If your Maurader is similar to the rifles with which I had problems, it is unfortunately an an issue you will be managing through any changing condition.
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Benjamin Marauder WOES!
- Thread starter profsrgary
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Ammo makes a huge difference you need to determine what your gun likes to eat. And when was the last time you cleaned the barrel? As you get to know your gun they all have different levels of dirty they want to be at to perform at their best. Some barrels after cleaning need a few rounds shot through them to start to be a tack driver.
Also I didn't see any mention of what scope you are using?
Most of my issues with accuracy were related to either fouling of the barrel and or a cheap scopes.
(Never skimp on the optics) I know this is a hard one to accept but think of a good scope as an investment. Start with the best scope you can afford and then as you get deeper into the sport only the gun will need to be upgraded. And a good quality scope will hold it's resale value better.
Hope you solve your issue!
Have a Great Day!
Also I didn't see any mention of what scope you are using?
Most of my issues with accuracy were related to either fouling of the barrel and or a cheap scopes.
(Never skimp on the optics) I know this is a hard one to accept but think of a good scope as an investment. Start with the best scope you can afford and then as you get deeper into the sport only the gun will need to be upgraded. And a good quality scope will hold it's resale value better.
Hope you solve your issue!
Have a Great Day!
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elk0102 I totally agree with your statement. Last evening I took the rifle squirrel hunting and set up with my trigger stick and then looked for a knot on a dead tree to test. I found a knot on a blowdown at 26.5 yards and shot two shots that touched each other with poi spot on. Securing the barrel band has eliminated the 1" poi shift but I am sure it will affect elevation as the temp changes and the barrel band size changes. I do doubt that it will be appreciable. When I have time I will pull the barrel band and put it in the refrigerator and then let it warm up to room temp. measuring it under both conditions which will allow me to calculate the poi change. I suspect the poi to be a little lower when the band is cold. The rifle is now shooting the JSB 14.3 gr. Diablos through a small ragged hole at 30 yards but they are not the pellets I want to use for squirrels. I will probably use a rimfire until I can get the Terminators to group well. I don't expect them to group like the JSB's but in the past I had no problem getting dime size groups at 30 yards.
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toku58 I agree with your statement on optics but that is not the problem here as securing the barrel band has eliminated the problem of windage shift. When punching holes in paper I try to find the ammo that shoots the tightest groups however when hunting game the terminal effect has to be weighed into the equation. Although the Diablos shoot lights out they don't provide the terminal effect that the terminators do. For this reason my goal now is to get the Terminators to group tighter. I am willing to accept a slight bit of accuracy loss compared to non hunting pellets. As to your statement on cleaning and lead fouling that is also very true as I have found over the years. I also know that H and N pellets are harder then JSB so I am going to clean and start from scratch. I have also noticed that if a rifle is shooting well with a pellet and you shoot pellets of another brand that can throw things off. At present my goal is to get the terminators to group dime size groups at 30 yards. My barrel was seasoned with the Terminators but when I started testing I switched to CPHP's to save a little money and due to the fact I have so many. Thanks for your input and I will update after the weather improves. Gary
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No I have not but I have heard they shoot well in many rifles so thanks for the suggestion. I will order a tin when I place my next order to P.A. I now have the Terminators shooting 3/8" groups at 30 yards with no poi shift being caused by temp. changes. This is better than before this problem arose. Before I placed the oring in the barrel band and rotated the shroud 1/4 turn counter clockwise I was shooting 3/4" groups average at 30 Yds.Thanks for the input. Gary
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While I am an advocate of the free floated barrel the Mrod does not actually have a free floated barrel. A free floated barrel is one not hindered by anything connected to the rifle. The Mrod gives that up with the barrel shroud which is why many members recommended loosening the shroud or removing it altogether. I have mine loosened 1/4 turn and secured by the barrel band with an o ring. There is actually very little contact between the air tube and the stock which may be why this is working so well. The barrel band expands and contracts approx. .002" when the temp changes from 35 degrees to 72 degrees. This equates mathematically to a poi shift in elevation of about a tenth of an inch at thirty yards. The fact that the barrel band is black will make this greater when the rifle is left sit in the sun so painting it a lighter color may be needed in the future but for now I am satisfied. Removing the shroud was suggested and would actually make the Mrod barrel free floating but I didn't try that because I like very much how quiet the rifle is. One thing I find very interesting is when I secured the shroud to the barrel band the groups were poor. I mean like 1" plus at 30 yards but when I loosened the shroud they immediately shrunk dramatically. What I have done to correct this issue defies everything I have learned in 60 years of shooting and I can't give anyone a solid reason why it works but I will continue to monitor and see where it leads me. Thanks for your suggestion, Gary
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O.K. Guys after days of testing in both warm and cold temps as well as various pressures this is what I have done. The barrel was cleaned and no pellets except the Terminators were tried. I have found that some pellets do not play well with others. The shroud was removed and turned end for end and backed out 1/4 turn from tight. I inserted an o ring on the barrel and pushed it into the band to stabilize the shroud/ barrel assemble. No shooting over 2600 # of pressure and none under 2000#. I only get about 28 shots in this range but they will group under 1/2" if I stay within these pressures. While I was at it I converted the rifle to a left hand bolt since I shoot left handed. I also stopped lubing my Terminators with White Lightning chain lube as I was getting first shot fliers. The lube works great on JSB pellets in my Gamo but not in the Mrod with the terminators. I pulled a dry patch through the barrel which eliminated the first shot fliers so I stopped lubing and the first shot fliers disappeared. The results are. First shot accurate in both cold and warm temps and groups under 1/2" at thirty yards.This is not the answer for all rifles but it seems to be the answer for my Mrod. I started this thread because of the poi shift caused by temp. changes and I feel that the loosening of the shroud and o ring in the band is what corrected the problem. Barrel cleaning and lube elimination decreased the group size which is now better than ever for these pellets. There is one other thing I want to mention because I feel it is critical. When shooting this rifle it is IMPERATIVE to rest it in the area immediately in front of the trigger guard. This is where I naturally place my hand but for some of the tests I rested the gun directly on the Caldwell and because of the length of the rest the front section had to be placed near the front of the stock and the results were poor. Thanks again, Gary.
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Gary, great essay on your Marauder experience. I think you are on to something.
Shot Cycle and Barrel Harmonics.
You have described in great detail the testing (hot/cold) and changes you have made in relation to the external components of the Marauder along with pellets and lube. The possibility of internal adjustments to support your efforts could be your ticket to sub-moa @100.
Have a great time and keep us posted.
Patrick
Shot Cycle and Barrel Harmonics.
You have described in great detail the testing (hot/cold) and changes you have made in relation to the external components of the Marauder along with pellets and lube. The possibility of internal adjustments to support your efforts could be your ticket to sub-moa @100.
Have a great time and keep us posted.
Patrick
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It is well known that the shroud on the Marauders tend to move on the bind in the threads and the oring and push the barrel around. One solution has been to fix the end to the barrel guard (band) with screws or orings. But now you are involving the differential expansion and vibrations of the air tube. I think the better solution is to just use a shorter shroud so it no longer has any leverage to move the barrel. The first short shroud I ordered online to try without chopping up the stock shroud in case I didn't like it. I have no before and after groups and haven't been outside with the Marauder .25 yet but it is shooting through one hole so far from the bench at my 12 yard indoor range. The thread peaks were too high on this shroud and it made it difficult to screw on. And I knew this idea would be a success. So I took the shroud from my new regulated .177 Marauder to a local machine shop to have him cut it in half and copy the threads. It turned out perfect and he charged me $50 for both and said he could do it again now that the settings are saved much cheaper next time. The .25 is still nearly zero report at 41 FPE and is pictured below with one of the baffles removed to make it a bit shorter. I may take out another one and see if it is starting to get louder.
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My Marauder FT .177 with half shroud and 5 out of 7 baffles. In theory, this might also have a beneficial side effect of placing the mass of the rear shroud bushing at the first point of the golden ratio of the extended barrel length where it would have the most dampening effect on barrel harmonics. I am right now at 7.5 inches from the crown. If I put one more baffle back in it would be at the ideal 6.8 inches. The inverse of 1.618 times the free barrel length of 17.5 inches.
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Another solution to the wandering baffle problem of the Marauder uses a strip of hobby foam sheet or sticky foam around the inside of the barrel band.
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My POI changing was completely solved by installing two o-rings in the barrel band. Cheap and easy to try.
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