FAQ – Questions & AnswersCategory: Brass Ammo FAQHow to bump size rifle brass?
Victor Young asked 1 year ago
Can i bump size rifle brass?

6 Answers

Best Answer

Rotorm Staff answered 8 months ago
“Bumping” brass generally refers to resizing the shoulder of a fired brass cartridge casing to ensure proper chamber fit for subsequent firings. This process is often necessary when reloading brass for precision shooting disciplines.
The steps to “bump size” your rifle brass are as follows:

  1. Inspect and Clean Your Brass: Before beginning, ensure your brass casings are clean and free of dirt, debris, or any noticeable defects that may impair their usability or safety. Many reloaders use a sonic cleaner or tumbler for this purpose.
  2. Lubricate the Brass: Apply case lube to your brass to ensure smooth functioning in the resizing die. Be sure to lubricate the body and the inside of the neck. Avoid getting lube on the shoulder as it may cause dents.
  3. Measure Your Brass: Use a precision micrometer or similar tool to measure the shoulder of the fired casing. This will provide you with the initial measurement of the shoulder before bumping.
  4. Set Up Your Full-Length Sizing Die: Position your full-length sizing die in your reloading press. Adjust it according to the manufacturer’s instructions. The die should be set to slightly push back the shoulder of the casing.
  5. Bump the Shoulder: Place a lubed casing into the shell holder and raise the ram of the press, pushing the casing into the full-length resizing die. This will “bump” the shoulder back slightly, resizing the brass to ensure a proper fit in the rifle chamber.
  6. Check Your Work: After bumping the shoulder, measure the brass again to verify that the shoulder has been moved back. The general rule is to bump the shoulder back .001-.002 inches for bolt action rifles, and .003-.005 inches for semi-auto rifles to ensure reliable chambering. However, these figures can vary depending on your specific firearm and load.
  7. Clean the Brass Again: After resizing, you should clean the brass again to remove the lubricant.

Remember, always follow safe reloading practices. Improperly reloaded ammunition can cause harm to both the shooter and the firearm. When in doubt, refer to a reputable reloading manual or seek advice from an experienced reloader.
Finally, it’s worth mentioning that the repeated resizing or “bumping” of brass will work-harden it and eventually lead to case failure. Always inspect your brass for signs of potential failure, like cracks or separations, and discard any suspect pieces.

Jordan Staff answered 1 year ago

To bump the size of rifle brass, you’ll need to use a sizing die.

  1. Start by measuring the case length and diameter of the brass.
  2. Once you have those measurements, you can purchase a sizing die that will fit your needs. For example, if you have a .308 Winchester rifle, you would need a sizing die that is specifically made for that cartridge.
  3. Once you have the sizing die, place it in your reloading press and adjust it to the correct height.
  4. Next, apply some case lube to the outside of each case and insert them into the sizing die.
  5. Carefully lower the press handle and allow the cases to be sized down to their new dimensions.
  6. Finally, remove the cases from the die and proceed with the rest of your reloading process.

How to bump size rifle brass?

Lewis Staff answered 1 year ago

To bump the size of rifle brass, you will need to use a sizing die.

First, measure the length of the cartridge and then subtract 0.010 inches from that measurement. This is the amount you will need to adjust the die when sizing your brass.

For example, if a cartridge measures 2.010 inches in length, you would set the die to size it at 1.990 inches.

Be sure to check your reloading manual for more specific instructions on how to adjust your dies for different cartridges.

How to bump size rifle brass?

Cruz Staff answered 1 year ago

There are a few things you can do to bump the size of rifle brass.

  • One option is to use a Lee sizer die, which will resize the brass and also bump it up to the size you need.
  • You can also use a Wilson case trimmer to trim the brass down to size.

Whichever method you choose, be sure to use caution and take your time so that you don’t damage the brass. Happy reloading!

How to bump size rifle brass?

Antony answered 1 year ago

There are a few things you can do to bump size rifle brass.

  1. One method is to use an annealing compound, which will help to soften the brass and make it more malleable.
  2. You can also use a sizing die that is one size larger than the die you normally use.
  3. You can use a lubricant on the case mouth to help it slip over the expander ball in the sizing die.

How to bump size rifle brass?

Rotorm Staff answered 8 months ago
To bump size rifle brass, you will need the following:

  • A reloading press
  • A full-length sizing die
  • A case gauge
  • A set of calipers
  • A brass brush
  • A powder drop
  • A primer pocket swager
  • A bullet seating die
  • A crimp die


  1. Deprime the brass.
  2. Clean the brass in a tumbler.
  3. Measure the case head with calipers.
  4. Set the full-length sizing die to bump the shoulder back by 0.001-0.002 inches.
  5. Mount the die in the press.
  6. Size the brass.
  7. Check the case head with calipers to make sure it has been bumped back the desired amount.
  8. If the case head is not bumped back enough, repeat steps 5-7.
  9. Clean the brass again.
  10. Load the brass with your desired powder and bullet.
  11. Seat the bullet and crimp the case.

Here are some additional tips for bump sizing rifle brass:

  • Use a case gauge to make sure the brass is properly sized.
  • Clean the brass after each firing to remove any copper fouling.
  • Use a brass brush to clean the inside of the case neck.
  • Swage the primer pocket if it is too large.
  • Seat the bullet to the correct depth.
  • Crimp the case to prevent it from expanding too much when fired.

Bump sizing rifle brass can help to extend the life of your brass and improve the accuracy of your reloads.

  • What is bump sizing? – Bump sizing is the process of sizing the shoulder of a rifle case back by a small amount. This is done to prevent the case from becoming too tight in the chamber after repeated firings. Bump sizing can help to extend the life of the case and improve the accuracy of your reloads.
  • How much should you bump the shoulder? – The amount you bump the shoulder will vary depending on the cartridge you are reloading and the chamber of your rifle. A good starting point is to bump the shoulder back by 0.001-0.002 inches. You can then adjust the amount of bumps as needed to get the best results.