Wolff Springs 45 colt NMV’s. What weight?

[Tall John]

Looking for advice on what weight Wolff hammer Springs work best for 45colt NMV’s with Federal std LP primers.

 

I put in an #18 and am getting too many FTF’s using Choice Ammo 200 grain cowboy loads with Fed primers.

 

I'm 45 minutes from my range so would prefer solid advice vs trial & error.

 

TIA!

[Eyesa Horg]

Running 15# in ours for years. They don't like CCI though. Never an issue with Federals.

[Beartrap SASS#57175]

18lbs should pop primers with no problem.

Are the pistols short stroked?

[Larsen E. Pettifogger, SASS #32933]

1 hour ago, Tall John said:

I'm 45 minutes from my range so would prefer solid advice vs trial & error.

Based on what you have said no one can tell you for certain.  Like the other posters all of my NMV's have springs that are below 18#.  You need to figure out if your particular guns have excess internal friction and correct that.  You also need to make sure your primers are fully seated.  I recently had some unexpected misfires and it was the primer punch in my press had gotten out of adjustment.

 

Oh, just remembered I bought another a pair of NMVs recently and got misfires with my normal spring set-up.  Turned out they only had about .030" of firing pin protrusion.  Swapped them for extended firing pins and everything is now fine.

Edited November 17, 2025 by Larsen E. Pettifogger, SASS #32933

[The Original Lumpy Gritz]

IIRC, NMV came with 17lb hammer spring. 

[Tall John]

9 hours ago, Beartrap SASS#57175 said:

18lbs should pop primers with no problem.

Are the pistols short stroked?

not short stroked but I did install one of the Montado hammers I bought from you with the 18lb spring.  I’ll try a 19lb spring and see if that makes a difference.

[Tall John]

8 hours ago, Larsen E. Pettifogger, SASS #32933 said:

Based on what you have said no one can tell you for certain.  Like the other posters all of my NMV's have springs that are below 18#.  You need to figure out if your particular guns have excess internal friction and correct that.  You also need to make sure your primers are fully seated.  I recently had some unexpected misfires and it was the primer punch in my press had gotten out of adjustment.

 

Oh, just remembered I bought another a pair of NMVs recently and got misfires with my normal spring set-up.  Turned out they only had about .030" of firing pin protrusion.  Swapped them for extended firing pins and everything is now fine.

Thanks for the feedback, note that the ammo I’m using was from Choice Ammunition.  200grn RNFP’s with Federal Primers (confirmed by lot#) and Starline Brass.

 

I’ll try the 19lb spring that came in my shooter’s pack and see if it solves the problem. If not I’ll order the next size pack. And if that doesn’t work, I’ll go see BOOMSTICK JAY

 

this ammo ran great in my Jim Bowie EMF-1873.

[SGT. ELI 35882 GUNFIGHTER]

I run 10lb. springs in mine with all the proper work done, so you have more than a spring issue going on. 

[Tall John]

Well, I figured out my problem.  Wolff shipped me the wrong hammer springs in one of my two spring packs

 

Ruger I.D. 5.32mm

wolff I.D.  4.78 mm

 

Likely these smaller springs are for single sixes or something else.

 

i opened the other spring pack I bought (same stock number and these are the same diameter as the Ruger and they slip right on!

 

 

[The Original Lumpy Gritz]

8 minutes ago, Tall John said:

Well, I figured out my problem.  Wolff shipped me the wrong hammer springs in one of my two spring packs

 

Ruger I.D. 5.32mm

wolff I.D.  4.78 mm

 

Likely these smaller springs are for single sixes or something else.

 

i opened the other spring pack I bought (same stock number and these are the same diameter as the Ruger and they slip right on!

 

 

The springs you received are for the Original Vaquero that came from the factory with 23lb hammer springs. 

NMV factory hammer spring is 17lb. 

Look at how different the length is.....

You really need to call WOLF!

[Larsen E. Pettifogger, SASS #32933]

23 minutes ago, The Original Lumpy Gritz said:

The springs you received are for the Original Vaquero that came from the factory with 23lb hammer springs. 

NMV factory hammer spring is 17lb. 

Look at how different the length is.....

You really need to call WOLF!

The ID on the OMV, NMV and Single Six is the same.  So let's just leave it as Wolf bagged a mystery spring.  To make matters even more confusing when Ruger went from the OMV to the NMV the mainspring was shorter to make up for the space taken by the in-the-grip safety block.  Current NMVs no longer have the safety block and use the old OMV length spring.  H is the safety block and I is what is currently used and is the same as the OMV.

 

Edited November 18, 2025 by Larsen E. Pettifogger, SASS #32933

[The Original Lumpy Gritz]

2 minutes ago, Larsen E. Pettifogger, SASS #32933 said:

The ID on the OMV, NMV and Single Six is the same.  So let's just leave it as Wolf bagged a mystery spring.  To make matters even more confusing when Ruger went from the OMV to the NMV the mainspring was shorter to make up for the space taken by the in-the-grip safety block.  Current NMVs no longer have the safety block and use the old OMV length spring.

I'll bet he received a NMV 'lock' spring.

Wolff Gunsprings will make if 'rite'.

[Tall John]

called ‘em today.  Replacements on the way! No charge!  Great customer service from Wolff!

Edited November 19, 2025 by Tall John
Update