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PostPosted: Wed Oct 04, 2017 4:12 pm 
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Joined: Sat Sep 03, 2005 9:25 am
Posts: 3432
Location: Ontario, Canada
My Canadian detuned Optimus was shooting reasonably well but never had the accuracy of my full power version. The full-power I detuned to 800fps and this detuned Canadian version I uptuned to 630fps. My review in the other sub-forum section explains the details on the two rifles.

After pushing a bunch of pellets through the detuned Optimus, I discovered that the bore was far from acceptable. It started off tight at the breach and then got tighter right after the block. About 3" from the muzzle it got loose. I tried polishing with JSB Paste mixed with jeweler's rouge but that wasn't enough. A fresh crown didn't seem to help either.

It took some lengthy thought but I decided to sand the bore as per directions from chevota. Sanding by hand seemed like a radical approach to fixing a bad barrel. I ended up splicing a couple of bamboo skewers together to give a 2 foot rod with 1/8" thickness. This worked out well when I taped and wrapped a 4" wide strip of 320 grit. The constricted areas in the barrel were easy to find while sanding. I focused on them until they relaxed. Then I moved to 600 grit and finally some JSB Paste on a patched q-tip that I threaded into a .177cal cleaning rod. I touched up the crown with a brass screw and a JB/rouge blend. The breach seal was changed to a fitted 109 Viton o-ring that I thinned a bit from the back side (sanded).

All accuracy testing was done with a Leapers 3-9AO adjusted to 9X. I shot all groups from the same shooting area and from the same rest combo. I did not remove the barrel or touch the block washers, breach plunger, or trigger. All I did was sand the bore and lightly touch up the crown that already looked great from a previous crown polishing.

--- 50 yards – 5 shot groups ---August 2017
H&N Sport - 2.78, 2.15, 2.54, 1.61, 1.90, 2.38 -- Ave = 2.23" ctc
JSB Exact - 2.49, 2.12, 2.98, 2.45, 2.96, 2.22 -- Ave = 2.54" ctc

The following groups were from yesterday. Post barrel sanding. All groups were recorded and not cherry picked from a big batch.

--- 50 yards – 5 shot groups --- October 3, 2017
Stoeger Match – 1.31, 1.38, 1.60, 1.04, 1.39, 1.03 –- Ave = 1.29” ctc
JSB Exact – 1.91, 2.20, 1.93, 2.02, 1.66, 1.13” -- Ave = 1.81" ctc

My .177cal 800fps Optimus was always more accurate than the milder version. Here is what the 800fps version did this summer at 50 yards. Both rifles now seem to shoot about the same accuracy at 50 yards. I hope they stay shooting this well!

--- 50 yards - 5 shot groups --- July 2017
JSB Exact - 1.47, 1.50, 1.56, 1.18, 1.15, 1.56, 0.73, 1.09, 1.11, 1.50, 1.49, 1.25, 1.05, 1.46, 1.39, 1.56, 1.07, 1.34, 1.17, 1.69 – Ave = 1.32" ctc


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PostPosted: Wed Oct 04, 2017 4:16 pm 
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Location: Ontario, Canada
Here is a pic of the 109 Viton o-ring stretched into the Optimus groove. It works well.

The other pic is the finished crown on this rifle. I used the common method with a domed brass screw, polishing compound (JSB Paste + rouge) and a drill.


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PostPosted: Wed Oct 04, 2017 4:29 pm 
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Location: Thunder Bay,On.
So its YOU buying up the stoeger 8.18s from GMK.....lol...I'm going to buy the rest before you return....nice groups....I read that 2 inches CTC at 50 yards is considered pretty darn accurate for break barrels so you definitely have THAT covered....Im still pulling 2-2 1\2 inch groups at that distance ( same ammo ) with a couple of my guns....I..might have to look into barrel sanding...... :D

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PostPosted: Wed Oct 04, 2017 4:30 pm 
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Location: Ontario, Canada
Here is a pic of the spliced skewers. I split one end and made the other into a wedge. The pieces were carefully fastened with epoxy and sanded to size. The process is like footing a cedar arrow. The bamboo should be much stronger than the crooked 1/8" wood dowels from hardware stores.

The sandpaper was fastened to the skewer with Scotch tape. You can adjust the thickness with how many times you wrap the paper around the skewer. You can also add shims of regular paper under the sandpaper to create more pressure when sanding. Chevota explains all this in his excellent guide. I don't want to seem like I'm pirating his material that took a lot of time and experimenting to put together. I just found that it worked well for me.


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PostPosted: Fri Oct 06, 2017 3:51 am 
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Location: United States
I'm glad you posted that b/c a lot of people think I'm crazy for suggesting it. That and the warnings I put in there about ruining the barrel if you're not careful has scared people off as well. So maybe your success will get more people to try it.


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PostPosted: Sat Oct 07, 2017 9:39 am 
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Joined: Wed Dec 21, 2005 11:27 pm
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Location: Toronto
That's a very clean barrel crowning job. 8)

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