9mm COL & short chamber

[hot chili powder]

I have a CZ P-07 Duty. The chamber is short, heard this about CZs, so must make COL shorter then manuals suggest, any problem with this? Also, when doing plunk test the cartridge does not always freefall out, may need a little shake of barrel then it drops freely. Have had no noticable problems with feeding or chambering. the pistol shoots well for me & my 72 yr old eyes. Anyone have thoughts on this? My COL seems to vary by .003" to .005" no matter what style bullet I use, mostly Nosler & Everglades JHP. Tried DGBullets (coated lead RN) & they must be seated a bit deeper. All are 115gr, so that's my story, now your turn!

 

[fxvr5]

First, the loaded round should fall out on its own, or it hasn't truly passed the plunk test.

You can set the OAL at whatever is required as long as you reduce the powder charge if the OAL is less than the published length in your data.

OAL will normally vary a few thousandths. No problem.

 

[rfwobbly]

You could actually have multiple issues going on.

First, the loaded round should fall out on its own, or it hasn't truly passed the plunk test.

This is true. The test I setup for myself is that the round has to...
1. Fall all the way into, and then back out of the chamber using only the weight of the bullet
2. While all the way in (and head spaced properly) be able to rotate freely

How you get there depends upon a lot of testing to prove what the actual problem(s) are.

Hope this helps.

 

[Charlie98]

so must make COL shorter then manuals suggest, any problem with this?

A cartridge with small internal volume, like the 9mm, is very sensitive to changes in OAL... so if you are seating the bullet deeper into the case, you will need to reduce your load and work back up to it. Further, and maybe the CZ owners can suggest something, you might be able to find a bullet with a different profile that would allow normal seating depth and still pass the plunk test.

 

[hotshot357]

I found that SNS Casting has a 135grain bullet that has been re-profiled to be used in short lead barrels. I purchased 1000 of them and they work like a charm !!! I'm loading mine at 1.150 and they pass the plunk test.

 

[JDGray]

Unless your using a max load, you will most likely be safe loading a bit deeper. I like Power Pistol for this reason, 6.0gr is far from a max load, gives me plenty of room for error, plenty of zip with 115, 124gr pills.

 

[cutthroatdave]

Unless your using a max load, you will most likely be safe loading a bit deeper. I like Power Pistol for this reason, 6.0gr is far from a max load, gives me plenty of room for error, plenty of zip with 115, 124gr pills.

How much is "plenty of room for error" I am asking because last night I seated qty. 4, 124 gr FMJ RN bullets too deep. I am most likely going to pull them and not shoot just to be safe but I am curious to hear what others have experienced.

 

[higgite]

How much is "plenty of room for error" I am asking because last night I seated qty. 4, 124 gr FMJ RN bullets too deep.

How much is "too deep"?

 

[LeftyTSGC]

The OP (at least I have not seen) never stated what his COAL is. There are many options for bullets that have short profiles that a short COAL doesn't mean much based on the profile of the bullet. If you take the recommend bullet and COAL in your load manual you can see how long the bullet is, add the bullet and case length and subtract the OAL. then you can see how much of the bullet is actually seated in the case. If your type bullets seat the same in the case with their load but you have a short profile then the COAL will not be as much a factor. You do want to be careful not to cause pressure spikes or load to short, but there are ways of figuring it out, the COAL in the reload manuals is based on their particular setup. Your COAL is based on your particular setup. Using caution of course to stay within specs.

 

[lordpaxman]

How much is "plenty of room for error" I am asking because last night I seated qty. 4, 124 gr FMJ RN bullets too deep. I am most likely going to pull them and not shoot just to be safe but I am curious to hear what others have experienced.

It depends...On how much did you reduce the COL, what powder, what bullet type and weight, and in some measure your gun including jump to the lands. If you’re running a really squirrelly powder like Titegroup, 10-20 thousandths shorter COL on an almost max load can cost you your gun or more. Your FMJs are harder to push down the barrel than a lead or coated, given the same dimensions. If I have to shorten COL, I make sure I’m using published data for the powder charge and start at the minimum. I also have a few guns that usually will allow a longer COL and will first test in those working my way down in COL. I chrono those loads and get an idea of how they perform before going too far, with the understanding that loads perform differently in different guns. Good luck!

 

[murf]

suggest you clean your chamber and try the plunk again.

luck,

murf

 

[tightgroup tiger]

He hasn't answered a post since his OP on Mar 19th.
Think it's a drive by post. Not wasting my time.

 

[cutthroatdave]

It depends...On how much did you reduce the COL, what powder, what bullet type and weight, and in some measure your gun including jump to the lands. If you’re running a really squirrelly powder like Titegroup, 10-20 thousandths shorter COL on an almost max load can cost you your gun or more. Your FMJs are harder to push down the barrel than a lead or coated, given the same dimensions. If I have to shorten COL, I make sure I’m using published data for the powder charge and start at the minimum. I also have a few guns that usually will allow a longer COL and will first test in those working my way down in COL. I chrono those loads and get an idea of how they perform before going too far, with the understanding that loads perform differently in different guns. Good luck!

I am shooting an M&P shield, I used Power Pistol for powder and the deepest was .063" too deep, another was .059 too deep, based on a desired 1.150" COAL. Two of them were only .010" too deep and I shot them without issue today. Thanks for the input.

 

[cutthroatdave]

The OP (at least I have not seen) never stated what his COAL is. There are many options for bullets that have short profiles that a short COAL doesn't mean much based on the profile of the bullet. If you take the recommend bullet and COAL in your load manual you can see how long the bullet is, add the bullet and case length and subtract the OAL. then you can see how much of the bullet is actually seated in the case. If your type bullets seat the same in the case with their load but you have a short profile then the COAL will not be as much a factor. You do want to be careful not to cause pressure spikes or load to short, but there are ways of figuring it out, the COAL in the reload manuals is based on their particular setup. Your COAL is based on your particular setup. Using caution of course to stay within specs.

So far I have stayed with published data in my reloading, usually from Hornady's book. I'm trying to get to point with my skill level in shooting lets me know when one load is more accurate than another. The only thing I've figured out so far is how far I have to go and how much I don't know.

 

[LiveLife]

I have a CZ P-07 Duty. The chamber is short, heard this about CZs, so must make COL shorter then manuals suggest, any problem with this? All are 115 gr, so that's my story, now your turn!

For my load development, I will use the barrel to determine the "max OAL" that will allow the round to drop in the chamber freely with a "plonk" and spin without hitting the rifling then fall out freely. Then I will feed/chamber the dummy round (no powder, no primer) from the magazine without riding the slide and incrementally decrease the OAL until round reliably feeds/chambers which is my "working OAL" - https://www.thehighroad.org/index.p...rel-find-a-max-o-a-l-with-your-bullet.506678/

For my powder work up, if my "working OAL" is significantly shorter than published OAL, I will consider reducing the start/max charges by .2-.3 gr. And once I identify the powder charge that produces the smallest groups, I will incrementally reduce the OAL (without compressing powder charge) to see if group size gets smaller. If reducing the OAL does not shrink the group size, I will use longer OAL. If reducing the OAL shrink the group size, I will use shorter OAL - https://www.thehighroad.org/index.p...-and-discussions.778197/page-10#post-11419509

I am shooting an M&P shield

These are max/working OALs that work with my M&P Shield 9mm and different bullets - https://www.thehighroad.org/index.p...col-for-reference.848462/page-2#post-11465109

M&P Shield 9mm, factory barrel

NOTE: Max OAL listed. Recommend "Working" OAL of 1.050" for 95 gr FMJ, 1.130" for 115 gr FMJ/RN and 1.135"-1.145" for 124 gr FMJ/RN but use the OAL that works with your barrel without compressing powder charge:

• Montana Gold 95 gr JHP: 1.090"
  
• RMR 95 gr FMJ: 1.135"

• X-Treme 100 gr RNFP: 1.100"

• Berry's 115 gr RN: 1.169"
• Berry's 115 gr HBRN-TP: 1.169"
• Hornady 115 gr HAP: 1.130"
• HSM 115 gr RN: 1.169"
• PowerBond 115 gr RN: 1.169"
• Rainier 115 gr RN: 1.169"
• RMR 115 gr FMJ: 1.169"
• RMR 115 gr FP MW: 1.145"
• RMR 115 gr JHP Mini MPR: 1.110"
• Speer 115 gr TMJ: 1.169"
• Winchester 115 gr FMJ: 1.169"
• X-Treme 115 gr RN: 1.169"
• Zero 115 gr FMJ: 1.169"

• Berry's 124 gr RN: 1.169"
• Berry's 124 gr HBRN-TP: 1.169"
• Hornady 125 gr HAP: 1.120"
• HSM 124 gr RN: 1.169"
• MBC 124 gr RN Hi-Tek (SmallBall): 1.080"
• MBC 124 gr CN Hi-Tek (Cone 9): 1.165"
  
• PowerBond 124 gr RN: 1.169"
• Precision Delta 124 gr JHP: 1.135"
  
• Rainier 124 gr RN: 1.169"
• Remington 124 gr FMJ: 1.169"
  
• RMR 124 gr FMJ: 1.169"
• RMR 124 gr FP MW: 1.140"
• RMR 124 gr JHP MPR: 1.105"
• Speer 124 gr Gold Dot HP: 1.169"
  
• Speer 124 gr TMJ: 1.169"
• X-Treme 124 gr RN: 1.169"

• RMR 135 gr FP MW: 1.115"

• RMR 147 gr FMJ: 1.160"
• RMR 147 gr FP MW: 1.130"

 

[Walkalong]

He hasn't answered a post since his OP on Mar 19th.
Think it's a drive by post. Not wasting my time.

He may be reading the thread, just not posting yet.

 

[Walkalong]

Maybe.......

 

[cutthroatdave]

For my load development, I will use the barrel to determine the "max OAL" that will allow the round to drop in the chamber freely with a "plonk" and spin without hitting the rifling then fall out freely. Then I will feed/chamber the dummy round (no powder, no primer) from the magazine without riding the slide and incrementally decrease the OAL until round reliably feeds/chambers which is my "working OAL" - https://www.thehighroad.org/index.p...rel-find-a-max-o-a-l-with-your-bullet.506678/

For my powder work up, if my "working OAL" is significantly shorter than published OAL, I will consider reducing the start/max charges by .2-.3 gr. And once I identify the powder charge that produces the smallest groups, I will incrementally reduce the OAL (without compressing powder charge) to see if group size gets smaller. If reducing the OAL does not shrink the group size, I will use longer OAL. If reducing the OAL shrink the group size, I will use shorter OAL - https://www.thehighroad.org/index.p...-and-discussions.778197/page-10#post-11419509


These are max/working OALs that work with my M&P Shield 9mm and different bullets - https://www.thehighroad.org/index.p...col-for-reference.848462/page-2#post-11465109

M&P Shield 9mm, factory barrel

NOTE: Max OAL listed. Recommend "Working" OAL of 1.050" for 95 gr FMJ, 1.130" for 115 gr FMJ/RN and 1.135"-1.145" for 124 gr FMJ/RN but use the OAL that works with your barrel without compressing powder charge:

• Montana Gold 95 gr JHP: 1.090"
  
• RMR 95 gr FMJ: 1.135"

• X-Treme 100 gr RNFP: 1.100"

• Berry's 115 gr RN: 1.169"
• Berry's 115 gr HBRN-TP: 1.169"
• Hornady 115 gr HAP: 1.130"
• HSM 115 gr RN: 1.169"
• PowerBond 115 gr RN: 1.169"
• Rainier 115 gr RN: 1.169"
• RMR 115 gr FMJ: 1.169"
• RMR 115 gr FP MW: 1.145"
• RMR 115 gr JHP Mini MPR: 1.110"
• Speer 115 gr TMJ: 1.169"
• Winchester 115 gr FMJ: 1.169"
• X-Treme 115 gr RN: 1.169"
• Zero 115 gr FMJ: 1.169"

• Berry's 124 gr RN: 1.169"
• Berry's 124 gr HBRN-TP: 1.169"
• Hornady 125 gr HAP: 1.120"
• HSM 124 gr RN: 1.169"
• MBC 124 gr RN Hi-Tek (SmallBall): 1.080"
• MBC 124 gr CN Hi-Tek (Cone 9): 1.165"
  
• PowerBond 124 gr RN: 1.169"
• Precision Delta 124 gr JHP: 1.135"
  
• Rainier 124 gr RN: 1.169"
• Remington 124 gr FMJ: 1.169"
  
• RMR 124 gr FMJ: 1.169"
• RMR 124 gr FP MW: 1.140"
• RMR 124 gr JHP MPR: 1.105"
• Speer 124 gr Gold Dot HP: 1.169"
  
• Speer 124 gr TMJ: 1.169"
• X-Treme 124 gr RN: 1.169"

• RMR 135 gr FP MW: 1.115"

• RMR 147 gr FMJ: 1.160"
• RMR 147 gr FP MW: 1.130"

Thank you, this is great information. I have been measuring the COAL with calipers. My biggest concern with seating bullets too deep was with the increase in pressure that would result. I hadn't found anything that would tell me what the powder weight equivalent would be for pressure increase due to short COAL.

 

[LiveLife]

My biggest concern with seating bullets too deep was with the increase in pressure that would result. I hadn't found anything that would tell me what the powder weight equivalent would be for pressure increase due to short COAL.

What OALs were you using?

And what bullet weight and nose profile?

 

[lordpaxman]

Thank you, this is great information. I have been measuring the COAL with calipers. My biggest concern with seating bullets too deep was with the increase in pressure that would result. I hadn't found anything that would tell me what the powder weight equivalent would be for pressure increase due to short COAL.

Kudos for understanding shorter COL will result in higher pressures.
There are posts in this forum from someone that shows a graph, for a particular powder, for a particular load that shows the pressure increase due to seating depth decrease. My search capabilities cannot find it.
The problem is, there is no easy way to predict empirically how much pressure for how much less depth. There is a program called QuickLoad that attempts to do this, but it is just an approximation. There are many variables involved, and you’re dealing with a non-linear world.
I have used my chrono data for small changes in seating depth, like .005” increments, and tried to predict using a linear approximation for additional velocity change vs depth in the hope I’m in a relatively linear part of the overall curve. The cautionary note is this is for velocity, which is related to but is not pressure. It was also for N320 which is a forgiving powder. I hope this makes some sense. Good luck!

 

[JDGray]

How much is "plenty of room for error" I am asking because last night I seated qty. 4, 124 gr FMJ RN bullets too deep. I am most likely going to pull them and not shoot just to be safe but I am curious to hear what others have experienced.

Well, 6.0-6.6gr Power Pistol is the data for 125 jacketed bullets at 1.150", and I'm loading 115/124gr bullets at 1.150", at 6.0gr, so if I had to seat .010" deeper, it would not worry me a bit.

 

[sevt_chevelle]

I found that SNS Casting has a 135grain bullet that has been re-profiled to be used in short lead barrels. I purchased 1000 of them and they work like a charm !!! I'm loading mine at 1.150 and they pass the plunk test.

I have those bullets, and found that DG bullets offers the same bullet. They both hit the lands in my PCR at around 1.129

 

[sparkyv]

My CZ P-07 easily has the tightest headspace of all my 9mms. It's right at or up to 7 thousandths under SAAMI for RNs. I load to the CZ requirements and all the others are good to go.