Blown out patches? bore, crown, patching material, lube where to start?

[Tom A Hawk]

An easy way to confirm sharp muzzle as the cause is to start a ball then pull it back out and examine the patch for cut threads. These will tear under seating force if the patch is tight.

 

[deerstalkert]

if that razor edge the blue line is pointing at

isn't circumcising your patch, i will vote democrat. use the 500 grit. wrap a piece around a ball and spin it to knock off that edge.

 

[Loyalist Dave]

An easy way to confirm sharp muzzle as the cause is to start a ball then pull it back out and examine the patch for cut threads. These will tear under seating force if the patch is tight.

It can be tedious, but..., you install a ball on a ball puller tool on the end of a range rod, and then use a patch with that ball on the end of the rod. Push the ball down 4", remove and look at the patch. IF undamaged, repeat the procedure to 8" depth, remove and examine the patch. IF undamaged, repeat, until you find the first evidence of patch damage, and then you know where the problem starts.

You can then either polish the barrel down to that depth OR better yet, buy an inexpensive endoscope for your cell phone that will go to that depth, and you take a look and ensure that it's not a pit or pits causing the damage.

IF you go to the breech and back and the patches are fine..., then as suggested your patch isn't filling the grooves, and blow-by is causing the problem.

ALSO be aware of the "feel" of the rod..., IF you have even tension on the rod/ball tool with the patch a you descend the barrel, and you feel a momentary reduction of the friction, and then it starts again, you have a "ringed" barrel. A small spot where a misloading caused gas pressure to make an internal bulge, which won't necessarily show up on the outside of the rifle barrel. When a normally patched ball is fired and reaches the bulged area, that patch suddenly becomes slack in its grip of the ball, and gasses may seep around the sides and burn the patch. Further, the patch will slip away from the ball, and accuracy will go bad, but... may not show up much until beyond 50 yards.

I've known guys who stopped using a rifle because the accuracy "went bad" and no matter what couldn't get the rifle to shoot well again..., they had bulged the barrel. OH they tried to figure it out, but never thought to check for a bulge.

LD

 

[longcruise]

Considering all the advice given, and all has value, you could just do it all!

That said, I've dealt with somewhere between 10 or 12 ml barrels that had this same problem. All were cured! I do all of these steps at once. No point in doing one thing and testing then doing another. This isn't load development, it's bore conditioning.

First, polish the crown. The thumb method described here above works fine. Start at 220 and work down to 400. This is a 15 or 20 minute procedure.

Next is cleaning up the bore. Again, the suggestions above will work or at least help but for the absolute best either lap with a poured lead slug or firelap. I'm only suggesting firelap. Get this kit from Midway Wheeler Bore Lapping Kit
Follow the instructions using about 20 lead conicals using only the most coarse grit. The other two grits are excellent for modern cartridge barrels but unnecessary in your ml barrel. Forty grain charges are adequate. Hollow base conicals work very well.

 

[DillyJamba]

gave it a few spins with 320 with the thumb followed it up with 500.

I think I broke the sharp edge I don’t want to overdo it

 

[DillyJamba]

Also ran a 0000 steel wool wrapped 50 cal cleaning brush down it for a few passes, felt no resistance or hang ups so I think I’m good to go on the rifling! Hopefully it was just the crown!

I’ll be testing tomorrow and will report back

 

[kelvinator]

Not Familiar with the GPR as I've never had one...but from all the pics it appears to have 5 land and groove rifling with the grooves approaching twice the width of the lands.
That's a lot of groove area for the patch to fill and seal.
Do barrels like this benefit more from a smaller ball and thicker patch combo?
Or a really tight fitting thick patch maybe?
And what about the lube, might something with a little more viscosity help?
Sorry, guess I have more questions than answers.

 

[deerstalkert]

Not Familiar with the GPR as I've never had one...but from all the pics it appears to have 5 land and groove rifling with the grooves approaching twice the width of the lands.
That's a lot of groove area for the patch to fill and seal.
Do barrels like this benefit more from a smaller ball and thicker patch combo?
Or a really tight fitting thick patch maybe?
And what about the lube, might something with a little more viscosity help?
Sorry, guess I have more questions than answers.

very good questions too.
now get ready for a storm of opinions and a few answers.

 

[Mulebrain]

What was your powder charge, or did I miss it somewhere?

 

[DillyJamba]

What was your powder charge, or did I miss it somewhere?

80 grains 2f, not really excessive from what I’ve read

 

[45man]

80 gr is fine but for some reason all of the 54's I have shot including mine prefer 100 gr of 2f. Mine actually is more accurate with Pyrodex. RS.
About the guys that lose accuracy, Bill Large told me a barrel gets "shot smooth" from the patches.
Old timers suffered from it often and would fill the bore with urine overnight. Too smooth is the problem with chrome bores. They can be real buggers to shoot good.
My barrel is an H&H and I use a ,535 bal and .020 patch but iit groups tighter with .022" by adding a cigarette paper to it.
I have a TC Contender rear sight on mine so I can adjust it. After I won a silhouette shoot most giuys were not done so when we set targets I would go to 200 meters and set steel chickens for fun. Jumping to 120 gr and raising my sight 17 clicks I could take 4 out of 5 down off hand. A lot of drop since each click is worth 1.66" at 100 uards.
I also found that I lose 140 FPS feom 80 degrees to 20 degrees so I went to 110 gr in the cold.

 

[kelvinator]

I also found that I lose 140 FPS feom 80 degrees to 20 degrees so I went to 110 gr in the cold.

Very interesting, and good to know.

 

[wiscoaster]

gave it a few spins with 320 with the thumb followed it up with 500.

I think I broke the sharp edge I don’t want to overdo it

Let us know how it shoots now.

 

[okawbow]

Modern pillow ticking is junk! It’s much weaker and can be thinner than the older American made cloth. You are much better off with well used 100% cotton denim. Try out some old blue jean or work bib denim. A nice snug load will work better than too loose also.

 

[Phil Coffins]

And don’t forget to piss in your barrel!

 

[DillyJamba]

Problem solved! Patches staying together nicely! Had a group with 3 shots touching at 35 yards and decent groups out to 45 (didn’t push it further!) hopefully I can tighten the groups up with some load development, and practice!

Steps I took

1. Sanding the sharp edge off the crown with 320 and following up with 500 grit

2. Switching patching material, the pillow ticking I was using seemed super weak compared to the drill cloth I’m using now (although it’s an extremely tight fit even with 530)

3. Ran 0000 steel wool down the bore for 5-10 strokes (I don’t think this was the problem but likely didn’t hurt)

Thanks to everyone who offered suggestions very encouraging results today!

 

[DrLaw]

Problem solved! Patches staying together nicely! Had a group with 3 shots touching at 35 yards and decent groups out to 45 (didn’t push it further!) hopefully I can tighten the groups up with some load development, and practice!

But did you pee into the barrel???

The Doc is not the least bit curious!

 

[DillyJamba]

But did you pee into the barrel???

The Doc is not the least bit curious!

Thankfully it didn’t come down to that. Hahahahaha

 

[ORBushman]

Problem solved! Patches staying together nicely! Had a group with 3 shots touching at 35 yards and decent groups out to 45 (didn’t push it further!) hopefully I can tighten the groups up with some load development, and practice!

Steps I took

1. Sanding the sharp edge off the crown with 320 and following up with 500 grit

2. Switching patching material, the pillow ticking I was using seemed super weak compared to the drill cloth I’m using now (although it’s an extremely tight fit even with 530)

3. Ran 0000 steel wool down the bore for 5-10 strokes (I don’t think this was the problem but likely didn’t hurt)

Thanks to everyone who offered suggestions very encouraging results today!

I've been following this and I'm glad to see you got the issue resolved! Learned a bit myself and who knows, your issues taught me and I may be able to pass them along to someone with the same issue down the road! Thanks to all and for helping this gentleman out!

 

[ETipp]

Modern pillow ticking is junk! It’s much weaker and can be thinner than the older American made cloth. You are much better off with well used 100% cotton denim. Try out some old blue jean or work bib denim. A nice snug load will work better than too loose also.

Modern pillow ticking works just fine for this ole boy.

I have the same type ML as the OP. It's a 1990 model and was as new when I received it. Use .018 red ticking I ordered from October Country, 90.0 grains of 3F BP and a .530 RB. Recovered patches looks like they could be reused. Accuracy is very good.

Also, when I first got my .32 Crockett squirrel rifle I was using .015 cotton patches from TOTW. They were being blown apart pretty bad and I know the charge was sufficient. Ordered .015 red ticking from October Country. Now recovered patches look very good.

I know not where October Country gets their red pillow ticking from.

I use TOTW Mink Oil for patch lube.

With that said, the OP may very well have another issue going on with his GPR.