Different Length Projectiles

[Bmeehan19]

So im fairly new to reloading about 2yrs 9 and 40. I have been loading Berrys 180 gn RNFP .401. Its time to experiment to find the best load for my RIA Pro Match. I bought Blue Bullets 180 RNFP and Bayou 180 gn RNFP. When I received them I noticed they are different heights. I was told, and it seems to work fine, to load out to 1.20. Im using w231 @ 4.1 gn which shouldnt be near max at my coal.

 

BRB measured small at .400 (.401) and .595

BYO were right on at .401 and .620

BB were right on at .400 and .630

 

All I ever seen mentioned is Coal and Ive never heard projectile length mentioned. When load data is posted what projectile length are they refering to?  .035 seems to be a substantial difference and could possibly make for a bad day if I was near max on my powder charge. 

 

So my long winded question is. What, if any, concern is projectile length when load data is given?  How would you decrease a load recipe in this case 10%, 20% etc...  Is there a formula or equation or a rule of thumb I dont know of?

 

thanks in advance

Bryan

Edited December 2, 2018 by Bmeehan19
Add pic

[MemphisMechanic]

Okay. The length in load data is a guide.

 

In the competition world we generally load as long as we can get away with - especialy for your doublestack 2011 because many of them are VASTLY more reliable with longer ammo.

 

Your guide isnt the book. It’s plunk and spin; load different length dummy rounds until you are long enough that it won’t spin freely when the round is plunked in the barrel. That means your bullet is contacting the rifling, which we don’t want.

 

I find my max OAL for a given bullet and barrel (you need check it uniquely for every gun and every bullet shape) then subtract .005” to ensure reliable feeding.

 

If a 147gr flat point won’t drop into a 9mm barrel once it gets to 1.155” .... I make sure all of my rounds come off the press under 1.150” so that I (literally) have some wiggle room.

 

Find your desired OAL that way, then load to the minimum charge weight in the book, and work your way up to desired PF with a chronograph. This almost always results in you loading significantly longer that book value, which only increases your safety margin by lowering chamber pressure.

 

Edited December 2, 2018 by MemphisMechanic

[Bmeehan19]

Great information. Thank you!  I guess I was “stuck” on the 1.20 coal. So I gather max coal for any given projectile will vary greatly based on shape. Can they be loaded to long in regards to case neck pressure holding the projectile tight enough and with enough surface area in the case neck for friction?

[MemphisMechanic]

Yes. But you’ll almost certainly run out of chamber length first.

 

1.180” to 1.200” isn’t uncommon for the custom built 40 S&W guns in Limited division. And that’s a huge length increase.

 

Edited December 3, 2018 by MemphisMechanic

[Hi-Power Jack]

You won't run into any problems with 4.1 gr WW231 - I use that in my 9mm.     

[SlappyMcTrigger]

Also check that they fit in your mags. Some guns will have enough freebore that your mags will actually be the limiting factor.