Plunk test vs chamber length 9mm

[KYHunter1]

I have a new 9mm auto and made a dummy round for both a 115 and 147 grain plated HP. To get the brass and bullet to fit the chamber seems I'm somewhere around 1.100".  Since the HP bullets do not have a round nose I recognize they will measure shorter than a round nose of the same wt.   my concern is this seems a slight bit short but do see OAL somewhat all over the place when looking at load data even within the same bullet weight for lead or plated or jacketed.    So when I drop the dummy round in my barrel this is what it needs to be to fit.   Does this seem reasonably.  Thank you in advance for your informed answers.   KYHunter1 

[BJB]

If 1.100" is what it takes for that barrel then that's fine.  You're good-to-go. 

For a HP that's not even very short.

[Farmer]

Depends on the throat and the ogives of the bullets. Mine with a fn runs at 1.095. 

[shred]

Yeah, "OAL" is a made up number that you can measure because measuring where it fits your chamber leade hits the bullet ogive is hard.  But if a round fits your barrel and mags, the OAL is OK.

[MemphisMechanic]

If you chwck most factory JHP loads, they’re similarly short. 1.100” is fine.

 

Just start somewhere between minimum and no more than 50% of book max, and work up slowly with a chrono.

[Farmer]

Making your own max oal gauge is simple and makes checking your bullets in your gun fast & easy. 

[KYHunter1]

A hearty thanks to all of the contributors.   It's reassuring to get feedback and know you are in reasonable territory or getting outside the lines.   KYHunter1 

[Hi-Power Jack]

16 hours ago, Farmer said:

Making your own max oal gauge is simple and makes checking your bullets in your gun fast & easy. 

 

Might need a different OAL Gauge for each bullet type you use.

[Farmer]

On 6/17/2020 at 8:16 AM, Hi-Power Jack said:

 

Might need a different OAL Gauge for each bullet type you use.

Not at all. I just take an old fired case that the bullet just slides into with a little pressure. Take your bbl out, just start a bullet into the case, insert into the chamber and press it home. Carefully remove and measure. That’s your MAX OAL, so subtract .010-.020 or whatever will fit your mag and go. Most of the time if you fire a hot load with a plated bullet it will stretch the case enough for a slip fit. If it gets a little loose just squeeze the sides a bit. It takes a little monkeying around but once you got it it’s done. Right now I’m working on a gauge to check inside depth/taper of 9mm brass so they can be sorted by that method. FWIW Hornady brass will seat the heaviest bullet, it has the straightest wall. (Least internal taper/thickness)

Edited June 18, 2020 by Farmer

[shred]

That's how the rifle guys do it except they usually tap the flash hole and put a screw there so it can push the bullet out until it touches the lands.

 

You'll want to do that with a jacketed bullet as lead and coated lead can give false readings.

 

[SteelCityShooter]

On 6/17/2020 at 11:16 AM, Hi-Power Jack said:

 

Might need a different OAL Gauge for each bullet type you use.

And for every gun.  Even "identical" guns may not accept the same COL for a given bullet and you should test every gun and bullet combination individually.

 

For example, I have two S&W 5" M&P9 2.0 pistols, one a standard version bought in 2017 and the other a CORE model bought early this year.  They should be identical twins other than the CORE's machined recess.  However, using Montana Gold 124 gr JHP bullets, the older gun will easily accept a COL of 1.148" while the CORE gun will not go into battery with those loads and requires an COL of no more than 1.120 to chamber properly. 

[shred]

The main reason is chamber reamers aren't cheap, so manufacturers buy them sized at maximum-SAAMI spec and run them until they wear down below minimum, then toss them and repeat, so any given barrel is probably somewhere between one extreme and the other.

 

There are other ways to make a chamber but if they use a tool to do it, the same applies...

 

This is why the SAAMI minimum spec for a chamber is larger than the largest in-spec round for that chamber.

[KYHunter1]

This is all very interesting information and not in many reloading manuals.   Even some do not state if the oal is maximum or minimum.  What is challenging to understand or adds confusion is when books state do not seat too deeply or pressure will be excessive.  Both terms are objective and when you have a bullet that must be seated deeper to fit the chamber adds concern based on the seating warning.  Lots of honest and real world practical 

feedback.    Thanks.   KYHunter1 

[Sarge]

4 minutes ago, KYHunter1 said:What is challenging to understand or adds confusion is when books state do not seat too deeply or pressure will be excessive.  

Pressure could be excessive if the charge stays the same. So when you have to go shorter you simply reduce the charge accordingly.

[Farmer]

On 6/22/2020 at 7:19 AM, shred said:

That's how the rifle guys do it except they usually tap the flash hole and put a screw there so it can push the bullet out until it touches the lands.

 

You'll want to do that with a jacketed bullet as lead and coated lead can give false readings.

 

You do it with every different brand or shape bullet that you are going to use. Make a reference chart and occasionally check a new batch to be sure nothing changed much. Doesn’t matter if it’s lead, plated, jacketed or silver. Adding a screw to the back just makes it more difficult to measure and can give false readings if your not careful. 
On OAL per loading I usually subtract .1 grain per .010 seated deeper than book spec. and test from there. If loading close to max go .2 per .010 or more. Always work up carefully. 

Edited June 23, 2020 by Farmer

[tdp88]

1.1 will be fine, especially with the bullet you're using. 

[PistolToter]

Specs say 1.00 to 1.169 so you're good to go.

[Sarge]

13 hours ago, PistolToter said:

Specs say 1.00 to 1.169 so you're good to go.

Nothing could be further from the actual truth. This and many other oal threads prove that. 

[DMTJAGER]

I am having to increase my knowledge of HG reloading considerably 

I recently posted a request for help here and was the recipient a sharing of exceptional knowledge.

After I was educated as to my mistake and the cause of it I took the time to seriously analyze the situation and determine why I didn't possess this knowledge even after more than 3 decades of reloading 

I discovered the cause for my error and ignorance was due to habits and assumptions I developed in the very earliest stages of my reloading career 

I had only ever used standard non plated FMJ bullets for all my HG reloading in round or flat  nose configuration 

I would always set my max length on a loaded round based on the length of a factory loaded round I knew functionedin in my HGs. Then load my rounds and do what is now known as a "plunk test" I called it a chamber fit test. 

This worked flawlessly for me until I tried coated bullets 

I know now I made a mistake in assuming that the fact my coated bullets were 124grn round nosed they would work if set to the same length as my 124grn FMJ and nope they didn't 

My 124grn FMJ that function perfectly have a max length if 1.147 but my 124grn polymer coated bullets max length must be 1.1135 considerably shorter.

I now know I should never assume anything in reloading regardless of no matter how much or how many years of past experience you have.

I always did this when reloading for my 7 different rifle calibers and have no explanation as to why I didn't apply that same rule to reloading my HG calibers 

I guess familiarity truly breeds contempt or in my case ignorance