|West Hurley barrels are softer steel than the original
Colt and WW II barrels and have a tendency to "shoot-out" the rifling faster. I
suggest that you replace your worn-out W/H barrel with a WW II GI barrel when the time
comes. Glen Whittenberger mentions his approach to extending W/H barrel life in TCN # 22.
D.W. Richardson has covered several different barrel removal techniques in multiple issues
of TCN (#27,42,53).
Does your W/H tend to burst fire on the semi-auto setting? Odds are that the rocker or the pivot pin holes aren't in quite the right location. Most frequently the pivot pin hole is out of vertical alignment (usually too low). There are two solutions. First, build up the top of the rocker with weld and then re-shape it to its 0 original profile (effectively raising it up into contact with the bolt's T- slot while on the semi-auto setting). At the same time make sure that the rocker isn't too tall now so it doesn't contact the bolt while on the full-auto setting. This approach allows you to save your original W/H trigger housing but will keep you from being able to drop-in an unmodified replacement rocker in the future. Second, if the pivot pin hole is also out of front-to-rear or left-to-right alignment, the easiest fix is to completely replace the W/H trigger housing with one from a WW II GI parts set. The GI housing was gauged when it was made for correct dimensions - I'm not sure that can be said of all of the West Hurley production guns.
Most of the West Hurley gun's by now already have GI surplus bolt's, locks, and actuators in them; if your gun doesn't, then by all mean's get the GI part's installed. The GI parts were all quality-control inspected when they were manufactured; by using parts of "known" quality when you're troubleshooting a ore air job, it helps to isolate the problem by eliminating other possible le causes. This is the single biggest reason to use only factory-made FMJ ammunition when you are out test firing your Thompson for malfunctions (you've eliminated reloaded ammunition as a possible 'source of your problem's).
After you complete any repair job or alteration to your Thompson, as the gun's owner it is your responsibility to make certain (to the best of your ability) that all controls, ESPECIALLY THE SAFETY, work properly.
Other note's on West Hurley gun's: I've noticed the fewest feeding problems with C CO. brand GI 30 round magazines. Based on measurement's of various TSMG mag's in my possession, the C CO. mag's' feed lip's are longer (than other's) before the lip's begin spreading -resulting in better control of the cartridges during the feeding cycle. This may help to explain Chris Martin's experience in #87. I've had the best results using only C CO. mags (along with WW II production drum's) in my West Hurley guns.
West Hurley Semi-auto (ONLY) users: With the Clinton high capacity mag ban in place since Sept.'94,it may be easier and cheaper to modify your magazine catch to work with full-auto nags rather than modify the expensive full-auto mags to work with your semi mag catch. Full-auto mags' locking notch is a round hole on the back of the rib. Semi-auto nags have an oval shaped hole to account for the height difference of 0.1 inch between the full and the semi trigger housings (see D.W. Richardson's article and drawings in TCN # 30). The oval cut notch of the modified semi nags allows them to sit in the correct relationship to the bolt through the feeding cycle. The same thing can be accomplished using full-auto (unmodified) nags by lowering the height of the locking stud on the mag catch by 0.1". Please refer to the diagram on the following page.