.30 Marauder project begins

I unboxed the gun, filled it to 3000psi and cranked it up to full power. I shot a few 43gr eunjins over the chrony to document stock power. This photo is shot #1, #2 was 724, and #3 went 718.


After getting some stock chrony numbers, I tore the gun down to start the process.



Got the airtubed honed to a nice smooth finish so the hammer can have a nice slick surface to ride on.



After honing the tube, I completely degreased and cleaned it out. Once clean, I installed the new Hill valve, gauge block, and reinstalled the fill assembly. I filled it to 2000psi and after 6 hours it appears she is sealed tight and no signs of any leaks.


Even though this gun is going to end up a .30 caliber, I want to test it as a .25 until I get the .30 barrel and bolt. Since 43gr eunjin pellets are only 1 grain lighter than the 44gr JSB .30 pellets, I should be able to do alot of testing and tuning that will be useful for the .30 project. I went ahead and prepped the stock .25 Green Mountain barrel.


Just a couple of things to note. This guns airtube was one of the worst I have seen as far as burrs and uniformity of the ID. The hone cleaned it up, but it took much more work than normal. On a positive note, after slugging and inspecting the bore, I believe this barrel was made with a fresh mandrel. Pushed a number of pellets and slugs thru it and it feels very consistant and should be a shooter. To bad I am not using this barrel and it will just collect dust on the shelf after the .30 barrel gets here. I also noticed that the serial number is on the breech instead of the airtube like all the rest of my Marauders. Not sure when Crosman made that change as it hasn't been 5 or so months since the last Marauder I purchased?

Starting this project has once again reminded me that I enjoy working on guns as much as I do shooting them!! I think my biggest joy is turning these "cheap" "beginner" "entry level" Marauders into precision instruments!!

No leaks for near 24 hours so I finished putting it back together. Already had a hammer that I polished awhile back so I swapped it for the stock hammer. I put a 12.5lbs hammer spring in, set the barrel back in the breech and bolted her up. last night I opened the barrel port to .185 and then deburred the new hole and gave one final jb/kroil treatment. I made a .185 TP to match the valve exhaust and barrel port. I filled the gun to 3000psi and cracked a few over the chrony with 43gr eunjins. #1 873, #2 went 870, and #3 864.


That is a 145fps gain over a stock gun. The only changes thus far is honing, polishing, and the Hill valve and gauge block, and a 12.5lbs hammer spring. In all honesty, My last WAR valve could do no better than the results I just got from the Hill valve. Now, this is all fine and dandy, but these numbers are all from the .25 GM barrel with 43gr eunjins. I hope that I will be able to get similar resuts from the TJ .30 barrel and 44gr JSB's from this same power plant. Time will tell, but I am very pleased with this Hill valve thus far!!

I still want to get the trigger worked over and then I will be ready for the .30 barrel and bolt.

I hope the .30 will give similar results!! If I get a scope before the .30 kit arrives, I will most definitely shoots some groups.

Just got done working on the trigger. Polished everything up and removed the "lawyer" spring. Put some silicone spray on all the trigger group pieces, and reassembled. Got out my trusty Lyman digital pull scale and started tuning the trigger. I hate a 2 stage trigger and fortunately the Mrod trigger group is very easily adjusted to single stage. Zero creep and breaks like a glass rod!! Here are the results of a 10 pull average.

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I had called Roy at Mountain Air earlier today to verify that he had recieved my check for the .30cal kit. I just got a return phone call from him and sounds like my kit might ship out in the next couple of days. The magazines from Airgun labs and .30 pellets from Pyramyd should be here by tomorrow. Can't wait to get my remaining parts and pellets!!

I would rate it "as new". I have owned a number of refurbs and normally can never tell the difference between new and refurb. If it is a true refurb, it has been returned to Crosman and they completely go thru them to make them as good as new.

Just went to the post office and picked up my .30 Mags from Lloyd @ Airgun Labs. They fit the breech perfectly and are very well made.

Since I replace or modify the majority of the parts on the gun, refurbs are a good opportunity for me to save some money.

4 tins of .30 JSB's have arrived. Just waiting on the .30 kit and work will resume.

Scope arrived today, but the rings did not. USPS showed today as estimated arrival for the .30 kit, but tracking hasn't updated since last Thursday? Hoping to have it by the middle of the week.

.30 kit arrived from Roy @ Mountain Air today!! Picked up from usps at 12:45pm EST and fired the first shoot minutes ago just before 2:00pm. Very easy to swap to .30 with this bolt and barrel. First rate quality parts!! Only thing I did was open the barrel port to .185 to match the valve and TP. I will admit that this barrel felt bad. pushed a few pellets to get bore measurements and it felt good half way then gets loose till muzzle exit.(This barrel is unchoked) Time will tell if it is a shooter or not? Have to head to work, so will get back at it tonight after work. Here are some photos of the barrel and bolt, also the first shot over the chrony. Keep in mind gun is not tuned and only had 2500psi in it. The results are almost identical to what this gun was doing at this pressure with the .25 barrel an 43gr eunjins,

I believe the gun is complete and ready to sight in and test for accuracy. Shot nearly a full tin of pellets tuning tonight and I am happy with the results!!

In all honesty, whatever you can get with 43gr eunjins in .25 cal should be pretty damn close to what the gun will do as a .30 with 44gr JSB's. My results with the .30 were almost identical to the results when this gun had the .25 barrel with 43gr eunjin's. I shot alot of strings tonight, and even comparing notes to my .25 Marauder with WAR valve shooting 43gr, you would never know whether it was the .25 or .30 as numbers at many different tune settings were all but the same. I was able to get upwards of 880fps, but without a bell curve. I had to back down the power to get a nice curve. This .30 with 44 jsb's is shooting almost the exact same numbers as my .25 marauder shooting 43gr eunjin's with a WAR valve.

I don't want to jump the gun since I still have to see if this thing can hit the broadside of a barn, but I am really happy thus far!! The quality and performance of the Hill valve and gauge block is much better than I would have expected. I didn't think it would make as much power as my WAR valves. Well, I was wrong. The barrel and bolt from Roy at Mountain Air are of stellar quality and if the barrel shoots good, I will have to give the .30 conversion kit 5 stars!! I will give an update once I can shoot some groups. Here is the finished product with a 4-16 BSA Contender SF with cmd reticle.

Winds are variable at 8mph with gusts up to 12mph temps 60. I quickly got the scope close on paper and fired a few more for a total of 14 shots(2 mags). I wanted to get an idea of accuracy, so I filled back to 3200psi loaded a mag full of 44 jsb's and shot this group at 30 yards rested off my kids outside toy box. Bullseyes on this target are 1/4". This is a 7 shot group.

While this is not real impressive, considering the lack of a suitable rest and a decent breeze, I am happy thus far. I actually had the first 6 in the exact same hole and threw the 7th a little high and right. .30 pellets sure make a big hole compared to even .25!!