RN vs RNFP vs FP COL?

[sl33py]

Hey all. I'm just getting into reloading and could use some help.

I have the Lyman, and Hornady reloading books (both latest). Unfortunately neither has any load data on two of the bullets i have (9mm 135gn RNFP and FP).

I have 4 bullets in varying weights and styles (not very smart as i have to adjust my seating die each time i swap - live and learn). I'm looking forward to testing them out and figuring out which i like best in the long run and i'll stick with just that one (if can easily source).

Sorry to be long winded, my question is regarding COL, especially for the odd 135gn bullets. I have one set that is FP, and one that is RNFP.

I've only loaded up about 15 rounds of each(124 RNFP, 135 RNFP, & 147 RN are at 1.150-1.155) in varying charges in .2 increments (Titegroup 3.2, 3.4, 3.6). Hope to chrono these w/ a buddy tonight after work. Hodgdon shows min-max for 124 @ 3.6-4.1 so might be too light... I'll ensure all cycle my Sig P320 carry (3.9"), and chrono to get close to factory velocity. Then i'll adjust from there.

The recommended charges i've found have all been 135 LRN of titegroup 3.2-3.6 @ 1.150, how should i adjust COL for the 135 FP? I am working off someone else's load data and i know this is somewhat dangerous, so i will start at 3.2 and make sure no signs of pressure in primers before moving up to 3.4 and again to 3.6. These were using Bayou LRN, so my xtreme 135 FMJRNFP should seal less and be lower pressure (and velocity) so i hope i have some additional safety "wiggle room". The odd ducks will be the Hi-Tech coated LFP 135's i need to figure out COL. Haven't loaded any of these untili i figure this out.

Looking at the loaddata.com min-max are shown as 1.095 to 1.169 - so does that really mean that any 124/135/147 is OK anywhere in that range? That doesn't seem to jive with the COL's i'm seeing in the book for the regular 124/147 bullets.

Appreciate any info and enlightenment you can share!

 

[LiveLife]

Since most published load data were tested using single shot universal barrel fixtures (instead of actual pistols), even when using the same bullet type as tested, your results may differ (in terms of chamber pressures/muzzle velocities) and us reloaders must independently determine which OAL will reliably feed/chamber rounds from the magazine for our different pistols and which powder charges will reliably cycle the slide and extract/eject spent cases while monitoring accuracy.

When I am conducting load development with a new bullet and find varying published load data, I first determine the working OAL/COL that works with my pistol/barrel/magazine and conduct powder work up using the most conservative load data, especially if I am using shorter OAL than published - http://www.thehighroad.org/showthread.php?p=8864541#post8864541

If your barrel is oversized (.357"+ compared to typical .355"-.356") with longer leade/freebore that requires longer working OAL, you may need to use more than published max charges.

Look at the comparison picture below of various 9mm bullet shapes and you'll notice difference amount of bullet base/bearing surface length that will produce different depths of bullet seating even though they are the same bullet weight (Different bullet seating depth will produce different chamber pressures with the same amount of powder charge). The different nose shapes (ogive) will require different working OAL so the bullet nose won't hit the start of rifling when chambered.

So, instead of going crazy using different OALs and powder charges:

1. Use your barrel to determine the max OAL
2. Feed/chamber the dummy round (no powder/no primer) from the magazine to determine the working OAL
3. Conduct powder work up from most conservative published start charge in .2-.3 gr increments
4. Determine the powder charge that reliably cycle the slide and extract/eject the spent cases
5. Increase the powder charge in .1 gr increments towards max charge while looking for accuracy trends/nodes
6. Optional: Chrono identified accurate loads to verify muzzle velocities and lower SD numbers

 

[Captaingyro]

It's not such a bad idea to try different bullets...you'll be doing that for most of your reloading career. One thing that helped me was realizing that seating dies are relatively cheap. Buy two or three, number them, and then keep notes on which die is adjusted for which bullet.

 

[sl33py]

Thanks BDS! re-read that linked discussion a few times - great info!

Couple questions - how do you make the "test case" that is loose enough to push the bullet into it when it touches the rifling in the barrel? I saw a video on youtube w/ a rifle cartridge that the guy cut a "V" out of the brass to let the bullet slide back easily - is something like that needed?

Thanks Captaingyro - i guess it'll give me the practice to work this up again and again. I am going to log what works and chrono #'s - looking forward to tinkering a bit and comparing a couple powders as well. With scarcity sometimes, i'd like to have a couple options with the "recipe" already dialed in for a run of ammo to reload. Also going to compare a couple rounds w/ CCI vs Federal SP primers to see if it makes much/any difference. I'm collecting brass and next up is some .45 ACP reloading!

Just getting a bit impatient to get some loads confirmed and ammo loaded to go shoot! I am going to shoot some steel plates tonight w/ factory ammo and shoot the chrono between. Can't wait to have a good confirmed "recipe" to load and take my own vs factory!

Really appreciate the info and help!

 

[LiveLife]

how do you make the "test case" that is loose enough to push the bullet into it when it touches the rifling in the barrel?

You can use such tool to determine max/working OAL but I just use a regular case and bullet.

With the barrel out of the pistol, I will resize a case to make sure it freely drops into the chamber with a "plonk" (hence the plunk test) as overly expanded case won't fully chamber even after being resized.

Now knowing that my resized case will fully chamber in the barrel, I then flare the case mouth and starting with SAAMI OAL/COL of 1.169" with .377" taper crimp for .355 diameter bullet (.355"+.011"+.011"=.377" and .378" taper crimp for .356" bullet), I will incrementally seat the bullet deeper (say .005" increment) until the dummy round drops in freely with a "plonk" and spin without hitting the rifling.

 

[sl33py]

You can use such tool to determine max/working OAL but I just use a regular case and bullet.

With the barrel out of the pistol, I will resize a case to make sure it freely drops into the chamber with a "plonk" (hence the plunk test) as overly expanded case won't fully chamber even after being resized.

Now knowing that my resized case will fully chamber in the barrel, I then flare the case mouth and starting with SAAMI OAL/COL of 1.169" with .377" taper crimp for .355 diameter bullet (.355"+.011"+.011"=.377" and .378" taper crimp for .356" bullet), I will incrementally seat the bullet deeper (say .005" increment) until the dummy round drops in freely with a "plonk" and spin without hitting the rifling.

thanks for the step-by-step bds!

I was reading the linked thread and was wondering if i could actually "push" the case and seat the bullet that way... Your step by step clarified that for me.

I'm ok sacrificing a case to see if i can modify one to easily do this. If that doesn't work, i'll try incrementally seating a bullet until it plonks in correctly for my barrel.

Much appreciate the detail and help!

 

[Toprudder]

Here is a case I made for determining max COL for a given bullet and gun. Seat bullet long, then just push into the chamber. Remove and measure. I reduce the COL at least .020 from that max length, more if necessary for mag fit and feeding reliability.

 

[sl33py]

Thanks for the example Toprudder - i can easily make that w/ a dremel, a sacrificial case, and a few minutes spare time. Instead of guessing and using some COL's i found for 147 (figuring more case volume since a smaller 135gr bullet), i'll try this first.

I'm visual and this totally makes sense!