.177 P-rod conversion help!

.177 P-rod conversion help!

Joined: February 24th, 2006, 12:19 am

August 9th, 2012, 5:12 am #1

Okay, I took the plunge and bought parts to convert my P-rod a .177, and it hasn't gone as smoothly as I hoped. I bought a LW barrel from a 1701, and I had Jim Gaska turn down a .22 bolt to fit it. All I had to do was put in the new barrel, file a small flat for the set screw for the shroud bushing, and swap out the bolts. Pretty simple. I already had a single shot adapter for it, so I was set. Today I got to shoot the gun for the first time, and after getting the speed where I wanted it (starting in the low 800's and peaking at about 825 fps), I shot it for groups. I was sorely disappointed. Of the 5 pellets I tried, not one would group consistently! The pellets were CPHP's, RWS Hobby, RWS Meisterkugeln, Crosman Destroyer EX, and Predator Polytips. I shot mostly Destroyers, as they shoot well from my Benji 397, and I had a bunch on hand. No matter what pellet I shot, groups would shift, seemingly randomly. Sometimes it would stack 3 right in the same hole, then the next one would go an inch left or right. Then the next one would be half an inch low. This happened with all brands and types of pellets I tried. Here are the things I checked:

-Barrel set screws were tight
-All scope ring screws were tight
-Pellets were going into the barrel straight
-There were no errant limbs or blades of grass to deflect the pellets
-I kept the magnification of the scope the same throughout the shooting
-Shroud was not touching the barrel band
-Breech seal was tight
-Consistently placed the forearm in the same spot on the rest each time
-Consistent cheek weld
-I shot my Talon SS to make sure it wasn't something I was doing - stacked pellets in the same hole, and trimmed blackberry vines at 30 yards, no sweat

With the exception of the occasional flyer, I did not have any problems like this with the gun when it was set up as a .22 (after I crowned the barrel.) I don't think it's the barrel - LW barrels are NICE, and the crown looks good. The only other thing I can think of is my transfer port. I opened it up to .109 (7/64ths) when it was a .22 to optimize air flow. Do you think it is possible that too much air is getting through to the small pellet, and creating turbulence of some sort that is throwing my accuracy? I have an extra port - should I stick it in and see how it does, and just open it up to get the speed I want? It is an aftermarket port made by Mark Gravelle, so it is extra tight - I could start small and just increase in size a little at a time, I suppose. If it isn't the transfer port, what else could it be? Is there something I am overlooking?
Thanks in advance for the help,
Chris
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Joined: November 21st, 2009, 6:21 am

August 9th, 2012, 9:16 am #2

I understand your frustration, but why not rule out what you can then ask? I could see if you were asking should you purchases a T/P if you didn't have one to save some money . Try out that then if you have the same issue ask. I would try that before I even asked. When I had mine converted I did not have a issue but I didn't open up the T/P so I guess that cold be it. Then again might not be . Just try it and then let us know, the more you can rule out the better advice you would probably get. Heck I would have done that before recrown. But hindsight is always 20/20 i. I'm not trying to sound rude but you could read This that way so if I offend you I'm sorry.
Take Care,
Don
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Joined: July 19th, 2003, 12:46 pm

August 9th, 2012, 1:45 pm #3

try cleaning your barrel. Then try 1 type of pellet. If you switch something else, clean your barrel.

cp lead does not mix with jsb lead. this could be your problem.

and try using the marauder pistol transferport....the blue one.

Dutch



Self proclaimed shootinist sumbitch...there ever was almost!!
Its hard bein shootinst sum bitch...welp not its not.
started @ 227 compressor fills in 6/22/08
180 compressor fills and I have broke even
And aaain't it grrreaaat to be livinnn in the USA.
I never whacked a pigeon, starling, or sparrow that didn't deserve it!!!
1544 and countin....on pigeons..
starling count started 14--
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Joined: February 11th, 2002, 6:01 pm

August 9th, 2012, 3:17 pm #4

Okay, I took the plunge and bought parts to convert my P-rod a .177, and it hasn't gone as smoothly as I hoped. I bought a LW barrel from a 1701, and I had Jim Gaska turn down a .22 bolt to fit it. All I had to do was put in the new barrel, file a small flat for the set screw for the shroud bushing, and swap out the bolts. Pretty simple. I already had a single shot adapter for it, so I was set. Today I got to shoot the gun for the first time, and after getting the speed where I wanted it (starting in the low 800's and peaking at about 825 fps), I shot it for groups. I was sorely disappointed. Of the 5 pellets I tried, not one would group consistently! The pellets were CPHP's, RWS Hobby, RWS Meisterkugeln, Crosman Destroyer EX, and Predator Polytips. I shot mostly Destroyers, as they shoot well from my Benji 397, and I had a bunch on hand. No matter what pellet I shot, groups would shift, seemingly randomly. Sometimes it would stack 3 right in the same hole, then the next one would go an inch left or right. Then the next one would be half an inch low. This happened with all brands and types of pellets I tried. Here are the things I checked:

-Barrel set screws were tight
-All scope ring screws were tight
-Pellets were going into the barrel straight
-There were no errant limbs or blades of grass to deflect the pellets
-I kept the magnification of the scope the same throughout the shooting
-Shroud was not touching the barrel band
-Breech seal was tight
-Consistently placed the forearm in the same spot on the rest each time
-Consistent cheek weld
-I shot my Talon SS to make sure it wasn't something I was doing - stacked pellets in the same hole, and trimmed blackberry vines at 30 yards, no sweat

With the exception of the occasional flyer, I did not have any problems like this with the gun when it was set up as a .22 (after I crowned the barrel.) I don't think it's the barrel - LW barrels are NICE, and the crown looks good. The only other thing I can think of is my transfer port. I opened it up to .109 (7/64ths) when it was a .22 to optimize air flow. Do you think it is possible that too much air is getting through to the small pellet, and creating turbulence of some sort that is throwing my accuracy? I have an extra port - should I stick it in and see how it does, and just open it up to get the speed I want? It is an aftermarket port made by Mark Gravelle, so it is extra tight - I could start small and just increase in size a little at a time, I suppose. If it isn't the transfer port, what else could it be? Is there something I am overlooking?
Thanks in advance for the help,
Chris
First is your TP. .107 is huge. Go bck to the factory one at .081. You may get better performance by going even smaller. Second, try a "quality" domed pellet. Much as I love destroyers, they are not precision pellets. And lastly, slow the gun down to 700-750 and rerun all your tests with the pellets again. Find one it likes, then start runnig the speed back up.

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Joined: May 14th, 2004, 4:11 pm

August 9th, 2012, 3:53 pm #5

Okay, I took the plunge and bought parts to convert my P-rod a .177, and it hasn't gone as smoothly as I hoped. I bought a LW barrel from a 1701, and I had Jim Gaska turn down a .22 bolt to fit it. All I had to do was put in the new barrel, file a small flat for the set screw for the shroud bushing, and swap out the bolts. Pretty simple. I already had a single shot adapter for it, so I was set. Today I got to shoot the gun for the first time, and after getting the speed where I wanted it (starting in the low 800's and peaking at about 825 fps), I shot it for groups. I was sorely disappointed. Of the 5 pellets I tried, not one would group consistently! The pellets were CPHP's, RWS Hobby, RWS Meisterkugeln, Crosman Destroyer EX, and Predator Polytips. I shot mostly Destroyers, as they shoot well from my Benji 397, and I had a bunch on hand. No matter what pellet I shot, groups would shift, seemingly randomly. Sometimes it would stack 3 right in the same hole, then the next one would go an inch left or right. Then the next one would be half an inch low. This happened with all brands and types of pellets I tried. Here are the things I checked:

-Barrel set screws were tight
-All scope ring screws were tight
-Pellets were going into the barrel straight
-There were no errant limbs or blades of grass to deflect the pellets
-I kept the magnification of the scope the same throughout the shooting
-Shroud was not touching the barrel band
-Breech seal was tight
-Consistently placed the forearm in the same spot on the rest each time
-Consistent cheek weld
-I shot my Talon SS to make sure it wasn't something I was doing - stacked pellets in the same hole, and trimmed blackberry vines at 30 yards, no sweat

With the exception of the occasional flyer, I did not have any problems like this with the gun when it was set up as a .22 (after I crowned the barrel.) I don't think it's the barrel - LW barrels are NICE, and the crown looks good. The only other thing I can think of is my transfer port. I opened it up to .109 (7/64ths) when it was a .22 to optimize air flow. Do you think it is possible that too much air is getting through to the small pellet, and creating turbulence of some sort that is throwing my accuracy? I have an extra port - should I stick it in and see how it does, and just open it up to get the speed I want? It is an aftermarket port made by Mark Gravelle, so it is extra tight - I could start small and just increase in size a little at a time, I suppose. If it isn't the transfer port, what else could it be? Is there something I am overlooking?
Thanks in advance for the help,
Chris
My barrel loves JSB Express 7.9 pellets.

Jeff P
Last edited by pad617 on August 9th, 2012, 3:55 pm, edited 1 time in total.
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Joined: February 24th, 2006, 12:19 am

August 9th, 2012, 4:27 pm #6

I understand your frustration, but why not rule out what you can then ask? I could see if you were asking should you purchases a T/P if you didn't have one to save some money . Try out that then if you have the same issue ask. I would try that before I even asked. When I had mine converted I did not have a issue but I didn't open up the T/P so I guess that cold be it. Then again might not be . Just try it and then let us know, the more you can rule out the better advice you would probably get. Heck I would have done that before recrown. But hindsight is always 20/20 i. I'm not trying to sound rude but you could read This that way so if I offend you I'm sorry.
Take Care,
Don
No offense taken, Don. I asked before doing it because getting to the TP involves tearing the gun down to get to get it out. Taking it apart, drilling out the TP, reassembling, shooting it, and then doing it all over again 4 or 5 times just to MAYBE find the problem doesn't sound fun. I just figured if someone else already found an inner diameter that worked, I would save myself time and more frustration.
Chris
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Joined: September 21st, 2007, 12:13 pm

August 9th, 2012, 5:04 pm #7

Okay, I took the plunge and bought parts to convert my P-rod a .177, and it hasn't gone as smoothly as I hoped. I bought a LW barrel from a 1701, and I had Jim Gaska turn down a .22 bolt to fit it. All I had to do was put in the new barrel, file a small flat for the set screw for the shroud bushing, and swap out the bolts. Pretty simple. I already had a single shot adapter for it, so I was set. Today I got to shoot the gun for the first time, and after getting the speed where I wanted it (starting in the low 800's and peaking at about 825 fps), I shot it for groups. I was sorely disappointed. Of the 5 pellets I tried, not one would group consistently! The pellets were CPHP's, RWS Hobby, RWS Meisterkugeln, Crosman Destroyer EX, and Predator Polytips. I shot mostly Destroyers, as they shoot well from my Benji 397, and I had a bunch on hand. No matter what pellet I shot, groups would shift, seemingly randomly. Sometimes it would stack 3 right in the same hole, then the next one would go an inch left or right. Then the next one would be half an inch low. This happened with all brands and types of pellets I tried. Here are the things I checked:

-Barrel set screws were tight
-All scope ring screws were tight
-Pellets were going into the barrel straight
-There were no errant limbs or blades of grass to deflect the pellets
-I kept the magnification of the scope the same throughout the shooting
-Shroud was not touching the barrel band
-Breech seal was tight
-Consistently placed the forearm in the same spot on the rest each time
-Consistent cheek weld
-I shot my Talon SS to make sure it wasn't something I was doing - stacked pellets in the same hole, and trimmed blackberry vines at 30 yards, no sweat

With the exception of the occasional flyer, I did not have any problems like this with the gun when it was set up as a .22 (after I crowned the barrel.) I don't think it's the barrel - LW barrels are NICE, and the crown looks good. The only other thing I can think of is my transfer port. I opened it up to .109 (7/64ths) when it was a .22 to optimize air flow. Do you think it is possible that too much air is getting through to the small pellet, and creating turbulence of some sort that is throwing my accuracy? I have an extra port - should I stick it in and see how it does, and just open it up to get the speed I want? It is an aftermarket port made by Mark Gravelle, so it is extra tight - I could start small and just increase in size a little at a time, I suppose. If it isn't the transfer port, what else could it be? Is there something I am overlooking?
Thanks in advance for the help,
Chris
you are shooting I don't think the answer for your accuracy problem is TP size. I'd think that it might be a barrel issue of some kind..possibly a too big barrel TP hole, or slight TP hole burr,either of these could shave skirts or more likely some sort barrel instability. If you can shoot it without the shroud ect., just using the barrel to breech attachment, you may see a reduction in group walking.When testing just be careful not to bump the unsupported barrel.
As far as ammo, In my personal experience I have never found a L/W barrel that didn't do well with H&N FTT's.
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Joined: December 25th, 2009, 8:47 pm

August 9th, 2012, 6:59 pm #8

Okay, I took the plunge and bought parts to convert my P-rod a .177, and it hasn't gone as smoothly as I hoped. I bought a LW barrel from a 1701, and I had Jim Gaska turn down a .22 bolt to fit it. All I had to do was put in the new barrel, file a small flat for the set screw for the shroud bushing, and swap out the bolts. Pretty simple. I already had a single shot adapter for it, so I was set. Today I got to shoot the gun for the first time, and after getting the speed where I wanted it (starting in the low 800's and peaking at about 825 fps), I shot it for groups. I was sorely disappointed. Of the 5 pellets I tried, not one would group consistently! The pellets were CPHP's, RWS Hobby, RWS Meisterkugeln, Crosman Destroyer EX, and Predator Polytips. I shot mostly Destroyers, as they shoot well from my Benji 397, and I had a bunch on hand. No matter what pellet I shot, groups would shift, seemingly randomly. Sometimes it would stack 3 right in the same hole, then the next one would go an inch left or right. Then the next one would be half an inch low. This happened with all brands and types of pellets I tried. Here are the things I checked:

-Barrel set screws were tight
-All scope ring screws were tight
-Pellets were going into the barrel straight
-There were no errant limbs or blades of grass to deflect the pellets
-I kept the magnification of the scope the same throughout the shooting
-Shroud was not touching the barrel band
-Breech seal was tight
-Consistently placed the forearm in the same spot on the rest each time
-Consistent cheek weld
-I shot my Talon SS to make sure it wasn't something I was doing - stacked pellets in the same hole, and trimmed blackberry vines at 30 yards, no sweat

With the exception of the occasional flyer, I did not have any problems like this with the gun when it was set up as a .22 (after I crowned the barrel.) I don't think it's the barrel - LW barrels are NICE, and the crown looks good. The only other thing I can think of is my transfer port. I opened it up to .109 (7/64ths) when it was a .22 to optimize air flow. Do you think it is possible that too much air is getting through to the small pellet, and creating turbulence of some sort that is throwing my accuracy? I have an extra port - should I stick it in and see how it does, and just open it up to get the speed I want? It is an aftermarket port made by Mark Gravelle, so it is extra tight - I could start small and just increase in size a little at a time, I suppose. If it isn't the transfer port, what else could it be? Is there something I am overlooking?
Thanks in advance for the help,
Chris
Keep your speed under 750. My TP is .076. 7.9 and 8.4gr pellets are stupid accurate.

Good luck my friend. (I have 1 TP left)

Also, read my reply to Dutch's post below.


Head Gopher and Assistant
Match Director Ashland Air Rifle Range
Ashland OR

Regards,


Mark Gravelle
Last edited by mark600 on August 9th, 2012, 7:01 pm, edited 1 time in total.
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Joined: February 24th, 2006, 12:19 am

August 10th, 2012, 10:32 pm #9

Okay, I took the plunge and bought parts to convert my P-rod a .177, and it hasn't gone as smoothly as I hoped. I bought a LW barrel from a 1701, and I had Jim Gaska turn down a .22 bolt to fit it. All I had to do was put in the new barrel, file a small flat for the set screw for the shroud bushing, and swap out the bolts. Pretty simple. I already had a single shot adapter for it, so I was set. Today I got to shoot the gun for the first time, and after getting the speed where I wanted it (starting in the low 800's and peaking at about 825 fps), I shot it for groups. I was sorely disappointed. Of the 5 pellets I tried, not one would group consistently! The pellets were CPHP's, RWS Hobby, RWS Meisterkugeln, Crosman Destroyer EX, and Predator Polytips. I shot mostly Destroyers, as they shoot well from my Benji 397, and I had a bunch on hand. No matter what pellet I shot, groups would shift, seemingly randomly. Sometimes it would stack 3 right in the same hole, then the next one would go an inch left or right. Then the next one would be half an inch low. This happened with all brands and types of pellets I tried. Here are the things I checked:

-Barrel set screws were tight
-All scope ring screws were tight
-Pellets were going into the barrel straight
-There were no errant limbs or blades of grass to deflect the pellets
-I kept the magnification of the scope the same throughout the shooting
-Shroud was not touching the barrel band
-Breech seal was tight
-Consistently placed the forearm in the same spot on the rest each time
-Consistent cheek weld
-I shot my Talon SS to make sure it wasn't something I was doing - stacked pellets in the same hole, and trimmed blackberry vines at 30 yards, no sweat

With the exception of the occasional flyer, I did not have any problems like this with the gun when it was set up as a .22 (after I crowned the barrel.) I don't think it's the barrel - LW barrels are NICE, and the crown looks good. The only other thing I can think of is my transfer port. I opened it up to .109 (7/64ths) when it was a .22 to optimize air flow. Do you think it is possible that too much air is getting through to the small pellet, and creating turbulence of some sort that is throwing my accuracy? I have an extra port - should I stick it in and see how it does, and just open it up to get the speed I want? It is an aftermarket port made by Mark Gravelle, so it is extra tight - I could start small and just increase in size a little at a time, I suppose. If it isn't the transfer port, what else could it be? Is there something I am overlooking?
Thanks in advance for the help,
Chris
I changed my TP and cleaned my barrel, as well as polished the crown, port, and bore. Put it all back together, and even though it was grouping a little tighter, the POI was still shifting with all ammo types. So I decided to fill the gun to about 2700 psi and shoot 25 pellets to see what would happen. First shot landed right where I wanted. The second was half an inch right. Next was half an inch high. Fourth was about a quarter inch left. Then a quarter in right. Then high. Then dead center again - for the next 15 shots! Then it began to wander again. So, I pumped it back up to 2700 psi and did it again, and it did the same thing - danced around the bull for about 5 or 6 shots, settled in for about 15 shots, and then began moving again. So, it would appear it is being pressure sensitive, and my gun groups best between about 2550 psi and about 2000 psi. I was hoping to get more than 15 usable shots, but it beats the shotgun pattern I was gettiing yesterday, that's for sure! Does anybody know of a way to make it less pressure sensitive? If not, I'll be okay with what I've got.
Thanks for all the help,
Chris
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Joined: July 19th, 2003, 12:46 pm

August 17th, 2012, 2:57 am #10

don't mix different pellets.

clean the barrel if you use jsb and then switch to crosman pellets.

the alloy doesn't agree.

This is how my silhouette/prod was set up. 2 turns inward to striker. 5.5 to 6 turns inward on hammer tension. Stick the blue transfer port for the marauder pistol in it.

I got 18 very consistent shots @ 12 fpe using 10.5 from the box. They should feel tight when you push them in with the bolt.
This rig won the Nationals for PFT unlimited for me. Hope that helps....

maybe you should just use the bolt intended for the 1701 also...do you have an oring on the tip of the bolt probe?

Dutch



Self proclaimed shootinist sumbitch...there ever was almost!!
Its hard bein shootinst sum bitch...welp not its not.
started @ 227 compressor fills in 6/22/08
180 compressor fills and I have broke even
And aaain't it grrreaaat to be livinnn in the USA.
I never whacked a pigeon, starling, or sparrow that didn't deserve it!!!
1544 and countin....on pigeons..
starling count started 14--
Last edited by Dutch.22 on August 17th, 2012, 2:58 am, edited 1 time in total.
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