I have a Para Ordnance high-capacity frame that I use with several slides of various calibers.
As one might expect from a multi-caliber system, slide-to-frame fit varies, depending on which slide is used.
However, there is visible slop in the slide-to-frame fit.
How loose is the slide?
Yup, its a little loose.
There are a dozen loads that will put 20 rounds in less than two inches at 25 yards.
Two-inch groups wont win any bullseye matches, but its more than sufficient for most shooting tasks.
Several examples of 20-shot groups powered by Vihtavuori N350 are shown in Figure 1.
All groups are less than two inches.
The gun was fired while mounted in a Ransom Rest at 25 yards.
ARansom Restholds the gun by the frame (Figure 2).
When this gun is placed in the Ransom Rest, I can wiggle the slide a little from side-to-side.
It has little, if any, vertical play.
I wondered how much the loose slide-to-frame fit affected my groups.
Naturally, I would need ammunition that would normally produce a tight group so that have non-overlapping groups.
I had plenty of loads that fit that description.
So I tried it.
1 is a 20-shot group.
The maximum spread is 1.37 inches, which results from the vertical distribution of hits.
The maximum horizontal spread is 1.02 inches.
2 shows two groups of 10 shots each on one piece of paper.
For the group on the left, I pushed the front of the slide to the left and down.
For the group on the right, I pushed the front of the slide right and up.
Some methodological details are necessary: I gently pushed the slide in the direction as noted.
I didnt hold the slide there when the gun was fired (that could get painful).
Once the slide was moved to the side, it stayed there.
This is where it starts to get interesting.
Note that this is wider than the horizontal spread of the 20-shot Target No.
In fact, that 20-shot group would easily fit in-between the left group and right group.
I fired 170 rounds during that test session by pushing the front of the slide to the side.
But this was rare.
At least, that is possible with the fliers is see with accurate ammunition.
Its not unusual to see several fliers with inaccurate ammunition.
2 falls into the not readily explained category of fliers.
Ive replicated the two-group effect with different bullets.
Another example is shown in Figure 5 with Hornady 125 grain HAP bullets powered by Alliant Power Pistol.
The horizontal spread of the 20-shot group is 2.00 inches (Target #3).
What does the two-group phenomenon mean?
Does it mean that slide-to-frame fit is not important?
Barrel fit is the most important.
This small experiment demonstrates that a little slop in the slide-to-frame fit might not necessarily result in poor accuracy.
At least for this pistol, the slide tends to return to about the same position when fired.
If your slide has a little slop in its fit with the frame, take heart.
It might shoot fine in spite of it.
Accuracy performance can be improved when the slide-to-frame fit is tightened by preventing the slide position to wander.
A more precisely fit slide will shrink group size and prevent fliers that result from errant slide position.
