Barrel Tuning

[booster]

I've been working on some Digicon Straight Customs, Maruzen M93R's and Tanaka's to increase range, as well as to serve as a holstered gun that could contend with Snipers, without "being" a Sniper. Obviously allot of it has to do with the bucking material, applied surface area and barrel tolerance. After having very good initial success with the 6.01mm PDI's on the Maruzen I thought I had resolved the barrel issue. Although the barrels (and at times guns) have to be modified to deal with the different clearances and hop-up designs, I decided on the PDI 6.01mm x 170mm for the Maruzen (although the KM 6.04mm x 160mm wasn't far behind in performance). My plan was to I finish working up different hammer springs, valves, firing pins and hop-up combinations. My effort wasn't to necessarily build faster guns, although here in the States it's not as much a concern. Range was my goal.

 

The Maruzen has the smallest hop surface of the three and the material is the most soft....very soft. It is also the most thin, so I was careful in NOT over-setting the hop-up. Also, the only two types of bb's I was using were the Guarder .28's and the SGM's. I had changed the hammer and hammer spring so it was shooting at the mid-century mark on propane @95 °F.

 

Suddenly the hop became inconsistent. I figured it was a torn bucking, and after taking it apart I found it torn where it hits the base of the cut-out.

 

I never thought thought of dressing the barrel machining cuts as I was assuming they were finished. In all fairness to PDI stainless takes an edge allot sharper than brass, plus the KM's weren't de-burred or dressed either. It's a drag to damage a bucking that's not easily replaceable. If you have some needle files, 400-600 grit paper, or a dremel and some small stones you might want to consider checking hop-up cut out before installing your new barrel. I will from now on.

 

The KM barrel hop cut matched the stock Maruzen barrel. Here are some some pics on the differences between the KM and PDI hop cut-outs, and how I made them match with a carbide cutter.

 

PDI Versus KM:

 

Where bucking tore:

 

Modified PDI barrel (on the right):