Chronos, load development and Recoil Springs

[Chapo]

Loaded some 115s with 8.6-8.9 of HS6 with 7lbs recoil spring at 1.165" OAL with reamed barrel.  Based on the powder splatter of the no-shoot white target, seems like all my loads were dirty which means I am over working the compensator.  This might lead me to believe that I need to lower the powder charge below 8.6gr (lowest I shot). But, the string of 8.6grs yielded 166PF.  So I can't go any lower or I'll loose the Major. 8.8grs seemed the best on recoil and my wrist (175 PF).

 

So if I understand correctly, I would have to increase my load from 9grs to maybe 9.5grs to probably shoot the flattest, but I would venture to say this would almost take me to like 180-185PF and lots more of gasses and splatter coming out of comp.  Attached video of my testing.  Please share thoughts..... Also ordered AA7 to give it a try and compared results to HS6

 

 

[zzt]

C, HS-6 is a filthy powder.  There is nothing you can do about it.

 

I think you should stick to 124s.  You have too much gas jetting out the front.  I would not go up to 180 PF trying to make it shoot flat.  Try AA7 and 124s.  BTW, you need a heavier recoil spring.  Also, it looks like you are forcing the gun down with your left hand.

[Chapo]

Zzt, thanks for the feedback !! why a heavier recoil spring if the gun seems to be in battery?  What do you estimate would happen with 115s and AA7? Thanks 

[zzt]

It's not a question of going into battery.  Your slide speed is excessive.  At the end of the stroke it slams into the frame and tilts the gun up.  At least half of your muzzle rise is due to that.

 

Try progressively heavier springs.  You can't tune a CM as well as a 20121, because you don't have as many options.  So use the heaviest spring that allows the slide enough dwell time to properly feed the next round.  Then adjust your grip so the gun returns to zero.

 

Your weak hand index finger should be under the trigger guard, not wrapped around it.  You have an up/down/up/down/up/down wiggle as the gun returns to zero.  That means your grip is not proper and you are trying to force the gun down.  The middle row of knuckles on your right hand should fit in the crease behind the first row of knuckles on your left hand.  You rotate your left hand forward like you were shaking hands.  The back, fleshy part of your left palm must go over your right hand finger and press against the grip.  Your left thumb is placed horizontally on the front of the frame.  Do not touch the slide.  60% of your grip comes from your left hand.

 

CM comps are not very efficient.  There is no getting around that unless you change something.  I believe a 115 with AA7 at major will make more gas than your comp can handle.  A 124 will make less gas at major, so you have a shot at redirecting all the gas before if exits the front of the comp.

 

When you have more gas than your comp can handle, you can add side ports, like this Brazos comp.  The fourth chamber has two side ports.  Their purpose is to redirect any remaining gas so it doesn't jet out the front.

 

You can also add poppels behind the cone.  Poppels always flatten the gun.  They rob gas from the comp, which will help you.  I have this barrel in my backup Open gun.  There are three 5/32" poppels in the barrel.  Three 5/32s are the equivalent of two 3/16s.  I cannot fit enough AA7 or SWMP in the case to get any gas jetting out the front with a 115.  It shoots super flat, and my hand strength is nothing to brag about.  

[Chapo]

Your feedback is very valuable great sir. Thank you. Do you Recommend any replacement comps that would fit the Czechmate?

[jubi351]

A lot of people with CMs run the Seb comp. 

 

[RangerTrace]

I've never jacked with springs because I depend on my gunsmiths to do their thing.  No doubt I could squeeze a little more performance out of the gun if I did. However, I do take the time/money to get a nice feeling load to make PF easily.  For example, at the advice of Bruce Gray, I'm going from 147s to 124s.  I loaded up some RMR 124 grain match winners yesterday with 4.0 grains of N320 to 1.125".  They were exactly 125 PF today, so I bumped to 4.2 grains and loaded 200 for tomorrow nights match.  

[Chapo]

26 minutes ago, jubi351 said:

A lot of people with CMs run the Seb comp. 

 

Do they ship to the US?

[jubi351]

I would assume so, I've personally seen two CMs in North Carolina using them.

[Hollow-Point]

17 minutes ago, Chapo said:

Do they ship to the US?

Yes they do

[Chapo]

Will have to give ‘em a try

[Mlussoro]

14 hours ago, zzt said:

 

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.

I feel as 124s are softer, but I’m used to supercomp . Where 115s are snappy 124s or 125jhps are noticeably flatter and don’t hit in the hand. Less dot movement as well. 

[zzt]

8 hours ago, Mlussoro said:

I feel as 124s are softer, but I’m used to supercomp . Where 115s are snappy 124s or 125jhps are noticeably flatter and don’t hit in the hand. Less dot movement as well. 

 

Then your comp/setup could not handle the extra gas.

[Mlussoro]

Meh semantics I like 124s you like 115- I’m not Gona argue about it , my chaos, check and sti all run great on 124s with little to no muzzle rise at all

[Chapo]

Zzt, bought some AA7. Should get here next week. Based on my video and your feedback, I’m gonna try 124s with AA7. I like loading to 1.165” but at what grains should I start? I’m thinking 9.2 to 9.8 of AA7. Thoughts?

[zdali]

7lb recoil spring?? This isn't 2011 land dude. At best you'll eat slide stop pins, and at worst the barrel recoil lug itself. There's a reason why they come with 14lb from factory.

[zzt]

11 hours ago, Chapo said:

Zzt, bought some AA7. Should get here next week. Based on my video and your feedback, I’m gonna try 124s with AA7. I like loading to 1.165” but at what grains should I start? I’m thinking 9.2 to 9.8 of AA7. Thoughts?

 

Sounds about right.  I'd start with ten rounds at 9.4.  Use a 9 lb. recoil spring to start.  Shoot one round and see what happens.  If you have to adjust spring weight, do it.  Save at least five rounds to chrono.  That will tell you where you have to be, charge-wise.  Then make a ladder from 168 PF to 172 see what feels best.

[Chapo]

Thanks. Will report later how it went when I get the powder…

[Chapo]

So I went to the range today and shot 9.4-9.8gr of AA7 through my Czechmate.  Loaded to 1.165" with 124gr Everglades CMJ.  Used a 9lb Spring.  But I am confused by the results... What are your thoughts..

 

9.4: PF 191, SD 19. 

9.6: PF 178, SD 12

9.7: PF 177, SD 6

9.8: PF 175, SD 15

 

It seemed to me that the higher the powder charge, the softest it got in my hand, but the splatter increased with more powder.  Should I lower the powder and start maybe at 9.1gr AA7 to see how the gas look like? Thinking this might be harder on the hand?

 

Attached the splatter test

 

 

 

Edited March 21, 2023 by Chapo

[Hollow-Point]

The higher the charge the lower the PF?

[Chapo]

Yup. That has me perplexed 

[VeilAndrew]

Is 191PF accurate? Did you mean to type 181PF? That is very high regardless.

[Hollow-Point]

Yeah the numbers seem to be off? Wonder if the chrono is off? 

[Chapo]

Well it’s been shot before. And I feel loose plastic inside.  But seems to be working….

[zzt]

I'd go for 9.6 or 9.7 and call it done.  Invest in a new chrono.  Having tried most of them, I like the Pro Digital Chrono with Bluetooth the best.  Fewest compromises, easy to use and accurate.