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10/20/2017 1:01:18 AM
9/22/2017 12:11:25 AM
Posted: 9/8/2005 4:49:10 PM EDT
Here's the problem: when I fire the second to last round in my 20 round mag from a bench rest position, the round fires and I hear an extra "sproing". The bolt locks back and the last round disappears. Literally disappears. It has happened six times and I have yet to find the extra, unfired round. Admittedly, my shooting bench is next to some woods and poison ivy, so I can't go to far back to look, but I can find all my spent brass easily.

This is a new build 16" midlength. Totally reliable with 4 types of ammo, except for this. Only happens when benchresting (i.e. firing with handguard resting on sandbag and not being held down with hand.) Does not happen when firing offhand.

This has only happened with one magazine, a new 20 rounder from Brownells. I can't test it with other mags as they are all 30 rounders and are to long to fire from my bench rest setup. I've measured the magazine lips for the 20 rounder and they have the same spacing as the other mags.

I'm assuming that this is the mag or should I look for something else? Thanks in advance.

Link Posted: 9/8/2005 4:54:28 PM EDT
Sounds like that mag only holds 19 rounds. Count them as you load it to verify.
Link Posted: 9/8/2005 5:04:23 PM EDT
Mine will make that same sound off the bags on the LAST round. All cases impact the same area and all are accounted for. I'd go with Dilbert on this and count 'em out loading/shooting. Might also try the factory mag or others, count them going in and coming out while listening for the telltale noise.
~m38a1
Link Posted: 9/8/2005 5:12:49 PM EDT
Thanks for the reply, but once it started I've only been loading two rounds, so I doubt that I've miscounted.
Link Posted: 9/8/2005 6:19:55 PM EDT

Originally Posted By Ladonia:
Thanks for the reply, but once it started I've only been loading two rounds, so I doubt that I've miscounted.



So you load two rounds, fire one, "spoing" and the other is plain-old MIA????
Link Posted: 9/8/2005 6:59:10 PM EDT
Bad mag,
When the carreir passes back of the top round and the buffer slams off the back of the receiver extension, the top round is being danced out of the mag, and it and the spent case are both being ejected out of the port.

If needed, start off with/use a New USGI 30 round mag (read you now buy them for like $12, and is a good time to junk all the knock off clones/ questionable 10 roundmags that you may have collected.
Link Posted: 9/9/2005 7:56:17 AM EDT
That's what I suspect. I just wonder why it only happens when benchrested and not when handheld. At first I thought it might be because the forearm was lifting up off of the sandbags and then falling back down, knocking the last round out when it hit, but this all must happen faster than that and be completed before the rifle returns to the sandbags. I assume that Brownells will replace the mag, which I only bought to use for benchrest type work.

Thanks to all.


Originally Posted By Dano523:
Bad mag,
When the carreir passes back of the top round and the buffer slams off the back of the receiver extension, the top round is being danced out of the mag, and it and the spent case are both being ejected out of the port.

If needed, start off with/use a New USGI 30 round mag (read you now buy them for like $12, and is a good time to junk all the knock off clones/ questionable 10 roundmags that you may have collected.

Link Posted: 9/9/2005 7:57:32 AM EDT
That's it. My guess is that the rounds are off in the poison ivy, but I'm not willing to search there. I would have guessed that they wouldn't have taveled as far as the spent casings, but that is evidently not the case.


Originally Posted By M38A1:

So you load two rounds, fire one, "spoing" and the other is plain-old MIA????

Link Posted: 9/9/2005 11:52:50 PM EDT
Ladonia,
If this is a new 30 round USGI Type mag, you need to pull it apart and clean/ lube it, and need to break it.

To break it in, use a pencil and shove the follower all the way down and let it snap back up 20 times. Do this first, then pull the mag down to clean and lube.

A for the reason that it may only be happening on the bench is during bench shooting, you hold the rifle more solid (read less movement), and the buffer impact to the back of the receiver extension is greater that when shot free hand. This extra little jolt is the reason that the last round is being danced out, and again breaking the mag in and lubing it should solve the problem (as long as the mag is a USGI type, and not a knock off clone (read usa mags).
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