A closer look at 147gr 9mm Gold Dot ammo

[MilitaryArms]

[ame]http://www.youtube.com/watch?v=UVXVW1od8Xk[/ame]

 

[db1959]

Thanks!

Question, how long do you keep your carry ammo before you shoot it and load new rounds?

 

[MilitaryArms]

I wanted to update my comments about setback.

Below are two rounds. One is noticeably shorter than the other. That's because it's the first round in my magazine and it has been chambered several times over the last few weeks. Yes, this round is only a couple of weeks old.

The reason it's shorter is due to the setback (bullet being pushed into the case) caused by the act of chambering the round. Each time you chamber the same round, the more the bullet gets pushed back into the case. This is something many people don't think about.

Why is this a problem? Because as the bullet gets pushed further back into the case it increases the pressure generated by the round when it's fired. If the bullet is pushed back far enough, it can cause an unsafe pressure build-up which results in things like the infamous Glock "ka-boom".

To avoid this problem, I keep fresh rounds in my magazine and never use the same round in the number 1 slot for very long. I move it down the stack and move a new round to the #1 position fairly regularly.

 

[jayhawk]

Repped! Thanks for the excellent visual example of setback.

 

[sadclownwp]

How dare you post a review like this. Now I have to go out and buy a few boxes of the 147 grain Gold Dots too.

 

[MilitaryArms]

Thanks!

Question, how long do you keep your carry ammo before you shoot it and load new rounds?

As a general rule I don't keep the same ammo in my carry magazine for more than 2-3 months. During this time I will rotate the #1 round in the mag so that I can avoid setback problems.

That's not to say there's any scientific calculation I've devised to determine this 2-3 month time frame. It's what feels right to me.

 

[iamaclone45]

To avoid this problem, I keep fresh rounds in my magazine and never use the same round in the number 1 slot for very long. I move it down the stack and move a new round to the #1 position fairly regularly.

Excellent video, as usual.

I also rotate my carry rounds. Every time I un-chamber a round it finds itself going towards the bottom of the magazine. I also visually check round heights, as you have shown, on a somewhat random basis.

 

[nailknocker]

I don't understand the compression theory here. You have X amount of powder that exerts X amount of pressure regardless of compression, unless the bullet is jammed so tightlly that it can't be shoved free by the explosion. Then a split casing would be the result. Am I missing something? Data please

 

[jayhawk]

I don't understand the compression theory here. You have X amount of powder that exerts X amount of pressure regardless of compression, unless the bullet is jammed so tightlly that it can't be shoved free by the explosion. Then a split casing would be the result. Am I missing something? Data please

Probably the best place to go for data would be a reloading manual. Decreasing the volume of the case will increase the pressure...this is especially critical in low volume handgun cartridges, which can indeed lead to the possibility of bulged casings and split casings as well as increased wear on the firearm or even KBs.

Rifle cartridges can have the opposite problem on the other hand. Too little depth can place the bullet to close to the lands and cause a pressure spike.

 

[Rob377]

I don't understand the compression theory here. You have X amount of powder that exerts X amount of pressure regardless of compression, unless the bullet is jammed so tightlly that it can't be shoved free by the explosion. Then a split casing would be the result. Am I missing something? Data please

Not quite. Case volume has a big effect on peak pressure. If the bullet gets set back too far, case volume decreases, and peak pressure increase. Powder doesn't explode, it burns.

 

[INyooper]

I've not heard/read of setback with 9mm as much as with .40, though that may be my own bias, as it's what I shoot (along with 45). Still, good to remember and practice regardless of the caliber.

In addition to rotation of the chambered round, I've read (maybe here? ) where someone uses a sharpie to mark rounds that have been chambered. When he has a mag full of marked up rounds, he uses them for range ammo. Just another way to keep track. It's all good.