Light strike with GP100

[Buck13]

I fired a dozen rounds of double-action last weekend, and had one light strike misfire, on the second round in a string. Primer was CCI 500, I think, and had a smaller than usual dent. It fired normally on a single-action second strike.

The gun is nearly new: somewhere between 150 and 200 rounds in. A few of the rounds have been reloads with IMR4227, which is leaving a bit of poorly burned powder, and more of them used Unique, which I thought was burning better at this pressure (light for .357, but over .38 +P load). The 4227 in .357 cases in this session was right at the beginning, followed by a bunch of Unique from .38 cases. When I got home and went to clean it, the cylinder was dragging badly, which seemed to be due to some powder residue under the extractor star. It was turning OK while shooting, but it's possible that the case was not perfectly chambered due to glop somewhere.

I generally inspect primers after seating to be sure they are not grossly mis-seated, but I won't swear I seat every one to precisely the same depth. Does the GP100 have a reputation for light DA strikes, or should I blame my priming job or loose chambering?

 

[Certaindeaf]

Did you buy it new or change springs? Seat your primers well and keep the area under the star free of oil and dump empties with the gun vertical.

 

[MrBorland]

Does the GP100 have a reputation for light DA strikes

No. If someone tuned it by messing with the springs, though, all bets are off. If it's stock, it's likely due to a combination of the relatively hard CCI primers, and, as Certaindeaf suggests, crud-induced "soft" seating of the rounds in the chambers. Also check for residual crud in the chambers from shooting .38spls, which might prevent the longer .357mag cases from fully seating.

Primer was CCI 500, I think, and had a smaller than usual dent.

The primary dent the firing pin puts in the primer is actually kind of small, whether the round goes off or not. That bigger dent we all see in fired cases happens when combustion pressure causes the case to slam back into the FP and recoil shield.

 

[PO2Hammer]

My new GP100 if far less tolerant of high primers than any other .357 I've owned.
I have always primed on my press's built in primer arm and never had a misfire with any of my .357's including revolvers and carbines until I bought my GP100. I had quite a few FTF's with the GP100 so I set up a dial indicator on a stand to accurately measure primer depth. (my hands aren't sensitive enough to feel them accurately).
I found I was leaving quite a few primers high.
Bought a Ram prime to more accurately seat them. My press is too heavy and smooth to 'feel' them into the pockets so I set it up so primers are seated ~.003" below flush with the ram at the top of the stroke.
Checked every one with the dial indicator to make sure, but I still had a couple FTF's in the GP100. No problems in any other gun.

It may not be a weak hammer strike, it could be excessive head space or that the firing pin doesn't have enough protrusion (how far is sticks out of frame). That is an issue with Redhawks, and with the same frame mounted firing pin, I suspect it might be the problem with my GP100 as well.

I don't shoot factory ammo, so if I call Ruger I'm sure my handloads will get the blame. Not sure what I'm going to do.
I'm trying to figure out a way to accurately measure headspace and the firing pin protrusion so if I call Ruger I have some factual evidence.

 

[GP100man]

Buck

Weigh the double action pull , I can then go from there .Easily done with bathroom scales & a walking cane . Ensure revolver has no ammo, then place cane on scales (note weight or rezero) now place the cane handle on the trigger & push it thru a dry fire noting weight . Not as accurate as most but will give us a figure to work with.Do it ten times & average.

But here`s a few things to look at even if new .

Check the hammer , scratches on the sides mean frame drag & that robs kenetic power from the hammer & lengthens locktime.

To remedy this measure the clearence between frame & hammer subtract .003" & order shimms from Lance (Google trigger shims & his site will pop up)

But to make sure ya have good ign I recommend the shims & a 12# hammer spring (balance between liter & lock time) & I`ve found this combo to pop even SRM primers.

Lance sells packages for Ruger DA/SA revolvers , so ya may even want to shimm the trigger & DA pawl.Shimming makes the Rugers trigger pull smoother & alot more consistent !!!

Next ,push the firing pin forward .055" is minimum, & some even mill some of the hammer face that hits the frame a bit , I do this last & tricky to keep square.

Last but least check endshake (measure barrel gap while holding cyl forward then back .003" is ideal)

 

[ArchAngelCD]

Buck,
Most times when a primer fails to ignite but fires the second time it's usually a improperly seated primer. You're GP100 might be more sensitive to this than other revolvers you own although I have never hear the GP100 as having that problem.

I'm guessing your primers were a little high especially since they went off the second time. The first trigger pull completes the seating and the second sets it off.

 

[niner4tango]

A quick and fun test of hammer power is to cock the revolver, drop a pencil in the barrel, eraser first, point the muzzle straight up and pull the trigger. I use a Bic pen, but the idea is the same. My stock GP100 will launch a Bic at least 10 feet in the air, so watch the ceiling.

This is normally done for SA, since the pen won't allow you to cycle the DA action. I guess you could stage the trigger until the cylinder lined up and then drop the pen in....

 

[230RN]

A long time ago I was taught to rotate the case 180 degrees in the shell holder after the priming stroke, and stroke it again. I forget where I learned this, but I think it was from a bench rest shooter. It's become automatic to me now.

The one time I've had to double-tap a primer was in a revolver whose mainspring had been worked on to lighten the DA weight by someone other than myself. (Really!)

Also, you should check your loading process to make sure no oily things (like sizing lube) could have got on the primer or in the primer pocket.

Primers are supposed to have their primer composition pellets crushed slightly in seating to sensitize them. I think I read that in Hatcher's Notebook, but I don't want to look it up right now. You'll notice provision is made for that by the fact that the anvil in a new primer protrudes slightly from the primer so the anvil can indeed crush the priming pellet when the primer is seated.

Terry, 230RN

 

[Bobson]

I don't shoot factory ammo, so if I call Ruger I'm sure my handloads will get the blame. Not sure what I'm going to do.

Buy a box of factory ammo, or maybe two-three different types/brands of ammo. Measure the primer seating depth with your dial indicator on a few rounds in each box, and record what you find. Then fire the boxes.

If it really is a problem with the gun's firing pin, rather than your handloads, it's logical to believe the same problems will happen with factory ammo. If the issue does not repeat itself, simply seat your primers to the same depth of the most reliable box of factory ammo from now on.

Else, call Ruger and tell them about the problems you experienced with factory ammo.

 

[GP100man]

I thought I typed this ,but I did`nt .

All the tuning & tricks on DA revolvers of all makes won`t make up for a primer that`s not bottomed out in the pocket.

I run my finger over every single primer I seat to feel for proud primers .

 

[Tony_the_tiger]

You need to send it back to Ruger. They'll send you a call tag and it'll be back in 3 weeks.

 

[Mag_357TX]

I have the same problem using those primers on my 38 and 357 handloads. That's why I don't rely on handloads for SD, they are strictly range ammo. Usually the primer isn't seated deeply enough and the firing pin merely pushes it in all the way, rather than applying the adequate amount of force to detonate it. Usually if you chamber it and fire it a 2nd time, it'll go boom. If not then you may have forgotten to charge the casing to begin with (not saying that's ever happened to me....not saying it hasn't either lol..._).

But yeah sometimes running your finger across it isn't enough to notice a high primer. Try standing it up on a flat surface, then you'll know for sure.

I'll be interested to find out if it is in fact a problem with the gun itself, cause it'll be the first I"ve ever heard of a problem with a GP100.

 

[Buck13]

Buck,
Most times when a primer fails to ignite but fires the second time it's usually a improperly seated primer. You're GP100 might be more sensitive to this than other revolvers you own although I have never hear the GP100 as having that problem.

I'm guessing your primers were a little high especially since they went off the second time. The first trigger pull completes the seating and the second sets it off.

This is probably the best explanation. This misfire was with reloaded ammo. I've fired a few cylinders of factory ammo DA without problems.

Next time I get the guns out, I'll check for signs of hammer drag, etc., but I'm still pretty new to reloading: just a few hundred rounds during the last six months. Very likely that it's my mistake.

 

[ArchAngelCD]

This is probably the best explanation. This misfire was with reloaded ammo. I've fired a few cylinders of factory ammo DA without problems.

Next time I get the guns out, I'll check for signs of hammer drag, etc., but I'm still pretty new to reloading: just a few hundred rounds during the last six months. Very likely that it's my mistake.

Don't beat yourself up over this, we all have growing pains. Mistakes are good as long as no one gets hurt and we learn from them. A slightly raised primer should be the worst thing you do while reloading...

 

[GP100man]

On my GPs A proud primer (.004")will cause binding of the cyl , primer dragging on the recoil shield.

But some priming systems work on the heigth or distance of the case head & if you used 1 of these ya may have a slightly deeper pocket resulting in an improperly seated primer, this has happened to me & bout drove me NUTTS:banghead:

Also tite pockets can deform/flatten the primer(with the seating tool) to the point ya just can`t "feel" the primer seat.

I`ve run into all the problems above !

GP

 

[gamestalker]

You said reloads, so my first thought would be high primers, after that a damaged FP, or a spring problem. I bought a DA S&W that was 100% unless I used DA, and then it was only a now and then misfire. After trying everything I could to diagnose the culprit, it turned out to be the FP had a chip on the tip. It was about .002" short of spec., just enough to give me fits. I replaced it with a new FP and have not a had another misfire since. Take the FP out and inspect it for length, and damage. And while your at it, I would check to make sure the spring is fully tensioned.

GS

 

[PO2Hammer]

Buy a box of factory ammo

Good advice, but that's not going to happen. I take great pride in not ever buying .357 or .38 spl factory ammo.
I checked my gun, looks like there's plenty of firing pin protruding.
There are quite a few drag marks on the hammer and a lot of side to side play, so I think I'm going to tune it up myself with some polishing and the shims. I'm also looking for a more stout mainspring. The trigger pull could be a little heavier without bothering me.