9mm VV 3N37 weird ring on brass

Proutfoo

Proutfoo

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I just opened a new container of 3N37 since my usual supply of N340 was depleted. I loaded up 2 loads, one with 115gn plated bullets, and another with Hornady 147gn XTP. Here is the load data

115gn copper plated bullet
5.6 gn 3N37 (starting load according to the VihtaVuori reloading guide)
OAL 1.145

I shot 3 through my CED M2 chronograph today and they metered at 958, 1018 and 986. Reloading guide says they should be at 1129 (??). I was shooting from a G17 gen3 from about 15 feet from the chronograph. One of the casings shows the ring in the picture below

second test:

147gn Hornady XTP HP
4.7gn 3N37 (starting load again...)
OAL 1.145

I shot 3 again through the chronograph, they metered at 874, 914, 898. Reloading data suggests this would be normally 979. This time, 2 of the 3 casings showed the ring on the pics below.

1.png

2.png



this ring doesn't go all around the case, it goes about 2/3 around. I can run my nail along the case and feel a bump/rise when I get to the ring.

My instinct tells me somehow I have high pressure, yet the load data as well as the velocity seem low. Any ideas???


In both cases, the brass used is CCI Blazer, once-fired from the same G17
 
I am googling around trying to figure out what they could represent. I have shot thousands of reloads through my G17s using N340 and I have never seen these. I never used a chronograph until today, so I wonder why I would have almost 100 fps less than what the loading manual would indicate to expect yet have what I am currently considering a sign of overpressure. Curious the primers seem fine and the recoil felt as normal.

I am finding info about unsupported chambers in Glocks causing bulges and perhaps lines, anyone ever seen such a thing?
 
Proutfoo said:
I am googling around trying to figure out what they could represent. I have shot thousands of reloads through my G17s using N340 and I have never seen these. I never used a chronograph until today, so I wonder why I would have almost 100 fps less than what the loading manual would indicate to expect yet have what I am currently considering a sign of overpressure. Curious the primers seem fine and the recoil felt as normal.

I am finding info about unsupported chambers in Glocks causing bulges and perhaps lines, anyone ever seen such a thing?
Click to expand...

I've heard about the unsupported chamber thing with Glocks and have had some FTE's when using reloaded range brass in an SR-9.
Perhaps the ring has only become apparent after 2 firings? The FTE brass that I measured was only a couple of thou bigger at the back end so maybe it took being fired twice to become noticeable?
As for velocity,the OAL length for the 115gr load seems long as Hodgdon recommends 1.125". Believe it or not that .020" can make a 3-4% difference in case volume.
 
My guess is that since you are using a very slow burning powder you are getting more case expansion then you would with a faster burning powder and this is causing the case swelling.

As for your velocity unless you are using exactly the same barrel as manufacture is using you will rarely get the same results.
 
1. Fire a factory loaded round and see if you get the ring, if you get a raised ring there is a reamer defect in your chamber.
2. If you do not get the ring with a factory round then I would say you are sizing too far down the case and your die is causing the ring.
3. From your photos it look to me the ring is where the die stopped sizing the case.

Below on the bottom a properly sized case and on the top a case sized too far down the case and pushed up the brass below the sizing ring.

9mm%20sizing_zpsuaadrkik.jpg
 
Last edited:
indeed. I just ran a few more through the sizer as I was making these individually to work up the load and I do see the ring. easier to spot when the case gets a bit dirtied from shooting. well thats a relief. I can toss this brass and adjust my dies better. thanks for your help folks.
 
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