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9mm Major, MG JHPs and Czechmates


JWBaldree

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Getting ready to start loading 9mm Major for my new Czechmate. I order 1K each of Montana Gold 115JHPs, 124 JHPs and 121 JFPs. In the two barrels that came with the gun, the JHPs will plunk test properly at 1.09 in the first and 1.06 in the second barrel, with the 121's going 1.10 and 1.07. I've been reading up and asking around, some guys say screw it and load to short OALs, some run just FMJs (my 147gn plated minor load at 1.16 will plunk just fine), and some break out the throater and make room in the barrel for JHPs at 1.16 or greater. 

 

Option 2 is out as I want to run JHPs or the JFP as that bullet profile will be different than anything else I load, and scream "MAJOR", do not put in anything but the Czechmate. So, should I work up with the short OAL's or break out the throating reamer, or some combination thereof? Is there a minimum safe OAL for 115 to 125 gn bullets? How about a safe maximum OAL?  I have read about some people loading 115 JHPs at 1.18 to 1.20, but that seems like vey little bearing surface for the case to grab onto. I've been loading for 30 something years, but 9mm Major has me confused and cautious.

 

 

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I used to load to 1.17" but agreed with you that there was "too little bearing surface",

so I now load at 1,16" with the MG 124 JHP's.

 

I shoot an STI, so have now problem with these - I've loaded down as low as 1.145"

but would be afraid to go down to 1.09" - let's see what some of the CZ experts say,

but I'd want to get to a throat reamer, myself.    :) 

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I am relatively new to loading for 9mm major, but depending on what powder you are using, 1.09 with, say the MG 124s, is going to be a compressed load and you are going to have issues with pressure.  Get the barrel reamed and then you have a much greater range to work up your loads out to 1.18 OAL.

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Loaded Major from 1.145 to 1.180 several different pistols

They all shot good groups with low SD

I usually run at 170-175 PF since that's were the comps seem to settle out well

BUT

it seems to be fairly common for CZ owners to get their barrels reamed?!?!?!

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I run 115gr Montana Golds RN at 1.145 oal over 7.4gr of AutoComp.  If I remember right the PF is 171 through my Czechmate.  I don't use the JHP for exactly the reasons you are discussing (loading very short)

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I agree 1.06 is way too short for 9mm Major. I think you are looking for an Earth Shattering Kaboom.  I would get the barrel reamed so you can load out long. I loaded 9mm Major I loaded out to 1.160 to 1.170, never has an issue with bullet tension. 

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I have reamed the throat on my Czechmate  +0.050 .  Now I can load any bullet.  The CZ mags will limit you to less then 1.160 if you want it to run.

I have used MG 124jhp & PD124jhp   6.8gn Auto-Comp @ 1.155 168pf.   PD 115gn jhp  7.6gn N350   @ 1.140  167pf.  

I am now using 125gn Blue Bullets.  8000 in my Czechmate.  6.6gn Auto-Comp @ 1.155 169pf.  6.9gn N350 @ 1.150 168pf.  7.0gn N350 @ 1.150 170pf

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4 hours ago, kneelingatlas said:

I ream by hand, just a few twists will do it.

That's how Matt Cheely does it as well. I took a barrel to him once. A few turns and that was it!

Edited by Sarge
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On 2/13/2017 at 11:35 AM, mjmagee67 said:

I agree 1.06 is way too short for 9mm Major. I think you are looking for an Earth Shattering Kaboom.

 

I don't think this is true.  While loading longer allows you to drop more powder before the tipping point after which velocity starts to drop off, I don't think it's possible to blow up your gun with a suitably slow powder under a 124 or lighter bullet.

 

I haven't collected any data, but I presume most "Kabooms" are the result of fast powder double charged under a heavily bullet (throw in an unsupported chamber for good measure) ;)

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8 hours ago, kneelingatlas said:

 

I don't think this is true.  While loading longer allows you to drop more powder before the tipping point after which velocity starts to drop off, I don't think it's possible to blow up your gun with a suitably slow powder under a 124 or lighter bullet.

 

I haven't collected any data, but I presume most "Kabooms" are the result of fast powder double charged under a heavily bullet (throw in an unsupported chamber for good measure) ;)

You probably won't make major with a slow powder loaded that short. It would be one hell of a compressed load. 

 

I was given a bunch a 38 Super so I had the chamber reamed and now have no problems. Open guns are fun to shoot but for some reason I like Production. 

Edited by mjmagee67
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5 hours ago, mjmagee67 said:

You probably won't make major with a slow powder loaded that short. It would be one hell of a compressed load. 

 

I was given a bunch a 38 Super so I had the chamber reamed and now have no problems. Open guns are fun to shoot but for some reason I like Production. 

 

I hate to derail your predictions with my experience, but I have made major loads at 1.100" and 1.077" using SP2 (similar to 3N38) and HS6 :cheers:

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4 hours ago, kneelingatlas said:

 

I hate to derail your predictions with my experience, but I have made major loads at 1.100" and 1.077" using SP2 (similar to 3N38) and HS6 :cheers:

Interesting......I've used Auto Comp and 3N37 both filled the case pretty full, I would worry about the bullet being pushed back out over time. But het I gave up on 9mm Major.

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1 hour ago, mjmagee67 said:

Interesting......I've used Auto Comp and 3N37 both filled the case pretty full, I would worry about the bullet being pushed back out over time. But het I gave up on 9mm Major.

How much WAC you using?!? I run 7.8 with 115's and its nowhere near full. I could easily seat to around 1.10 without compressing i'm guessing.

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1 hour ago, Sarge said:

How much WAC you using?!? I run 7.8 with 115's and its nowhere near full. I could easily seat to around 1.10 without compressing i'm guessing.

8.2 to 8.3 ish with 115gr PD HP.........haven't loaded 9mm Major in a while. My gun has 3 popple holes so it takes a little more powder than if it didn't.

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21 hours ago, kneelingatlas said:

I don't know why people are so worried about compressing powder.  I load 9.4gr of SP2 under a 115gr and it fills the case pretty close to the brim, what's the big deal?

I've heard the OAL  "can" growing on compressed loads if the neck tension isn't great, as we all reload mixed brass, we never really are 100% sure on the shape of the brass. Didn't want my gun/ mag to get jammed up. So I stayed away from compressed pistol loads, I do load compressed loads on my 30-06 and 204 Ruger.

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11 hours ago, mjmagee67 said:

I've heard the OAL  "can" growing on compressed loads if the neck tension isn't great, as we all reload mixed brass, we never really are 100% sure on the shape of the brass. Didn't want my gun/ mag to get jammed up. So I stayed away from compressed pistol loads, I do load compressed loads on my 30-06 and 204 Ruger.

Mine grew for sure. But I was using Dillon die. I use a Udie now so not sure if they would still grow if I were using the same loads.

 It never concerned me and would only do so if I were already loading as long as the gun could handle.

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1 hour ago, Sarge said:

Mine grew for sure. But I was using Dillon die. I use a Udie now so not sure if they would still grow if I were using the same loads.

 It never concerned me and would only do so if I were already loading as long as the gun could handle.

I would be very concerned if I had to load short with a compressed load because the lead on my barrel was so short. Like it seems the OP has to do. If he is loading at 1.10 to keep from hitting the rifling and he loads a compressed load, that seems like a recipe for disaster. Wouldn't want the round to grow to the point where it jams the bullet up against the rifling. 

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