Chronos, load development and Recoil Springs

[Chapo]

I've developed loads many times, but something always goes wrong: run out of rounds, unable to get reliable chronos, etc.  I tend to reload about 25 of each load, shoot like 5 out the chrono and then decide on recoil spring based on feel.  But seems to me like I'm doing something wrong.  I never get to that perfect backwards recoil instead of up/down.   My question is: which order do you follow when developing a load? How many rounds do you reload and when do you decide on the recoil spring.  When testing rounds, do you look for dot rise and acquisition IOT select recoil springs?

 

House keeping: I have a CZ Czechmate open gun.  I am trying to switch from 124s to 115s.  Being looking at starting at 8.5-8.8gr of HS6.  Got 7, 8, 9, 10, 11, 12 and 13 recoil springs to test.  Last match I shot 8.1 HS6 under a 124g CMJ at 1.135-1.139" OAL but the recoil and dot acquisition was bad.  This new test will be with a new reamed barrel and load to 1.165".

 

Hopefully I'm making sense.

[zdali]

Roughly this:

1. Prep brass. 
2. work out OAL for the barrel/projectile combo.
3. load N sets of 10 rounds in .2 grain increments
4. shoot said rounds from rest, over chrono, for groups (yes I'm lazy)
5. pick the best group that makes PF 
6. pick recoil spring for said load
7. ???
8. profit

 

 

[Chapo]

Good idea

[Hollow-Point]

I know that 115 CPRN over 8.1 HS6 @ 1.163 makes 146pf in my Czechmate. I also load 25. Chrono 10 and “seat of the pants fee” test the rest…

[zombywoof]

video of gun during recoil, slo mo.

[DavidSeavey]

I think you're going to want to try different powders under 115s if what you want is a flatter shooting gun.   i started my cm with hs6 and felt it was more voilent than many others.  i'm using shooters world major pistol now, AA#7 is said to be basically the same powder too.  ive heard some can get enough 3n38 for major i think but maybe not with a 115.

 

you also have to still grip the gun, that'll help more than anything i think if youre already in the proper category of open 9 major powders, even on the faster end.

 

and you could have your slide and barrel cut for poppel holes if to flatten it out more, gonna take more powder for PF and hit your hand a little harder.

[Hollow-Point]

I was actually able to grab some AA7 recently too. I loaded up some ladder tests and will chrono and see how they feel soon…

[zzt]

For a Czechmate you definitely want to use SWMP or AA7.  You CAN get enough in the case without spilling when the shell plate turns.  

 

IMO, a chrono is useless when developing a load.  You'll need it later.  I also load a ladder with .2gr difference.  I don't bother to chrono, because I'm sure I'm going to make PF.  I shoot each load into a white no-shoot target from 1" away.  When I start to get more than a tiny bit of splatter out the front, I stop. You can keep that load, or drop back .1gr.  That load is the softest load in your gun.  It should also be flat.  Any more powder than that will make the gun shoot flatter, but it will hit your hand harder.  The reason is the excess gas jetting out the front increases felt recoil.

 

Now you chrono your load.  My gun is configured differently than yours.  11gr of SWMP under a 115 JHP @ 1,161"  OAL is the best.  However, It spills when the shell plate turns.  So, I dropped back to 10.8g.  Once you have the load, you tune your gun to it by varying the recoil and mainspring weights and the radius on the firing pin stop.   If it returns to zero you are golden.  If high, you need a heavier spring somewhere (usually the recoil spring).  If too low, use a lighter spring.

[Hollow-Point]

16 minutes ago, zzt said:

For a Czechmate you definitely want to use SWMP or AA7.  You CAN get enough in the case without spilling when the shell plate turns.  

 

IMO, a chrono is useless when developing a load.  You'll need it later.  I also load a ladder with .2gr difference.  I don't bother to chrono, because I'm sure I'm going to make PF.  I shoot each load into a white no-shoot target from 1" away.  When I start to get more than a tiny bit of splatter out the front, I stop. You can keep that load, or drop back .1gr.  That load is the softest load in your gun.  It should also be flat.  Any more powder than that will make the gun shoot flatter, but it will hit your hand harder.  The reason is the excess gas jetting out the front increases felt recoil.

 

Now you chrono your load.  My gun is configured differently than yours.  11gr of SWMP under a 115 JHP @ 1,161"  OAL is the best.  However, It spills when the shell plate turns.  So, I dropped back to 10.8g.  Once you have the load, you tune your gun to it by varying the recoil and mainspring weights and the radius on the firing pin stop.   If it returns to zero you are golden.  If high, you need a heavier spring somewhere (usually the recoil spring).  If too low, use a lighter spring.

I also ladder .2gn increments. Interesting on the white target. I’m also close to your COAL, I’m at 1.163…

[Chapo]

 Zzt, can you explain you shooting into the white no shoot target process?   Not sure I follow

[Sarge]

1 hour ago, Chapo said:

 Zzt, can you explain you shooting into the white no shoot target process?   Not sure I follow

I presume white just shows spatter easier. 

[Chapo]

Ok call me dumb, but what splatter are we talking about?  This is what I’m interpreting, you shoot your string of same powder weight on the white cardboard, then as you continue you observe gasses on the white board?

[DukeSoprano]

 

[shred]

First off, you're never going to get all the up/down out of the dot with ammo.  

 

We used to shoot 9x25 Dillon back in the day-- loads like 20gr of H108 and you could get the dot to recoil down, but you couldn't get it to go nowhere.  Even if you could, shot calling would be awful.

 

Ask some of the top open shooters what they use.  It's unlikely to be some crazy load.  Max M used to run 125 gr bullets and 7625 because he liked some movement in the dot and he did ok.  Back when Todd Jarrett was Sailer-ing everyone he ran 121s and 4756.

 

 

[zzt]

10 hours ago, Chapo said:

Ok call me dumb, but what splatter are we talking about?  This is what I’m interpreting, you shoot your string of same powder weight on the white cardboard, then as you continue you observe gasses on the white board?

 

The thread Duke posted explains more thoroughly.

 

You only have to shoot one or two shots of each powder charge to see what happens.  I hold the end of the comp 1" away from the no-shoot (easier to see the splatter).  There are two possible scenarios, soft and flat.

 

Soft:  you want to fully 'work' all the baffles in your comp with no gas (or very little) jetting out the front.  That's what the white board tells you.  You start with the lightest load in your ladder.  Progress to hotter loads and see what happens.  At some point the splatter coming out the front will increase.  You'll know you went too far.  The load you shot just before will feel softer, because there is no gas jetting out.  You can try an in-between load if you like.  Anything hotter than that will hit your hand harder.

 

Flat:  there is no rule that states your gun must shoot soft.  If it isn't as flat as you like, go hotter and put up with the increased recoil.

 

For a long time I shot a 10.2gr load of SWMP under a 115 JHP.  It made 169 PF.  Across many strings the slowest shot made 168 PF.  One shot made 167, so I knew I was safe at the chrono station.  I'm now shooting 10.8gr.  I have no idea what the PF is.  I know it makes major and is flatter and softer than the 10.2 load.  If I had more case capacity to work with, I'd go higher than 10.8.

[Chapo]

Duke, that link explained it perfectly.  Thanks.  Now I know how to proceed

[Chapo]

Makes sense zzt. Thank you so much!!

[Mlussoro]

What’s your load now? I think hs6 is to punchy, gave up on that powder right away, I run 38 sc in many of my guns, the CM is my first 9major gun, 8.2 3n38 is soft with 115s as I worked my way up to 124s over 8.0 even no softer yet! 
wolf 8lb recoil spring purrs like a kitten. I had thoughts of drilling popple holes for more gas but this thing doesn’t move  at least for me.  By the way RN or cmj can be loaded to 1.17 oal without reaming barrel and run perfect in mags.  Enjoy good sir 

[Chapo]

Mlussoro, I am developing a load with cmj 115s and hs6. Staring at 8.6gr and going up to 8.9gr. I have a 9lb spring right now but will try a 7 and 8 to see which is is flatter. I’m considering maybe switching to aa7 powder if hs6 splatter is too dirty. Thoughts?

[zzt]

I'm surprised if M makes major with a 115 and so little powder.  Maybe he has an extremely fast barrel.  I can literally not fit enough 3N38 in the case to make major with a 115 JHP.  I'm using it up for Open minor for SCSA.

 

My buddy started with a CM.  He was running 9.x 3N38 under a 124 to make major.  His rounds kept growing until they wouldn't chamber.  He switched to CPE and eliminated that problem.  I told him to go to SWMP.  I sold him 2 lbs. to try.  He did and said it felt like cheating.  It was much softer and flatter than the CFE load. 

 

C, unless you have gobs of HS-6 to use up, just go to SWMP or AA7.  More gas, lower pressure, softer and flatter.  I hate HS-6.  Dirty and the dot doesn't track right.

[Powder Finger]

On 3/10/2023 at 7:28 AM, shred said:

First off, you're never going to get all the up/down out of the dot with ammo.  

 

We used to shoot 9x25 Dillon back in the day-- loads like 20gr of H108 and you could get the dot to recoil down, but you couldn't get it to go nowhere.  Even if you could, shot calling would be awful.

 

Ask some of the top open shooters what they use.  It's unlikely to be some crazy load.  Max M used to run 125 gr bullets and 7625 because he liked some movement in the dot and he did ok.  Back when Todd Jarrett was Sailer-ing everyone he ran 121s and 4756.

 

 

Not to mention shooting out of perfect position or off balance 

[shred]

6 minutes ago, Powder Finger said:

Not to mention shooting out of perfect position or off balance 

Yup, chasing "ultimate flatness" is a fools errand...

 

[Powder Finger]

When I found it years ago I immediately started figuring out how to de-tune it. No one wanted to listen to the fact that the energy is still there and has to go somewhere 

[Mlussoro]

4 hours ago, Chapo said:

Mlussoro, I am developing a load with cmj 115s and hs6. Staring at 8.6gr and going up to 8.9gr. I have a 9lb spring right now but will try a 7 and 8 to see which is is flatter. I’m considering maybe switching to aa7 powder if hs6 splatter is too dirty. Thoughts?

Aa7 major pistol autocomp are all decent powders to look at, and the obvious cost it developing loads kinda sucks, with trying different powders, I have an abundance of 3n38 so I use it in all my comp guns.  Any reasoning for 115s 

[zzt]

16 hours ago, Mlussoro said:

Any reasoning for 115s

 

You need more powder to make major with a 115.  More powder = more gas.  That means softer and flatter if your setup can handle the additional gas.