Archive | February 2017

Rifle Stocks In Broad Strokes

Rifle stocks are seemingly simple things. They are the thing you bolt all the actual gun parts to and which keep you from holding all the actual rifle parts themselves. Why should they be so complicated then? Simple, they’re the interface between the oodles of different body shapes and the oodles of different gun shapes and even more oodles of use cases.

Trying to pair a stock with a rifle can’t be done without some vision of what the use case will be or you have a good chance of ending up with a rifle that doesn’t work well for its intended purpose. You can sort the things that matter into some very simple categories: Style/Form Factor, Materials, Bedding, Weight, Cost.

Figure 1 Conventional hunting rifle stock with short comb. Good for low mounted scopes with backup iron sights used from field positions. Short curved pistol grip works for everything from offhand to prone but can put a thumb in your nose on hard kicking rifles. Trigger actuation has a small amount of up in the angle that is not ideal for precision shooting. The definition of a general purpose stock.

Figure 1 Conventional hunting rifle stock with short comb. Good for low mounted scopes with backup iron sights used from field positions. Short curved pistol grip works for everything from offhand to prone but can put a thumb in your nose on hard kicking rifles. Trigger actuation has a small amount of up in the angle that is not ideal for precision shooting. The definition of a general purpose stock.

There are also some terms of stock construction that you should familiarize yourself with such as: comb, heel, toe, butt, grip, fore end, cast-off/on, length of pull, and pitch. We’ll ignore some of the fine detail here and cover the broad strokes. If you want to know more see some of the links, pictures and examples at the end of this article.

Styles are many and sometimes it’s less than obvious how to categorize what might be an element of one particular style or another versus what is simply variation within a style. The basic style of the stock needs to be able to position your eye in line with the sights in whatever position the gun is meant to be used in, provide a solid base to mount the action to and allow recoil to be absorbed. A stock that’s just right for shooting offhand while standing will be very differently shaped than one that’s meant to be shot from a bench rest or one that’s optimized for prone shooting.

Figure 2 Tactical rifle stock with no drop at comb & no raised cheek-piece and no drop at heel. Optimized for shooting through low mounted scope from a rested or prone position. Recoil is straight back. Comb is too high for low profile iron sights. Nearly vertical pistol grip puts trigger motion straight back. Narrow fore end and other weight considerations like barrel fluting make this a well laid out long range hunter.

Figure 2 Tactical rifle stock with no drop at comb & no raised cheek-piece and no drop at heel. Optimized for shooting through low mounted scope from a rested or prone position. Recoil is straight back. Comb is too high for low profile iron sights. Nearly vertical pistol grip puts trigger motion straight back. Narrow fore end and other weight considerations like barrel fluting make this a well laid out long range hunter.

In broad categories you have combinations of the following: wide fore end, narrow fore end, flat fore end, curved fore end, short fore end, long fore end, flat comb, raised comb, rollover comb, straight grip, curved grip, pistol grip, thumbhole grip, flat butt, curved butt, one-piece, two-piece, fixed butt, collapsible butt, folding butt, and probably 50 other things I’m leaving out.

The fore end is the part generally forward of the grip. I’ve always thought that there is missing terminology here because the part of the stock the action is supported by in my view should not be considered part of the fore end. The fore end to my mind should be everything that is forward of the receiver. This would rationalize the nomenclature in a way that stocks for lever action rifles which with very few exceptions don’t have any wood underneath the receiver and rifles with one-piece stocks. That’s an argument for another day.

Figure 3 Rimfire Metallic Silhouette rifle thumbhole stock with radical drop at heel and very high cheek piece for standing offhand shooting. This scope appears to be mounted too low to be used. This rifle would not be very usable for anyone who still has cheek bones. Nearly vertical pistol grip for straight back trigger pull.

Figure 3 Rimfire Metallic Silhouette rifle thumbhole stock with radical drop at heel and very high cheek piece for standing offhand shooting. This scope appears to be mounted too low to be used. This rifle would not be very usable for anyone who still has cheek bones. Nearly vertical pistol grip for straight back trigger pull.

Fore ends that are slender and curved on the bottom are generally more comfortable to shoot off-hand quickly. The curved profile fits the hand nicely. A flat fore end is optimal for shooting from some sort of supporting structure or device like sand bags or a bipod. Most shooters will find any corners to be less than comfortable for offhand shooting. There are notable exceptions to this rule in sports like metallic silhouette which is shot standing off-hand unsupported. Many shooters in that sport opt for a hold on the rifle that places the fore end on the finger tips with the tip of the thumb supporting the rifle closer to the magazine or trigger guard. While the flat fore-end works there, the shooters are taking a good bit of time for each shot. Hunters taking much quicker shots on average would not generally adopt such a stance or hold. A flat fore end allows for the rifle to rest evenly and flat on bags or rollers and for easy attachment of attachment systems like Anschutz rails and Picatinny rails to which gobs of nifty gadgets can be mounted.

The grip is the part your trigger hand holds. Grips vary from proceeding nearly straight back from the trigger guard to the comb (where your cheek goes) all the way to completely vertical and may or may not be part of the actual butt stock. Modern Sporting Rifles like AR/AK/FAL pattern rifles and their various kin tend toward a separate pistol grip. Most conventional bolt action hunting rifles have a pistol grip that’s part of the main stock and which curves gently downward and rearward blending into the butt section. Lever guns like the Winchester 1894 and some versions of the Marlin 336 tend toward straight non-curved grip sections that transition abruptly into the butt section. Generally target rifles with grips very near to vertical have some benefits in ergonomics as it allows the pull on the trigger to be more purely straight back. What is a benefit on the target range isn’t likely to be the case in the wild lands on a hunt where you need more flexibility and a more general purpose pistol grip profile like the common curved or straight forms are appropriate.

Figure 4 Hunting rifle with Mannlicher style stock and no drop at comb. For use iron sights. Could work with a scope but a proper cheek weld would be difficult or impossible. Long curved pistol grip has more upward pressure exerted on the trigger than is ideal for precision shooting.

Figure 4 Hunting rifle with Mannlicher style stock and no drop at comb. For use iron sights. Could work with a scope but a proper cheek weld would be difficult or impossible. Long curved pistol grip has more upward pressure exerted on the trigger than is ideal for precision shooting.

Now comes the butt section. There are a lot of parts here as most of the way a stock lays out is defined by various parts of the geometry of the butt section. The butt itself as a bit of nomenclature is both the very rear section that contact your shoulder and the stuff behind the grip. This is another area where I think we’re missing useful additional terminology but I’ll continue to avoid that discussion for now.

In the butt section will be the comb. As mentioned before that’s the bit that your cheek rests on. Its height is critical to aligning your eye with the sights in the vertical plane. If you’re not able to rest your cheek on the comb and see your sights then you need to raise or lower either the sights or the comb until you can for both your comfort and for the best results in your shooting. A very low comb like on a Winchester 1894 is great for use with iron sights but horrible for use with a scope unless you add a cheek piece that raises your head up high enough to see through the scope. A very high cheek piece that gets your head up high enough for a scope with a large objective bell will likely prevent the use of low mounted iron sights.

Figure 5 XLR Industries aluminum chassis stock. Recoil is straight back and stock is fully adjustable to get your eye where it needs to be. Pistol grip helps trigger pull go straight back while pistol grip angle is very comfortable.

Figure 5 XLR Industries aluminum chassis stock. Recoil is straight back and stock is fully adjustable to get your eye where it needs to be. Pistol grip helps trigger pull go straight back while pistol grip angle is very comfortable.

At the very back of the butt there are 2 positions that determine a lot of the overall geometry of the rifle. That is the heel and toe. The heel is the point at the uppermost, rearmost part of the butt. The toe is the bottom most, rear most point. The angle of those two points relative to an imaginary line drawn from the heel to the tip of the fore end determines the pitch, or up/down angle of the stock. The distance vertically from the heel to the top of the comb is the drop at comb.

Figure 6 Injection molded polymer Choate Varmint stock w/ internal aluminum bedding block. Low-ish mounted scopes work best due to low comb height. Pistol grip brings trigger pull straight back but is very nearly truly vertical which can be uncomfortable. Drop at heel of around an inch brings some muzzle rise when shooting on the bench.

Figure 6 Injection molded polymer Choate Varmint stock w/ internal aluminum bedding block. Low-ish mounted scopes work best due to low comb height. Pistol grip brings trigger pull straight back but is very nearly truly vertical which can be uncomfortable. Drop at heel of around an inch brings some muzzle rise when shooting on the bench.

A large drop at comb helps raise the action of the rifle relative to the butt. This is handy for shooting from the standing position as it helps keep your head and neck straight up and down which helps with your inner ear working with your brain to sense what level is so as to not cant the rifle. Any drop at comb will increase the uncomfortable perceived effects of recoil along with making it harder to recover from recoil. The M16 stock and most lever gun stocks come straight back from the axis of the bore to the shoulder providing a very straight path for recoil forces to travel down. That’s fine for a light recoiling gun but might not be so great for a hard kicking rifle. Just like with a pistol, raising the bore line above the comb line will cause more muzzle rise to be experienced. Just like with a single action revolver, muzzle rise takes energy to happen and allowing it to happen can lessen perceived recoil on the shoulder.

The drop at heel versus drop at comb determines the actual distance covered by the butt plate/recoil pad/butt. Too small a difference between the drop and heel and drop at comb will make for a sharp feel to the butt under recoil.

Figure 7 Winchester 1886 with radical cast-on (pushes action toward the chest) for a shooter with cross dominant vision. Also called a “cripple stock”. Very rare in modern times.

Figure 7 Winchester 1886 with radical cast-on (pushes action toward the chest) for a shooter with cross dominant vision. Also called a “cripple stock”. Very rare in modern times.

The cheek piece may or may not be of the Monte Carlo rollover style. A Monte Carlo cheek piece can add cast off by pushing the butt of the rifle a bit to the right without having to cut the whole stock with the cast off built in. The stock can also be cut with that cast off/on built in to the whole butt and pistol grip sections. Cast off moves the receiver toward the shoulder. Cast on moves it towards the chest. High end adjustable stocks sometimes have adjustments for cast but it’s not super common nowadays.

Finally in the geometry area we have length of pull which is the distance from the middle rear of the butt plate to the trigger. The length of pull is not determined by any single rule of thumb but has a lot to do with shooting style. If you use the old stand-by rule of the distance of your forearm from bicep to bent trigger finger you may find that on heavy recoiling rifles that your thumb and nose get brought together without it having been planned beforehand. Also if a shooter tends to crawl their head forward on the stock they may have an unplanned meeting between their head and the ocular bell of their scope.

Figure 8 David Tubb's competition rifle with radically positioned scope for chin-over-comb hold.

Figure 8 David Tubb’s competition rifle with radically positioned scope for chin-over-comb hold.

In an ideal world, where recoil management is concerned, your rifle bore axis will be in a straight line to just below the heel of the stock. Having the bore and the heel aligned in a straight line helps to bring recoil energy straight back so the rifle returns straight forward. This allows hugely faster follow-up shots and; more usefully, allows the shooter to much more easily spot their own impact. This is because muzzle rise is mitigated thanks to a bit of physics. Since physics is both boring and heavy on math I’ll skip the gory details.

Some stocks are designed with recoil mitigation in mind. Others like those popular in metallic silhouette actually substantially accentuate muzzle rise as a sacrifice to other matters, in this case avoiding canting the rifle. Standing straight up without craning your neck is better for balance thanks to the way the inner ear works. The accentuation of muzzle rise is not a problem in metallic silhouette for various reasons but it is for shooting from a supported position such as is common in long range hunting or banging at steel.

Figure 9 Butt stock geometry elements.

Figure 9 Butt stock geometry elements.

When shooting prone from a bipod, or off a backpack, or with the rifle laid across a log, or rock or mound of dirt you’re going to want to be trying to get as directly and straight behind the rifle as possible, as low as possible and to achieve a natural point of aim. So done, upon firing the straight back recoil path of a rifle in a stock with little or no drop at the heel lets the energy travel right into the shoulder pocket and for the shoulder to return to its former position in a straight line.

With the bore slightly below the level of the heel of the stock such as we see in the AR-10 and AR-15 platforms (and let’s not forget about the Nemo Arms Omen line of magnum AR platform rifles) recoil energy is just about as straight back as it could be and spotting your own shot and delivering fast follow-up shots gets surprisingly easy.

Figure 10 Anschutz Olympic rifle with fully adjustable stock. Recoil control isn’t given much thought on this .22lr. This stock is optimized for offhand unsupported accuracy.

Figure 10 Anschutz Olympic rifle with fully adjustable stock. Recoil control isn’t given much thought on this .22lr. This stock is optimized for offhand unsupported accuracy.

Suffice it to say, if you can see that the elk you just drilled was hit a bit high in the chest because you see the bullet hit you’re more prepared and able to decide to deliver the second shot quickly and minimize suffering on the part of the animal. Conversely, if you hit it square in the pump and it takes to running off you’ll be much less likely to unnecessarily destroy any more meat if you know it’s going to be quickly lethal and you know you shattered the shoulder. Everyone loves as few shots being loosed as possible in the wild lands during hunting season. It’s better for everyone’s hunt to keep the noise down.

For steel shooters being able to spot exactly where your shot landed and even watch it fly through the air is always helpful and entertaining. Adjusting your hold becomes easy when you know for sure how far off the last shot was. In games like PRS winning matches versus coming in second is frequently a matter of a single point. You often have more than 1 shot at a target but you don’t likely get to have a spotter working for you (any spotter will be scoring, not so much helping). Being able to see your impacts whether on steel or off steel means faster follow-ups and higher 2nd round hit probabilities.

Figure 11 Traditional single shot Swiss Shuetzen rifle for standing position shooting. An example of extremes in buttstock design. Lots of muzzle rise comes from this layout.

Figure 11 Traditional single shot Swiss Shuetzen rifle for standing position shooting. An example of extremes in buttstock design. Lots of muzzle rise comes from this layout.

Materials selection is another big area full of complexities. The bulk of materials used in factory rifle stocks are good and strong and stable though some have seriously sub-par options available. A good stock shouldn’t have any flex in it. Flex is the enemy of consistency. High end stocks are very rigid and often, though not always, very light. They get there with exotic materials and rather expensive manufacturing processes. There’s a reason they cost that much after all.

The lower end of package rifles and bargain line rifles will commonly come with an injection molded plastic stock that’s got a lot of flex in it. If you can avoid or replace those. The fore end on these will often flex enough to contact the barrel which is not normally good for accuracy or consistency. On the upside such stocks usually have some sort of metal pillars serving as bedding. On the downside, they’re intended more as ferules than as bedding blocks and serve as such. Wood stocks of the traditional regular wood variety can subtly change dimension due to changes in environmental conditions. There are good solutions for bedding and finishing that trim that problem to a manageable level. Aluminum stocks are generally impervious to flex. As well, every fiberglass or kevlar stock I’ve ever seen has been similarly rigid to aluminum. In the recent decades laminated wood stocks have become common and popular. They offer the visual appeal of wood with a lot more resistance to swelling or contracting due to moisture and great rigidity. Bedding of a laminated stock should be given the same attention you’d give any traditional wood stock, or any other stock for that matter.

 Figure 12 Big Bore Double Rifle. The recoil tolerability limits of the human body made manifest in wood and steel.


Figure 12 Big Bore Double Rifle. The recoil tolerability limits of the human body made manifest in wood and steel.

Bedding is a long and fraught subject and many times methods are combined. You can pillar bed, which uses pegs of metal usually which the receiver rests on and which the bolts that hold it down go through and press against. These are fixed into the stock in a variety of methods, most usually a snug hole and some adhesive/epoxy. You can epoxy bed which is to use a great gooey gob of epoxy to form the spot the action will rest in. This nets a perfect fit between the action and the bedding surface. You can also so a skim bed which is to use a much thinner layer of epoxy to do the same thing. Depends on the inlet done to your stock as to which is appropriate for you. I do an epoxy skim bed on my aluminum chassis stocks which have an aluminum bedding block machined into them and on my fiberglass stocks and on my wood stocks. Some aftermarket fiberglass stocks and even some wood stocks come with an aluminum bedding block actually fitted into them. These are great for maintaining a more conventional look but having all the greatness that can come from an aluminum bedding block. Whatever bedding system you go with, take the time and effort and cost to do it or have it done properly.

Weight is a function of material and mass. You want to have your rifle balanced correctly which means that the lightest stock material may not actually suit your combo or needs. Where weight limits aren’t a factor things like heavy metal (mercury/tungsten/lead) stock inserts can help to fix the balance. Composite stocks like carbon fibre/kevlar/fibreglass often need some weight added to the back to bring the rifle into balance. Wood and laminate stocks tend to balance pretty well without special measures. Aluminum stocks tend to shift the weight rearward. The chronicler is of the opinion that the best balance is to have the balance point directly under the closed bolt head.

Figure 13 Steyr HS-50 Anti-Materiel Sniper Rifle. Straight back recoil path for the hard kicking .50BMG. Even with a big brake it’s a big kick.

Figure 13 Steyr HS-50 Anti-Materiel Sniper Rifle. Straight back recoil path for the hard kicking .50BMG. Even with a big brake it’s a big kick.

Cost. Ahh yes, the thing that causes otherwise rational people to buy garbage. If you want a simply functional stock you can get one cheap but, don’t expect it to do much but hold the rifle away from your skin. If you want a really good stock it’s going to cost you. You can go anywhere from buying a replacement “tupperware” injection molded stock used on E-Bay for nearly free to spending many thousands for some of the fancier and bespoke stocks. As you put cool features like aluminum bedding blocks or glass and pillar bedding the price can soar. Super awesome finishes of hand rubbed boiled linseed oil are going to have heart stopping prices tied to them.

When you go to put a rifle together or just to buy one off the rack, be sure that you’re thinking about what you’ll do with the rifle and pick the stock that best suits that use case. You’ll be glad you did and you’ll have more fun in the field.

Links:
https://en.wikipedia.org/wiki/Stock_(firearms)
http://www.chuckhawks.com/rifle_stock.htm
http://home.insightbb.com/~bspen/fit.html
https://www.icslearn.ca/~/media/files/pdf/samplelessons/025-gunsmith-career-diploma.pdf?la=en

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