Adding Weight to a P320 Trigger

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Adding Weight to a P320 Trigger Empty Adding Weight to a P320 Trigger

Post by Asa Yam on 11/17/2019, 4:02 am

In another thread, I asked the question "How does one add 1/2 lb. to the pull weight of a P320 trigger?"  After experimenting, here is one solution.

Experimental Equipment:

  • Box-stock SIG P320.  Trigger pull weight:  IIRC, in excess of 5 lbs.*;
  • Grayguns P320 Competition Trigger System w/ curved trigger.  (See https://grayguns.com/product/grayguns-p320-competition-trigger-kit/ );
  • Wheeler Engineering Trigger Pull Scale.  (Non-digital unit.)

Procedure:

  • Verify pistol is unloaded;
  • Remove magazine, then remove slide;
  • Remove trigger pack from grip;
  • Disassemble trigger per video at https://www.youtube.com/watch?v=p_Legc6I1eQ (Alma Cole's video);
  • Install Grayguns kit parts per video, managed to lose the safety lever spring in the process.  (It turns out, in this gun, it isn't needed!);
  • Reassemble pistol;
  • Perform 3 function checks.  Pistol functioned correctly (missing spring not an issue);
  • Weigh trigger.  3.5 lbs.  No good for bullseye shooting SO;
  • Reverify pistol is unloaded.
  • Repeat pistol disassembly;
  • Remove trigger pack from grip;
  • Remove triggerbar from trigger pack;
  • Remove Grayguns Trigger Bar Spring from pack and lever.  NOTE:  The spring included in the Competition Trigger System is of slightly smaller diameter (.003" less) than the stock part - this is mentioned in the video;
  • Install SIG Trigger Bar Spring (i.e., original part);
  • Reassemble trigger pack;
  • Reassemble pistol;
  • Perform 3 function checks.  Again, pistol functioned correctly; 
  • Weigh trigger. Consistent trigger break just above 4 lbs.  Will see if this value falls over time.

Plan to verify long-term pull weight stability of this installation by firing pistol.  If trigger weight drops below 4 lbs., the following options are still available:

  1. Order replacement Trigger Bar Springs.  At $4 each from SIG, don't think it will break the bank to have a few spares, and;
  2. Think about installing stock Sear Springs in place of Grayguns units. Two pairs (4 springs) come w/ kit, again, wire diameter is smaller than that of a stock part.

Impressions:

  • Pull of modified trigger is lighter;
  • Pistol appears to be more controllable when dry firing (sights move less);
  • Overtravel stop tube really does reduce overtravel.

Will report more after live firing pistol.  Until then, hope this helps.

* = EDITED TO ADD:  Trigger pull on another unaltered P320 was 7 lbs.


Last edited by Asa Yam on 11/17/2019, 1:50 pm; edited 1 time in total (Reason for editing : Added note about trigger pull measurement of another stock P320.)

Asa Yam

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Post by Ghillieman on 11/17/2019, 12:51 pm

This is great info! I may look into doing these mods on my M17 copy. Now, is there a bomar style sight replacement?
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Post by LenV on 11/17/2019, 1:01 pm

"Weigh trigger.  3.5 lbs.  No good for bullseye shooting SO;"


That's not exactly true. Only CMP reguires 4lbs and only for EIC matches. For bullseye if its a .45 you need 3.5lbs. For everything else 2.5 is ok.
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Post by Asa Yam on 11/17/2019, 1:47 pm

LenV wrote:That's not exactly true. Only CMP reguires 4lbs and only for EIC matches.
And that's what matters.  Hence the search for a 4 lb. trigger conversion.

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Post by LenV on 11/17/2019, 4:12 pm

I suppose I was referring to the word "Bullseye". Slartybartfast would appreciate this. On another thread we're talking about the new 2020 regulations for CMP. I have always considered Bullseye matches under the purview of the NRA and EIC matches under the CMP. It appears that will be another term we will need to qualify. Well, kinda. There hasn't officially been any "Bullseye" for the last 4 years or so. I'm glad you figured out how to make it legal for EIC matches.

Len
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Post by Asa Yam on 11/18/2019, 12:08 am

Ghillieman wrote:… Now, is there a bomar style sight replacement?
SIG sells adjustable rear sights for P320s, but the holes for mounting them on an X5 pistol are different than those on the M17 and standard P320s.  It appears that SIG has discontinued the X5 pistol, probably in favor of the X5 Legion.  P320 X5 and X5 Legion adjustable rear sights are made by Dawson Precision ( https://dawsonprecision.com/ ), but their website does not show this part.  Dawson makes Bomar and LPA type rear sights, it might be worth finding a gunsmith to see if one can be installed on your M17.

The pistol in the video appears to have a Bomar type rear sight installed, not sure who did the work.

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Post by Asa Yam on 11/24/2019, 5:34 pm

Firing Test #1:

Went to range yesterday morning.

Conditions:  Mostly cloudy, cool (32 F), and humid (but dry).

Target distance:  25 yards.  Did not use reduced center for slow fire.

Trigger pull before firing:  Weighed repeatedly, most readings at 4 lbs.  1 reading in high 3s (3.7 lbs?).

Scores:

  • Rapid fire:  64-0x.  One miss, due to unintentional discharge.  Best guess, probably eased up on trigger instead of maintaining squeeze;
  • Timed fire:  76-0x.  10 shots hit, no misses;
  • Slow fire:  75-0x (10 hits, no misses);
  • TOTAL:  215-0x;
  • Total rounds fired:  30;
  • Trigger pull weight after firing:  4 lbs (single pull).


Impressions:

  • Was it easier to break clean shots?  Yes.  Lighter trigger makes it easier to control pistol;
  • Trigger stop positive?  Yes, just need to remember to maintain trigger squeeze through recoil.  See Timed and Slow fire scores;
  • Improvement in scores?  Hard to say, but think so.  Previous high score with a match conditioned .45 and ball ammo was a 245;
  • Will P320 upgrade work in an M17?  Unsure.  Trigger packs between the two models are nearly identical, aside from the M17 trigger bar, and the manual safety.  The manual safety does come apart on the right side, am unsure how to perform disassembly.  Note the safety in the M17 replaces the upgraded pin in the Gray Guns upgrade kit.  Both parts hold the upgraded sears in place in their respective trigger packs.


Future plans:

  • Practice - a lot.  The 245 score mentioned above was with a year of practice, one or two days each week;
  • Try shooting trigger pack in another P320.  Pistol used seemed a little loose, but had previously performed well in Ransom Rest tests.

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