Franchi Affinity Stock Adjustment
Overview
My kids bought me a Franchi Affinity in 20 gauge. I'm big time happy as the Affinity is, (as of this writing), the latest in Franchi's redesigned inertia operated semi-auto's. Lightweight, slim, and fast cycling. I'll admit I dropped a lot of hints for this exact gun as I had spent considerable time researching lightweight semi-autos. The Affinity design is better than the Benelli M2 IMO, because the recoil spring is in the forearm, thus all important parts are accessible without tools.
Anyways, as is true with most shotguns nowadays, the Affinity comes with a shim kit that allows adjustment of drop (comb/heel) and cast. And as is all too often, the Affinity has wonderfully weather & scratch resistant stock that has a comb height low enough for a midget.
Being a noob to all things stock-fitting related, I bought a copy of "Stock Fitter's Bible" by Rollin Oswald so that I would at least have a rudimentary grasp of the fundamentals before I started "adjusting" things.
I joined a Trap & Skeet club, and I bought two cases of target shot shells. The club is close to my house and I don't have to throw my own clays. I figure that learning to shoot a shotgun is like any other shooting discipline I've mastered - you gotta get the rounds in. I'd love to try Sporting clays, but for now Trap is hard enough. Once I get the gun and I working together I'll try my hand at Skeet.
The following is the process I went through to get this sweet little pop gun to shoot nicely for me.
Experts, Pointers, Opinions and Advice
Most folks want to be helpful. Some actually are. Some have "unexamined notions". And unfortunately, some like to "help" you whether you want it or not. Now I'm not the most gentle when it comes to telling somebody they are wrong, but I'm not above taking advice. So I've had to learn to take time out to listen to "experts", politely entertain "opinions", and be open-minded about "pointers". But there are some things that just grate on me:
20 gauge is worthless - Now I bite my tongue and keep silent. I suspect it is some sort of macho thing nowadays. 50 years ago people recognized the purpose behind 28, 20, 16 and 12 gauges, but now folks only seem to see the 12 gauge - and I think it is a general education failure. A correctly made 20 gauge frame is smaller in height and width which makes it lighter and easier to maneuver.
A 12 gauge is more "powerful" - I don't know why people think an ounce of 7 1/2 shot @1200fps from a 12 gauge is meaningfully different from an ounce of 7 1/2 shot @1200fps from a 20 gauge.
A shotgun without a mid-bead should be thrown in the dumpster - evidently a mid-bead is the end-all of shotgun aiming devices. Never mind that for the first 300 years of shotguns there was no "mid-bead".
Stand with your (heel to toe, heel to instep, oblique with feet parallel to the trap house, etc.) - some positions are certainly better, but there is some self-discovery required to find a position for you that allows you to swing and keep your face planted on the stock.
A 20 gauge is a short-range gun - now there is a little bit of truth to this if we use unequal payloads. A typical store bought 20 gauge target load is 7/8 - 1 oz whereas a typical 12 gauge target load is 1 - 1 1/8 oz. Both run about the same velocity. More pellets equals more usable pattern at a greater distance. So the advantage does go to the greater payload when standing at the 27yd line.
And there are some good pointers too:
Don't chase the bird so much - start with the muzzle pointed about 2 feet over the trap house corners from stations 1 & 5, or over the middle from stations 2,3,4. Good advice as I'm slow and tend to lift my head when chasing the birds.
If your head moves you miss - Yep, definitely have to keep my head in the same position every time. For now that means my cheek has to be welded to the comb.
Shoot at the apex in trap - it is easier to shoot clays when they've just stopped rising.
Gamers versus Hunters
Kind of funny to watch the expert trap shooters who can't mount their gun and break a surprise clay. Why can't they? Because in their game, they are allowed to pre-mount the gun and then call for the bird when ready. I don't know about you, but I've never walked around in the field with the gun mounted calling "pull" when I wanted the quail to flush.
Trap is a regulated sport and the rules state a maximum payload, shot size and velocity (1 1/8 oz, 7 1/2, and 1290fps I think). So there's no place for my 1500fps hand loads .
So as far as the basics of shooting form, etc. - trap is an excellent starting point. There are other sports better suited for the hunter, but a guy has to start somewhere.
Terminology
They say a picture is worth a thousand words
Initial POI
A couple of things to remember here: First, a shotgun puts out a cone of shot, not a single bullet, so there's no need to get bent out of shape pursuing MOA accuracy. Second, none of this POI exercise matters if you don't get a good repeatable gun mount. I'm not trying to sell Rollin's book, but it really is a good idea to get a handle on the gun mount basics before putting lots of little holes in 48" paper or marks on a pattern board. Third - this field stock lacks fine adjustment and I'm squishy - i.e. my cheek has way more variability to it than the adjustments of my stock, so there is a basic accuracy tolerance here that I need to accept.
There are a couple schools of thought on measuring Point Of Impact:
The "swing up" method - target paper at eye-level or higher when standing with the gun mounted. Stand at 20 yds from target, mount the gun, point the barrel down at an object below the "bullseye" on the target paper. Shift your focus from the object below to the "bullseye" and bring the muzzle up and fire when alignment seems correct. Use a full-choke and repeat this 3 or 4 times using target loads.
The "rifle" method - basically mount the gun and aim it rifle-style at the bullseye. You can do this offhand but make sure you squeeze rather than jerk the trigger. Full-choke, 3 or 4 shots of target load fodder. Otherwise use a shooting bench where you can mount the gun with proper check on comb placement without being scrunched over the shotgun. The idea is to be as precise as possible. Some say 13yds, some 16yds, etc. The closer, the more likely the wad is going to cut holes in your target paper.
Regardless of the distance, the relationship between the center of your pellet pattern, versus the "bullseye" and stock fit adjustment is easily calculated. What can be difficult is visualizing where the true center of your POI is, which is why I think a Full-choke and 7.5 - 9 shot is best.
Swing up (I put a highlight circle over the pattern)
Rifle style (I think the center is plenty visible)
So the key from these pictures is that the pattern is high and slightly to the left (I'm right-handed). The 16 yd pattern needs to come down about 1.5 inches and move to the right about 1 inch. The 20 yd "swing up" pattern needs to come down about 5" and to the right about 1.5 inches (30" dia outter circle). The two different approaches yield similar, (but not exactly the same), results. One mistake I made here was not marking 1" reference marks to make movement estimation a bit easier.
Stock, Shims, Barrel Rib and Confusion
The Affinity comes with a 5 piece shim kit which is darned hard to understand. The Affinity stock uses a fixed recoil pad which precludes the use of standard spacers. The Barrel Rib is tapered starting taller at the receiver and shorter at the bead (which contributes to shooting high).
Shims (L -> R - RB (original), RD, RA, RZ, RB, RC )
I have an extra RB shim because I bought the shim kit separately.
The shims are keyed and reversible. (R) is for right-handed cast changes. Flip them over and they're marked (L) which is for left-handed cast. The letter after the "R" must be some secret Italian code because none of the manuals explain the shim system. There are 3 shims that increase drop and 2 that decrease it.
Dimensions
The shims increase drop and cast progressively (cast-off is how us right-handers move the POI to the right - pattern follows the butt of the stock), RB the least and RD the most. Relative to the original (RB), RC increases cast-off by 0.005" and drop by 0.020". RD increases cast-off by 0.006" and drop by 0.035".
So I took my calipers and measured shim thickness in the same 4 corners of each of the 4 shims that would work for increasing drop. My POI work was done with the shim marked "original". Since I wanted to lower the POI, I needed to increase the drop. To give and idea of what I was doing, the second set of dimensions shows a delta of .020" from the original. .020" x 13" (length of stock from shim to butt pad) is amount of downward stock movement (.26"). (.26" x 1440(40 yds in inches))/34" = 11". This means my POI should move down 11" at 40 yards, 5.5" at 20 yards, etc. The delta for the cast is .005", so .005 x 13" = .065". (.065" x 1440")/34" = 2.75" at 40 yards, 1.37" at 20 yds, etc.
Despite all that measuring and arithmetic, it is near impossible to tell what the effect will be because the fit to individual's body muddies the results. Probably the best way would be a bore mounted laser which you could shine on a grid board from some useful distance away (I suppose the grid could be scaled for distance so that one could see the error relative to 20, or 40 yards. Sounds like a product idea). Another way is to have a helper stare down the barrel and see if your eye, rib, & bead line up - while you are aiming at their eye. But since I don't have such a device, or a helper, it is off to the patterning board. The patterning board is hard to fool.
Stock
The Affinity has the recoil spring in the forearm, so the stock is just a simple bolt with a 15mm nut (use a short socket and a long extension to address it). The recoil pad has a dogleg in it but is otherwise normal, held on with 2 long wood screws. Franchi doesn't sell spacers, but instead sells complete recoil pads for adjusting LOP. However, a little creativity and a flexible material would allow a fellow to save a little money. Just remember that the effect on LOP is roughly 3 - 4 to 1 meaning that the movement of your face is 3 - 4X greater than change in LOP.
My First Adjustment
To cut to the chase, I changed to the second stock shim, (marked RC), which moved my stock down (increased drop) and to the right (cast off).
Stock Pitch Before and After
I still don't really understand the role of pitch - I guess I need to reread Rollin's book.
This is the starting pitch - up against a wall with butt pad flat on the floor, RB shim.
A closer look at the before pitch
This the "after" pitch - after I changed to the RC shim
When you just view the pitch change by itself it seems huge. After all, the muzzle moved down 3/4". But Pitch is just the start of adjustments with the goal of being able to mount this shotgun without hunching way over the stock.
Now the correlation to my fiddling is check POI again. And I'll update this after I go to the range tomorrow.
New POI
16 yard POI with the new RC shim (ignore the RD on the photo - I goofed)
20 yard POI with the new RC shim (ignore the RD on the photo - I goofed)
So this pattern is still a little high, but not bad at all. I shot a couple rounds of trap afterwards and I'm busting them consistently. BUT, I'm not "smoking" them yet, so I know that there's plenty of room for improvement.
Shooting Form
I suppose I should have put this section first, but it is the area that I'm weakest at. Fortunately I've read Rollin's book, so I kind of know what I want - even if the shotgun isn't going to give it to me easily.
When you read about these high-end guns, with their proper stocks and all, you get sick when you look at the mediocre stocks on field guns. But it's OK as I want a hunting shotgun that works for me, not some safe queen for playing games. I'm not a gamer.
What do I need?
I need to be able to see my quarry.
I need to be able to repeatably align my head & eye
I need to be able to hold my head & eye position while swinging to my target.
See my quarry
Should be pretty obvious, but after reading Rollin's book ("Stock Fitters Bible") and some practical experimentation, I can see how this can get messed up. If I have to lift my head off the comb to see - I'll shoot over my target. If I have to look through the top of my glasses when my cheek is on the comb, then I'm going to lose the target as it rises quickly, or I'm gonna lift my head (and shoot high). If the muzzle covers the target then I'm going to lose the target until I swing past. This is all stuff that Rollin covers, but it wasn't until I had a little practical experimentation that I began to understand what the issues were.
I'd really like to be more "heads up" or upright. I'd like to be looking through the center of my corrective lenses. I think part of the solution is to increase the Length Of Pull and then raise the comb.
Repeatably align my head & eye
Every time I mount the shotgun, regardless of the conditions, my eye has go into the same position relative to the rib and front bead. Now my eye can't get there by itself, so that means my head has to get to the same position every time. And my head can only go so far by itself which means at least the part of my body my head connects to has to get into position. I don't know anyway around the fact that this only comes through practice.
Hold while swinging
My targets move - I'm not hunting Turkeys. So I've got to move the shotgun so that the muzzle points to where the target will be, calculate the exact moment and break the shot. The entire time I'm swinging I need to maintain my head/eye position.
My Second Adjustment
So I bought a jar of Thermomorph Moldable Plastic Pellets as a way to get around the goofy dogleg in the Franchi recoil pad. I backed the screws out until the desired gap, blocked it up with some rubber strips, and then squished in some warm plastic to make a solid base. Worked pretty good although I should've figured out a way to roll it smooth and a way to dye the naturally white material.
Once the sun was shining on a Saturday it was off to the trap & skeet club where I can set up my patterning board without bothering anyone.
Unexpected Results of LOP and Pitch Change
I wanted to do two things:
I wanted to be a little more upright, i.e. "heads up" in my form.
I wanted a longer Length Of Pull (LOP).
I had the general idea that lengthening LOP would increase drop at heel, and thus shift my POI downwards. Why? Because the stock already angles downward, therefore increasing it's length means that my mount point is lower. Anyways, that was my thinking. Since I was lowering my POI, I figured that I would put a pad on my comb to raise my cheek up - thus countering the POI shift. Well, one of my favorite Yogi Berra misattributed quotes comes to mind right now ""In theory there is no difference between theory and practice. In practice there is. "
Here's the recoil pad spacer I created with some ThermoMold plastic (white beads you heat to 150*F so they become pliable). Note that I decreased the pitch slightly as well as increased the LOP.
And the following was a shocker - not what I had expected at all. 3 shots at 20 yards holding the bead under the bullseye.
So I thought for sure that I must've messed up. After all, I've read Rollin's book so by now I must know what I'm doing. So I put up another sheet of paper, grabbed 3 more shells and tried it again from 20 yards, this time holding dead on the bullseye.
So at this point I was expecting to hear the theme from "The Twilight Zone" and Rod Serling's narrating how I'd crossed into another dimension. So I hastily duct-taped a 1/2" thick chunk of closed cell foam onto the comb of my stock, grabbed 3 more shells and aimed at a wad-cup tear. The pattern moved up! Whew! At least something worked like I thought it should.
Theories, Conspiracies, Excuses, and Explanations
First of all, I violated the 1st rule of experimentation - change one variable at a time. I changed two - LOP and Pitch. Second, I don't really understand what Pitch does beyond keeping the heel of the recoil pad from hanging up on your clothes when mounting.
But the pattern board doesn't lie. My POI shifted way up and to the left. Not only did my understanding of drop at comb not work out, I somehow managed to change my cast as well. No wonder I couldn't hit the broad side of a barn after I made the changes!
OK, there is a rationale explanation which I stumbled across while perusing shotgunning forums looking for answers. Basically it has to do with the structure of the human face, and the cheek bone in particular.
My chubby face let me down
My cheek bone, as is normal, is not perfectly round. Nor is the thickness of flesh uniform around it. So when I was hunched forward, the comb was pressed against the flat, thick part of my cheek depression. When I rotated my head more upright due to the increase LOP, I rolled up on the point of the cheek bone and the comb pulled into the thin part of my cheek. There is a deeper depression at that point of all faces and I suppose you could remove your dentures, smile, or clench your jaw to alter it. That is why a simple LOP change had such a non-intuitive effect on POI.
Here is a good example of what I'm talking about. When I hunch forward, it is the area marked "thick" that is lying on the comb. When I move my head more upright, I roll onto the point of the curve below "thick" which raises my head and the comb slides into the area marked "thin". Raising my head raises the POI and pulling the comb into the "thin" area shifts the cast. Stare at that picture for a bit, (and don't make political assumptions as I didn't vote for him but he does have good cheek bones), rotate it forward and back in your mind and it will make sense after a while.
Next Steps
Now that I think I have a handle on what happened with the LOP change, I'm going to revisit my shims to see if I can get to where I want. And then of course, back to the patterning board.
My Third Change
Now I'm going with the RD shim. This is the maximum drop I can get with the shims. And I'm pretty sure I'm going to need some sort of cheek pad to correct the cast and lift my cheek up (raise POI). I kept my homemade LOP spacers, but I'm going to do it right this time - one variable per change. And I'll do this at the patterning board because it is the only way to tell what is happening.
Here is the pitch with the RD shim installed
The Pattern Board
All of the following were shot with the Improved Modified (IM) choke because I forgot my Full Choke.
3 shots, 20yds - first attempt, IM Choke
Same thing a second time
OK, the pattern is a little high and to the left. But I'm noticing that the pressure against my cheek matters.
Now for the LOP increase
Raised the POI as I expected and it also corrected the cast somewhat.
Seems like I've gone as far as I can with the shims as my head is up high-enough. If I'm going to lower the POI I'd have to raise the bead and/or rib.
Here's the 30 yard pattern with the El-Cheapo Federal 7/8oz, 1210fps 7 1/2 shot, IM Choke - LOP increased by 1/4"
And here is the 30 yard pattern with the other El-Cheapo fodder - Herters 1oz, #8 shot @1160fps - LOP increased by 1/4", IM choke
and lastly, here is the POI of the Herters, at 20yds, 3 shots over the previous 30yd pattern - just to see if there is a difference (and there is)
Conclusion after 3rd change
I'm past the point of changing the POI with shims. My eye placement is getting pretty consistent and my mount is repeatable.
To lower the POI, I'm going to have to raise the rib and/or raise the bead. Or I'm going to have to teach myself to bury the bead in the rib for my sight picture. I'm at the point now where I can bust 20/25 from the 16 yard line consistently and I'm not chipping as many as before. So I think I'll leave it alone for now and explore my options with the bead and rib.
The Federal cheapo fodder patterns better than the Herters, (Cabelas house brand). ATA rules allow 1 1/8 oz @1290fps, 1oz @1325fps, 7/8 oz at 1350fps - so I can see where a guy could do a lot of fiddling with handloads.
CONCLUSION in all caps
Here's what I've learned from this exercise:
Shooters can twist themselves into all sorts of positions to make a shotgun shoot where they want. Rollin mentions this in his book, and now I understand. Basically once I got the stock drop to a certain point, additional drop accomplished nothing. Why? Because I had figured out how to look flat down the rib and my mount was good enough.
The Pattern board does lie to certain extent. Mainly has to do with the confusing interactions between body and shotgun.
Shotgun makers want to force you too shoot a certain way. E.g. because I have a tapered rib, I will always shoot high.
Smoking a clay has more to do with the skill of the shooter than the fine adjustment of the shotgun.
I like shooting stuff!