I'll preface this by saying I'm just a country bumpkin with access to a small 100 yard range. I'm not a professional, I'm not a competition shooter, I don't even have any serious rifle training, but I have put about 5000 rounds through this rifle. Over the time I've used it I've: changed stocks, suppressors, slings, and optics a few times. Obviously I'm completely unqualified to say how good a rifle it is for any real use but I can make some observations about my interactions with this particular rifle. Hopefully, these observations might possibly be useful to others looking at this rifle.
The APC 300 came to me as a pistol. The barrel is a thicker profile where the balance of the weapon as a pistol is forward of the trunnion when empty and at the trunnion with a full magazine with only iron sights. I added a pistol brace while waiting on a Form 1. The pistol brace has a 10.5" length of pull, and the softer rubber of the brace makes for a poor stock as to be expected. There are two stock options I am familiar with, the Folding and Retracting Stock, and the Folding Stock. There is also a Helmet Stock, but I don't own a helmet and didn't buy this option.
The Folding and Retracting Stock has 3 settings, collapsed, midway, and completely out. This stock is pretty heavy at about 15oz. When attached to the rifle the point of balance for the rifle shifts to between the magwell and trigger when empty. The point of balance is at the magwell with a full magazine. The stock can be divided into 2 sections, the adapter portion which is 2" long and drops the stock comb height 1.5" from the rail. The second section is the adjustable stock portion which has a collapsed length of 6", mid length of 7", and fully extended length of 8". When using this stock I tended to rest the front of my face against the adapter piece's upward slope and cheek on the comb; a sort of nose to charging handle approximation. I found this comb height allowed me to mount an Aimpoint without a spacer comfortably. However mounting a Bravo 3 with a built in 1.5" height mount meant I ended up with a jab weld on the comb. There is an adapter for the Folding Collapsing stock to raise the comb height of the stock, its slips into the grove on the side of the comb and raises the height even with the rails. I found this worked well to gain a normal cheek weld when using 1.5" mounts; the piece looks flimsy but was stable for my range shooting. As a side note I tended to miss resting my face against the upward slope of the adapter when using the comb adapter.
The Folding Stock is a single plastic piece with the same sloping comb as the Folding and Retracting Stock. Here the adapter portion is 2.5" long with a 1.5" drop in comb height. Unlike the Folding and Retracting Stock in this stock the transition in height is a gentle slope rather than a straight diagonal. The length of the second section of the stock is about 6.5" - some of the measure here is perturbed by the gentle sloping of height transition. This stock is very light, at about 8oz. When attached to the rifle the point of balance is between the trunnion and magwell when empty and at the magwell with a fully magazine. This is with iron sights only. This stock does not have the ability to increase the comb height with and adapter. As with the Folding and Collapsing Stock and I can get a cheek weld using an Aimpoint without a spacer, a chin weld with 1.5" mounted optic like the Bravo 3, and with a Scalarworks 1.93" Aimpoint mount I have no stable weld.
The front handguard is short. The 12 o'clock length of the guard is 6" long when measured from the reciprocating charging handle, while the 3,6,9 o'clock lengths of the guard are 8" long. The top is scalloped short to expose the adjustable piston. The 12 o'clock picatinni runs the length of the upper, while the 6 o'clock picatinni runs 7" stopping at the trunnion, and the 3 and 6 o'clock are plastic rails measuring 5" in length each. Personally I end up holding at the front of the 8" portion and wrapping my thumb over the scalloped portion for the piston adjustment. I have tried mounting a light offset at the 1 and 11 o'clock positions using the 12 o'clock rail and found I couldn't push the button on the back of the light with my normal front hand position. I tried using a tape switch at 9 o'clock which was workable with my forward hand but not ergonomic and definitely cramped.
I've tried this rifle with 3 suppressors: SRD762, Osprey 9 (sub only), and Sandman-K. As a side note, the instruction manual states the adjustable gas block has subsonic and high velocity settings. These are designed for subsonic ammo used with a suppressor, or high velocity ammo used without a suppressor. The manual goes on to state subsonic without a suppressor may short stroke, while high velocity with a suppressor may damage the hydraulic buffer built into the stock adapter. I have not seen this information publicly posted by B&T in any advertising material. The SRD762 shifts the balance of the rifle back in front of the trunnion with either stock. The Osprey 9 and Sandman-K had a balance point at the magwell with either stock with a full magazine.
My range is rather limited, I have about 25 ft of width from 0 to 100 yards to place targets, I don't have any where to run and get in fun positions. From standing and shooting targets across the width I have from low ready I find the rifle weight leans into my forward hand. Moving between targets does not exhibit much over travel even with the longer SRD762. There is a noticable forward recoil impulse from the heavy bolt carrier and bolt entering into battery at the end of each shot which is unique compared to a lower mass bolt carrier system. I'm not experienced/qualified enough to say if this is overall better, worse, etc. I just know its feels very different than other rifles.
When used with a suppressor the hand guard area gets hot. It did not matter which suppressor SRD762, Osprey 9, Sandman-K, nor type of ammo subsonic or supersonic. I did find it happened a bit faster with supersonic ammo (yes the manual says don't do this) heating up to be very uncomfortable after 4 magazines. Using subsonic ammo required about 6 magazines. These are not mag dumps, but shooting about 1 shot every 1-2 seconds and leisurely reloading. The hand guard heats from the front and top which leads me to think the heat is from the gas block which is in direct contact with the hand guard. The 3 and 9 o'clock plastic rails remained OK to hold but the metal portions all became rather warm. Unsuppressed this same heating did not happen within 9 magazines (that is the most I bring to the range). The subsonic ammo used was Hornady Sub-X and the supersonic was ADI SMKs (aka Australian Outback).
The APC 300 came to me as a pistol. The barrel is a thicker profile where the balance of the weapon as a pistol is forward of the trunnion when empty and at the trunnion with a full magazine with only iron sights. I added a pistol brace while waiting on a Form 1. The pistol brace has a 10.5" length of pull, and the softer rubber of the brace makes for a poor stock as to be expected. There are two stock options I am familiar with, the Folding and Retracting Stock, and the Folding Stock. There is also a Helmet Stock, but I don't own a helmet and didn't buy this option.
The Folding and Retracting Stock has 3 settings, collapsed, midway, and completely out. This stock is pretty heavy at about 15oz. When attached to the rifle the point of balance for the rifle shifts to between the magwell and trigger when empty. The point of balance is at the magwell with a full magazine. The stock can be divided into 2 sections, the adapter portion which is 2" long and drops the stock comb height 1.5" from the rail. The second section is the adjustable stock portion which has a collapsed length of 6", mid length of 7", and fully extended length of 8". When using this stock I tended to rest the front of my face against the adapter piece's upward slope and cheek on the comb; a sort of nose to charging handle approximation. I found this comb height allowed me to mount an Aimpoint without a spacer comfortably. However mounting a Bravo 3 with a built in 1.5" height mount meant I ended up with a jab weld on the comb. There is an adapter for the Folding Collapsing stock to raise the comb height of the stock, its slips into the grove on the side of the comb and raises the height even with the rails. I found this worked well to gain a normal cheek weld when using 1.5" mounts; the piece looks flimsy but was stable for my range shooting. As a side note I tended to miss resting my face against the upward slope of the adapter when using the comb adapter.
The Folding Stock is a single plastic piece with the same sloping comb as the Folding and Retracting Stock. Here the adapter portion is 2.5" long with a 1.5" drop in comb height. Unlike the Folding and Retracting Stock in this stock the transition in height is a gentle slope rather than a straight diagonal. The length of the second section of the stock is about 6.5" - some of the measure here is perturbed by the gentle sloping of height transition. This stock is very light, at about 8oz. When attached to the rifle the point of balance is between the trunnion and magwell when empty and at the magwell with a fully magazine. This is with iron sights only. This stock does not have the ability to increase the comb height with and adapter. As with the Folding and Collapsing Stock and I can get a cheek weld using an Aimpoint without a spacer, a chin weld with 1.5" mounted optic like the Bravo 3, and with a Scalarworks 1.93" Aimpoint mount I have no stable weld.
The front handguard is short. The 12 o'clock length of the guard is 6" long when measured from the reciprocating charging handle, while the 3,6,9 o'clock lengths of the guard are 8" long. The top is scalloped short to expose the adjustable piston. The 12 o'clock picatinni runs the length of the upper, while the 6 o'clock picatinni runs 7" stopping at the trunnion, and the 3 and 6 o'clock are plastic rails measuring 5" in length each. Personally I end up holding at the front of the 8" portion and wrapping my thumb over the scalloped portion for the piston adjustment. I have tried mounting a light offset at the 1 and 11 o'clock positions using the 12 o'clock rail and found I couldn't push the button on the back of the light with my normal front hand position. I tried using a tape switch at 9 o'clock which was workable with my forward hand but not ergonomic and definitely cramped.
I've tried this rifle with 3 suppressors: SRD762, Osprey 9 (sub only), and Sandman-K. As a side note, the instruction manual states the adjustable gas block has subsonic and high velocity settings. These are designed for subsonic ammo used with a suppressor, or high velocity ammo used without a suppressor. The manual goes on to state subsonic without a suppressor may short stroke, while high velocity with a suppressor may damage the hydraulic buffer built into the stock adapter. I have not seen this information publicly posted by B&T in any advertising material. The SRD762 shifts the balance of the rifle back in front of the trunnion with either stock. The Osprey 9 and Sandman-K had a balance point at the magwell with either stock with a full magazine.
My range is rather limited, I have about 25 ft of width from 0 to 100 yards to place targets, I don't have any where to run and get in fun positions. From standing and shooting targets across the width I have from low ready I find the rifle weight leans into my forward hand. Moving between targets does not exhibit much over travel even with the longer SRD762. There is a noticable forward recoil impulse from the heavy bolt carrier and bolt entering into battery at the end of each shot which is unique compared to a lower mass bolt carrier system. I'm not experienced/qualified enough to say if this is overall better, worse, etc. I just know its feels very different than other rifles.
When used with a suppressor the hand guard area gets hot. It did not matter which suppressor SRD762, Osprey 9, Sandman-K, nor type of ammo subsonic or supersonic. I did find it happened a bit faster with supersonic ammo (yes the manual says don't do this) heating up to be very uncomfortable after 4 magazines. Using subsonic ammo required about 6 magazines. These are not mag dumps, but shooting about 1 shot every 1-2 seconds and leisurely reloading. The hand guard heats from the front and top which leads me to think the heat is from the gas block which is in direct contact with the hand guard. The 3 and 9 o'clock plastic rails remained OK to hold but the metal portions all became rather warm. Unsuppressed this same heating did not happen within 9 magazines (that is the most I bring to the range). The subsonic ammo used was Hornady Sub-X and the supersonic was ADI SMKs (aka Australian Outback).