round nose bumped flat

[30hrrtt]

The practice of bumping a round nose boolit flat is talked about from time to time. Does somebody have a before and after picture. I don't have any round nose boolits but I'm contemplating getting a few new molds for some 30 cal rifles and if it works, it would open the possibilities. I could use them as cast for target and bump them flat for hunting.

[303Guy]

Not sure there would be any need to bump them flat for hunting. More likely one would be wanting to reduce expansion.

25-303 118gr at about 2800fps.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-402F.jpg

Some 303 Brit boolits.

Plain cast at about 1800fps.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-010F-1.jpg

This is how it started out.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-226F-1.jpg

This one was also a round nose once.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-602F_edited-1.jpg

[Shiloh]

I have NEVER found one of my .30 cal boolits with the gas check still attached.

Shiloh

[longbow]

My understanding is that bumping flat both provides a meplat and also enlarges the nose a little in diameter so snugger fit for bore ride.

I have not done it but do have an article in the Lyman Cast Bullet Handbook describing the practice using a Lyman 311284 if memory serves.

If you are interested, I could send you specific details or scan the article and send it.

Longbow

[lwknight]

At rifle velocity, round or flat in soft lead will make no difference to the target.
Even pointed boolits expand plenty well. They also get the nose deformed easier. Especially in a tube feed. A flat meplat cuts better holes in paper for target practice spotting.

However bumping the bore rider might be of benifit but, somehow I don't see it being noticeable.

[jdgabbard]

My next question is why bother bumping flat? There is a variety of FN boolits available for those that need those types of boolits, and plenty of RN designs as well. Lots of people use the 358430 with great success with 50/50 alloy. And it is a RN design...

[Dollar Bill]

Frank Marshall bumped 311284s to expand the nose to better fit the throat of the rifle. Don't recall the rifle for sure, but believe it was a Savage in 30-30. I read that article 30 some years ago and since then, have taken a few deer with my old Marlin pushing 311284s, flat pointed, at about 1700fps, in the Tennessee woods. The majority shot clear thru, straight path even when breaking ribs. Recovered one, one time, quartering shot. Recovered the bullet out of the left ham.
"Even pointed boolits expand plenty well. They also get the nose deformed easier. Especially in a tube feed." That's a questionable practice. Pointed bullets in tube magazines.
A flat meplat is basically a pointed bullet that already has the expansion started under controlled enviroment. They expand better on game, maintain their original path thru the game better, and generally are more accurate. BC suffers, but at most hunting distances, the loss in velocity is minimal.
Some folks don't have money to buy alot of molds, or anything else for that matter. We make do with what we have, buying the stuff you can make work no matter what the application. The 311284 has served me well over the years as both a hunting bullet and out to 600 yds as a target bullet.

[405]

For hunting my only question would be why? If the bullet is really hard the thing won't expand much if any no matter the shape of the front. If it is reasonably soft even the bullets without any meplat will form one upon impact. :-?

The next question I have about bumping a flat on a non-meplat bullet is how can the balanced, concentric form of the nose be maintained during the bump without the use of a special nose bumping die designed specifically in all dimensions for that exact nose? Seems like there would be a risk of damaging the concentricity or deforming the nose (balance). Haphazard hollow pointing would be similar with potentially the same negative outcome. All this seems folly unless maintaining accuracy is secondary to the whole issue--- be it hunting or target :confused:

[303Guy]

405 makes a good point.

Have a look at the difference in HP expansion in fine, dry, seasand.

HP 209gr 100% retention.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-452F.jpg

FP 246.5gr 99.8% retention. (First one).
http://i388.photobucket.com/albums/oo327/303Guy/MVC-451F.jpg

[NHlever]

Well, there is that theory that permanent wound channel size is at least partly determined by meplat size. I have bumped round nose boolits flat, but unless you have a positive stop it is very hard to control the size of the flat. The best luck I had was using a top punch with the shape I wanted. I also had a problem with bending some boolits, and not being able to control the bore riding diameter as well as I would have liked. It's worth a try though for those interested. I think Frank Marshall used a stack of washers to form his depth stop, but I haven't messed with it since I read his article.

[longbow]

I am not that much of a hunter and especially with small bore (.30 cal. is relatively small) so can't speak from experience having shot game.

The meplat issue has been researched in detail and generally with hard cast boolits the permanent wound channel is largely determined by velocity and meplat size. A soft alloy or soft pointed cast boolit should do fine even pointed and at moderate velocity. However, if you want to push velocity beyond 1600FPS or so then harder boolits are pretty much a requirement so may limit expansion to unacceptable levels for a pointed or round nose boolit. Then the meplat is a solution.

405 raises a valid point about bumping and concentricity. I know why some people bump ~ to produce a meplat or to expand the nose a bit for better bore ride or both. It seems to work but if I were posed with that problem I would lap the nose of the mould to fit my bore which is easily done and if I wanted a meplat, I would make a simple file die to give me a sharp edged meplat.

I have some articles by C.E. Harris that Dale53 sent me and amongst them is a good article on flat poining .22 bullets for better effect on game. I made a simple file die per C.E.Harris and made some flat point .22's for testing. Expansion in a Bullet Test Tube was dramatically improved over round nose. For hard cast boolits a nice sharp edged meplat would be formed at whatever size you wanted (70% seems a recommended size).

So, the short story is that the meplat is for better effect on game and bumping to provide better bore ride. Both can be accomplished in the sizing die at once. I would lap for the bore ride and file a flat point for the meplat rather than bump.

FWIW

Longbow

[303Guy]

Interesting read, longbow.

Expansion in a Bullet Test Tube was dramatically improved over round nose.I'd be interested in hearing more about your Bullet Test Tube. I've had heaps of fun with mine. We should start a thread.[smilie=1:


I have NEVER found one of my .30 cal boolits with the gas check still attached.I've been wondering about this, Shiloh. Mine might be staying on because they are cast in position. Also, driving my boolits fairly hard may be bumping the lead into the gas check - don't know.

[Rusty W]

I have a couple 30cal boolits I shot from an '06 using around 18gr of Unique. They still have the check on them. I use the Hornady crimp on type with a Lee push through sizer. I found them after I went to look at the group on the paper. They went through 2-3" of green elm tree and were laying on the ground. I picked them up and put them in the truck. I'll see if I can get a pic and post them tomorrow.

I could only find one of the two boolits. Here's a pic of it.