Seating depth for 9mm

[Morrey]

Hello all. I'm experienced loading mostly rifle and pistol (revolver) ammo for my .38/.357 Mag, but new to pistol auto loader reloading. I am adjusting my new 9mm dies on my Dillon press and wanted to reach out for the best seating depth (COAL) that experienced loaders have found to be most accurate.

I'm loading Win 231 (start with 4.5 grains) and 115 grain round nose heavy plated match bullets from RMR. I'm shooting thru my Glocks which are a G26 and a G43, so figure on a 3.5" barrel.

My question is seating depth and I see conflicting information. I measured a factory RN round and it measures 1.135, but loading data says 1.10. I set my seating die up with the factory round as my depth gauge for starters. I made several dummy rounds and put into the Glock mags...they load and chamber just fine at 1.135. BUT, loading data says 1.10...and I suppose deeper seating will cause a slightly higher pressure, but all is in the safe range.

So...any thoughts on the seating depth I should use?

 

[gamestalker]

How they compare to a factory cartridge isn't important.

Use the plunk test, then once you've determined what clears the lands, adjust OAL as necessary so they fit the magazine, and feed reliably. I personally seat them to the longest oal that will fit and function in the firearm I'm loading them for.

GS

 

[CZ9shooter]

Whatever fits and functions the best in the gun(s) you are loading for.

If you start low and work up, a short length (if you should need one) shouldnt be a problem.

 

[Jim Watson]

Do factory loads use RMR bullets? Does your manual specify RMR bullets?
No.
You are on your own as to seating. Your rounds must fit the magazine and the chamber and make the trip from magazine to chamber.

Loading long as gamestalker says is a reasonable approach.

 

[LiveLife]

Win 231 and 115 grain round nose heavy plated match bullets from RMR ... G26 and a G43

My question is seating depth and I see conflicting information. I measured a factory RN round and it measures 1.135"

While RMR 115 gr HM RN profile (ogive) allows the working OAL/COL to be 1.160"+ with different pistols/barrels, I tend to load 115 gr RN bullets shorter around 1.135" to increase the neck tension to build chamber pressures faster. This may be the reason why the factory round measured 1.135".

With many 115 gr FMJ/plated RN bullets using 1.135" OAL, 4.6 gr of W231/HP-38 will start to reliably cycle the slides and extract/eject spent cases in my Glocks, especially for subcompacts with stiffer recoil springs. I use 4.8 gr as my reference load as 4.8 gr load produces greater accuracy than 4.6 gr load.

If I am using powders that are less dense/more fluffy so the powder charges will get compressed at 1.135", I will use longer 1.160" as I did for WST/BE-86 - http://www.thehighroad.org/showthread.php?p=9655361#post9655361

BTW, Walkalong has an excellent thread to determine max and working OAL for your powder work up - http://www.thehighroad.org/showthread.php?p=8864541#post8864541

wanted to reach out for the best seating depth (COAL) ... to be most accurate.

In theory, using the longest working OAL/COL will minimize high pressure gas leakage around the bullet and produce more consistent chamber pressure for greater accuracy. I found an exception with 115 gr FMJ/RN bullets with shorter bullet base (as compared to 124/125 gr FMJ/RN or 115 gr FMJ/RN bullets with hollow base). Depending on powder and charges, seating the bullet deeper from SAAMI max of 1.169" produced greater accuracy.

With W231/HP-38 and 4.5 gr powder charge, 1.160"-1.169" OAL may not even reliably cycle the slide of your Glock 26/43, especially with a new recoil spring assembly. You could always conduct comparison range tests to see which OAL produces greater accuracy.

 

[Conservidave]

1.125 is what i use for the same bullet in a RIA 1911

 

[LiveLife]

Morrey, you are very welcome and glad I was able to help - PM sent.

Keep us posted with your range report.

 

[Walkalong]

115 grain round nose

I load various 9MM RN bullets at 1.130 to 1.135 OAL.

they load and chamber just fine at 1.135.

Then you're golden.

I would be very surprised if they did not function well at that OAL.

 

[UziLand]

I use "light loads" in my S&W M&P 5". 115gr RN plated, 4.5gr of SR7625 at
a COAL of 1.10. Pleasant to fire, burn clean and accurate.

 

[Morrey]

Just got back from firing the GLOCK 9mm with handloads...flawless! This was just a fit and function test, accuracy next. I loaded 115gr round nose RMR Hard Match over 4.7 grains of Win 231 with a COAL of 1.135". Was a very pleasant round. Shot two mags, perfect cycling, ejecting, firing. Spent cases looked perfect.

Now that the load tested out (I don't like to load more than a few before firing), I'll test the accuracy on the next shoot. Maybe play with the grains a tenth up and a tenth down, then maybe the seating depth a tad up and see what happens with my baseline accuracy.

This was my first go with an autoloader round, and I thank you all for the good advice. A shout out to BDS who has been sending the plays in from the sidelines. Thanks coach!

 

[LiveLife]

You are very welcome and glad I was able to help.

Looks like now you just need to tweak the load a bit for greater accuracy.

Keep us posted with another range report.