluminum cases removed |
| Primer Pocket | Boxer unless otherwise stated |
| Headstamp | Mixed headstamp unless otherwise stated |
| Deprimed | No; cases normally retain their spent primers |
| Annealed | No |
| Processing Level | Washed & Polished; not fully processed |
| Quantity | Customer receives the quantity advertised for this product |
Common Uses for .300 RUM Brass
The .300 Remington Ultra Magnum is a high-capacity .30-caliber rifle cartridge commonly associated with hunting and long-range rifle applications. Once-fired .300 RUM brass provides reusable cartridge cases for reloaders who already load this cartridge and want to perform their own case preparation and component selection using current published reloading data.
Quality Standards & Processing (Click to expand)
Washed & Polished .300 RUM Brass
This .300 RUM once-fired brass is wet washed, then dry tumbled and polished before packaging. Steel and aluminum cases are removed during sorting.
Washed & Polished describes the cleaning level of this product. It does not mean the brass is fully processed or ready to load. US Reloading Supply does not currently anneal its once-fired brass.
What to Expect from Once-Fired Brass
Once-Fired Brass is an industry product classification for previously used cartridge cases; it is not a representation that every individual case has been fired exactly one time. Cases may show normal evidence of prior firing and handling, including cosmetic marks, discoloration, minor dents, or variations in case-mouth condition.
No inspection process is perfect. Every reloader should inspect every case before reloading and remove any case that does not meet their standards for continued use.
For additional information about our standards and what to expect from previously used cartridge cases, see our Once-Fired Brass Information page.
Technical Specifications (Click to expand)
The .300 Remington Ultra Magnum is a standardized centerfire rifle cartridge. The specifications below are cartridge-reference information and are separate from the condition or processing level of the brass being sold.
| Specification | Details |
|---|
| Official Designation | 300 Remington Ultra Magnum |
| Common Abbreviation | 300 RUM |
| Cartridge Type | Centerfire rifle |
| Bullet Diameter | .308 in nominal |
| Maximum Case Length | 2.850 in |
| Published Trim-to Length | 2.840 in |
| Maximum Cartridge Overall Length | 3.600 in |
| Shoulder Angle | 30 degrees |
| Rim Diameter | .534 in nominal |
| Case Design | Beltless, rebated rim |
For authoritative cartridge and chamber dimensions, see the SAAMI 300 Remington Ultra Magnum cartridge and chamber drawing. The link opens directly to the .300 RUM drawing on PDF viewer page 121, which is printed page 108 of the standard.
Reloading Notes (Click to expand)
Inspect and Prepare Each Case
Because this product is washed and polished rather than fully processed, normal case preparation remains the responsibility of the reloader. Depending on the individual case and the reloader's process, preparation may include depriming, resizing, measuring case length, trimming when necessary, inspecting the case body and mouth, checking primer-pocket condition, and completing a final inspection before loading.
Check Case Length
The SAAMI maximum case length for the .300 RUM is 2.850 inches. Published reloading data commonly specifies a 2.840-inch trim-to length. Previously fired cases should be measured during case preparation rather than assumed to remain at a particular length.
Mixed-Headstamp Brass
Unless otherwise stated, this product may contain mixed headstamps. Different manufacturers' cases can vary, so reloaders seeking greater consistency may choose to sort their brass by manufacturer or headstamp before loading and should evaluate a change in brass using appropriate current published reloading data.
Use Current Published Reloading Data
Use current published reloading data for the .300 Remington Ultra Magnum and the specific components being used. This product page provides brass and cartridge-reference information and is not a substitute for a current reloading manual or component-manufacturer data.
Cartridge Information (Click to expand)
About the .300 Remington Ultra Magnum
Remington introduced the .300 Remington Ultra Magnum in 1999. Commonly abbreviated .300 RUM, it is a large-capacity .30-caliber centerfire rifle cartridge with a beltless case, rebated rim, and 30-degree shoulder.
The cartridge's design traces its lineage loosely to the .404 Jeffery case architecture. Unlike many earlier commercial magnum rifle cartridges, the .300 RUM does not use a belt. Its 2.850-inch maximum case length and 3.600-inch maximum cartridge overall length place it in the full-length magnum cartridge class.
.300 RUM vs. .300 SAUM
The .300 Remington Ultra Magnum and .300 Remington Short Action Ultra Magnum are different cartridges. The shorter cartridge is commonly called the .300 SAUM or .300 RSAUM. Brass, dies, and published load data for one should not be assumed to apply to the other.
This product is specifically .300 Remington Ultra Magnum (300 RUM) once-fired brass.
Frequently Asked Questions (Click to expand)
Is this .300 RUM or .300 SAUM brass?
This is .300 Remington Ultra Magnum (300 RUM) brass, not .300 Remington Short Action Ultra Magnum (.300 SAUM or .300 RSAUM) brass.
Is this new brass?
No. This product is Once-Fired Brass, US Reloading Supply's product classification for previously used cartridge cases.
Is this .300 RUM brass cleaned?
Yes. The brass is wet washed, then dry tumbled and polished before packaging.
Is the brass deprimed?
No. Cases normally retain their spent primers unless otherwise stated.
What type of primer pocket does this brass have?
This product is supplied as Boxer primer pocket brass unless otherwise stated.
Can steel or aluminum cases be included?
No. Steel and aluminum cases are removed during sorting.
Should I sort mixed-headstamp .300 RUM brass before reloading?
Reloaders seeking greater consistency may choose to sort mixed-headstamp brass by manufacturer. Cases from different manufacturers can vary, so a change in brass should be evaluated using appropriate current published reloading data.
Has this .300 RUM brass been annealed?
No. US Reloading Supply does not currently anneal its once-fired brass. This product is sold as Washed & Polished rather than fully processed brass. Reloaders who include annealing in their case-preparation process should follow their established procedures and equipment guidance.
How many times can .300 RUM brass be reloaded?
There is no fixed number of reloadings that can be guaranteed for previously fired .300 RUM brass. Case life depends on the individual case, firearm, load, sizing practices, and other factors. Inspect each case during every loading cycle and discontinue use when its condition no longer meets your standards.
How many .300 RUM cases will I receive?
You will receive the quantity advertised for the product being purchased. Package quantities for this product may vary.
Is Washed & Polished brass ready to load?
No. Washing and polishing clean the cases but do not complete normal case preparation. Inspect and appropriately prepare each case before loading.
