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HSS will fit Ruger MK III and MK II series pistols (except 22/45 versions).

  • MK II was manufactured from 1982-2005, followed by MK III manufactured through Dec 8, 2016.


HSS is will fit with MOST earlier Ruger Standard and MK I pistols. These were manufactured from 1949-1982. Most people with Ruger Standard and Mk1 pistols have installed the HSS with no problems at all.  See 1965-1976 exceptions and remedies below.


HSS will fit Volquartsen Scorpion pistols that are not 1911 style (they are copies of Ruger 22/45 versions).


HSS will fit AMT Lightning pistols (unauthorized clones of the Ruger MK II).

HSS WILL NOT FIT ANY 22/45 pistols. See below.

HSS WILL NOT FIT ANY MK IV pistols. See below.

All other Ruger MK I and Ruger Standard Pistols should be compatible​.  If you have more information that can help narrow the "problem range", please let us know.  Thank you.

To see what year your pistol is, go to the Ruger website:

Ruger Manufacturing Inconsistencies from 1965 to 1976

In 1965-1969, Ruger had manufacturing inconsistencies with the "perpendicularity" of, the "sear spring retaining pin", commonly referred to as the "cross-pin" on this website.  The right end of the cross-pin may be a few thousandth of an inch higher (towards the top of the gun) than the left side.

In 1970-1976, Ruger had manufacturing inconsistencies in the clearance under the "sear spring retaining pin", commonly referred to as the "cross-pin" on this website.  A minimum clearance space under the cross-pin of 0.035 inches is required to install the HSS.


Summary of possible fitting required for MK I pistols (1965-1976)

1965-1968 For sn 334991 and above: minor fitting MAY or MAY NOT be required. (Pistol cross-pin may not be perpendicular to handle.)

Typically, 1965-1968 models only need a very slight widening of the upper right corner of the HSS cross-slot.  This can be done quickly with a small jeweler's file (file info below).  Alternatively, putting a taper on the right end of cross-pin may help realign the cross-pin back into the hole, if holes only slightly misaligned.

1970-1976 For sn 10-58067 to 13-49225 need fitting or may be incompatible.  (HSS slot needs to be made deeper)

There are SOME pistols in this 1970-1976 range where it would be necessary to take a significant amount of material off of the HSS to make the slot deeper.  Most however, only need a little material removed.  You will need to measure clearance under the cross-pin to evaluate. The normal clearance under the cross-pin is usually at least 0.035 inch. 


You can measure the available clearance under the cross-pin in your pistol by using an automotive feeler gauge of the "bent wire" type, typically used for spark plugs, etc.  Some people have “pinched” or “filed” the end of a paper clip to fit under the pistol’s cross-pin, and then measured the result to find that clearance.

TEMPORARY NOTE FROM HSS CORP: The HSS normally needs about .035 inch clearance under the cross-pin.  We have a few HSS items with deeper cut slots, that may fit some MK I models from 1970-1975. Call for more info on special fitting of  these. Tom @ 256-527-3527

Note: a small round file that fits the HSS slot is available at Lowe's stores as part of a small 6-piece set, item number 0159850, for $3.98. 


What are 22/45 pistols and MK IV pistols:

HSS is not compatible with any Ruger MK 22/45 pistol.

All Ruger 22/45 pistols (both Mk III and MK II versions) have an entirely different handle, a more vertical handle, which is modeled after the popular model 1911, 45 caliber, pistol.   All of these pistols do not have a cross-pin and use a different kind of sear spring, so the HSS is not compatible with any of these. 


HSS is not compatible with the new Mk IV models.

The MK IV models began to be sold in Dec, 2016.  These have a "tip-off" barrel design, wherein the barrel can be rotated off of the frame, after depressing a release button.  These have a totally new interior handle design.

We have a money back guarantee on our HSS.  If you would like to try the HSS on one of these earlier pistols, we will gladly refund your purchase price if it does not fit.  Just let us know the details about what pistol and what year it did not fit.

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