What does the indents on the pellet tell you? Marauder accuracy issues and uneven pressure in barrel

[Bramezy]

Hi all. I think I know the answer but I am not an expert.
I have a custom Gen1 .20 Marauder. Its not accurate. So I decided to look into it and see why.
With the barrel off ive pushed pellets thru it both ways and I get the same result each time.
On the head the flat spot goes from none to more. See pics and video.
Any saving this?

 

[Hateful McNasty]

Ya, i find this


Is better than this


Thats any gun ..

 

[Bramezy]

Ya, i find this
View attachment 572983

Is better than this
View attachment 572982

Thats any gun ..

My pics are loading, im more worried about the uneven pressure on the head where it flattens the edge out in an uneven pattern. Not the rifling but maybe the rifling is uneven too? same issue?

 

[nervoustrig]

The usual suspects would be a burr at the barrel port or a very tight choke. Try pushing a pellet partially in from each end, then back out to inspect.

 

[Bramezy]

Another video. Was clear in person seeing the uneven markings.

 

[Bramezy]

The usual suspects would be a burr at the barrel port or a very tight choke. Try pushing a pellet partially in from each end, then back out to inspect.

That’s what this thread is about.
I did that and these are my results.
Looking for info on the results.

 

[jarmstrong]

history? new gun or well used? is the barrel leaded up?
20 cal maurader sounds like Airgun Revision, I don't see them putting out a flawed barrel with port or crown problems, but ya never know, shot happens,,,
ya I cant spell shot worth a shot

 

[Bramezy]

history? new gun or well used? is the barrel leaded up?
20 cal maurader sounds like Airgun Revision, I don't him them putting out a flawed barrel with port or crown problems, but ya never know, shot happens,,,
ya I cant spell shot worth a shot

Gen1 Mrod so its used and no its not from AR. Was told its never been accurate but I did not scrub it with a brush yet. Could do that tonight and push another pellet thru it and see but I did patch it before pushing these pellets.

 

[rdtricks]

With a know less than stellar barrel there are a couple of things you can try that may improve the accuracy and if done judiciously will not cause the barrel to be less than at the start. 1) Cleaning the barrel completely and verifying all leading has been removed with a bore light. 2) Polishing the barrel with products like Flitz or Bore-Bright. 3) Heavily polish the barrel with a more agressive polishing paste or Fire lapping compound.

I have saved a couple of barrels with this technique. It does take time and the need to go slow and check your work is tedious. If done correcly and carefully you will be amazed at the improvement in accuracy and possibly shot-to-shot consistancy.

 

[Hateful McNasty]

I had one gun i pushed and it felt tight then loose then tight all along thr length of the barrel... It shot good but loose fit/small pellet s were a no go .. lots a flyers .

Had one that was hard to group and worked the barrel with steel wool patch and compound a few good times and got tight groupings ( dont be aggressive ) . But not much you can do of the barrel/bore / leade is drilled a tad oversized . Your just at the mercy of hoping to find fat pellets that dont fall through..lol ( R W , cough, cough, S .22's) .

 

[Bramezy]

With a know less than stellar barrel there are a couple of things you can try that may improve the accuracy and if done judiciously will not cause the barrel to be less than at the start. 1) Cleaning the barrel completely and verifying all leading has been removed with a bore light. 2) Polishing the barrel with products like Flitz or Bore-Bright. 3) Heavily polish the barrel with a more agressive polishing paste or Fire lapping compound.

I have saved a couple of barrels with this technique. It does take time and the need to go slow and check your work is tedious. If done correcly and carefully you will be amazed at the improvement in accuracy and possibly shot-to-shot consistancy.

Was my thoughts too as I have everything to try this already and with nothing to lose, why not. Was hoping someone was like oh yeah, mine did that and I did this and it worked well. Im not looking for hole in hole but much better than 1" plus at 25yds. 1/2" groups would be ideal at worst. Ill play with this this week and see what I can get to.

 

[nervoustrig]

In your original post you described pushing a pellet through it both ways, which I interpreted as fully through both ways.

I was recommending to push a pellet into the breech end some distance and then back out again. Does it have the suspect marking? If so, the issue is near the breech end…likely either a barrel port burr or poorly cut leade.

Then do the same at the muzzle end. Does it have the suspect marking? If so, the issue is near the muzzle…likely either an overly tight choke or poorly cut crown.

 

[Franklink]

What the heck kind of rifling does this .20 have?

Most .20 conversions are done with LWs, and they're 12 land and grooves. I've heard of guys using HW .20s but they're also 12 land and grooves. Yours is looking like maybe six? lands and grooves???

I'm very interested to know the source of the .20 barrel in your Marauder.

In the vid, it almost reminds me of a 3 groove TJ, with the narrow land imprints....but I'm unaware of TJ ever offering a .20. My next guess would be one of the old Korean guns, like a Career, as their rifling was comparable, if memory serves. The Career barrels can be quite accurate....

 

[Bramezy]

What the heck kind of rifling does this .20 have?

Most .20 conversions are done with LWs, and they're 12 land and grooves. I've heard of guys using HW .20s but they're also 12 land and grooves. Yours is looking like maybe six? lands and grooves???

I'm very interested to know the source of the .20 barrel in your Marauder.

In the vid, it almost reminds me of a 3 groove TJ, with the narrow land imprints....but I'm unaware of TJ ever offering a .20. My next guess would be one of the old Korean guns, like a Career, as their rifling was comparable, if memory serves. The Career barrels can be quite accurate....

Apparently an old crosman barrel made to fit the Marauder.

 

[Hateful McNasty]

What the heck kind of rifling does this .20 have?

Most .20 conversions are done with LWs, and they're 12 land and grooves. I've heard of guys using HW .20s but they're also 12 land and grooves. Yours is looking like maybe six? lands and grooves???

I'm very interested to know the source of the .20 barrel in your Marauder.

In the vid, it almost reminds me of a 3 groove TJ, with the narrow land imprints....but I'm unaware of TJ ever offering a .20. My next guess would be one of the old Korean guns, like a Career, as their rifling was comparable, if memory serves. The Career barrels can be quite accurate....

I was researching that " what barrel" he got myself and came back here looking at his pictures and scratch my head ...lol i eas like " dont look 12 but then dont look 10 ..

If nothing else reach out to that air gun revision dude hes a Benjamin guru i guess . He may have a parts pile gun that he could let go cheap if nothing goes right on that one .