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Eureka! Undocumented Feature On The 1927a1


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#1 Bob B

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Posted 10 August 2004 - 04:48 PM

I was examining my Numrich 1927A1 and taking measurements (thanks Craig!) with a view to moving forward on some of the modifications I've been considering. As I nodded, nearly napping, suddenly there came a tapping ... Ah, but I digress. In the course of my ponderings I discovered something I never noticed before - an apparently undocumented feature of the 1927A1. (On the other hand, maybe the only one who never noticed it was me - wouldn't be the first time!)

Among the improvements I had planned for my baby was the neat rocker-lever-actuated bolt holdback feature pioneered by PK in Lionheart's "Project X", but I discovered the '27A1 (or at least my 1975 Numrich model) already HAS a bolt holdback feature that I've never seen discussed and isn't mentioned in the original documentation that came with the gun. It's not hidden or anything, just sort of "hiding in plain sight".

Just forward of the large hole at the rear of the actuator slot (the hole through which the actuator knob is withdrawn for disassembly), is another smaller hole that matches the diameter of the actuator shaft just below the relieved area that rides in the actuator slot. If the bolt is drawn back so that the actuator knob aligns with this smaller hole, and pulled about 1/8" in an upward direction, the actuator shaft engages this hole perfectly and locks the bolt in the open position. To release the bolt, a slight rearward pressure is placed on the actuator knob while simultaneously pushing it back down to the point where it disengages the hole and is free to slide forward. It may take a little wiggling to get this to work easily if the sliding surfaces aren't smooth and lubricated, but it works!

I don't know if later Numrich production had this feature (mine is in the serial number 800 range), or whether the current Kahr models have it, but it seems to do the trick just fine. Makes both the rocker-lever holdback modification and/or the "third hand" accessory unnecessary for the '27A1. Can't understand why Numrich never documented this, not even with their drum magazines, since obviously it was designed for this purpose as well as for easier cleaning.

Damn! Now I've gone and ordered the parts, what the heck am I gonna use that fire selector lever for? Unless ...... !!! Oh well, I can dream, can't I? tongue.gif

'27A1 owners?

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#2 Norm

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Posted 10 August 2004 - 04:56 PM

My 27A1 has that notch also. It was the original "bolt holdback" feature on the 27A1.

Unfortunantly, they tend to wear out quickly (when used, due to the spring pressure) and the bolt will slam shut when you don't want it to. ohmy.gif

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#3 Sgt

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Posted 10 August 2004 - 09:52 PM

That is an interesting bit of information, Bob. Thanks for sharing! On a related note, I was curious about your Numrich; does it have the strong springs that plague our Kahr guns? Since yours is earlier, I wondered if it might have a different and lighter recoil design.
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#4 Bob B

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Posted 10 August 2004 - 11:54 PM

Norm,

It did occur to me that reliability would be reduced as the squarely-cut surfaces become more rounded. Since my 27A1 is as-new I thought I'd forestall this possibility by undercutting the forward edges of the receiver hole to a slightly negative angle (say 5 degrees or so from the perpendicular) and turning a shallow matching groove at the engagement point of the actuator shaft. This would provide positive engagement and eliminate any rounding due to wear. This would probably work to restore the holdback function to badly worn surfaces as well, and could be done (carefully) with nothing more than modelmaker's files.

Ralph,

No way of making a comparison as to the spring strength, but must say it's no lightweight - takes a pretty good pull. Does your Kahr have the described actuator knob holdback feature?
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#5 Norm

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Posted 11 August 2004 - 06:43 AM

Sgt.

Yes, they do have the same massive springs as the new Kahr 27A1's do. sad.gif

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#6 PK.

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Posted 11 August 2004 - 07:43 AM

There is virtually no difference in the design of the later WH and Kahr guns. The early WH guns exhibit some differences, the second hole hold open being one of them. It was quickly dropped for obvious reasons. Unless you can harden the steel at the interface Bob B, your undercut idea will work for only a very short time.

It is noteworthy that the design of the actuator did not change with the early elimination of the second cut out in the receiver. The actuators sold by Kahr today will function in these very early receivers as a bolt lock. I find this strange, as the actuator would be cheaper to make and be stronger with out this unnecessary capability.

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#7 Sgt

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Posted 11 August 2004 - 09:36 AM

Bob--
I've got the more recent Kahr, which doesn't have that hold open notch. I planned to have the hold feature which others have done with their selector switch, but was financially side-tracked by my recent M1a1 purchase.
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#8 giantpanda4

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Posted 11 August 2004 - 02:26 PM

I apologize if this sounds stupid - I don't have a Westie here to look at.

But - If you were to drop this thing down and the inertia moves the bolt back 1/8" down - could it fire?

If so, it is no wonder NAC says nothing about it. If you were using it as a third hand - be careful...
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#9 PK.

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Posted 11 August 2004 - 08:44 PM

The actuator slides in the bolt ~1/8” vertically to engage the cutout in the receiver top, the bolt does not move, but is retained in the fully open position by the actuator engaging the cutout in the top of the receiver. When released, the bolt goes home as usual and the actuator can not move vertically again until the bolt is moved all the way back.
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#10 Zamm

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Posted 13 August 2004 - 04:57 PM

Bob,
I don't recomend using the hold open slot which was originally designed in the early
West Hurley guns. The first few months I had mine, this was the only way to hold the bolt open for cleaning
and inserting a drum. The damm thing never quite worked right, let go sometimes and was rough as hell on the frame and actuator. I remember how sharp the opening got on the frame.
Interestingly, I had a fire problem with the gun and sent it back.
When they returned it, it had this magic little pawl catch installed in the magazine ramp.
I was a very happy camper after that, and low and behold, after the final shot in a mag the bolt would lock open!
The original mag (a 20XX Bridgeport) that came with the gun was modified so the bolt would not slam into
the mag follower after the final shot. It was cut and peened down so as to depress back into the mag as the bolt closed home to an empty chamber.

Here is a photo of the actuator lock cut-out in the reciever
user posted image
And here is the original modified mag follower shipped with the early Westys
user posted image
Cheerio, Zamm
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#11 Bob B

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Posted 13 August 2004 - 11:48 PM

Thanks guys for all the good advice. I think the rocker lever holdback wins hands down for reliability and just plain sexiness! PK, you have a real winner there.

PK: You're of course right about the steel not being up to the task - the hardness of my receiver averages HS 24 on the Scleroscope (corresponding to about 2 on the Rockwell C scale) and the trigger frame averages only about HS 23 (below the Rc conversion table limit). No idea what steel Numrich used, but it's pretty mild stuff - definitely not the 4130 specified for the originals. Heck, I've seen readings higher than that on generic cold-rolled!

Zamm: Thanks for posting those - a picture is worth a thousand words! The magazine that came with mine also was modified as shown with a ramp instead of a stop. I've long wondered about the consequences of the bolt slamming home on an "un-ramped" mag, but since I've never fired the piece this wasn't a pressing question. I wonder if Numrich still has the parts for the "magic pawl" retrofit. That'll definitely be needed if I ever take this shooting.
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