Push Test


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buddhas
February 17, 2013, 02:53 PM
What is a" Push Test" and how do you accomplish it?

Thanks, buddhas

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holdencm9
February 17, 2013, 03:05 PM
First, measure OAL of cartridge.

Then, put the nose of the bullet on the bench and push with moderate force...maybe like 30 lbs?

If the OAL changes, then you may have inadequate neck tension and have bullet setback issues.

rcmodel
February 17, 2013, 03:08 PM
The "push test" is what some people use to see if they think they have enough case neck tension to keep bullets from slipping in the case during feeding.

You push on the bullet, or you push the loaded round against the bench and see if the bullet slips.

In actuality, something like a .223 or .308 should take upward of 70 pounds to move the bullet in the case. Perhaps 50+ with most all auto-pistol rounds and all revolver calibers.

You will hurt yourself trying to push 70 pounds on a bullet tip with your fingers.

So if you can push a bullet back in the case with your bare hands?
You are in the wrong line of work.

You should be Superman.

rc

gamestalker
February 17, 2013, 03:18 PM
With AL handgun bullets I like to use two methods of testing to be sure the bullet is holding well. First of course is pushing it against the bench with some good force. Than I like to take it and drop it from 4' or so on to a wood surface to prevent deformation, and then letting it land on the nose. If the OAL doesn't change then it's holding well. The drop test helps me to feel confident that impact experienced during feeding isn't setting the bullet back.

As for crimped rimmed or revolver cartridges, I don't do anything more than just inspect the crimp to ensure it is deep enough.

And with bottle neck cartridges, unless they are a FMJ or solid copper, I just grab hold of it and push on it as hard as I can. I don't push those against anything cause I don't want to flatten the tip or deform it.

GS

James2
February 17, 2013, 03:44 PM
I have heard of the push test, however never use it. It has been my experience that properly sized and crimped brass/bullets stay put.

GLOOB
February 17, 2013, 03:56 PM
I have heard of the push test, however never use it. It has been my experience that properly sized and crimped brass/bullets stay put.
Poor neck tension usually has nothing to do with proper sizing and crimping. It's usually a result of too thin and/or overworked brass.

If you use a single stage or a turret, pay attention to the feel of the expander. If you feel little to no resistance, that piece of brass may have poor neck tension. Those are the cartridges you will want to press test.

rcmodel
February 17, 2013, 04:00 PM
I have more then one set of dies that needed the expander button turned down .001" or .002" to get proper neck tension.

And it seems to be more common then it used to be.
Especially with one certain brand of very popular dies today.

Don't rule that out.

rc

matrem
February 17, 2013, 05:30 PM
I don't crimp rifle rounds at all. Neck tension is what's important.
I've needed to "sand down" a few expander balls as well.
Thirty tears ago, bought a 7 Rem mag neck sizer & the expander ball was right at .284. Sheesh..

I also needed to do that to the next to last set of rifle dies I purchased.
Usually about .0025 press fit is adequate IME, and I've averaged removing about .0015 on those 3 or 4 that were too loose (big).

ArchAngelCD
February 17, 2013, 05:34 PM
Thirty tears ago, bought a 7 Rem mag neck sizer & the expander ball was right at .284. Sheesh..
While it's very serious there's really no reason to shed tears over it! :p ;)

matrem
February 17, 2013, 05:44 PM
If you had the limited budget & lack of "experts" I had to go to back then, tears may not be out of the question. ;)
EDIT: A half inch too far left on keyboard (t & y) and yet 179 degrees, 59 minutes ,59 seconds to the right on most topics... dang it.

rcmodel
February 17, 2013, 05:49 PM
+1

While I agree it is not a huge problem if you know it is?

It can be a huge dangerous problem, if you are a new reloader and don't know it is.

rc

BWB
February 17, 2013, 06:03 PM
No mention yet of autoloading handguns. Here is where the demons lurk for the unwary. If a bullet slamming the feed ramp is pushed back in the already small powder capacity case it can significantly raise pressures beyond dangerous levels. The 9 mm and .40 S&W already operate at quite high pressure and bullet setback can get you off the map. I personally suspect this could be the cause of many of the "kabooms" we hear about.
Here a good periodic push test is a good idea, especially since most of us, myself included, tend to get casual about the condition of mixed range pick up brass, and seemingly everlasting handgun cases loaded in large volume.

bds
February 17, 2013, 06:05 PM
+1 to bullet setback increasing chamber pressure (especially powder compression) that could contribute to KaBoom with near max/max loads.

I used to use the "push test" to check neck tension but I don't anymore as simply pushing on the bullet nose won't duplicate the operational impact forces of slide cycling. Instead, now I check neck tension by measuring OALs before and after I feed/chamber the dummy/test rounds from the magazine and releasing the locked back slide without riding forward which better duplicates the forces on the bullet nose when it slams/bumps the barrel ramp surface.

An illustration of this would be pushing on a 10d nail that's halfway in a 2x4 vs hammering with the hammer. The impact force exerts far greater force than static force due to momentum of the slide pushed by the recoil spring tension (Force = mass x acceleration).

When I took some test rounds that successfully passed the push test and fed them from the magazine, I was able to measure significant decrease in OALs. This proved to me the push test was inadequate QC test for checking neck tension.

rcmodel
February 17, 2013, 06:10 PM
Thats the way I do it too.

But I don't bother measuring them.

I mark a ring around the bullet / case neck joint with a black Sharpie pen.

Then chamber some of them and see if the black line is still there.

If it's gone, you have bullet slip.

rc

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