GP-100 Mainspring Replacement Experience

[22/45 Fan]

I have a new 4.2" GP-100 that I replaced the OEM 14 pound main spring and 12 pound trigger return spring with Wolff 12 pound hammer and 8 pound trigger return springs. The trigger pull improved noticeably and reliability is still 100%.

Now I've swapped in the Wolff 10 pound hammer spring and the trigger pull is MUCH better but I haven't determined reliability and won't be able to until later in the week. So, as a preview of coming attractions, what is the Forum members experience with a 10 pound main spring? Is it strong enough?

 

[roylt]

Should be fine.

 

[s4s4u]

I have had a 10 in mine for years. Tried a 9 but had light strikes.

 

[magpouch]

For me the 10 pound was just not quite enough spring. Worked maybe 90% of the time. Close but no cigar I went with the 12 and am happy.

 

[Jimbo357mag]

A general rule of thumb is Federal primers are the softest, Winchester is in the middle and CCI are the hardest. The type of primer may make a difference. I think I went with the 10# mainspring and a lighter trigger return spring as well.

 

[RoninPA]

I built a PPC gun from a GP100 and went with the 10 lb hammer spring and the 8 lb trigger return. That said, all we ever used when building our loads were Federal primers, they are the softest and gave us the best reliability. If you shoot just factory ammo, you might find that you need the 12 lb spring in there to give good strikes with all brands.

Our competition load was .38 spl cases, Federal 100 primers, 148 gr HBWC bullets (flush or almost flush, light crimp), 2.5 gr of RedDot or Solo 1000 (we found the Solo 100 was cleaner burning than the RedDot). This load pushed the bullet just over 700fps (minimum speed for the competition) from a 6" bbl and was VERY accurate from 7-50 yds.

 

[glockman99]

Reliable ignition over a light action...Go with the 12 lb. Wolff mainspring...

 

[22/45 Fan]

Reliable ignition over a light action...Go with the 12 lb. Wolff mainspring...

If the 10 pound spring does give reliable ignition I'd much rather have the better trigger pull. If it doesn't, I still have the 12 pound spring and can reinstall it in 5 minutes. I was just wondering what other's experience has been and most of it seems very positive. I'll have my own data later this week.

 

[Rainy Day Shooter]

I prefer factory springs myself. CCI primers and lighter springs spelling unreliability for me.

 

[s4s4u]

CCI primers

There are others.

 

[xtratoy]

If you are a reloader, prime 6 cases with CCI small rifle primers. If they go bang with a healthy firing pin indentation you are good to go. Rifle primers are thicker than pistol primers.

 

[22/45 Fan]

Time for a followup. Yesterday I took my GP-100 to the club for our weekly informal combat shoot. The gun ran 100% for 120 rounds of my .38 Special reloads with WSP primers, 125 gr coated LRN bullet and Titegroup. No problems or misfires of any kind.

Also, based on xtratoy's recommendation, I primed two empty cases with WSR small rifle primers (I don't have CCI anything) and fired them in the GP. Both went off with no problems.

So, in my particular gun, the Wolff 10-pound hammer spring seems to work perfectly and has greatly improved both the DA and SA trigger pulls. YMMV.

 

[Thel]

Mine runs with the 9 lb mainspring and 8 lb trigger return spring but has been tuned and smoothed. Lock time does increase the lower you go. With this combo the double action is 7.4 lbs and single about 2.5. It has worked with a cross section of ammo (Federal, WW, Corbon and such). Have not run CCI magnum primers yet.

 

[22/45 Fan]

Just for fun I may try the 9 pound spring someday but the 10 pound spring works so well and trigger pull is now so good, I think I will stop there for a while.