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Author Topic: Question regarding M1A spindle valve.  (Read 2993 times)

VR-21

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Question regarding M1A spindle valve.
« on: April 16, 2010, 10:39:45 AM »
I'm a relatively new M1A owner, and am curious to know if there's any problem with continuous operation of the rifle with the spindle valve turned off, allowing manual extraction of fired cases.  There's no mention of it in the SA owners manual, and the Dept. Of The Army manual that came with it only mentions that the valve was used to facilitate grenade firing. I find it a nice feature at public ranges, as I don't bounce cases off adjacent shooters and (here's the real reason) I hate to pick my fired cases up off the ground (I've had a serious case of handloaders disease for decades). Any wisdom from more seasoned M-14/M1A shooters would be appreciated.


VR-21

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Re: Question regarding M1A spindle valve.
« Reply #1 on: April 20, 2010, 10:55:43 AM »
For what it's worth, I went ahead and called Springfield Armory's customer support and they told me that is doesn't harm the rifle at all.

Coronach

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Re: Question regarding M1A spindle valve.
« Reply #2 on: April 20, 2010, 11:22:01 AM »
Interesting. I was wondering what the answer would be.

Here's a followup question to which you might know the answer: does switching the spindle valve change your POI, due to varying the amount of gas going out through the port?

Mike
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VR-21

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Re: Question regarding M1A spindle valve.
« Reply #3 on: April 21, 2010, 11:09:42 AM »
Here's a followup question to which you might know the answer: does switching the spindle valve change your POI, due to varying the amount of gas going out through the port?

So far I haven't noticed any change in group size or POI.  I've only worked with the rifle at 100 yds. thus far and that may be the reason.  I plan to take the rifle to the range early next week, and I'll set up two targets at 200 yds. and shoot them  carefully...one in each mode.  That should give a better indication if there's any POI change.  In fact I'll set up a chronograph too.  I'll be back with my results no later than the following Friday.

Coronach

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Re: Question regarding M1A spindle valve.
« Reply #4 on: April 21, 2010, 12:08:29 PM »
Excellent. I'm curious to hear the results. If there is no meaningful change, that will certainly make keeping track of brass a lot easier.

Mike
OhioNot stressed, but I am a carrier.

VR-21

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Re: Question regarding M1A spindle valve.
« Reply #5 on: April 30, 2010, 07:03:55 PM »
Well, I took the rifle (Springfield Armory 'Standard' version) to my local range last Wednesday and today... set up two targets at 200 yds. and a chronograph. I fired three series of twenty rounds each (handloads using the Hornady 150 gr. BT-FMJ and CBC cases) over the chronograph...five with the spindle valve turned OFF, followed by five with the spindle valve turned on.  I then fired five rounds at each of the 200 yd. targets to see if there was any effect on POI and grouping in either mode.

There was only a 6.4 fps difference in velocity between the two modes in the first series.  The rifle shot 2679.2 fps with the valve OFF, and 2685.6 fps with the valve  ON.

There was an interesting development. I ended my shooting on Monday after the first series of 20 rounds because I felt that the handload I was using was too hot.  While my powder charge was within Hornady's published 7.62 X 51 data (sixth edition)  for the bullet and powder I was using, and there were no outward signs of excessive pressure like flattened/cratered primers (there was in fact still some radius on them), it was very difficult to manually extract the fired cases. This wasn't noticeable while firing the rifle with the spindle valve ON. I went home and reduced the powder charge by 1.0 grain and returned to the range today.

I fired the remaining two series of 20 rounds in the same fashion as before.  The second  series used the CBC cases that I used before, and the third series used WCC-07 cases.  I had no difficulty with manual extraction with any of the fired cases today.  The second series (with the CBC cases) gave 2601 fps with the valve ON, and 2591.6 fps with the valve OFF (10.6 fps difference).  The third series (with the WCC-07 cases) gave 2579.5 with the valve ON and 2579.8 (.3 fps difference) with the valve OFF.

There was absolutely no noticeable difference in group size or point of impact in either mode of operation in any of the (6) 200 yd. groups I shot.

JesseL

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Re: Question regarding M1A spindle valve.
« Reply #6 on: April 30, 2010, 07:09:21 PM »
Interesting. Thanks for posting the results of your research.
Arizona