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luketmv

Urgent help needed! load not cycling the gun properly

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Here is the problem, I am using N320 with 124 gr FMJ. The gun is an M&p Pro.

c.o.l = 29.05 mm

N320 = 3.8 gr

The bullets are crimped well enough however the gun is not cycling, most of the cases end up stove piping or remaining attached to the ejector and being put back into battery again. Basic problem is there is not enough force to cycle the gun properly, please help me solve this, i do not think more powder is the solution. Someone suggested shortening the rounds however i do not know by how much. is 1mm too much? Too little? is this even the solution? Please help

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I'd guess that your OAL (1.144") is probably okay - doesn't

sound like it should be shorter - but wouldn't hurt to do

The Plunk Test.

What's the velocity?

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cant say..... this is a new load for me and dont have the chance to chrono.

Edited by luketmv

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Stove piping might mean too little powder ???

n320 vihtavuori say maximum load should be 4.0 gr.

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You are half a grain too light on charge. 4.2 - 4.3 is about right for 124 with 320

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I used 1.135" OAL in my m&p Pro

You could also change your recoil spring weight. If you're using the stock spring, try a 13lb. It was the best weight spring I found for mine.

Sent from my iPhone using Tapatalk

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Is the pistol properly lubed? Are you using grease or a light oil? Grease will slow down the slide and could lead to or contribute to whats going on.

The easiest solution would probably be to up the charge.

You could always get an aftermarket guide rod and a weaker recoil spring, also.

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Increase the charge .3 gr and retry. Make sure that slide is lubed. Too dry it galls up. It won't cycle properly if dry.

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You could try some factory rounds in it and make sure the gun is functioning properly.

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You are half a grain too light on charge. 4.2 - 4.3 is about right for 124 with 320

I agree with Sarge.

I just checked my test data for my 5" Pro. 4.0gr Up to 4.3gr of VVN320 is what I've used with several different 124gr bullets . if I were you I would get a chrono and start again increasing your powder charge .1 of a grain at a time.

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. if I were you I would get a chrono...

+1

Edited by Pat Miles

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Sounds like an echo, but get a chrono. N320 is a fast powder. It takes close to (or over) the published max to make minor PF and I know my M&P really doesn't cycle well until you get right at or above minor.

Get a chrono (I recommend a ProChono Digital - last I checked you could find them for $100 or less at some places), and then load several rounds in 0.1gr increments. Shoot them going from lower to higher until you get a load that averages at around 130pf. That's your load.

As to shortening the rounds - it will increase pressure (and increase velocity too) which may be enough "oomph" to work the action. Overall though you still want to get a chrono. Without one you're kinda reloading without really knowing what the ammo is doing. If you're picking medium burn rate powders that you just want to work then that's ok, but if you're using fast powders trying to make target loads I don't advise it.

Edited by MGMorden

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As to shortening the rounds - it will increase pressure (and increase velocity too)

With increased pressure does not always come increased velocity. Most powders will plateau with velocity output while the pressure continues to rise.

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What they all said. Get a chrono. Your powder charge is too light. I use 4.2 gr N320 with a 124 FMJ OAL 1.135. Get a chrono. and, get a chrono.

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What they all said. Get a chrono. Your powder charge is too light. I use 4.2 gr N320 with a 124 FMJ OAL 1.135. Get a chrono. and, get a chrono.

I was away and that is why the chrono wasnt an option, i will now try to chrono some slightly different loads however yesterday i had the chance to try out come rounds which i shortened to 28.4mm and they were working much better but still had a few stoppages, do you think at that length it is a safe load 4.0gr to test?

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Yes. Your loads are just too light. Load some at 4.2 as well and try them too

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Everything said is good advice. I also suggest that you try some factory ammo. If it will not run then call S&W. If you call them with problems with reloads they will tell you its your ammo. There might be an issue with your extractor, but, like everyone else said, you most likely need to tip the powder can a little more.

A chronograph is a very wise investment. It helps prevent pistol-bombs.

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Everything said is good advice. I also suggest that you try some factory ammo. If it will not run then call S&W. If you call them with problems with reloads they will tell you its your ammo. There might be an issue with your extractor, but, like everyone else said, you most likely need to tip the powder can a little more.

A chronograph is a very wise investment. It helps prevent pistol-bombs.

def not the issue any other ammo flies through the gun, its definitely the load just cant understand since im almost at the maximum of the vihtavuori guides. im already increasing the pressure.

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Everything said is good advice. I also suggest that you try some factory ammo. If it will not run then call S&W. If you call them with problems with reloads they will tell you its your ammo. There might be an issue with your extractor, but, like everyone else said, you most likely need to tip the powder can a little more.

A chronograph is a very wise investment. It helps prevent pistol-bombs.

def not the issue any other ammo flies through the gun, its definitely the load just cant understand since im almost at the maximum of the vihtavuori guides. im already increasing the pressure.
If factory ammo is GTG, up the charge. You may have gotten a slow lot or your scale is slightly off, etc., or it might be a combination of those and other factors. The only way to confirm is with a chrono.

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Published loads are pretty conservative and only serve as a rough starting point for what we do

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