Magazine accuracy?

Saw a Facebook post about magazines affecting accuracy of a semiauto pistol, and would like to hear the experts (HM's specifically) discuss.
Does a magazine have an effect on pistol accuracy, and if so, how? Do you have "most accurate" magazines and "less accurate" magazines?

There certainly was an effect on the M14. Military armorers would bench-test rifles with magazines and look for 2 or 3 that would group together. They didn't accuracy check magazines for pistols, but would check functionality.

jwax wrote:Saw a Facebook post about magazines affecting accuracy of a semiauto pistol, and would like to hear the experts (HM's specifically) discuss.
Does a magazine have an effect on pistol accuracy, and if so, how? Do you have "most accurate" magazines and "less accurate" magazines?

I can see in some cases where the top bullet could press up on the bottom of the slide creating upward pressure tightening the slide. 
Otherwise, I don't see how a magazine can affect accuracy!

I can't tell you why or how much but it does have an effect. It must be something with consistent tension but I don't know a good way to test that other than to shoot some groups.

Anyhow 100% function is the most important box to check, but after that if you tested some why would you not compete with the one or two that grouped the best?

If Jon Shue says he uses one tuned magazine, it’s worth testing them.

Based on RR testing, I've  seen some mags that just flat shoot better than the next one in a particular pistol. I've attributed this to a mag feeding differently than another probably slightly different lockup as a result. You see the same thing with the 1st round loaded verses cycled rounds.

Ive wondered about fitted 45 mags that don’t drop free but fit tightly.  My Leutenegger has two of them

In a word, yes. 
A few years back I ransomed 15 different magazines. 3 were far better in repeated blind tests. 2 were way below acceptable. All were used randomly and were all dependable otherwise. I engraved the best ones as SF mags. the rest of them were all very close in average group size. 
I used my standard long line load of 4.5 BE, Zero 185 JHP and TZZ once fired brass.
Al

Yes.  The reasons for different printing at the target are different tensions from stripping the round as it's taken into the chamber.  Everything from spring tension to round tipping, through lip dragging will affect how the slide closes.  Most shooters will never notice, but higher levels take everything into account.  State Championships are often won/lost by a point or an X.

Would it be safe to say that any semi auto (9mm, .38SPL, etc.) would have the same effect, or is the "magazine effect" only observable in .45?

I have an Accuracy-X Pro rebuilt by Jon Shue and, in addition to the normal total rebuild, he used a surface grinder to relieve the magazines where the trigger stirrup rides.

Interesting.

RoyDean wrote:I have an Accuracy-X Pro rebuilt by Jon Shue and, in addition to the normal total rebuild, he used a surface grinder to relieve the magazines where the trigger stirrup rides.

Interesting.

Keefer did that too I believe.

That’s a reason that I only load 5 in any magazine. You could not prove it by my scores .

 In my case “ There’s no reason for it, it’s just our policy”

Wes Lorenz wrote:From September 10, 2019: 
https://www.bullseyeforum.net/t13139-accuracy-testing-article-in-shooting-sports-magazine#113919

Which magazines were used in the third photo?

Wilson’s

My HS magazines were selected and adjusted for me in the 70s by coach Miller.  Coach Miller in turn had learned most of what he knew from Joe Benner.  So there's that.

Another thing I have seen was Roddy testing a 45 in the Ransom.  I was scoping each shot falling into a nice tight group.  Then one was out of group a little.  Roddy without scoping, immediately said that shot was out of group.  I asked how do you know that?  Roddy said the ejected case hit a different spot on the block wall adjacent the Ransom. 

Little things make a difference...

A friend and I were testing with a Ransom Rest years ago and out of the various magazines on hand Metalform 7 round round-follower magazines gave the best results for my bitsa* SA Range Officer. Not by much but it was noticeable, so I now have SF magazines. 

*the RO evolved over time bit by bit into a full Bullseye pistol.

Math majors use the Statistically Significant with all kinds of qualifying coefficients to determine that one result is or is not typical. I have Bench Rest Rifle friends who need 10 groups before they select a setup. God help me l don’t have that patience but their message was one point doesn’t make a line. Here, you make your best effort and run with it and see if the improvement is measurable over time.

Assuming you find a single "best" magazine, is there a preferred method for (loading in) slow fire? I'm honestly not sure, most likely doing it wrong. Is the preferred (Bruce's) method to insert a magazine with 5 rounds, rack slide, fire 5 shots, table gun, reload the magazine, and repeat?

I have 2 mags that I use. I load 5 in each. Shoot 4 from the first then reload and shoot the last 6. Slide only stays back on last.

tovaert wrote:Assuming you find a single "best" magazine, is there a preferred method for (loading in) slow fire? I'm honestly not sure, most likely doing it wrong. Is the preferred (Bruce's) method to insert a magazine with 5 rounds, rack slide, fire 5 shots, table gun, reload the magazine, and repeat?

Not that it improves my current level of shooting, but I use the same process as when I Ransom test.
Load 5 shoot 4 and then reload with the next 5.

If I'm reading this right, the last round, being the one that locks back the slide, will have a different POI then the previous 4 rounds? What could account for that? The bullet has long left the barrel before the slide even begins moving, either locking back or not.

Very different conversation from magazine accuracy, but interesting nonetheless!

Not always. For some it's just a matter of keeping the same "feel" for 9 of the shots, with the last shot being the only different one.
Further Olympians shooting rapid, it's a difference.

One explanation I read is that my Marvel without last shot hold open was designed that way to ensure consistency in feeling among all shots, including the last one.