Proper 9mm HP OAL

[PiratePast40]

I've had a few failures to feed with Freedom Munitions 124g hollow points in my M&P Pro. The bullet hangs up on the upper surface of the breech face. It happens randomly in the middle of the magazine, and all the magazines seem to be identical. At least no observable differences.

Since this was only happening with the 124g HP rounds, I measured 5 each of the HP and round nose rounds. HP's were 1.060 +/- .003. Round nose were 1.150 +/- .002.

Is the length of the hollow points about what would be expected?

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[Mikej]

Don't understand. The (bullet) goes nose first into ramp then into the chamber. The (breach face) is against the base of the shell when the slide is fully forward, (in battery). Do you mean the nose of the bullet jambs at an angle, bullet up, against the back top of the chamber? Or into the ramp?

As I understand (hasn't happened to me) some hollow points will grab the ramp with the somewhat sharp front nose of the bullet. Or, if the cartridge is too short for the particular gun will sort of deflect off the ramp and up into the back top of the chamber and wedge, blocking the slide open.

I load my own 9mm at an OAL that allows the slide to close without the bullet hitting the groves in the barrell. That happens to be 1.085" with Montana Gold 124gr HPs.

Mike

 

[PiratePast40]

Don't understand. The (bullet) goes nose first into ramp then into the chamber. The (breach face) is against the base of the shell when the slide is fully forward, (in battery). Do you mean the nose of the bullet jambs at an angle, bullet up, against the back top of the chamber? Or into the ramp?
Bullet nose does not enter chamber.

As I understand (hasn't happened to me) some hollow points will grab the ramp with the somewhat sharp front nose of the bullet. Or, if the cartridge is too short for the particular gun will sort of deflect off the ramp and up into the back top of the chamber and wedge, blocking the slide open.
^^^ This, it jams against the top of the chamber and wedges the slide open.

I load my own 9mm at an OAL that allows the slide to close without the bullet hitting the groves in the barrell. That happens to be 1.085" with Montana Gold 124gr HPs.

Mike

 

[Mikej]

My guess would be the OAL is short for your gun then. I've been lucky I suppose, have not had that issue.

 

[AMProducts]

I think you're too short. Max OAL for 9mm is 1.160". What tends to happen is if you seat the bullet deep enough that the ogive is inside the case mouth the round will hang up on the case mouth/feed ramp. The problem you're describing sounds like your crimp/sizer isn't working the way it's supposed to. I highly recommend pulling the barrel out of your gun and try to drop a live round in the barrel and see if the round goes all the way forward.

In any auto pistol you want a very minimal amount of crimp as most of the headspace is set off the case mouth, rounds that are over-crimped can slide further into the chamber and may not be struck by the firing pin, and over-crimping tends to raise a bulge just behind the crimp, for 9mm I only recommend taper crimping, if you have a roll crimper, throw it out it's part of your problem.

My target load is an Xtreme 124gr RNFP loaded out to 1.140", it cycles like goose laxative through my FNX.

 

[Mikej]

AMP, those rounds aren't "Home Rolled", Freedom Munitions.....

1.060" sounds really short to me. I thought my 1.085s I load was short.

 

[AMProducts]

Oh, I thought freedom munitions was the MFG of the bullets.

Either way, check for case bulge, I do a lot of consulting work (not for freedom munitions) and I've noticed case crimping issues are common in "factory reload" ammo, especially when the "factory" is being run by people who are not reloaders. Lately, there have been a lot of people who got into the reloading business because ammo prices were so high, without a lot of experience reloading, as a consequence quality has really suffered.

If you really want to be definitive, do the barrel-chamber check test like I said. It's possible you might have just gotten a crappy batch.

 

[PiratePast40]

Went through all my different brands of ammo and here's what I came up with on length:
Fiochi FMJ - 1.16
PMC FMJ- 1.16
Hornady Zombie - 1.08
Gold Dot - 1.08
FM 124 g HP -1.06

All brands, including the FM 124g HP, the brass sits on the shoulder inside the barrel, and the primer end sits the same distance above the end of the barrel the same distance. That is, flush with the locking tabs with room for the extractor hook.

Based on those observations and measurements, it doesn't look to me that there is anything wrong with the ammo. The FM HP's may be a little short, but they sit in the chamber correctly.

My thoughts now go back to the magazines or the extractor hook. When I was shooting this Sunday, the gun had about 450 rounds through it since last cleaning. I've read about cleaning the extractor hook so that it won't cause binding and am wondering if that has been my issue all along. The failure to load has been sporadic and not very frequent, but still only with the FM 124g HP. I cleaned the gun when I got home Sunday and didn't inspect the hook at that time. Just cleaned and brushed it like normal so can't really say if it being dirty was an issue.

Does it sound like I'm on the right track, or totally off base?

 

[AMProducts]

You know, I've had all kinds of guns that decided not to run and it took me many trips to the range to get it all figured out. What I would suggest is blasting out the area behind the spring with some carb cleaner (this will remove all of the oil that sticks the dirt in there) and then using some toothpicks get out all the crud you can.

I don't remember you telling us what kind of gun you're shooting it in, but these kinds of problems are common with springfield XD's which are really sensitive to bullet shape and COL.

 

[PiratePast40]

Thanks for the advice. I thought I had the extractor hook pretty clean but was surprised how much gunk I just got out of that small area. Spring is pretty strong, making it difficult to clean back in there. I pretty much flushed it with CLP and then used q-tips and toothpicks to finish drying it out.

Gun is the newest version of the M&P Pro (striker fired). Still not 100% sure that the extractor is the cause of the failures to feed, but will be looking closer now.

 

[ma96782]

For autoloaders, when I do a switch to another bullet, I don't do actual measurement for my initial rounds.

Try this for a STARTER..........



You might still have to tweek the rounds to get good feeding.

Aloha, Mark

 

[AMProducts]

Thanks for the advice. I thought I had the extractor hook pretty clean but was surprised how much gunk I just got out of that small area. Spring is pretty strong, making it difficult to clean back in there. I pretty much flushed it with CLP and then used q-tips and toothpicks to finish drying it out.

Gun is the newest version of the M&P Pro (striker fired). Still not 100% sure that the extractor is the cause of the failures to feed, but will be looking closer now.

I don't think the extractor is the issue if it's hanging up before the case gets all the way into the chamber, it's more likely a cartridge over-all-length issue (that ammo may just be too short).

 

[PiratePast40]

I don't think the extractor is the issue if it's hanging up before the case gets all the way into the chamber, it's more likely a cartridge over-all-length issue (that ammo may just be too short).

My theory was based on some reports that a dirty extractor hook may tilt the bullet and cause it to be off center in relation to the barrel. Really not sure if that's it, just trying to consider everything.

Looking at the picture above, all my ammo appears to fall in the acceptable range.

For what it's worth, shot 100 rounds of the hollow points this weekend with no failures. In fact, the 124 grain HP ammunition is much more accurate than 115g FMJ. The FMJ is consistently 2 inches low at 5 yards while the 124g HP is dead on at that distance.

 

[cookie]

For autoloaders, when I do a switch to another bullet, I don't do actual measurement for my initial rounds.

Try this for a STARTER..........



You might still have to tweek the rounds to get good feeding.

Aloha, Mark

Just because,,, try to chamber a resized case to see how it fits into the chamber like the above test.