Accuracy Tests: Preliminary Results

Ignoring the “first round flyers” (described in previous blog) which I think are an artifact of our test procedure, the group sizes and shapes I fired on the Ransom Rest this past Saturday in my factory-new (December 2004) Smith and Wesson Model 41 were:

My “read” of the above shapes is that we had varying degrees of vertical stringing in more than half our test groups.

But Ed Masaki commented elsewhere that at least some of this may be due to variations in muzzle velocity and the consequent longer flight time and greater bullet drop. My rough calculation shows that a 1% change in muzzle velocity translates to a rise/drop of about 0.1" at 50 yards (using 850 ft/sec as the nominal velocity).

For inexpensive ammunition, I’m expecting poorer quality control by the manufacturer might show up as variations in muzzle velocity (as well as in other attributes). Realistically then, a velocity change of 5% (which seems credible) would account for a vertical spread of 0.5" all by itself. If I then factor out that 0.5" vertical distance from the “vertical oval” shapes, most of the above groups would be almost round.

That believable variation in muzzle velocity would, as Ed Masaki has suggested, explain the vertical elongation in many of the groups we recorded.

But how then do we explain the nicely rounded groups from the cheapest (Remington Target 22) to the most expensive (Federal Gold Match)?

Good question, and I don’t have an answer.

My real “bottom line” is that I’m beginning to think I’m expecting too much from my Ransom Rest tests. Although my pursuit of “the whole answer” is interesting and fun to a degree, I’m also in danger of losing sight of my original purpose which was to see 1) if there’s any significant difference in new S&W 41s, old ones, and one that has been hand-tuned (Clark barrel and other work), and 2) and most importantly to my shooting, which ammo shoots best in my (factory new) 41.

All of the above results are from my 41. (I don’t have Joe’s data yet from his Clark’d 41.) From the above data, I have to say that Federal Gold Match and PMC Pistol Match look better than what I’ve been using (CCI Standard Velocity), but not by a whole lot (20-30% maybe). Since the X-ring at 50 yards is about 1.7" in diameter, the above results suggest my scores might be more indicative of my abilities by using the Federal Gold Match or the PMC Pistol Match in competitions.

But I worded that last sentence very carefully since an errant round has almost equal probability of improving, or worsening, my score. An “accurate round” does not mean a better score. It only means it will more accurately record how I released it. Better ammo might well show me to be a poorer shooter.

As of this moment, I haven’t seen Joe’s data (he was running the other Ransom Rest in our tests). He was shooting CCI Standard Velocity only, and a whole bunch of 10 round groups in his Clark’d S&W 41. Our goal was to see how much variation we might expect from group to group. (Joe observed the first round flyers I was also seeing.) (And Joe did some other tests as well.)

If he sees groups ranging up to 2.5" and down to 1.5" (or less) with a single brand of ammo in a single gun, then it would seem we need to shoot a whole lot more rounds in each brand to ensure statistical significance.

As somewhat of a footnote to the day’s testing, I put my low-end Springfield Armory Mil-Spec 45 that has received a nice trigger job and some other reliability tweaks (thank you Mike Kelly in Phoenix) but nothing else. The barrel, bushing and slide are all unmodified. I fired only two 10 round groups of some wad ammunition reloads (from Neil at NSK Sales) but please note that the gun did poorly (not the ammo) because, in earlier tests with Winchester white box from Walmart, the results were even worse.

Using the wad loads and shooting at 50 yards, I observed the “first round from the magazine” flyer (consistently high and slightly right across four magazines) as we were seeing from the 41s, one WTF flyer almost 12" (!) left and low of group center, and group sizes of the remaining rounds of 4" to 6" in diameter. That one “WTF” shot was shot #3 of 5 in the second magazine and have no explanation for it other than suspecting that the Mil-Spec burped rather badly on the lockup for that one shot. (Gee, does that mean those wild 5-ring shots are not my fault? I wish that were so but, no, I can see the jerk pulling the trigger just by watching the front sight. Those are my 5-ring shots, not the guns.)

Note that a 6" group with a perfect hold would place all the shots in the 8-ring or better. But with an 8-ring wobble added to a 6" group, we’re looking at not much better than 6-ring shooting. (As before, it’s important to remember that a “flyer” has almost equal probability of increasing or decreasing the score. Accuracy doesn’t mean better scores: it means scores that accurately represent the shooter’s ability.)

But the Ransom Rest testing of a 1911 is inherently less meaningful that what we were doing with the S&W 41s – and it has everything to do with how the guns are constructed and how the Ransom Rest holds on.

In the 41s, the barrel is locked to frame and the frame is what the Ransom Rest holds on to. The sight you use when aiming is bolted to the barrel and so the whole assembly, from barrel to frame to Ransom Rest, in a single mechanical unit.

Not so with the 1911. With that gun, the Ransom Rest is not connected to the barrel. Instead, the Ransom Rest is clamped to hand grip which is connected to the slide (via the slots in the slide and frame) and, thence, to the barrel which is “locked in” to the slide when in firing position.

The Ransom Rest will, if used correctly, return the 1911’s grip to the exact same position for shot after shot, but that doesn’t guarantee where the barrel is aimed for each shot. Where the barrel is aimed depends on 1) the barrel to slide lockup, and then 2) the slide to frame fit. The repeatability of where your eyeball will send the shot, on the other hand, relies solely on #1, the barrel to slide lockup.

Bottom line: Some shooters can produce better results with hand-held (and most significantly “eye-aimed”) shots than the Ransom Rest with the 1911 pistol. Ransom Rest testing of a poor 1911 may suggest it to be more inaccurate than it actually is or, in other words, it’ll make a bad 1911 look worse.

On the other hand, a “good 1911” (which I will define as one in which the barrel to slide lockup is 100% perfect and 100% the same for every shot) will still look worse in the Ransom Rest than it actually is. Slide-to-frame fit is important, but far more so to the Ransom Rest than to the shooter who relies on his eyes to aim the gun, not just his arm as does the Ransom Rest.

Fun, fun, fun…