What causes a bullet to tumble?


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Skulptor
January 31, 2013, 01:42 PM
Has anyone noticed Titegroup causing lead cast bullets to tumble?? I'm working with 125gr bullets. (9mm in a P99) I started with 3.2gr of TG.
Could it be a softer lead in these bullets being the issue? This is the first I have tried of these altho I have worked up cast 115's and cast 147's..

I know that TG is a fast burn but I understand if "too fast" were the issue it would have large groups, not tumbling. My groups are pretty good.

I have been reading quite a bit and searching the internet and found that maybe the bullet may be spinning too slow as the patterns range from OK to good.

115 and 147 FMJ's shoot fine, as well as 147 cast lead from another manufacturer.

I also "plunked" the barrel for each and make them about .050 short of max.

I thought this was interesting.
http://www.acbsystems.com/boards/rohrbaugh/basefile/tumbling.htm

I can include more details if needed but after writing a nice long detailed post and then the computer ATE IT :fire:, I thought a pithy post was better this time.
Thanx...

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rcmodel
January 31, 2013, 01:52 PM
115 and 147 FMJ's shoot fine, as well as 147 cast lead from another manufacturer.If those bullet weights shoot fine, it has nothing to do with rifling twist, or spinning too slow.

By tumbling, do you mean you are getting bullets hitting the target completely sideways and cutting side-view bullet holes.

Or do you mean your paper target has non-circular holes & tears in it?

If the latter, that is often cause by a free-hanging paper target with no backer-board behind it so the bullet can cut a clean hole.

1. Check for bore leading.
2. Bump up your powder charge.
Your 3.2 grain charge is barely a minimum starting load by some sources, and way under a starting load in others. You may not have enough pressure to bump up the bullet & seal the bore.

Hodgdon says 3.6 is a starting load & 4.0 is max with a 125 LCN bullet.

rc

Skulptor
January 31, 2013, 03:00 PM
Thanx RC.
By tumbling, do you mean you are getting bullets hitting the target completely sideways and cutting side-view bullet holes

Yeah, Key Holing, was another term I saw used. I am shooting into IDPA cardboard targets so it isn't a "paper thing". The hole can be fairly dramatic so it's very obvious. These are round nose bullets by the way. I doubt that matters but.......

The bore is clean. And it can happen the first shot out of a clean barrel.

My charges were- 3.2, 3.4, 3.6, 3.8. The middle 2 were the worst. I am trying to find the lightest charge with best accuracy since I am doing this for shooting IDPA, for low recoil and less cost (which is why I am trying lead). Plus, I know it's best to start low and progress up. I didn't want to go to 4.0 but I may try. (I'm a bit over cautious, I guess) I do check the primers and bulge when I get "up there".

I also used those bullets with Win.231. 2.8gr., 3.0gr. and 3.2gr. and all failed to eject. But man was there some beautiful patterns! :what: :D I will be stepping that up as well.

Thanx a bunch!!!

GLOOB
January 31, 2013, 04:05 PM
Are you getting heavy lead fouling? The rifling isn't stripping the bullet, maybe?

Skulptor
January 31, 2013, 04:10 PM
Nope, doesn't really seem to be. The barrel seems to "lead" a bit but no more than anyone would expect. When I shoot lead, I always make sure the barrel is slicked up.
Thanx.

blarby
January 31, 2013, 07:22 PM
What causes a bullet to tumble?

Physics.

rodregier
January 31, 2013, 07:45 PM
I found a large jump to the leade in the barrel throat with cast lead bullets can cause tumbling in 9mmx19. Seating the projectile further out was helpful in eliminating it.

Once of the nicest molds for 9mmx19 cast bullets I found was the Saeco-Redding #377. Great design for minimizing the jump without forcing long seating of the projectile (leaving too little inside the case).

http://www.redding-reloading.com/online-catalog/88-bullet-moulds-charts

twice barrel
January 31, 2013, 07:48 PM
Under size bullets (or over size bore) could also contribute to this.

Jim Watson
January 31, 2013, 08:10 PM
To shoot IDPA, that 115 gr bullet has to be going 1087 fps minimum so there is no point in ladyfingering the loads.
The Hodgdon starting load of 3.9 gr is only rated for 1075 fps and that in a tight test barrel that your mass produced gun will not likely equal.
Put in more powder and hope the bullet "bumps up."

I have seen more trouble getting a 9mm to shoot with lightweight cast bullets than any other combination.

fecmech
January 31, 2013, 08:16 PM
Twice barrel nailed it. you need bigger bullets. size to .357-.358.

Wylie1
February 3, 2013, 02:12 AM
My guess would be it would have to do with the length of your bullets and the speed they are traveling at a given didstance.

As the bullet slows out at a curtain distance the pressure wave invelopes the tail of the bullet making for unstable flight.

Plastic tipped TSXs are known to do this through .308s but I forget at what distance and speed.

I've seen a guy at the range shooting a .204 bullet that consistantly flipped or key holed right at 100 yards.

murf
February 3, 2013, 02:52 AM
don't crimp them so much (could be reducing the diameter). and measure the diameters of the 147 and 124 grain bullets and compare. the 124s may be a bit narrow as twice barrel was saying.

murf

greyling22
February 3, 2013, 09:32 AM
maybe it's just me, but I've never seen keyholing without accompanying leading. And I had/have a terrible time with leading in 9mm. It's a high pressure round that is often shot in guns with shallow rifling designed more for jacketed bullets, and sometimes have oversize bores.

If you had leading as well look for undersized bullets. Are you casting your own? Sometimes molds lie about what size they are actually dropping. It may say .356 but actually be dropping .355. Next I would look for too fast a powder generating too much pressure, to soft a bullet being shot too fast, too hard a bullet being shot too slow, bullet seated too deep, in that order.

bds
February 3, 2013, 10:06 AM
125 gr lead ... I also used those bullets with Win.231. 2.8gr., 3.0gr. and 3.2gr. and all failed to eject ... But man was there some beautiful patterns!
That's because you are using way too low of powder charges. I use 3.8 - 4.0 gr W231/HP-38 with 125 gr lead bullets. Produces accurate loads without leading or keyholing.

From 1999-2005 Winchester load data (http://www.thehighroad.org/attachment.php?attachmentid=159609&stc=1&d=1329800605)

http://www.thehighroad.org/attachment.php?attachmentid=176515&stc=1&d=1356273892


Current Hodgdon load data (http://data.hodgdon.com/cartridge_load.asp)
125 gr Lead CN W231/HP-38 OAL 1.125" Start 3.9 gr (1009 fps) 25,700 CUP - Max 4.4 gr (1086 fps) 31,200 CUP

Skulptor
February 3, 2013, 02:11 PM
Good stuff guys, THANX!!!

Is there a measurement to use for checking after I crimp? To put it another way:
Let's say I load a lead bullet (dummy), then pull it and measure the area where the crimp is. Is there a minimum there that a person can use? Just curious.

Thanx again!

noylj
February 3, 2013, 02:37 PM
Very confused.
Measure your lead bullet diameter.
Slug your barrel with a round ball of pure lead or lead fishing sinker—either must be about 0.360" in diameter or larger. Or, take your barrel to a gunsmith.
Determine the groove diameter of your barrel.
Lead bullets almost always need to be at least 0.001" larger than groove diameter.
I find lead bullets of 0.357-0.358" are almost always much better than the common 0.356" lead bullets, even if the groove diameter is actually 0.3550"
Make a dummy round. Pull the bullet. Measure the bullet diameter near the base of the bullet. Did it get smaller?
If so, you either need to use a larger expander die (a .38 Spl. expander is almost always better than a 9mm expander and this is a step that many people never seem to think about) or less taper crimp.
If your bullets are slightly small, buy some Lee Liquid Alox and apply a very light coating to the bullets. I put all my cast bullets (up to about 500) in a glass casserole dish, get all bullet on their sides, squirt in a little LLA, and hand shuffle the bullets around. If the bullets are all shiny/wet looking, then they have enough LLA. If the bullets are amber/brown, I used way too much LLA.
You can find cast bullet companies (see Penn Bullets) that will size to your requirements.
LLA is very tenacious and I find that if I get leading with some commercial bullets I buy, that the LLA eliminates or greatly reduces the leading.
Personally, I haven't sized any of my cast bullets since about 1975 and don't have any plans to. I pan lubed until LLA came out and have tumble lubed all my bullets since then. I don't know why people seem so "fearful" of trying as-cast bullets and will not even consider NOT sizing their bullets.

murf
February 3, 2013, 04:59 PM
you will need to measure the before and after diameter of the bullet. make sure you crimp the dummy round just like you did before, so we can make a legit comparison.

measure the "after" bullet anywhere it's been in the case. also, measure it right aft of where the case mouth was so we can get an idea if you are crimping too much.

also, measure the case diameter of the dummy round just behind the mouth (before you pull the bullet).

murf

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