Marauder accuracy issue

[JKaplanwit]

I took out my Marauder for the first time in months (I've been using my Condor and Crown). On a 10m shot, I was getting a spread of over 4" on 5 shot strings! I ran through a few clips and topped off the air to about 2700psi, hoping it just needed some breaking in after a long winter nap. No moderator. Pressure in steady/holding. Shooting from a bench, rigle in a solid stand. Indoors, so I know there is no wind issue. JSB pellets, and I'm checking them before loading the mag. I took the shroud off to check the baffles, check for lead buildup, and clean the barrel (there was nothing more than a nice coating). Everything seems tight and sturdy.

I am new to tinkering and maintenance, so beyond the basics and cleaning, I just don't know where to start to look. But I do know a source of experts that are great for knowledge and advice. Any suggestions on where to start? 

Thanks.

 

[profsrgary]

Is your breech seal still in place? If your rifle was shooting well and suddenly went to 4" at 10 yards there is something drastically wrong and the first place I check is the breech seal.

 

[leadfoot]

Scope/sighting system loose. Stock bolts loose. Try different pellets. Breech seal (Oring) not working well. (If gun ever fired with bolt open you may dislodge that Oring).

 

[profsrgary]

Does the gun sound the same shot to shot? Does it cock smoothly? If the gun was put away and subjected to moisture the hammer could be hanging up if there is oxidation present. What leadfoot said about pellets and stock screws and scope mounts are all valid and should be checked as well but it was shooting well with the pellets you are now using then I suspect it is an all of a sudden problem like oxidation on hammer or poppet or a seal blew out.

 

[profsrgary]

If you have a chronograph and check velocity and it is near what it was when you put away and holds steady then the problem likely is not oxidation. However if the chronograph shows an ES that is not in the normal range or an overly high or low velocity you know to look at the guns mechanical mechanisms. One thing to note is that the Mrod is noted for the striker adj. screw. (1/8") rotating ccw which increases stroke and velocity. 

 

[Yo]

If it's not the breech seal or transfer port issue Try shooting it without the baffles and endcap. YO!

 

[JKaplanwit]

You guys are great!!

Breech seal is missing. It must have blown out just before I put it away. 

Thanks a million!

 

[Yo]

Breech seal o-ring. YO!

 

[Yo]

 

Also check this is not cracked or wobbly. YO!

 

[Yo]

 

 

[Yo]

Breech barrel O-ring was hard to see with the Crosman barrel photos so this one is easier to see in contrast. It's for Marauder. YO!

 

[d_boom]

I well need to remember that one.