9mm coal for 125 JHP


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double d
December 16, 2009, 11:11 PM
Lyman's indicates 1.075" for the coal for 125 JHP's in 9mm. This seems
a bit on the short side to me. I normally load 124 FMJ RN to 1.135", but
I ran out. All that remains in the room is 125 JHP, and I have no experience with this bullet. Any advice would be appreciated.

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1SOW
December 16, 2009, 11:20 PM
The hollow point is shorter.

In a 125gr Zero bullet is about .03something shorter than 124gr Montana Gold CMJ.

I've been loading M.G. 124CMJ bullets at 1.135, and I'll be loading the zeros (if they come in) at about 1.1" and start at .2 grs less powder.

Others have said they were using 1.08"

I load light for a 130pf/1050+.

Edit to ref. walkalong's data: MGcmj: .592-ish Zero 125jhp: .567

Zero is about .025 shorter than my MGs. Using the same seating depth may not be the best load for the Zero, but it gives me a sanity check for starting the new load test.

And of course, as rfwobbly1 said, you can load longer ( reduce seating depth) by adding more powder.

double d
December 17, 2009, 09:35 AM
Thanks, 1SOW. I'll give that a try (load light and go shorter).

Walkalong
December 17, 2009, 09:53 AM
I have loaded the Zero # 161 9MM 125 Gr JHP at 1.080 O.A.L. with good success. The bullet is an average .567 long vs the longer FMJ bullets out there.

rfwobbly
December 17, 2009, 10:25 AM
Double D -

Given that most 9mm RN and round ogive HP will load out to nearly the SAAMI max of 1.169".... The COAL and the powder charge are a personal trade off. You can get higher pressure and the desired bullet speeds either by seating deeper OR adding more powder.

For a factory that's loading zillions of bullets a day, saving 1gr of powder per round represents a huge cost savings. They may choose to load this ammo short. Reloaders on the other hand have a choice. You can load longer in order to get more of your favorite "fluffy" powder in there (like Unique), or you can load shorter to save on more costly powders (like VihtaVuori).

Personal preferences for cartridge length also play a large part. When I'm shooting practical pistol matches, the last thing I want is a failure to feed issue. Therefore I'm going to want to work with a COAL that's out between 1.130 to 1.150" so that I can be sure that every round slips out of the magazine and into the chamber the same slick way. Let me stress.... there are certainly shorter COALs that will work reliably, that's just my personal preference.

"Leade" and "freebore" also enter the picture. Some European 9's (like CZ) demand a shorter COAL in order to enable the nose of the bullet to stay out of the rifling. Specifying a COAL of 1.075" would certainly get around that issue and allow the round to fit a wider selection of pistols. But again, this is totally dependent on the chamber/ bullet shape interplay on a select group of guns.

More information on the exact bullet and exact gun would help us help you.

rcmodel
December 17, 2009, 01:48 PM
Lyman is using a Sierra 125 JHP.

Other bullets from different manufactures may have a slightly different ogive or nose shape, and may require a different OAL to feed properly.
Or miss the rifling leade.

You have to figure out the necessary OAL depending on the shape of the bullet brand you are using.

rc

rfwobbly
December 17, 2009, 02:13 PM
Other bullets from different manufactures may have a slightly different ogive or nose shape, and may require a different OAL to feed properly.
Or miss the rifling leade.

You have to figure out the necessary OAL depending on the shape of the bullet brand you are using.

I fully agree. Here's a graphic I had previously posted that touched on this...

double d
December 17, 2009, 06:32 PM
Thank you very much for the information. I am shooting a S&W 952-1,
which accepts the 124 round nose at 1.135" very well. I have never run a
JHP through this gun. The 125 gr bullets are Zero, and I have no experience
with these either. This is not my carry weapon, nor IDPA gun. Strictly
paper punching with this 9mm.

With this information, I plan to load 3.9 grs of Bullseye at 1.08" and wortk my
way up (in stages) to 4.5 grs at 1.135". I suspect 5 of each will let me know
what the gun likes. I was just afraid to go down to 1.075" without some
advice. Thanks.

rfwobbly
December 18, 2009, 12:21 AM
Double -
I have no experience with the gun or the bullet. But you always want to know where you stand with new bullets. So take a new bullet and push it into a fired case. You'll see it's sort of a slip fit. Set the OAL way out past max and then slide the test cartridge into your naked barrel's chamber. Push the primer end of the case until the case mouth bottoms out on the end of the chamber. If the bullet hits anything it will get seated deeper into the case. Carefully remove that test cartridge and record the length. Do that several times until you come up with the same number. Subtract about .020" from that measurement and you'll have the max OAL for that bullet in that barrel.

Now pretend the OAL turns out to be 1.155". Being close to the rifling, 1.155" is going to give you your best slow fire accuracy. But if you want to fire 200 per in competitions, then maybe you might want to aim for 1.145" knowing that the OAL can wander by .010" without causing safety issues. Or maybe you want to load 5 @ 1.155", 5 @ 1.145", 5 @ 1.135", etc and fire those in a ladder sequence until you get a desired velocity or clean burning load.

There's just a lot of ways you can use the max COL information.

double d
December 18, 2009, 10:10 AM
Thanks, RF.
I'll go give that a try.

double d
December 18, 2009, 11:56 AM
The 125 JHP Zero bottoms out at 1.136" on my S&W 952-1 barrel.
At 1.135", I am really close to the max, so I will back it off to 1.126"
for this bullet in this gun, and try it for accuracy. I don't see much
sense in dropping back to the Lyman 1.075", but I will try different
powder loads at the 1.126" length.
Thanks to all for the help.

rfwobbly
December 19, 2009, 01:31 AM
If you got 1.136" on several tries with several sample bullets, then you might be able to use 1.126" but it would have to be the maximum and not the average OAL. Working with a number such as 1.120" might be somewhat safer and easier to measure at the same time. Then you could allow 1.120 +/-.005", in other words anything 1.115 to 1.125".

Remember, all presses deliver some variation in OAL. Please account for that.

Walkalong
December 19, 2009, 10:19 AM
Now that you know how short you must keep it as determined by your barrel, all you need now is to determine an O.A.L. shorter than that that feeds 100% in your gun.

In an very accurate gun like your 952, it may even prefer a certain O.A.L. for accuracy.

double d
December 19, 2009, 06:27 PM
Thanks RF and Walkalong. I know from experience the gun likes a 124 gr
RN at 1.135". I will find out Tuesday what it likes in the 125 JHP. Last night
I loaded some test rounds at 1.126, 1.120 and 1.115. I suspect it'll cycle
with all three, and once I find the best grouping, I'll play with powder loads
at the best coal. None of this would have been necessary had I not run out of 124 RN. Thanks again for your help.

Walkalong
December 19, 2009, 07:19 PM
Don't you hate it when you run out of your favorite bullet! :D

Maybe you will find a new "favorite", or at least a good enough substitute if you run out again.

The Zero #161 & #162 125 Gr JHP's shoot extremely well in my .38 Super. I bet they shoot well for you. :)

chineseboxer
December 19, 2009, 11:01 PM
Double -
I have no experience with the gun or the bullet. But you always want to know where you stand with new bullets. So take a new bullet and push it into a fired case. You'll see it's sort of a slip fit. Set the OAL way out past max and then slide the test cartridge into your naked barrel's chamber. Push the primer end of the case until the case mouth bottoms out on the end of the chamber. If the bullet hits anything it will get seated deeper into the case. Carefully remove that test cartridge and record the length. Do that several times until you come up with the same number. Subtract about .020" from that measurement and you'll have the max OAL for that bullet in that barrel.

Now pretend the OAL turns out to be 1.155". Being close to the rifling, 1.155" is going to give you your best slow fire accuracy. But if you want to fire 200 per in competitions, then maybe you might want to aim for 1.145" knowing that the OAL can wander by .010" without causing safety issues. Or maybe you want to load 5 @ 1.155", 5 @ 1.145", 5 @ 1.135", etc and fire those in a ladder sequence until you get a desired velocity or clean burning load.

There's just a lot of ways you can use the max COL information.
Wouldn't you want to be as close to the rifling as possible for best accuracy?? .020 seems alot to back off. I am a newbie myself, not doubting your knowledge, just curious what your feelings are.

Walkalong
December 20, 2009, 01:12 PM
Depends on the barrel etc, etc.

.020 off the lands in pistol is fairly close, and a good minimum to start at.

rfwobbly
December 20, 2009, 09:29 PM
Wouldn't you want to be as close to the rifling as possible for best accuracy?? .020 seems a lot to back off. I am a newbie myself, not doubting your knowledge, just curious what your feelings are.

Mr Boxer -
You are exactly correct. However, it's also important to account for the variation the press and dies are going to throw into the finished OAL. Not knowing what press or dies he's using, what exactly he uses the ammo for, etc, etc, I'd rather err to the safe side.

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