Accuracy International Chassis System Upgrade

25 October 2000
By Kevin Boland
Rifle in LBT drag bag, with both Maj. Econ's SOTIC 
Rifle data book and the NSW
Rifle in LBT drag bag, with both Maj. Econ's SOTIC Rifle data book and the NSW

The AICS 'upgrade' claims to increase stability zero retention etc., and for around 700-1400 US$ depending upon options, one would hope it had better. My own experience with the AI system had come from four rifles, one of mine and three of friends. Mine, as some will know, is on a Jerry Rice Nighthawk 700 action in .308. Two other are on custom .308's, HS Precision, and an Armament Technologies, 5R barreled one. The other is another's full AI .338LM AWM rifle. Does the stock justify its price tag - I honestly do not know, but then I will not go back either, and neither will they so I guess, yes it does.

A brief explanation:

A brief explanation of the AI chassis system is helpful for it is unlike most conventional rifle stocks. It consists of three major parts; the Frame and the left and right side panels. The Stock side panels, which can be had in differing colors, bolt on to the aluminum chassis.

Firstly, the good points:

It has a great ergonomic feel and balance, which must be experienced to describe. I was never a fan of thumbhole stocks but I have since had to change my mind. The weight of the stock is more than the H-S Precision supplied on the Remington PSS (from 1 lb. to 1.75 depending upon model) and more than the McMillan from the M24 did, but not by much. It is a GREAT deal lighter and handier than the "Ultimate Sniper" stock by Choate. My rifle weighs around 17.5 lbs. inc. Jerry's brake, my B&L Tactical, Badger Rings, Near Base, and Parker Hale steel bipod.

It is adjustable for length of pull (stock spacers) with all four spacer in the stock having the same (identical to the mm) length of pull as the HS Precision.

With an adjustable cheekpiece that is optional (I chose it) it allows for different cheekweld positions (from 0" to greater than 2" off the bore center line). At zero I find perfect cheekweld using a B&L Tactical and the Badger rings (standard height).

One difference HS or McMillan stock users will note is the thinner pistol grip, which I find a plus.

A folding stock option is also available - but I have not examined nor shot one so I will just mention it for completeness.

The thumbhole stock places the hand in a comfortable position for firing, and the trigger guard is rather large to protect against any unforeseen obstacle while being dragged, and the opening large enough for light-medium gloved hands.

For those too cheap (like me, until the failure of the Versapod) to buy an AI Parker Hale bipod relax. Either you can manufacture a pin, to convert it to a Versapod mount (my previous solution), buy a Parker Hale Adapter pin from Brownell's, or it comes with a flimsy Harris bipod adapter - which I discarded (and this Harris hole won't fit a Versapod or Parker Hale Handstop mount). The further advantage to the Parker Hale type pin is that it reduces the weapon's height, while still allowing a full sized bipod. The issue AI bipod is ideal for the gun however as the pin is integral with the bipod - but the feet are spring loaded. So I leave the bipod in my G-suit and have made a special pocket for it so I can attach it to the rifle after I am in position, (if I have to use the bipod).

The flat forestock allows for easy balance on a rucksack or other support. In positions other than the prone, the stock is also very manageable. From the standing, using Mike Miller's Quik-Cuff™ sling (given the modifications described below), the stock balances well and allows a relatively solid shooting position to be adopted. A small finger groove allows for comfortable purchase on the forestock. Comfortable and solid positions are also available from the sitting, and (for me, the dreaded) kneeling - again using Mike's sling.

The stock channel is very generous - lots of room for a straight tube and no worries about dirt getting in and causing contact, to give zero shifts.


On accuracy, using the Jerry Rice NightHawk it is very hard to judge, for I can shoot sub .25MOA groups with it, and I had not had it in another stock since Jerry's work was done. As well, the other rifles I have had experience in the AICS are also custom rifles. The decision was made to take the three rifles out with one stock PSS and an extra HS stock, and swap them around in the stocks. This method was reasoned at to give an AICS group and a non-AICS group. This proved to be more difficult than initially intended as the owner of the extra gun and stocks had bedded them with Marine Tex and was adverse to letting me touch them - as he has seen the abuse I subject my rifle to. Another 700 Police was located - unbedded - and the owner not quite so in touch with my haphazard ways allowed us to use his rifle. (Tee Hee)


RIFLE #1 NightHawk with Jewel trigger, Near 45 MOA base, Badger rings and B&L 10x Tactical
RIFLE #2 700 PSS non bedded, Badger Base and Rings, B&L 10x Tactical

Rifle 100m 400m 800m
R #1 AICS .23" 2.3" 5.1"
R #1 HS .56" 4.1" 7.8"
R #2 AICS .95" 5.2" 10.4"
R #2 HS 1.03" 6.4" 13.5"

As observed by the shooters, the AICS reduced felt recoil, making the rifle more pleasant to shoot. Although some criticism of being beside Jerry's NightHawk brake were made. I was wondering if the stock actually made that great deal of difference or if I have just become used to the AI and consequectly shoot it better due to familiarity.

The owner of the two guns I had tried to use, has noticed that in switching back and forth (he has his extra PSS stock) that his group shrink with the AI, but once again is this just familiarity?

Now there are some problems.

Now there are some problems. The stock panels are attached after mounting the receiver to the chassis and are affixed by eight 1-1/2" Allen headed bolts which can be easily misplaced if not careful - not the most practical method for a field duty sniper weapon. Yes, I would not take it apart in the field if I could help it - but give any infantryman idle time and look what gets lost/broken etc. What I would appreciate is a slotted head captive pin arrangement - with a half twist lock method rather than a screw nut combo.

Secondly the detachable magazine, (which has a beautiful constant force spring and is a nice touch to the design) is larger than the receiver opening. If you load from the magazine, it is possible (although unlikely) for a round to be caught under this lip and cause a malfunction - not acceptable in an issue piece (and not a problem with AI rifles). Unlike the M24 mag, this is not an issue of failing to seat the bullets to the rear, but as the next round chambers, pressure sometimes forces the next round forward and it will become caught (observed twice in one rifle and once in mine). The solution is to have a gunsmith, or other capable machinist mill out the receiver enough to give the necessary clearance - from .100" to .120". This portion of the feed ramp is not used by the AICS anyway so it will cause no problems if gone - although it will make conversion to a different stock a problem. This is not a big deal if dealt with ($20Cdn Fix), but annoying in a large dollar piece of kit. Using Federal GM2 (175MK's) the magazine is still pronounceable larger than the round, leading questions as to why the mag is so long? This was design as an issue system - so why the allowance for handloads, if it disturbs the integrity of the SWS?

Next, the sling swivels are atrocious. They look like lift brackets for cargo loading - any QD sling will flop around noisily and without positive purchase. One friend uses a C-6 (our MAG-58, the US M240) sling, which has large metal snaps - but not ideal, for it is just a big, canvas web sling. As a solution on mine Jerry Rice drilled and tapped the stock and installed QD mounts: one in the front accessory rail, and the other in the butt behind the handstop on the aluminum frame.

This allows for rock solid sling attachment, and I now would consider it a must on any AI system (including the full AI's AW and AWM). Then the cargo hooks can be removed and saved for a more usefully purpose like prepping your 4x4 for an airlift - they would likely support my Pathfinder. As a side note the issue AI sling is much like the sling on our C9 (M249 Minimi) more useful for carry than as a shooting support.

Next issue. The cheekpiece is a polymer, sort of slick to the touch. I found myself creeping up on it, and unable to return to the same cheekweld quickly. This was solved by adding a kisser which I made of para cord and gun taped to the cheekpiece so it that sticks out to my lip. This was then later replaced with a fabric covering of the cheekpiece and a rubber O-ring (thanks for the idea Greg). The para cord had (when exposed to dirt/water/mud etc) become so stiff as to cause discomfort when shooting.

While on the cheekpiece topic, the removable cheekpiece has to be removed for cleaning - or at least it does if you clean from the breach. If you have any sort of elevation applied to the cheekpiece it is tricky [short of scribing lines into the rails] to return to you zero height - causing more problems. The addition of a cloth or other cover and taping it to the cheekpiece can give enough lift to bottom out the cheekpiece - allowing for a more constant return position. The cheekpiece on the AI .338 was a velcro on and off design which seem to return to the same spot easily enough, and seemed cheaper to supply, but likely not as rugged that it seemed odd to have done the rifle this way.

The last sort of 'ready for duty' items were more gun tape (100mph if you will) two 2x2 pieces on the stock (to cover my trigger during a stalk). Then another three feet of 2" wrapped on the recoil pad (hey everyone loves gun tape and to replace the two by two's). Taping the forestock, accessory rail shut was also required - causing me to shake my head again at the design. This stock is allegedly for use on Military sniper weapons systems, so why the rail?

The last problem I noticed is common to most stocks and that it has a hollow ring if struck heavily on the buttstock - so don't bang someone over the head with it and you should be fine.

Further 'deficiencies' that have been proclaimed with this stock have been the lack of left handed action acceptance (does not bother me - but southpaws are mighty offended). Further the neglect to bring out the Long Action system. Which all apparently have been rectified if the ads in Tactical Shooter are to believed. 10 round mag YA Right?

Field Handling:

I guess nothing is complete without a field test. Mud, grass etc. So digging the ghillie out of the basement I decided to spend a week out and about living out of the ruck, and dragging packing and abusing the rifle (Sorry Jerry). As requested, I even packed my parka, wind pants and other assorted winter kit (bitch, bitch, bitch) to give (and get) a 4 season feel.

So cinching up the straps and strapping the drag bag to the ruck, off I went. I set up camp on the edge of our 900m range so my odd (and perhaps questionable) behaviour would not attract too much unwanted attention. I only packed enough water to drink and cook so - any dirt; mud etc. was there for the duration.

Fortunately the winter kit was in the ruck because it snowed July 1st (go figure). Wearing the Parka and mitts etc. was quite cumbersome and the AICS was awkward. The LOP was too long for me to get in good and tight. Although in fairness to the system, any winter ops would be best planned for and the rifle's adjustment stock spacers removed if necessary (for me they are).

I noticed at this time that the trigger is located smack dab in the middle of the trigger guard. This limits the advantages of the generously sizing. As a result heavy gloves are impossible (ND) - not a major problem for we usually use Arctic Mitts with light anti-contact gloves underneath - shake off the big clumsy mitts and you can shoot with the light ones then replace the heavies.

As I mentioned it rained and snowed - allowing me to really abuse the gun. Doing low crawls and a full-blown 300m stalk, on some unsuspecting silhouette shooters, the rifle was exposed to all sorts of Albertan landscape. The trigger guard performed admirably, there was hardly anything on the trigger - and the gun tape I had secured to cover the opening in frame was still intact. The bolt seems to project less from the side - likely due to the thickness of the stock panels. Even with me dragging it by the front sling swivel on it's right side (tsk tsk) only managed to come away with small amounts of grass - my thigh holster for my Browning always accumulates more.


Lastly, I figured I would mention something about bedding. Jerry Rice had mentioned that he just didn't feel right with a stock that wasn't bedded - but that since my rifle is shooting about .25MOA without it he'd start thinking about it. Now my friend Greg (a SC lurker) had bedded his 5R Rock Barreled AICS .308 and is experiencing great accuracy as well - so for my thoughts you probably can bed it if you want to, or if you want a field gun (to go jump etc.) with then don't.


In summation, I think the stock is great once so modified - it would be nice for an out of the box fit, but like most items, requires further work to customize it for you, the individual using it. I think for the price more work should have been done in field testing this - for that price it should damn well stand up and take the shot for me. There are some inexcusable (and dangerous) problems with the stock out of the box, and if I had not been so taken with shooting it - I would be furious. This is the fourth stock on my 700 (the final). I have had a McMillan M24 one (came with it from the provincial police force that sold it to me), the HS Precision (traded the Mc for it and some $ to one of the LE's from the agency that sold), and (don't laugh) the Choate USS. All have had some good and all some bad. I think with the modifications I have the best system, for me, that I can assemble, but as I am always learning, I am open to new ideas and suggestions.

For those who think I am being excessively harsh on this system, you may indeed be right, but I refer you to the price tag.

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