Unusual Circumstance - Looking for Input

[stephenprops1]

Yesterday I was shooting my Thompson Center, 45 caliber, percussion, Hawken rifle. I was using .445 patched, round ball. I was looking for lighter loads to help preserve my gun powder supply. I was using 40 grains, 35 grains and 30 gains of Pyrodex, P powder. My rifle has a set trigger. When I shot using the set trigger the hammer would fly back and **** the gun. (I have owned this gun for about 2 years and it has never done this before). ---- This is where the unusual circumstance occurred, when I shot the gun without using the set trigger the hammer did not automatically ****. --- Has anyone experience such a thing? I know of the usual reason, the nipple hole being too large. I did not modify the nipple in any way. It is fairly new. --- I have shot this gun two or three hundred rounds and this is the first time something like this has happened. I have previously used 60 or 70 grains of Pyrodex or Goex and did not experience this. ---- Any input would be appreciated.

 

[Robert an saa fan]

Please post your question in the percussion rifles section. Where you posted is not correct. You will get more help posting in the percussion rifles section of the forum.

 

[Notchy Bob]

I have a .54 caliber custom rifle that does that. I've only had it out once, and was shooting 60 grains of FFg under a .520" ball (the bore is undersized). The usual culprits in that scenario are an oversized flash hole and/or a weak mainspring. However, I don't think either of these conditions apply in my case, and it is puzzling. You and I were both shooting relatively low powder charges, and I'm wondering if the light load may have something to do with it. Maybe the lower charge has difficulty generating enough energy to overcome the inertia of the ball, and relatively more gas jets out through the flash hole. That's my hypothesis.

This probably doesn't happen when you don't set the triggers and shoot as with a single trigger because the continuous pressure of your finger on the trigger holds the sear arm up and pivots the sear nose down, so it can't engage the notches in the tumbler. The hammer may fly back, but the sear won't engage so the hammer drops back down. Set triggers "kick" the sear arm up, but don't hold it up. The sear spring then makes the sear engage the tumbler when the hammer moves back down.

Best regards,

Notchy Bob

ADDENDUM: Maybe the moderators can move this thread for you.

 

[Rifleman1776]

My rifle has a set trigger. When I shot using the set trigger the hammer would fly back and **** the gun.

Very odd, the use or not use of the set trigger should not have any bearing on this happening. Examine the inside of the lock to see if you have any broken parts. Some pics might help. Also, you mentioned the nipple as a possible cause. That could be. Switch to 'hot shot' style nipples and see what happens.

 

[rafterob]

The cause of the hammer blow back is that the nipple is burned out. The reason it does not blow back to **** when using the main trigger is because you are holding the sear out of junction with the tumbler. When you use the set trigger, once fired, nothing is holding the sear out of that junction and it is free to set back in there at blowback. Hope that makes sense.

 

[necchi]

I know of the usual reason, the nipple hole being too large. I did not modify the nipple in any way. It is fairly new. ---

The short answer for hammer blow back is a worn nipple. Nothing else causes it.
It began happening to you now, only because the nipple finally reached that point of wear.
The fix; Replace the nipple.

The trigger use issue is best explained by @Notchy Bob and @rafterrob;

This probably doesn't happen when you don't set the triggers and shoot as with a single trigger because the continuous pressure of your finger on the trigger holds the sear arm up and pivots the sear nose down, so it can't engage the notches in the tumbler.

He's right, all it takes is that nano-second of contact within the mechanism fall/function to change the position of the sear/tumbler engagement.

 

[hanshi]

I'm more inclined to blame you problem on the nipple. Is the hammer spring at full strength or weak?

 

[ohio ramrod]

I also think the nipple is the problem/

 

[stephenprops1]

I have a .54 caliber custom rifle that does that. I've only had it out once, and was shooting 60 grains of FFg under a .520" ball (the bore is undersized). The usual culprits in that scenario are an oversized flash hole and/or a weak mainspring. However, I don't think either of these conditions apply in my case, and it is puzzling. You and I were both shooting relatively low powder charges, and I'm wondering if the light load may have something to do with it. Maybe the lower charge has difficulty generating enough energy to overcome the inertia of the ball, and relatively more gas jets out through the flash hole. That's my hypothesis.

This probably doesn't happen when you don't set the triggers and shoot as with a single trigger because the continuous pressure of your finger on the trigger holds the sear arm up and pivots the sear nose down, so it can't engage the notches in the tumbler. The hammer may fly back, but the sear won't engage so the hammer drops back down. Set triggers "kick" the sear arm up, but don't hold it up. The sear spring then makes the sear engage the tumbler when the hammer moves back down.

Best regards,

Notchy Bob

ADDENDUM: Maybe the moderators can move this thread for you.

Thanks for your input.

 

[stephenprops1]

Thanks to all of you. I will replace the nipple and see what happens. (That nipple is fairly new. But I will replace it.)

 

[Christophero]

I do not agree that the only reason is a worn nipple. From the first time I shot my T/C 50 Renegade in the Fall 1987 with 90 grains of FFg experienced hammer blowback. 80 Grains is fine. I switched to 65 grains of FFFg and it has killed many deer over the years.

The Cherokee. 32, new in Spring 1987,also with the T/C manual loads would blowback at 30 grains of FFFg. 20 grains knocked squirrels out of tree tops so I was satisfied with that loading. Brand news rifles, new nipples but hammer blowback happened.

 

[deerstalkert]

I do not agree that the only reason is a worn nipple. From the first time I shot my T/C 50 Renegade in the Fall 1987 with 90 grains of FFg experienced hammer blowback. 80 Grains is fine. I switched to 65 grains of FFFg and it has killed many deer over the years.

The Cherokee. 32, new in Spring 1987,also with the T/C manual loads would blowback at 30 grains of FFFg. 20 grains knocked squirrels out of tree tops so I was satisfied with that loading. Brand news rifles, new nipples but hammer blowback happened.

interesting!
i wonder if a soft mainspring coupled with blowback is the cause?
have never experienced hammer/**** rebound . 30g in the .32 isn't a hot load by any means.

 

[Jim]

Many years ago, I had a brand new, very early Zouave from Navy Arms.

Right from Day One . . . .I had “hammer blow-back” with the Government load of 60 grs. 2F.

Rifle went down the road long ago, but I think it had a nipple with a too large office.

 

[Grenadier1758]

My Zouave from one of the many importers in the 1960's had blowback from the start. The nipple had a very large orifice. A new nipple solved the blowback issue.

 

[OldSmoky1967]

Yesterday I was shooting my Thompson Center, 45 caliber, percussion, Hawken rifle. I was using .445 patched, round ball. I was looking for lighter loads to help preserve my gun powder supply. I was using 40 grains, 35 grains and 30 gains of Pyrodex, P powder. My rifle has a set trigger. When I shot using the set trigger the hammer would fly back and **** the gun. (I have owned this gun for about 2 years and it has never done this before). ---- This is where the unusual circumstance occurred, when I shot the gun without using the set trigger the hammer did not automatically ****. --- Has anyone experience such a thing? I know of the usual reason, the nipple hole being too large. I did not modify the nipple in any way. It is fairly new. --- I have shot this gun two or three hundred rounds and this is the first time something like this has happened. I have previously used 60 or 70 grains of Pyrodex or Goex and did not experience this. ---- Any input would be appreciated.

The nipple is shot out. Replace. Back pressure and the hole being too big is the culprit.

 

[doubleset]

Nipples are cheap enough that you can order two or three different ones and try them. I have noticed some visible differences in dimensions (and hole diameters) in (new) nipples for the very same gun.

 

[Rifleman1776]

Thanks to all of you. I will replace the nipple and see what happens. (That nipple is fairly new. But I will replace it.)

Don't be upset. Consider nipples as disposable items. Buy several at a time. OTOH, I have found Hot Shot brand to last a very long time and seldom burn out. But, I still keep some extras.

 

[Christophero]

interesting!
i wonder if a soft mainspring coupled with blowback is the cause?
have never experienced hammer/**** rebound . 30g in the .32 isn't a hot load by any means.

I figured that was probably the case but was too young and impatient to send either back to T/C. Never felt handicapped with either rifle when hunting.

 

[Dude]

Is there someplace that gives specs for the different nipples by brand or manufacturer?

 

[necchi]

Is there someplace that gives specs for the different nipples by brand or manufacturer?

No.
All you can do is look at each makers website to find information about each one that's made.
I've done that. It's amazing!! Each maker has the best one available on the market!

But in honesty,, if folks read here about the topic of "caplock nipple",, in it's many varied forms. You'll find decades of experience shared here about which ones are good and witch ones are bad,, look for repeated comments through the decades,, it's all about the alloy's used and port size.
They all wear out,, at rates that include use and care.
So an individuals mileage may vary.