Relationship between muzzle energy and compensator

[Exlonghorn]

I am breaking in a new STI DVC-S.  The test fire target that shipped with the gun indicated 124gr +P ammo was used.  I normally practice with 115gr WWB in my other un-compensated guns.  So I figured I'd get a range of different ammo weights and velocities to see what works best.  Was surprised to see 124gr +P ammo running 380 muzzle energy and regular 124gr WWB running 396.  Is this typical that +P has less muzzle energy than non-+P for the same bullet weight?

[Guy Neill]

Generally you would expect the +P to give higher velocities - given equal bullet weights.  +P is, of course, referring to the chamber pressure, and, depending on the powder used, it may be that the pressure is, in fact, +P, but the pressure came about before higher velocities were reached.

 

In kinetic energy, the velocity component is squared in the calculation, so a faster bullet will give higher energy.  For the energies quoted, it would seem the 115gr has a muzzle velocity of 1245 fps while the 124gr is giving 1175 fps.

 

 

[Exlonghorn]

Glad I got the different ammos to try out.  It doesn't like to cycle anything under about 365 ft/lbs, but even that is inconsistent. Had repeated stovepipes and FTF on the following...

• Winchester White Box  9mm 115gr.  - Muzzle Energy: 362 ft.-lb.
• Remington UMC Handgun, 9mm, MC, 147 Grain - Muzzle Energy: 320 ft.-lbs.
• Federal Champion 9mm Luger Ammo 115 Grain FMJ Value Pack - Muzzle Energy: 323 ft.-lbs.
• Sellier & Bellot 9mm Luger 115gr FMJ - Muzzle Energy 418 ft. lbs (wondering if this is really the case...even the NATP and +P ammo didn't get this high)

Successfully and reliably cycled:

• WINCHESTER USA 9MM NATO 124GR FMJ - Muzzle Energy: 396 ft lbs
• Monarch® JHP 9mm 124-Grain - 351 ft.-lbs.

Tomorrow will try:

• Monarch 115gr 9mm Luger Steel Case (Lacquer Coated) - 453 ft lbs. (really curious about this but don't plan to make a habit out of shooting steel cased ammo)
• Hornady American Gunner 9mm Luger +P 124gr XTP - Muzzle Energy: 380 ft lbs.

[Sarge]

Why all the muzzle energy stuff? We deal in power factor typically when talking about competition guns. I have no idea what PF you are getting with any of the numbers listed.

  First thought is the gun probably need close to 1000 rounds through it before it’s even broken in unless the DVC’s are loose enough not to need it. Second thought, what # recoil spring comes in the gun from the factory? If it’s not a 7 or less change it once broken in.

[Guy Neill]

Here's how the above list of ammunition breaks down with respect to velocity and power factor;

Bullet                                           Power

Weight     Energy     Velocity     Factor

115           362          1191          137

147           320            990          146

115           323          1125          129

115           418          1280          147

124           396          1199          149

124           351          1129          140

115           453          1352          153

124           380          1175          146

 

We are normally more familiar with the velocities than the energies./  And, as Sarge said, power factors ( FORM OF MOMENTUM).

 

 

 

[Exlonghorn]

Sarge, that's a good point about the break-in period.  I only have about 200 rounds through it at this point, so it's got a ways to go before things settle in.  I should've calculated the power factors up front.  I've added the power factors below.  As I understand it, muzzle energy and power factor are somewhat synonymous.  Both are calculated using bullet weight and velocity.  PF favors slower, heavier bullets.  Muzzle Energy favors faster, lighter bullets.  Using power factor explains why the heavier, slower Monarch 124's outperformed the lighter WWB 115gr. in spite of having lower muzzle energy.  Lesson learned.  Using the power factor approach, these light but very fast Monarch 115's should be interesting.

 

I believe it comes with a 7lb spring, but I read another case of a guy who had the identical problem.  Will consider mounting the C-More optic on a 90deg. mount as one of the guys suggested, along with swapping out the spring after I reach 1K rounds.

 

DID NOT reliably cycle the following:

• Remington UMC Handgun, 9mm, MC, 147 Grain - Muzzle Energy: 320 ft.-lbs.  Power factor: 130.53
• Federal Champion 9mm Luger Ammo 115 Grain FMJ Value Pack - Muzzle Energy: 323 ft.-lbs.  Power factor: 135.70
• Winchester White Box  9mm 115gr.  - Muzzle Energy: 362 ft.-lb.  Power factor: 136.85
• Sellier & Bellot 9mm Luger 115gr FMJ - Muzzle Energy 418 ft. lbs   Power factor: 147.20 (wondering if this is really the case...even the NATP and +P ammo didn't get this high)

Successfully and reliably cycled:

• Monarch® JHP 9mm 124-Grain - 351 ft.-lbs.  Power factor: 140.37
• WINCHESTER USA 9MM NATO 124GR FMJ - Muzzle Energy: 396 ft lbs  Power factor: 141.36

Tomorrow will try:

• Monarch 115 gr 9mm Luger Steel Case (Lacquer Coated) - 453 ft lbs.   Power factor:  152.84 (curious about this but don't plan to make a habit out of shooting steel cased ammo)
• Hornady American Gunner 9mm Luger +P 124gr XTP - Muzzle Energy: 380 ft lbs.  Power factor: 145.70
• Will also run through more of the Winchester NATO rounds as 140 might be the magic number at this point

Some other possibilities after doing some searching...in order of increasing cost per round:

• Federal American Eagle 9mm Luger Ammo 124 Grain Full Metal Jacket PF 142.60
• Aguila 9mm Luger Ammo 115 Grain +P Full Metal Jacket PF 143.75
• Geco 9mm Luger Ammo 124 Grain Full Metal Jacket  PF 146.32
• Federal American Eagle 9mm Luger Ammo 147 Grain Full Metal Jacket PF 147.00
• Speer Lawman CleanFire 9mm Luger Ammo 147 Grain Total Metal Jacket PF 160.23

I imagine I'll get into reloading eventually...first things first.  Will see if I can get it to run with the higher PF ammo during the break-in period.

Oh, and I don't care for the STI mags.  UpLula's don't work very well on them.  I miss my incredibly reliable XD mags (that are now my wifes...haha).

 

 

[yigal]

14 hours ago, Guy Neill said:

Generally you would expect the +P to give higher velocities - given equal bullet weights.  +P is, of course, referring to the chamber pressure, and, depending on the powder used, it may be that the pressure is, in fact, +P, but the pressure came about before higher velocities were reached.

 

In kinetic energy, the velocity component is squared in the calculation, so a faster bullet will give higher energy.  For the energies quoted, it would seem the 115gr has a muzzle velocity of 1245 fps while the 124gr is giving 1175 fps.

 

 

[olstyn]

12 hours ago, Exlonghorn said:

DID NOT reliably cycle the following:

• Remington UMC Handgun, 9mm, MC, 147 Grain - Muzzle Energy: 320 ft.-lbs.  Power factor: 130.53
• Federal Champion 9mm Luger Ammo 115 Grain FMJ Value Pack - Muzzle Energy: 323 ft.-lbs.  Power factor: 135.70
• Winchester White Box  9mm 115gr.  - Muzzle Energy: 362 ft.-lb.  Power factor: 136.85
• Sellier & Bellot 9mm Luger 115gr FMJ - Muzzle Energy 418 ft. lbs   Power factor: 147.20 (wondering if this is really the case...even the NATP and +P ammo didn't get this high)

Successfully and reliably cycled:

• Monarch® JHP 9mm 124-Grain - 351 ft.-lbs.  Power factor: 140.37
• WINCHESTER USA 9MM NATO 124GR FMJ - Muzzle Energy: 396 ft lbs  Power factor: 141.36

 

Have you chronoed these loads through your gun, or are you going by what the boxes say?  If the latter, then it's pretty unlikely that those figures are accurate for your gun.

[Exlonghorn]

Olstyn, yeah I'm just taking the info off the websites.  I agree that a couple seemed intuitively unlikely. If I really get into this Open gun thing I'll look at chronos or maybe see if my range has one to borrow/rent.

 

So for today, everything I shot cycled properly.  Shot the Monarch 115gr until I noticed sparks when the rounds hit the back barrier (indoor range).  Nope, can't use that anymore.  That's okay...I wasn't a fan of shooting lacquer-coated, steel case ammo anyway.

 

Looks like WINCHESTER USA 9MM NATO 124GR FMJ is the winner at this point.  Put another 200 rounds through and didn't have a FTF.  Unfortunately, it's difficult to find this in bulk.  However, I found 2,000 rounds of  Federal American Eagle 9mm Luger Ammo 124 Grain Full Metal Jacket (PF 142.60) that worked out to $0.21/Round including shipping.  Would've liked to get closer to  $0.18/Round, but will keep working on that.  If anyone has a recommendation on ammo that is readily available in bulk and gets to at least a 140 PF, let me know!

 

Interestingly, I ended the day with 50 rounds of Sellier & Bellot 9mm Luger 115gr FMJ that weren't working yesterday.  No problems today, but will need to shoot more to verify.  

 

To Sarge's point, break-in appears to be a likely contributing root cause to yesterday's issues, along with having some pretty low power factor ammo in the mix.  Up to 500 total rounds through now and things are working well.

Edited April 8, 2019 by Exlonghorn

[superdude]

17 hours ago, Exlonghorn said:

Looks like WINCHESTER USA 9MM NATO 124GR FMJ is the winner at this point.  Put another 200 rounds through and didn't have a FTF.  Unfortunately, it's difficult to find this in bulk.  

 

 

If this helps:   

 

https://www.targetsportsusa.com/winchester-usa-9mm-ammo-nato-124-gr-fmj-q4318-p-697.aspx

 

https://www.budsgunshop.com/catalog/product_info.php/products_id/53428/winchester+ammo+9mm+nato+124+gr+q4318+full+metal+jacket+50%2fbx

 

https://grabagun.com/winchester-ammunition-q4318-9mmnato-124-fmj-50-rounds.html

 

 

[MikeBurgess]

One big thing your missing is how the manufacturer achieves the velocity they are specking for each round.  I can make 130 ish PF 9mm with anywhere between 2.5 and 7 grains of powder 

depending on what powder bullet and OAL combination I choose. with a compensator you need to understand that that powder is counteracting the recoil energy that cycles the gun, so two rounds with similar energy or momentum(PF) numbers may once the effect of the comp is taken into account have quite different side velocities. and with a new gun and factory springs you are very close to the functional limit depending on what ammo you choose.

[Hi-Power Jack]

20 hours ago, Exlonghorn said:

  If I really get into this Open gun thing I'll look at chronos 

 

If you get into Reloading, you should have a $75 chrono.      

[Exlonghorn]

superdude, that did help (don't know how I missed that on TargetSports). Thanks!

[superdude]

1 hour ago, Exlonghorn said:

superdude, that did help (don't know how I missed that on TargetSports). Thanks!

 

You're welcome! Glad it helped. Ammo is expensive! 

 

What happens to be in stock at the moment you search makes a big difference. I tend to check a couple of places when I'm looking for ammo. Saving even a little helps a lot.