More on the Hammerli P240
It bugged me while writing the former blog on the P240 that I couldn't dig up information I knew I had. The following barrel specifications are as published by Hammerli in their tech sheet dated December, 1977.
This makes a standard .357 projectile at least .003" and probably .004" oversize, which only further illustrates how careful you must be while reloading for the P240 in 38 Special. The tech sheet says further:
And we do know of course that many of the SIG-Hammerli P240 owners reload their ammunition in cal. 38 Spl WC and 32 S&WL WC we should like to emphasize once again the fact that our barrels have a tighter bore than is normal. The choice of the bore dimension is due to the fact that top accuracy was obtained when using various brands of commercial factory-made ammunition. The handloader must however take into consideration the exact bore dimensions when making the bullets very carefully.
It would be interesting to know if any of those tests involved higher than normal temperatures, since a fast-burning powder tends to increase pressure dramatically in very hot conditions.
Just to round out this topic, I'd like to add some hopefully helpful information to any P240 owners, just in case`they have any misbehaving magazines. The following are the factory-recommended gaps between magazine lips:
| Measurement | 32 S&W L | 38 Spl |
| Bore Diameter (lands) | .3052" + .001" | .3425" +.002" |
| Bore Diameter (grooves) | .3118" + .001" | .352" + .002" |
| Twist | 1 in 15.7" | 1 in 19.7" |
This makes a standard .357 projectile at least .003" and probably .004" oversize, which only further illustrates how careful you must be while reloading for the P240 in 38 Special. The tech sheet says further:
And we do know of course that many of the SIG-Hammerli P240 owners reload their ammunition in cal. 38 Spl WC and 32 S&WL WC we should like to emphasize once again the fact that our barrels have a tighter bore than is normal. The choice of the bore dimension is due to the fact that top accuracy was obtained when using various brands of commercial factory-made ammunition. The handloader must however take into consideration the exact bore dimensions when making the bullets very carefully.
It would be interesting to know if any of those tests involved higher than normal temperatures, since a fast-burning powder tends to increase pressure dramatically in very hot conditions.
Just to round out this topic, I'd like to add some hopefully helpful information to any P240 owners, just in case`they have any misbehaving magazines. The following are the factory-recommended gaps between magazine lips:
| Measurement | 38 Spl | 32 S&W L | 22 LR |
| Front lips | .378" | .338" | .224" |
| Rear lips | .295" | .295" | .204" |
posted by Warren @ 11:56 AM
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