Can a Magazine Affect Accuracy?

[bluto]

I was just at the range with my 2 CPO P220 SIGs. It was the first time that I've shot them side by side: same pistol, identical sights, nearly identical trigger, same American Eagle ammo, everything.

About halfway through (100 rounds/50 each) it was apparent that one CPO was shooting better than the other. One consistently grouped well, the other seemed to have some wild fliers on every target. On my last 50 rounds the magazine on the poorly grouping P220 was sticking badly when I hit the mag release to reload so I used the magazine from the better shooting P220. And what do you think happened? The poorly shooting P220 shot nearly on par with it's twin.

I'm just wondering if a poorly functioning magazine can affect how a bullet seats in the chamber as I know that there's always a bit of difference between seating the first round and the subsequent rounds fed from the magazine.

Any opinions? Thanks.

 

[presspuller]

I would think the recoil spring would have more to do with the round seating in the chamber more than the mag but what do I know.
I could see how a mag could slow down the speed of the slide/bolt that would might make some difference but I would not have figured it would be enough to show.
Do you see any scratches on the brass that might show it was rubbing on the mag or anything?

 

[Car Knocker]

If the feed lips on one magazine are spread a bit more open than on the other magazine, the cartridge would extend a bit further out of the mag and apply more pressure on the slide, creating more drag and slowing slide speed. Whether this would be significant as far as accuracy goes, I don't know.

 

[1SOW]

What range were your targets. Even a slightly deformed bullet won't show much deviation out to 15 yds. Were the holes clean? If the bullet didn't fly true it would show in the target holes.

Mags can cause feed/jamming problems, maybe even scratching the bullet/slowing the slide; but can a Sig fire a round that the slide hasn't fully chambered?? I haven't got my Sig breakdown manual handy, but doesn't the slide has to be fully forward before the firing pin will engage? I may be wrong. I often am.

With the bad mag, you could try manually chambering (pull fully back and release it) and extracting enough rounds where your problem would have shown up, and check that the slide goes fully into battery when released and also check the manually extracted cartridges for scratches etc.

I don't agree about the "bit of difference between the seating of the first round and subsequent rounds". The forces may be slightly different but the seating should be exactly the same.

 

[owlhoot]

A magazine certainly affects reliability, but there is no way it can affect accuracy. It can, however, impact your attitude and perception and thereby cause you no shoot more poorly with one gun than another. Try the faulty magazine in your "better" 220 and see what happens.

 

[bluto]

Thanks for the thoughtful replies.

I kinda' figured that it was probably coincidental and/or mental attitude but you never know until you ask. I will switch the mags around and check next time at the range to see if there's any scratching on the cases that might affect bullet seating. I sort of doubt it.

BTW, I was shooting at 25 yards, which is the distance that I do most of my shooting. Holes were clean. I'm sure that the pistol wasn't firing out of battery. Most likely the operator needs a tune-up.

 

[10X]

Accuracy is dependent upon the gun returning to battery the same way every time.

If the magazine is somehow putting an odd pressure and not allowing the gun to be in the same battery or consistent battery as the other magazine, the magazine could be causing accuracy problems.

I have had this happen with 1911s.

 

[Mad Magyar]

Accuracy is dependent upon the gun returning to battery the same way every time.

Interesting, never heard that explanation before citing the mag for the problem.....

 

[saltydog452]

I can't shoot well enough to tell the difference. But some of the folks at the MTUs used to claim that the mags made a difference. Bear in mind though that these guys and gals also claimed that they could, on occasion, out-shoot a Ransom rest.

salty

 

[rcmodel]

Some of them, on occasion, could!

rcmodel

 

[mpmarty]

Bear in mind though that these guys and gals also claimed that they could, on occasion, out-shoot a Ransom rest.

Nearly anyone can outshoot a ransom rest with a semi auto where the barrel locks into the slide and is not permanently attached to the frame like a Walther PP or PPK. A ransom rest is fine for testing revolvers and other archaic lead slinging devices but semi autos do not do well in ransom rests. The reason is the ransom attaches like a magazine and does nothing to orientate the slide to which the barrel is fixed.