A test of imbalanced bullets

[Bjornb]

After some back-and-forth with The Evil Boolit Brothers (Goodsteel and Sgt. Mike) we devised small test to try to quantify the effect that an imperfect cast bullet would have in a high velocity cartridge. We figured that Big Bertha, my XCB target rifle, would make a suitable test bench, and I prepared the test as follows:
20 bullets, NOE 165 gr. XCB variant, cast from Rotometals Hardball, visually inspected and weight sorted to within 0.1 grs, were selected. 10 of them were gas checked, lubed with Lars 2500+ and sized to .309, and then loaded over 45 grs. IMR4831. This load had given reasonable accuracy before, and had chronographed in the 2550 fps range, so no chronograph was used for this test.
The other 10 bullets were prepared like this:
119018119019
A 1/16" hole was drilled slightly off center in each bullet base, about 1/4" deep, to simulate an internal void in the bullet.
They were then prepped and loaded as described above, and fed to Bertha:
119020
119021119022
I'm sure I'm not the first person to run this test, but I wanted to show decisively the effect poor bullet casting has on target results. YMMV.

[Bullshop]

Simple and to the point, excellent demonstration!
One way to avoid such imperfections in cast boolits is to buy them from The Bullshop.:mrgreen:

[geargnasher]

So, how come your "good" bullets didn't all go into the same hole? :kidding:

Gear

[Bullshop]

My boolits all go into the same hole as long as the hole is big enough. :roll:

[FrankG]

At what distance were these shot ?

[Hannibal]

The Evil Boolit Brothers. That's got a nice ring to it. :guntootsmiley:

[JSnover]

There is a YouTube video of .22 rf bullets with their noses all hacked up, for the same purpose. Some were predictably wild, others were surpisingly accurate.

[Bjornb]

So, how come your "good" bullets didn't all go into the same hole? :kidding:

Gear

THAT, Gear, would have meant that I had found the Holy Grail and was lounging on a Caribbean beach with hula girls serving me drinks with little umbrellas!:2 drunk buddies:

[Bjornb]

At what distance were these shot ?

All shot at 100 yards Frank. Sorry for not including that.

[johnson1942]

this is why i swage all my bullets for all my guns.

[runfiverun]

That 45 gr 4831 load is the one I use in my 308 sept I use the h/sc version and .2gr more

[FrankG]

I am surprised they are still on paper at that distance or even cutting a clean hole being so out of balance .

[Bjornb]

I am surprised they are still on paper at that distance or even cutting a clean hole being so out of balance .

I thought the same before I shot them. (See Runfiverun's tag line).

[geargnasher]

:kidding:


kinda like this Gear .749" - bullet dia of .308 equals .442" five shots 100 yards with a issue in 1943 original barrel 1903a3 . I know it not exactly one hole but I'm working on it. :kidding:
Evil boolit brother #2 casted those 165 XCB boolits and evil boolit brother #1 fired them LOL

I'd get further along if Evil boolit brother number one would cast better boolits durn it...LMAO

OH, I thought one had to have a $1,500+ custom rifle with a superuberpremium5rrifledhandlappedreversetaperleft hand1-in-18twistheavyvarminttargetcrownedmatchchambered wondergun on a 23 -lb F-class chassis and a 6-oz. trigger to get under half an inch with cast bullets? I know what you did, you put waxed paper over the target to catch the lube spatter and powder burns, didn'tcha?!

Good shooting, Mike. It's a good feeling when you get an old warhorse to clump them all up like that, isn't it?

Gear

[geargnasher]

OK, I was changing the lightbulb in the bathroom this morning, slipped off the edge of the tub, and hit my head on the toilet tank lid. When I awoke, I had this thought: (not really)!

Cast bullet cores pretty close to final shape, use a swage-friendly alloy like 2-3" antimony and less than 1% tin. Make it a single-lube-groove design like 45 2.1's .30 Silhouette design. Swage them using a swage press and matching form die. Trapped air would bleed out around the ejector pin at the nose, I think. I know, all been done before....BUT.....here's my epiphany: Have a three-piece tool steel negative of the lube groove that are placed into the groove prior to swaging, then popped out afterward (could put little divots on the outer edge of the ends of the three pieces to help dig them out with a pick). Swaged, low antimony bullets have proven themselves to be better than cast, but keeping the lube grooves open during the process has been a challenge. The three-piece ring might just solve that, and I think it would be practical to use, though difficult to machine.

The bullets could be air cooled and would be 8-10 bhn right after casting, then could be oven heat-treated after swaging to achieve 20-24 bhn hardness.

See what EBC#1 thinks about that. He is rumored to have some precision machinery at his disposal, too.....

Gear

[Walter Laich]

There is a YouTube video of .22 rf bullets with their noses all hacked up, for the same purpose. Some were predictably wild, others were surpisingly accurate.
Saw that one too. Was surprised that so many hit the target

[garandsrus]

Liquid is not compressible so filling the lube grooves with lube before swaging should keep them unchanged after swaging.

[Love Life]

Liquid is not compressible so filling the lube grooves with lube before swaging should keep them unchanged after swaging.

Correct and was covered in the swaging section quite a few times, but I very much thank you for posting it here.

I emailed a couple companies to make me some swage dies to swage my 30 XCB after casting/lubing, but no replies yet.


BjornB, thank you for all of your time and effort here and if there is anything I can do for you to help please let me know.

[cbrick]

Outstanding test, thanks for the work and the post. I'm kinda surprised the bad bullets grouped as good as they did but it sure does prove the point, perfect bases with perfectly installed checks.

There was another such test (Harris maybe?) I think in the NRA cast bullet book. Very similar results.

Rick

[williamwaco]

OK, I was changing the lightbulb in the bathroom this morning, slipped off the edge of the tub, and hit my head on the toilet tank lid. When I awoke, I had this thought: (not really)!

Cast bullet cores pretty close to final shape, use a swage-friendly alloy like 2-3" antimony and less than 1% tin. Make it a single-lube-groove design like 45 2.1's .30 Silhouette design. Swage them using a swage press and matching form die. Trapped air would bleed out around the ejector pin at the nose, I think. I know, all been done before....BUT.....here's my epiphany: Have a three-piece tool steel negative of the lube groove that are placed into the groove prior to swaging, then popped out afterward (could put little divots on the outer edge of the ends of the three pieces to help dig them out with a pick). Swaged, low antimony bullets have proven themselves to be better than cast, but keeping the lube grooves open during the process has been a challenge. The three-piece ring might just solve that, and I think it would be practical to use, though difficult to machine.

The bullets could be air cooled and would be 8-10 bhn right after casting, then could be oven heat-treated after swaging to achieve 20-24 bhn hardness.

See what EBC#1 thinks about that. He is rumored to have some precision machinery at his disposal, too.....

Gear

Gear,

For a couple of years I have been doing something similar.

Cast conventional .357 bullets either 148 grain wad cutters ( 3 lube grooves ) or 150 grain ( one lube groove ) with conventional lube grooves. Lube them in a Lyman 4500. Then with BT Snipers dies, swage them into hollow point form factor. The lube grooves cannot be swaged when filled with lube. ( Lyman 50/50 lube will not compress. ) They shoot great and reduce average group size by about 20%.

[Love Life]

Gear,

For a couple of years I have been doing something similar.

Cast conventional .357 bullets either 148 grain wad cutters ( 3 lube grooves ) or 150 grain ( one lube groove ) with conventional lube grooves. Lube them in a Lyman 4500. Then with BT Snipers dies, swage them into hollow point form factor. The lube grooves cannot be swaged when filled with lube. ( Lyman 50/50 lube will not compress. ) They shoot great and reduce average group size by about 20%.

Swaging them eliminates voids...hopefully. I spoke of this on the original 30 XCB thread...or maybe it was one of the other threads that disappeared during the fracas.



Back to my hole.

[leftiye]

Try buggering up the bases and see what happens.

[runfiverun]

just lube them before swaging them, the lube is liquid under pressure and resists squishing of the lube groove.

i do some 223 boolits pretty much like Gear's post.
i have to push them slower than 2800 by quite a bit but they work great on varmints and are VERY accurate.
i also just squish the soft core of a jacketed bullet into shape and use a large primer cup as a psuedo [slightly undersized] gas check.
it works pretty darn well with tumble lube at velocity's in the 22lr+ velocity range and is super simple to make.

anyway what i do is use a batch of my sized,lubed, and checked, weight sorted boolits.
then run a batch through my 228 sized swage die, this reshapes them slightly and enlarges them too.
i then take them back out to the garage and run them through the lube sizer in a 227 die.
this squares the bases up exactly the same, and also may move some of the air out of the cast boolit.

[Any Cal.]

I figure @ 7 grains... not really a surprise that they don't shoot. The same deal but removing only 1/2-1 grain of lead may prove more informative, especially if someone else shot several groups. 3 groups of 7 of each type, shot in rotating batches by a shooter who could not identify the 'good' ones. I would bet the difference in group size would be very close to statistical differences betwen similar loads.

[Bjornb]

Any idea of the weight difference between the good bullets and the drilled bullets? Up till now I have been culling my castings to .5 grains. 2 tenths above and 2 tenths below. I might need to start segregating the bullets into smaller batches.

Marvin

I drilled 10 new holes exactly like those in the test, to the same depth. I saved all drill shavings, and weighed them on my Lyman electronic scale. They weighed 4.2 grains, making for an average 0.42 grains weight loss per bullet. It doesn't take much.

[chill45100]

Food for thought. What effect would the void have if indexed in the chamber uniformly? Granted that an unintentional void might not appear on the surface or in the same place every time. My silhouette rifle holds better groups with indexed loads. Just wondering for the sake of knowing.
chill45100

[Any Cal.]

By volume those voids should have been more than 2grains each, I think I was thinking 1/8" holes at the 7g figure. Maybe weigh the bullets before and after drilling, rather than the shavings.

[Smoke4320]

I just a similar test with Noe 311247 HP bullets.
This were rejects having shrunken in section on one side just in front of the first driving band.
Shot at 50 yds velocity approx 1015 fps out of a Noveski 10.2" 300 blackout & Yhm suppressor (Shooting faster would have opened groups much larger)
10 shoots measured 1.6"
Good bullets sorted to 1/2 grain get me between 1/2 to 3/4 " groups
So even at that slow speed & short distance unbalanced bullets made larger group sizes

[Bjornb]

By volume those voids should have been more than 2grains each, I think I was thinking 1/8" holes at the 7g figure. Maybe weigh the bullets before and after drilling, rather than the shavings.

OK I did that.

119719
Before
119720
After

[MBTcustom]

You're average booliteer has more weight variance than that in his castings as a matter of course (However, that doesn't mean those variations are off balance.).
This just shows how little it takes to blow a group at high velocity.
I have been involved with the high velocity pursuit since about .02 seconds after I realized that leading is not guaranteed to happen over 1800fps. The debate seems to have settled into two camps. One that seeks to make perfect boolits that are deformed evenly and another camp that says deformation is a given and to work around it. From the first, I believed that combining the two ideas was the way to achieve fast access to real world HV accuracy that the average Joe could reach.
This post shows that succinctly I think. Here Bjorn is using a rifle that does not stress an imbalanced boolit, and he has also disciplined himself to create very good quality projectiles and he walked right up to HV cast and gave it a kiss easy as you please. Took him less than 2 months to make it happen and he'd never done it before.
Some would say that it's just because his rifle is slow twist.
However, this thread shows very well that slow twist isn't all there is to the equation. He has to have both in order to get there.
In fact, If I ran his ammo in my 10 twist, the group would open up there as well even though both rifles are identical in the chambers and throats.
Excellent demonstration sir!

[cbrick]

119719
Before
119720
After

Another tip that may well help your HV testing. See those round boolit bases? They should be, need to be completely filled out and square/sharp edged. A more forceful, larger sprue puddle should help considerably. The easiest way to inspect boolit bases is when you open the sprue plate before you open the mold blocks, every base should be completely filled out without any rounded edges. When I'm casting match boolits any bases I find not perfect go straight into the sprue pile, don't care what the rest of the boolit looks like or what it may weigh, it's no better for shooting a match than shooting the sprue's would be.

Covering up a defect with a check or lube doesn't make it go away, it's still there and still a defect.

Rick

[Bjornb]

Another tip that may well help your HV testing. See those round boolit bases? They should be, need to be completely filled out and square/sharp edged. A more forceful, larger sprue puddle should help considerably. The easiest way to inspect boolit bases is when you open the sprue plate before you open the mold blocks, every base should be completely filled out without any rounded edges. When I'm casting match boolits any bases I find not perfect go straight into the sprue pile, don't care what the rest of the boolit looks like or what it may weigh, it's no better for shooting a match than shooting the sprue's would be.

Covering up a defect with a check or lube doesn't make it go away, it's still there and still a defect.

Rick

I was wondering how long it would take for an oldtimer to catch the round base. It didn't take long! The bullet was a cull, and as I was too OCD to use a perfectly good bullet just for this weight test, I figured this one would do just fine. It goes in the next melt.....:castmine:

[cbrick]

Ah, I see.

Hey, wait a minute, are you calling me old? :veryconfu

Rick

[Bjornb]

Old? Who's old?

Old-timerFrom Wikipedia, the free encyclopedia



Old-timer may refer to:


A veteran (http://en.wikipedia.org/wiki/Veteran)
An antique (http://en.wikipedia.org/wiki/Antique_car) or classic car (http://en.wikipedia.org/wiki/Classic_car) in Dutch and German as a legal definition (written unhyphenated)
Oldtimers (Pern) (http://en.wikipedia.org/wiki/Oldtimers_(Pern)), a group of dragonriders in the fantasy fiction series Dragonriders of Pern
A line of knives manufactured by Imperial Schrade (http://en.wikipedia.org/wiki/Imperial_Schrade)
Oldtimer Grand Prix (disambiguation) (http://en.wikipedia.org/wiki/Oldtimer_Grand_Prix_(disambiguation)), a name of two different historic motorsport events
The Oldtimers (http://en.wikipedia.org/wiki/The_Oldtimers), a 1974-75 Canadian television series

[btroj]

Ah, I see.

Hey, wait a minute, are you calling me old? :veryconfu

Rick

Why yes he is. Good thing is you won't remember it tomorrow.

[cbrick]

Why yes he is. Good thing is you won't remember it tomorrow.

Remember what? :veryconfu

Rick

[Any Cal.]

Well that makes the test more interesting, to me at least. Still not sure why the hole 'weighs' so little, but interesting to see that the small difference becomes so noticeable. None of my rifle cast were much closer than 1/2g, it makes me think that the results I got were not bad for the boolit quality...

[ABluehound]

My information is not as scientific. Through my own observations I have seen where bullets fired from my rifles (more so from auto-loaders) have tighter groups with a meplat cut into them even if it is slight. My suspicion is that even a tiny imbalance in the tip is more detriment to accuracy than a large imbalance at the rear and the meplat makes it more accurate because it keeps the gyroscopic mass of the projectile more central to rotation even after a traumatic feed. I am convinced that concentricity is the single most important factor of all, from barrel wall thickness to the bullet in flight.
Think of a generic high velocity .30 simplified for easy math: 1:12 rifling, 3,000 fps... equals 3,000 rotations per second and 60 seconds in a minute... that has that bullet zinging spinning at 180,000 RPM. Now for a 60 grain .223 from a 1:7 twist with a similar 3,000 Fps is spinning at around 309,000 RPM. If the wobble is at the front instead of the rear the gyroscopic stability is going to suffer more because percentage wise the bent tip is wobbling more than an imbalance in a heavy base with a tiny (by % of the cross sectional area comparison) void.

[cbrick]

My suspicion is that even a tiny imbalance in the tip is more detriment to accuracy than a large imbalance at the rear

I think that decades of testing this proves that your conclusion is wrong. The rear of the bullet steers the bullet and a minor flaw on the base is more detrimental to accuracy than a larger flaw on the nose. Think of it also as where most of the weight is, on the front or in the base?

Rick

[MBTcustom]

I think that decades of testing this proves that your conclusion is wrong. The rear of the bullet steers the bullet and a minor flaw on the base is more detrimental to accuracy than a larger flaw on the nose. Think of it also as where most of the weight is, on the front or in the base?

Rick

Also, damage to the nose is often closer to the centerline of rotation than damage to the base, and thus centrifugal force cannot have as dramatic an effect on it.
I once had the crazy notion of breaking my addiction to handloaded ammunition. I was just going to buy my ammo like a normal person does. Well, I had a Tikka T3 hunter in 30-06 and tried several different factory loads in it to find which one was the most accurate.
On a whim, I picked up some ammo that they were selling cheap at the local gun shop. I figured it would be good for blasting etc etc, and didn't really expect much because it had been shipped here from Africa and all the noses of the bullets (soft point spitzers) were mushroomed over in a very uneven manner. I figured what the heck.
Funny thing is, that was the most accurate ammo in that rifle! I could cover five shots with a dime every time at 100 yards with that ammo!
Didn't make sense at the time because I thought the same as you, but I know better now. (BTW, my twelve step program failed misseribly and I went on reloading binges. Now I just try to control my habit to the point that I don't go broke (most of the time that is).)
Conversely, damage to the base of the bullet, or an unsquare, unbalanced, or otherwise janky rear end will show pretty bad results as the OP demonstrated.

The importance of concentricity and ammunition RO has more to do with realizing a level of consistency over a lot than it does all by itself for each piece of ammo. Precision does not always equal consistency (ie you can be precisely wrong).
This is all a wash at the end of the day, but knowing why can often help you understand when, how, and where.

Not that I'm any expert. I'm still discovering what problems can be beat to death with precision, and where it matters. I used to think it was a cure all pill, but now I realize that precision only does you good when you have an entire system that is precise enough as a whole to make use of it. Knowing what to focus on, and having an accurate list of priorities that will lead to excellent accuracy is the goal. It's easy for me to get hung up on details that just don't matter. So often, I think I find myself bringing windex and a roll of paper towels and cotton swabs to a tornado disaster area. Lets get done with the bulldozer first, then we can talk about the cotton swabs. LOL!

In this case, I really think that the fact that our boolits are base pour, is really a detriment to consistent loads. Getting the base filled out properly in a well balanced manner is of paramount importance, and really comes down to the skill of the caster.
This is also why I sort my boolits by weight. If a variation in mass is present (it's either that, or you got an inclusion in your lead of some very light weight material) it is far more likely that it will be in the base of the boolit than at the tip. Right where it can do the most damage.

[Bjornb]

I think that decades of testing this proves that your conclusion is wrong. The rear of the bullet steers the bullet and a minor flaw on the base is more detrimental to accuracy than a larger flaw on the nose. Think of it also as where most of the weight is, on the front or in the base?

Rick

Rick,
thanks for the post. You are most certainly correct here. Just came from the range where I got some trigger time with my Ruger Gunsite Scout (I'm in heavy XCB withdrawal until Tim gets the new barrel fitted to Bertha). I loaded up some ammo with SMKs that ALL had meplat/HP damage, just to shoot them and not let them go to waste. After sighting in a Bushnell 3x9 scope the rifle shot this group of 10 (100 yards):
120630
(yeah I know, 10-shot groups, the 8th 9th and 10th were the 3 to the right, should have quit while I was ahead).
The BASES and BOAT TAILS were perfect on all these bullets. What kind of damage? Dropped on the floor, jammed into the lands while making dummy rounds, etc.
It's pretty clear that nose damage is less critical.