Bumping Bullets

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Last Post 06 December 2025

CBA Member

Wm Cook posted this 04 December 2025

This is as good a time as any to talk about bumping bullets. Does it help, does it not help? Is it practical for an every day shooter to put the pieces together or do you need to be a machinist?

Kieth put together a couple threads. (I’ll double check the links to make sure they work when I get on a computer.)

https://forum.castbulletassoc.org/thread/making-a-bump-die/

https://forum.castbulletassoc.org/thread/making-another-bump-die/

https://forum.castbulletassoc.org/thread/how-are-bump-dies-made/

I’m a machine shop illiterate and I can’t connect all the dots in his description. Not his fault. I’m just not that bright.

In the past five CBA BR Nationals we’ve averaged one in four that identified themselves as “bumpers”. Oddly enough only about 17% indicated that they “bumped” in 2025. The high point was back in 21 when about 6 out of 10 said they “bumped” their bullets.

Would “bumping” help John’s Tikka which has 20k+ rounds through his barrel? Maybe so?

I’d really appreciate some feedback from the group on this. Thanks, Bill C

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Lee Guthrie posted this 04 December 2025

The issue of "bumping" comes up frequently. Here are a bunch of articles in The Fouling Shot:

Bumping #14-5, 16-2, 18-13, 19-9, 19- 15, 20-16, 32-2, 44-22, 59-24, 60-16, 70-2, 79-4, 89-3, 131-11, 132-10, 134-8, 134-10, 144-15, 146-3, 153-9, 154-4, 172-3, 203-11, 237-4

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OU812 posted this 05 December 2025

Yes it is worth doing. I purchased a mini lathe few years ago to experiment. If my DA can do it, so can you. My last project was a custom 30 cal. bore rider made by Accurate Moulds that could be bumped to a required larger diameter. The bullet weight is about 178gr using linotype. Linotype must be queezed larger immediately after casting before bullet hardens overnight. The most important form section of die could easily be machined from aluminum. I wish NOE would make such mould and die, but it may hurt their mould sales. Once people figure out what shoots accurately... they stop buying.

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Wm Cook posted this 05 December 2025

Thanks Lee. I became a member around issue 278 and not sure how to research back issues. It would be nice to have though. It would also be nice to know what methods are currently being used.

For some reason I can't find a lot about bumping when searching the forum. The only work that had any meat to it was listed in my opening post. Searching on the internet gives about the same results. I'm guessing that means either that its useless or it's complicated to the point that you need to have a lath in your shop to get any benefits out of it.

The obduration of a cast bullet after it leaves the case is an unknown to me. It's a black box. I honestly don't know what happens to the shape of a bullet (be it 20/1 or Lino) as it gets pressure behind it. Understanding how accuracy is effected by the alloy being used, the tolerances of the bullet, leade, bore, is a work in progress for me. When I see a 4 and 1 or a 9 and 2, I'm OK if I can identify it as being a problem with man, material or method. But when it's "none of the above" that it becomes a problem for me.

Some would point to the kazillion other variables that can cause a big group and not press the conversation about bumping the nose. But there aren't too many breadcrumbs left laying around that will help me with my casting, handloading and bench practices. Wind is a different matter. Some day's I've got it wired, some days I don't. But as I keep trying to get a production class platform to consistently shoot 10 shot groups under an inch I've found more opportunity for improvement working with the components between the gas check and the first inch of the bore than anywhere else. And bullet to bore fit is my Achilles heel.

If an individual is using match grade casting, reloading and bench equipment and using match grade casting, handloading and bench practices there should be no reason for unaccountable fliers. Sorry for bloviating. I'll stay quiet now. Bill.

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OU812 posted this 05 December 2025

I may be able to help you and bump a few. What size do you need? I have .310 reamer for bands and .300, .301, .302 for bore ride section. Alloys of 18 bhn Linotype and softer 10 bhn. Lubed with LBT soft blue.

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Wm Cook posted this 05 December 2025

Thanks, I might take you up on that.

I have a project going in house using neck bushings and an arbor press. It’ll be Christmas before I pull together all of the pieces. If it works it’ll be repeatable. The few samples I worked with did make round bullets. It’s kind of exciting seeing a round bullet. As you said in another thread the key component seems to be the bullet to nose fit.

All of my bullets are out of round. And I know darn good & well that in and of itself solving that will not be the mystical cure. There a 90% chance that it’s just an itch that I want to scratch, but I would like to see 6 clean lands on the nose of my bore riders and not have a land snag on the fat side when chambering. Gotta keep trying, don’t you know 😊. Bill.

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DanLH posted this 06 December 2025

Bill,

Have you tried orienting the fat side the same direction when loading each shot? I always put my cavity dot up when I load the rounds.

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muley posted this 06 December 2025

Bill, one of our better shooters who has passed on was Dave Lee of the Northwest. He would go to a match with one -three cases and load at the bench with one case. He won many matches. I believe that cases can make a difference. when I have a shot go out , i set that case aside. when I have a few setasides I shoot them together and they seem to hold hands. u can make a "bump die" for ur single gun by using the throating reamer that was used to chamber the gun, that way the bullet will fit the throat.

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Wm Cook posted this 06 December 2025

Have you tried orienting the fat side the same direction when loading each shot? I always put my cavity dot up when I load the rounds

No I haven't Dan. All options are on the table though.

when I have a shot go out , i set that case aside

I shot with a guy that would take the case that caused the errant shot and flick it out in front of his bench. Past practices has been to shoot 20 cases at a time. Weighing the cases had no effect and as long as the necks were all turned concentric I would shoot them until they started loosing their spring back. In all honesty I would shoot 20 cases in a match or two and then toss them. I've never annealed either. But I am finding some nuggets in the bushing size that I'm using.

using the throating reamer that was used to chamber the gun

And, alas, when it comes to chambering, throating, I'm in the dark. For jacketed you just bought your own reamer and my smith cut them all the same. So much the same that I could (but didn't) interchange brass between barrels. So anything to do with lath work is in my blind spot. Again, just not smart enough.

Currently my focus is on how to make an imperfect bullet better fit the bore. I have records that show how accuracy differs between a borerider that's .001 smaller than another. So when I say bullet to bore fit it includes type of bullet (bore rider, sprtzer), tolerance (poor fit to bore) or undersized bore riders.

Its cold as everything around here

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MP1886 posted this 06 December 2025

Couple things. I'm sure you've heard of the swages or bump up die made for the 22lr. You can take the el cheapo 22lr stuff and bump it and make it shoot much much better.

Okay I have a bullet swage and I make dies for it. If I can duplicate the nose profile of what I'm wanting to swage I will swage a cast bullet and gas checking it and lubing it and swaging it improves it much. It has to be luble so that when you swage it you don't lose your lube grooves. And no it doesn't hurt the gascheck.

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CBA Regional Director

Tom Acheson posted this 06 December 2025

Two comments….if I were to get interested in shooting .30 cal. again, the bullets would be bumped. In 1998 I started bumping bullets for a .30 Kern and after that a .30PPC. Shot my best MATCH groups using bumped bullets in the .30 PPC.

We might think we have every load detail mastered so why bump? The largest unmasterable variable is in the mirror when we look at it. Tom

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John Alexander posted this 06 December 2025

"I shot with a guy that would take the case that caused the errant shot and flick it out in front of his bench."

This guy isn't very smart. Of all the factors that might cause a flier, a "bad case" is way down the list unless he is shooting a mixture of commercial and military brass.

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CBA Regional Director

Tom Acheson posted this 06 December 2025

Name is not important. At a Regional match in the mid 2000’s. Shooter next to me left his bench after our first 5-round 100-yard group. While the targets were changed he was in his camper swapping barrels on his HVY rifle. Upon his return to his bench, he said “if a barrel doesn’t shoot good right from the start, it never will “.

Interesting, aside from his concept…. He comes to match with several barrels AND he has the tooling and skill to quickly change out a barrel.

Yet another reason for poor performance. Tom

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Ken Campbell Iowa posted this 06 December 2025

factory barrels/chambers can definitely improve by shooting .... or by polishing/lapping ...

it could be that custom chambers that are already smoothed by the gunsmith will show indiscernable improvement by shooting..... and the main barrel may come lapped enough by the barrel people or the gunsmith.

Bumping Bullets

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