BBI / N320 Minor Load Development Frustration...Help!

[acceler8]

Hey everyone, I’m hoping someone can offer some help. I’ve been trying to develop a minor load for my G34 using VV N320. So far I’ve tried BBI 135s and 147s, and Xtreme 147 HPs. I’m using mixed brass and Winchester SPP. So far I have only been testing for accuracy, and haven’t chrono’d any of the loads.

For some reason, I haven’t gotten very consistent results. The first time out at the range, I tested the Xtreme 147s and BBI 135s using N320. For the Xtremes, I also loaded one batch using CFE Pistol. I shot 5 shot groups, rested on a bag, at about 20 yards. I first shot a control group using factory new Freedom Munitions 147 gr RN. The group measured 2.23”. Here are the results for my reloads:

• Xtreme 147 HP, 3.4 gr N320, 1.135” - 2.39” group

• Xtreme 147 HP, 3.9 gr CFE, 1.135” - 2.46” group

• BBI 135, 3.6 gr N320, 1.130” - 1.79” group (the 5th shot wasn’t on the paper, so I think this was a fluke with the 4 shots being 1.79”)

 

The next time out at the range I tested BBI 147s, using 3.4 gr N320, at OALs 1.120-1.160” at 0.010” increments. Same shooting setup, except this time I decided on 10 shot groups to hopefully get more conclusive results. The best group I managed was about 4” at 1.140” OAL, but the rest were in the 6-7” range.

 

In addition to shooting groups I’ve shot all the loads for feel. I decided that I preferred the feel of the BBI 135s so I decided to focus on those. This time I loaded 10 rounds each at 3 different powder charges (3.5, 3.6, and 3.7 gr N320) and 6 OALs (1.110-1.160” in 0.010” increments).

• 3.5 gr - Best group was 2.14” at 1.160” OAL. Not bad at all! However, all other OALs were over 4” groups.

• 3.6 gr - All groups were 4” or more.

• 3.7 gr - All groups were 4” or more. At 1.110” OAL, the groups were horrible! Only 4 shots made it on the paper.

I've shot good groups with the Xtremes, so I was starting to think my gun just didn’t like BBIs until today when I shot that one good group. I guess I could just switch over to the Xtreme 135s, but I’d like to get these BBIs to work. Maybe I can confirm the 3.5 gr at 1.160” makes PF, and just go with it?? However, I noticed another slight problem with this load. It will not pass the plunk test in my barrel. It takes slight pressure to chamber the last 0.020-0.030” and some force/wiggling to get it back out. OALs shorter than about 1.130” plunk just fine.

Anyone have any ideas what could be going on??

I tried attaching pictures of the groups but the "Insert image from URL" isn't working.

Thanks!

[MemphisMechanic]

You're doing this backwards. Trying to find an accurate load before figuring out what your gun will eat?!

Use the plunk test to find your Max OAL first. Stick with that unless you simply cannot work up an accurate load, and need to try going shorter.

Load a few and chrono until you figure out what charge weight is roughly 130 power factor with a chrono, and build up until you know what will be 133 to 135 power factor in your gun.

(most of us chase softest possible felt recoil and load to 127-130 power factor when new. Then figure out you can't tell 133 from 127 while shooting a stage, and it's usually more accurate, more reliable, and hits steel better)

With a 133ish power factor and a known-good OAL, play with the crimp you're using first to try to dial in accuracy. 90% of newer reloaders over-crimp. Juuuust remove all trace of belling from the case, and stop! Think of it as a de-flaring die. Not actually crimping. You do not want to deform the soft lead bullet or damage the coating on your BBIs. When pulled, you should barely see a ring around the bullet in the coating where the case mouth rested.

Try that for starters. 133-135 PF. Light crimp. Dialed-in OAL.

 

[HOGRIDER]

My G17 & G34 like the 135g RN coated along with 3.7g of N320 at 1.135"!

 

[Feegee Dean Matlock]

I shoot the 115 and 125 grain BBI in my open gun for 2 years now and they are super accurate and leave nothing in the comp. I know your not asking about open loads but I am just saying BBI is a very good bullet. Lot better than Xtreme.

[DesertTortoise]

disclaimer: As a reloader for 9mm, I'm probably only a few weeks ahead of where you are. But here on the internet, I'm an expert.

In my 34, anything longer than 1.15 is pushing it for max OAL /  "plunk test"

Rounds failing the plunk test are going to give you excessive headspace (which is bad) and feed unreliably

I've read here that any crimp beyond removing the bell affects accuracy and causes leading with plated and coated lead. Have you pulled any bullets to see what happening to the projectile? You are looking for shaving the projectile happening during seating and compression of the projectile caused by too much crimp (causes the round not to fully engage the rifling)

 

Edited September 12, 2016 by DesertTortoise

[rowdyb]

to me, a 2.5" group of 5 rounds at 20 yards would would be good to go and no need to chase my tail searching for "more better".

i've had issues with almost every plated or coated bullet i've shot at one time or another. with the exception of Berry's plated. Or montana gold or precision delta.

either the projectiles themselves were inconsistent in some way or i was doing something wrong at the press.

no one likes to hear it, and i bristle at it often as well, but maybe it's you? try another gun or another person. reduce the number of variables in the equation.

[nwhpfan]

Every day you shoot a test group of your loads you should shoot a group of FM.  That way you'll always know if it was you or not.

[acceler8]

Thanks for the replies, guys.

Honestly, I'm really not trying to find a load that's 125.1 PF and shoots sub 1" at 25 yards. I just want to find something 130-135 PF that shoots 2-3" at 25 yards so I can start cranking them out. I enjoy shooting and practicing much more than reloading, or tinkering trying to find the "perfect" load.

I have no doubt the problem is me, but I think the problem is at the press, not at the range. For example, the one good 10-shot group I got (out of 18) happened to be the 7th that I shot. I won't completely rule it out, but find it unlikely that I shot six bad groups, shot a great one, then shot another 11 bad ones. I'm just confused by the inconsistency I'm seeing, especially since all those test loads were loaded in the same session. I will also add that all have fed and cycled without issue. Even the longer ones that didn't freely plunk, but again, it only took very slight finger pressure with the barrel out of the gun to get them to fully chamber the last little bit.

The more I think about it, I have a feeling it's crimp related. I didn't think I was over-crimping, since I tried to only crimp enough to get the rounds to case gauge, but I'll double check it. I'll shorten them up so they plunk, pay attention to the crimp, and load up a few more test rounds to see what happens. I'll also try to remember to take some 124 gr HST I have to use as another factory loaded control group, and if I have time, I'll shoot some groups with my G19 and M&P9.

Will report back. 

Good group out of the 18:

Edited September 13, 2016 by acceler8

[acceler8]

This is about what most of the other groups averaged:

 

[AzShooter]

With coated bullets you don't want to crimp.  You simply want to take out the bell.  The bullets should stay in place and I've found them to shoot much better that way.

[oteroman]

Clays with 124gr. And under.
For bunny farts.....

[uewpew]

Acceler8,

Have you chrono'd the rounds?  Are you seeing much change in velocity from the different seating depths?

What kind of brass are you using?  I found that with some brass having thicker walls i had to flare the heck out of it to keep it from shaving the coating off during seating.  I sort my brass now and only use Win, FC, & RP for reloading my 9mm.  As for crimp, I use Lee dies and use only a 1/4 turn.  

[jeffm_norcal]

+1 on the crimp issue.  If you haven't pulled one yet, do that before anything else.  BBI are great bullets but suffer if over crimped.   I use 3.7 of N320 at 1.125 with 135s, in a S&W M&P Pro.  It makes a very consistent 134PF and is more accurate than I am.  A great resource for BBI loading issues is BBI itself BTW.  Chandler has always given me great tips and responds super quick.  

If length becomes a limiting factor consider getting a throat reamer from Brownells.

[IDescribe]

On 9/12/2016 at 11:43 PM, acceler8 said:

This is about what most of the other groups averaged:

 

You notice how those two high shots are right where your good group was on the other target?  I suspect that those were your two good shots of this string.  That lateral stringing on the other 8 shots, that's not ammo.  That's the shooter.  

Edited October 10, 2016 by IDescribe

[bandw1dth]

When messing with the crimp I've taken to measuring case wall thickness, multiplying by two, and then adding that to the bullet diameter. From there I just adjust my crimp die till I get the aforementioned value. That way the belling is completely removed and the case is nice and snug against the bullet.


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