New Bullet, How Much to Reduce Powder Charge

[9mmepiphany]

I decided to go with a heavier bullet for my IDPA revolver load and was wondering if folks here had any experience they'd like to offer. I'm shooting a 4" .38Spl revolver.

I'm currently loading a BNB Casting Hi-Tek coated lead RN NLG 160gr bullet over 3.46 grs of Clays, ignited by a Federal SPP, loaded to an OAL of 1.49". It is flying pass my Chrono screens at about 700pfs for a PF of about 112.

I've going to try the same company's 170gr RN NLG bullet which is about .030" longer and has a slightly different profile. When seated with my Redding Competition Seating die (very consistent), at the same setting as used with the lighter bullet, I'm getting an OAL of 1.50"

(Sidebar: another nice thing about the heavier bullet is that the base isn't flat but slightly beveled; makes placing the bullet in the case mouth a bit smoother)

What I need is about 650fps with the heavier slug to make a PF of about 110.

I was thinking about starting by reducing my load to 3.2 grs of Clays and work up or down from there.

Has anyone worked with this bullet weight and this powder who has found a unusually accurate load that I can try?

Thanks in advance

 

[ArchAngelCD]

Sorry, even though I load a 170gr Cast Bullet in the .38 S&W I don't load one in the .38 Special.

The charge you mentioned sounds like a good place to start. You will find the right numbers fairly quickly I'm sure.

Why are you going to a heavier bullet, just curious?

EDIT:
I don't know which bullets they use, this data is from the current Lyman Cast Bullet Handbook.
.38 Special Tested in a 4" Universal Receiver.

160gr Lyman #358311 OAL= 1.550"
Clays - 2.7gr 776 fps - 3.0gr 854 fps

170gr Lyman #358429 OAL= 1.537"
Clays - 2.3gr 722 fps - 2.9gr 824 fps

I'm not sure if the data helps but it can't hurt to have it. Your data seems a little high against what Lyman is publishing.

 

[9mmepiphany]

I have a friend who is atop tier revolver competitor in IDPA, USPSA, and ICORE, who I asked for a recommendation as to which bullet to use. He recommended the 170gr...said it worked so well that he hadn't even tried the 160gr or the 158gr slugs. What caught my eye was the bevel base of the 170gr which just seemed like it would make placing the bullet straight in the case mouth easier.

My understanding is that I won't really see any improvement in accuracy until I get pass 40 yards...IDPA now allows 50 yard shots on Standards stages

The price difference isn't huge. When buying the bulk packs the 160gr bullets are packaged in 2650 lots while the 170gr bullets are packaged in 2500 lots. Prices include shipping via USPA Priority Mail Med Flat Rate box (ordered Thurs night, shipped on Fri, arrived on Mon) and insurance http://www.bnbcasting.com/

 

[Walkalong]

Might load six at 3.0 and try them first, as Clays is very quick, and spiky at the top, but 3.2 sounds like where you may end up, considering the FPS you are getting now.

3.0 grs Clays and an X-Treme 158 @ 1.440 OAL gave me 637 FPS at 56 degrees, and coated generally runs around 50/75 or so FPS faster than plated of the same weight/shape in light .38/.357 loads with fast powder. 3.1 and a Berrys 158 gave 657. 3.2 and the X-Treme 158 gave 709.

I have not shot anything heavier than that in .38 Spl.

 

[mdi]

I don't shoot in competition, but whenever I change bullets I resort to the starting load as noted in my manuals...

 

[9mmepiphany]

If I intended to do that, I wouldn't be asking here.

Making Power Factor for IDPA is nothing close to pushing the cartridge's ragged edge. A pretty standard load is 3.2 - 3.5grs under a 158/160gr bullet to make a reliable PF to knock down steel

I'm so far off that edge that I'm not even going to lengthen my OAL to allow for the longer bullet. I figure with all that extra space in the case, a long bullet seated deeper might actually help consistency.

Once I settle on a powder charge, I'll likely play a bit with OAL. The old and new bullets both lack Lube Grooves and Crimp Grooves, so it does allow me a bit of latitude to explore accuracy at longer ranges...not that I'm complaining about < 4" at 50 yards

 

[9mmepiphany]

Might load six at 3.0 and try them first, as Clays is very quick, and spiky at the top

That sounds like a good idea. I might be pleasantly surprised.

I'm taking a bit of care here and will actually weigh individual charges while working up a load I have until the middle of August to settle on something

 

[Sunray]

3.4 grains of Clays is .3 grains over max for either a cast or jacketed 158(close enough to 160) for starters.
For reason known only to them, Hodgdon didn't test a 170 with Clays. Not seeing Clays and 170 grain bullet anywhere else either. However, it's typical to reduce by 10% and work up.
"...placing the bullet straight in the case mouth..." That's what the flaring is for.

 

[9mmepiphany]

3.4 grains of Clays is .3 grains over max for either a cast or jacketed 158(close enough to 160) for starters.

I'm shooting these loads in a S&W M-686. IDPA does require +P loads to make power factor. If I were using moonclips, it would require .357Mag level loads

"...placing the bullet straight in the case mouth..." That's what the flaring is for.

While that is a good starting point, placing a flat cylinder onto a flared opening doesn't make for inherent alignment. A beveled cylinder will always align more easily into a flared opening. It also helps maintain that alignment between stations on a progressive press, where a flat cylinder (base of bullet) will be inclined to tilt due to inertia at the beginning and end of the rotation between stations.

 

[Zendude]

Does a beveled base on a lead bullet affect the chance of leading in the barrel? It seems like a flat base would provide a better gas seal. I have not loaded plain lead bullets before, so I'm not familiar at all with plain lead bullet technology.

 

[9mmepiphany]

Don't know...these aren't plain lead, they are coated with a polymer coating

 

[GooseGestapo]

3.46gr? Seriously????

3.4-3.5gr is fine.
5.0 might lock up your gun.
7.0 if it'll fit in the case would likely split a cylinder.
But personally, I'd use just 3.0(+/- accuracy of powder measure), likely to be more accurate. Work up to required pf, quit there.

 

[9mmepiphany]

3.46gr? Seriously????

I know it sounds strange, but I was looking to load a "heavy " 3.4grs...3.4grs wasn't getting quite enough of a cushion for Chrono and I knew 3.5grs was excessive.

I would have settled for 3.45, but the metering insert wouldn't stabilize there when I tightened the lock ring. Set at 3.46grs, my throws would run between 3.44grs - 3.48grs during a 500 -800 round progressive reloading run

 

[hdwhit]

9mmepiphany wrote:
I would have settled for 3.45,...

Have you got the tools to reliably measure powder to the 1/100 of a grain?

Personally, I would like to be able to measure and throw powder in 1/100 grain increments so that I could know my 20.3 grain charges were really 20.30 and not 20.27 or 20.33. I am just not familiar with equipment that is both repeatable and precise enough to deliver charges to within 1/100 grain.

 

[jmorris]

Does a beveled base on a lead bullet affect the chance of leading in the barrel? It seems like a flat base would provide a better gas seal.

Often flat base bullets are more accurate than BB ones but FB are not as forgiving to less than ideal casting or rough handling.

Have you got the tools to reliably measure powder to the 1/100 of a grain?

I would assume when he said ""heavy" 3.4" is was taking 10 charges and dumping all 10 into the same pan on the scale. Then the scale read 34.5 grains and he moved the decimal over one because on average over 10 drops the scale had dropped 3.45 grains.

Kind of like if you drop a 3.4 grain charge and a 3.5 grain charge combined they weigh 6.9gn. 6.9gn divided by two charges = 3.45.

I am just not familiar with equipment that is both repeatable and precise enough to deliver charges to within 1/100 grain.

Repeatable is a lot cheaper than precision but either can be bought.

If you watch this one you can extrapolate that a kernel of 3031 for example weights about .017 grains, as 12 kernels weigh .2 gn. If you fast forward to the end you can see a 505 beam scale and photo switch that can detect the addition of a single kernel.



Even though it can repeatedly detect the difference of a single kernel you can't precisely set it to that because of the resolution of the fine adjustment on beam is to the tenth (.1).

If that's too crude for you one of these will do the job repeatable with precision for a couple thousand more dollars.

http://www.scalesgalore.com/product/index.cfm?product_id=5973

 

[9mmepiphany]

Might load six at 3.0 and try them first, as Clays is very quick, and spiky at the top, but 3.2 sounds like where you may end up, considering the FPS you are getting now.

Wow, you were right in the ball park

Loaded up some of the extras Tony included in the boxes... 1% extra (50/5000)... and took them out to the range today. 80 degrees, 30% humidity, about 1230hrs
BNB Casting Hi-Tek 2 coated .358" 170 gr RN NLG
W-W cases
Federal SPP
OAL 1.511"
4" S&W M-686

3.0 grs - 656fps; PF 111
3.1 grs - 670fps; PF 113
3.2 grs - 684fps; PF 116
3.3 grs - 710fps; PF 120

I only need 618fps to make the minimum PF of 105, but I'm thinking a PF of 115 should reliably take down steel and leave enough fudge factor during Chrono at matches. I'll put together some "heavy" 3.1 gr loads to try out for accuracy