Help Diagnosing 9mm Issue Please?

[LiveLife]

Different brands of bullets vary slightly in ogive shape, and will contact the rifling sooner or later then the bullet listed in the data.

Correct taper crimp should measure about .376" at the case mouth using .355" jacketed bullets.


I suggest you do this.

Completely 'color' a loaded round with a Magic-Marker or Dry-Erase marker.
And then force it into the chamber.

Where the marker ink rubs off the case, or the bullet, is your problem.

+1. I think rcmodel's method is the best way to determine why your finished rounds are not fully chambering as different brand bullets (even though they are same FMJ/RN profile) can have different shape (ogive) with different length of bullet base/bearing surface that engages the rifling.

And if it rubs off on the bullet - then reduce the COL?

I not only drop the round in the chamber but also spin it side to side slightly to enhance the marking. If the bullet is hitting the start of rifling to prevent full chambering and/or the marking is rubbing off, then you need to decrease the OAL/COL until you can fully chamber the round and spin freely.

So - if it rubs off the case: Then taper crimp needs to be adjusted down so as to reduce mouth diameter?

Not really and also depends on several things: chamber size, out-of-round bullets, variation in case wall thickness and tilting of bullets during seating.

As rcmodel posted, I usually use no less than .376" taper crimp for .355" diameter jacketed/plated bullets. Some plated bullets are sized slightly larger than .355" as factory sizer wears and if not changed out frequently, could be sized .3555"-.356". So with some plated bullets, I will use .377" taper crimp so as to not cut into the thin copper plating.

Most SAAMI spec barrels will allow taper crimp up to .380" unless the bullets are out of round.

How can bullets be out of round? From manufacturing and/or from handling during shipping. With plated bullets, by the time copper plating is done and bullets tumble cleaned/polished, they could be out of round and many manufacturers double strike (push through size) to ensure roundness of plated bullets. And shipping companies/USPS will rough handle the bullets from tossing boxes to dropping boxes and the impact force will squish jacketed/plated bullets with softer lead/alloy core. So by the time you receive the bullets at your door, they could be out of round.

Out of round bullets will produce out of round finished rounds at the case neck. I experienced this with different brand bullets as bullet diameter measured with calipers will show oval shaped bullets instead of round (when I measure bullet diameter, I will measure at multiple locations not just one location).

How did I know that the out of round bullets was the problem and not the amount of taper crimp? Because verified round bullets did not produce out of round case necks and they chambered without rubbing the barrel. When I measured the rounds that did not fully chamber or rubbed the barrel, case neck measurements were different and pulled bullets were out of round.

Another thing that could produce out of round case necks is tilting of the bullet during seating. When I was in a hurry during one reloading session with Winchester 115 gr FMJ bullets, I saw noticeable bulging of case neck on one side only. Caliper measurements shows out of round case neck which was the result of tilting of the bullet during seating. After me slowing down and more carefully setting the bullet on flared case mouth, the one sided bulging was less of an issue.

But when I noticed the slight uneven bulging of case neck continue, I got curious and measured the case wall thickness. To my surprise, depending on headstamp, case wall thickness consistency varied quite a bit. They ranged from being thin on one side like .010" to thicker like .012"+. Since case neck gets formed by the taper crimp, I think case wall thickness variation is less of a contributing factor to out of round case neck but will stack on top of out of round bullets.

If your finished rounds' bullet is not hitting the start of rifling but the case neck is rubbing the chamber from being out of round, what can you do? One option is using Lee Factory Crimp Die to post size the finished round so the dimensions are within SAAMI specs. Another option is to increase the taper crimp to the point where the finished rounds will fully chamber. But extreme use of these two options may reduce neck tension by reducing the bullet diameter while brass spring back that will result in bullet setback.

So if you are resorting to these options to "fix" the finished rounds' being out of round, I would check the neck tension by measuring OAL before and after feeding/chambering from the magazine and releasing the slide without riding it. If the bullet setback is more than several thousandths and you are using near max load data, you have issues that need to be addressed or you could experience over max chamber pressures.

 

[Jesse Heywood]

Since you are having problems and no one has mentioned the article by Walkalong
The Plunk Test

Now that all attempts of assembly have failed, it's time to read the instructions.

 

[Toprudder]

Here is something I made up (in different calibers) to help me determine the max COL for a given gun/barrel. Insert the bullet with a long COL, push down into the chamber, then remove. Measure. I repeat a few times for each barrel and take the average. Then I subtract about 0.020", making sure it will fit the magazine and feed properly.

 

[wally]

Completely 'color' a loaded round with a Magic-Marker or Dry-Erase marker.

Good "trick" but after getting some Dykem I'll never use it again, the Dykem is a far better "tattletail".

But I'd just make up a dummy round and walk down the OAL until it passed the plunk test.

If the problem is the brass, you got a bad set of dies and they'd need to be replaced, assuming you've correctly installed them into your press.

 

[RAT807]

Variables, account for them. Your bullets will vary in ogive length or bearing surface by .004 or more. If you do get a plunk with a dummy round at 1.100, the next round may plunk at 1.095. This is just considering variations in the bullets alone.
Bullet profiles... 125 gr Sierra FMJ will plunk at 1.169 in my G34. The bearing surface length was .290 - .293 for the 125gr FMJ. I set OAL at 1.165. The last 300 rounds of Sierra 125s the bearing surface is now .292 - .295. I'll be seating these a bit deeper.
Sierra 125gr JHP has a different profile and plunk at 1.096. I seat them to 1.090.
Dies... My resizer die sizes my case mouths to .372. My jacketed bullets are .355 so I flare the case mouth to .376. The plated bullets that measure .356 I flare the mouths to .377. I also put a slight chamfer on the case mouths and this helps the bullets slide in the tight necks.
Brass lengths.... If you have brass lengths from .742 - .750, the short cases will not flare to .376 or .377 depending on which bullet and the longer cases will flare more than .378. This will vary your neck tension. Also the varying lengths will give you inconsistant crimp diameters. Longer cases will get more crimp than shorter ones. The main thing you need to know is, the ogive length is what you need to find. I measure the case to ogive length and keep this with my load data as well as the bearing surface of the bullets. My max case to ogive (COG) length is .885 for my barrel. Anything under this length will plunk regardless of bullet profile. My loads OAL vary from 1.075 - 1.165 but the COG lengths are between .860 - .880

 

[otisrush]

1.088 plunks consistently for me I've learned. I spent a couple of hours last night fiddling with the dies getting it right. When things seemed right I loaded up 6 dummies and cycled them through the mag and chamber a few times. No issues.

Tonight I loaded up 20 rounds with 3.6gr Titegroup - the min load for this bullet on Hodgdon's website.

I hope to get to the range tomorrow just to see what they do.

Thanks everyone.

OR

 

[RAT807]

IF I have a new load to work up, I load 1 rounds for each powder charge. I start at the book minimum and go a few tenth over max. My gun is rated for +P+ ammo. I want to fine what cycles the slide, look for pressure signs and clean burning loads. I also load 5 rounds for a few mid range powder charges and shoot groups. Between the ladder test and the groups ( all shot at 25 yards), I already have a clue where to focus my next loads looking for better accuracy.
I hope your 20 rounds at minimum charge will cycle your slide or you will have a short range trip. I'd load more rounds at different charges.

 

[otisrush]

Thanks very much. I've been so focused on 1) getting stuff to fit and 2) what feels like a short OAL and 3) worried about increased pressures and 4) using a powder with a reputation of being hot I figured I'd consider it a success if they chambered and fired and if needed I work up from there. But it's smart to load up a few additional with some additional.

 

[Zendude]

I've been able to do a quick test with the dry-erase marker on a round. I've had limited time - so I did it quick and haven't tried it multiple times.

It appears the marker is getting rubbed off the case.

I'm figuring I should re-setup my expander and bullet seat/crimp dies. I don't have time to post a pic - but it seems on some rounds I can almost see some non-uniformity in the case about where the base of the bullet is. Maybe it's residual sizing from the expander. The bottom line is I think, in totality, I don't have confidence the expander and crimp dies are set up right - especially since sized cases drop in just fine. Something is happening after sizing which is causing the problem.

If that's bad logic please let me know. I hope tonight I should have some time to work on this.

OR

Are you using a separate die for crimping, or a just one die for seating and crimping?

 

[Toprudder]

The range is over an hour away from where I live, and I don't get the chance to go there as often as I would like. So, I like to gather as much data as I can from each range trip.

I typically load either 5 or 10 of each charge, starting at the lowest start charge I can find using multiple sources if possible. I like to have 4 or 5 steps between low and high charges. I also have a max velocity written down that I will not exceed. I have started bench-resting all shots now so I can also gather accuracy information. (BTW, it really pisses me off when my best accuracy was from a load that won't reliably cycle my gun - it has happened once :banghead: )

It can be hard to determine which load is clean/dirty when doing ladder tests, especially if I am trying different powders during the same trip. I typically only get a general idea about the powder overall. Sometimes all I have to do is look at the dark specks all over my arms to know it is dirty. Sometimes I will look through the barrel (taken out of the gun, obviously) to see how much ash is left in the barrel.

I generally will take the info gathered from one trip, and concentrate more on one load that looks promising, and shoot 50-100 of that load during my next trip so I can get a better idea of how clean it burns.

On more than one occasion, I've brought back loads that I did not shoot, either due to them not cycling the gun reliably, or reaching my max velocity or seeing pressure signs before I shoot the higher loads. That is what bullet pullers are for.

 

[boom boom]

Otisrush,
I feel your pain. Had a similar problem with a Sig P6 from the early 80's that had a short throat. Fed fmj fine but did not like a number of other bullet profiles. You can find some 9mm that will pass a check gauge but fail the plunk test using the gun's barrel as a check gage in a particular gun especially in older guns. BTW, don't buy a massive amount of 9mm bullets before you make sure that your gun likes that particular bullet profile. Bought a whole bunch of 124 gr. Oregon Trail lead bullets on sale that couldn't be used in that P6 I mentioned. Ended up having to buy a whole new 9mm S&W 3rd Gen that eats anything which was an expensive lesson .

 

[otisrush]

Thanks to the help in this thread I thought I'd report back and close this out:

I just returned from the range and what I brought worked flawlessly. Thanks to the advice here I loaded up 3 additional loads - only 5 rounds each. So in the session I just returned from I shot 3.6gr, 3.7gr, 3.8gr and 3.9 gr (124gr FMJ RN over Titegroup) and all four loads cycled the action perfectly. I suck badly enough with a pistol - and given I only had a few rounds of each - I don't know which load my gun likes best. I sensed I was doing better with the 3.8gr load. But at least now I know I can load up more in each charge and do some testing with more rounds.

Again, thanks for all the great help. I really appreciate it.

OR