KAC won a military contract

[pmclaine]

Talk of bolts, BCG and the gas system seem to be the rage. What is the better product, who builds better……yada, yada, yada.

Barrel matters most but all that unlocking, extraction, ejection stuff has to happen….

Without getting into specifics of KACs secret designs is there anything to expect on the operations parts coming down the pike? Has the stuff reached mature design?

Not same as KAC but some crossover I run an LMT CQB.

It came with 16” barrel and I stuck a twenty inch on there with no other mods.

Last cleaning I noted a small ghost mark where back of the gas key is hitting the lower above the buffer tube.

Replaced spring and buffer anyway before looking for two quarters width.

The idea of the Surefire BCG intrigues because of the shorter gas key.

What’s coming along for overgassed service guns if you are just a recreational shooter that appreciates the reliability but doesn’t have govt cash to buy lowers.

Guessing KAC would have the solution.

 

[Happiness Is A Warm Gun]

Dimpled barrels are cool, but they introduce risks and variables. Components used in model lines are based on application. Sometimes a dimpled barrel makes sense, sometimes it doesn't.

That makes sense. Would some of the potential issues be the greater chance for the barrel to rust or otherwise have durability problems, the harmonics being thrown off possibly affecting accuracy, and increased labor costs?

 

[Jack_L]

I have not done so yet. I have scoured the internet and have yet to find target examples beyond 200 meter for 14.5" ACC.
I have Applied Ballistics hit-probability given the all the relevant data input, but it is still just a computer model output. My muzzle velocities are
at 2400 fps and AB predicts 1496 fps @ 600 meters, close to trans-sonic.
AB predictions @ 1.0 & 2.0 MOA.......my target looks like an intermediate of ~ 1.5 MOA, as none of my shots were off the target. The 1.5 MOA is more in line with Bryan Litz's discussion on dispersion expectations.
Would really like to see others real target results at this range.

I would not expect to see much better than 1.5 MOA at 600 meters in real-world conditions with a 14.5" 7.62 with M118LR.

 

[Jack_L]

Without getting into specifics of KACs secret designs is there anything to expect on the operations parts coming down the pike? Has the stuff reached mature design?
...
What’s coming along for overgassed service guns if you are just a recreational shooter that appreciates the reliability but doesn’t have govt cash to buy lowers.

There's a whole bucket of worms when it comes to assessing "overgassing". To one user group, a gun is overgassed if recoil can be perceived, and to another if the ejection pattern doesn't line up with a clock direction the gun is overgassed. The real story is that some additional force is needed to ensure reliability in extreme environments, under less than optimal conditions, while shooting at extreme upward and downward angles. Most people in the US will never experience those conditions, or have any expectation to have to deal with those environments or conditions or use. To meet the needs of our product-driving customers the first requirement is that the gun must work in the places that they will use them. The problem with that is that once a suppressor is added to a gun that works in those conditions the added backpressure blow-back effect would cause the extraction and ejection phases of the cycle of operations to be accelerated, leading to ejection problems.

KAC approached this issue in a few stages, though some developments were parallel.

The first thing was improving ejection. We did this with dual ejectors in 7.62 rifles first. The dual ejectors allow more ejection force to be applied to the case head, while not requiring longer/stronger springs that could cause other issues. The design and location of those dual ejectors were changed on the 6.5 rifles, and that basic location was used in the 5.56 E3.2. The E3.2 dual ejector bolt will reliably get casing out of the gun even at a pretty high cyclic rate.

The KAC Mod 2 Gas system does a really good job of delivering consistent gas pressure to the bolt carrier, which does prevent the "fouling seal" of loose gas systems which leads to increased operating speeds as the pressure rises due to leaks sealing. Contrary to popular belief it's not really stopping all gas loss, it just makes it more consistent, especially when comparing clean and new to used and fouled. We use our own port locations, places where they make the most sense rather than some arbitrary location based on a front sight post that doesn't exist.

The final piece of the puzzle is the suppressor. We started working on low/no backpressure suppressors several years ago, and that design concept moved into production suppressors (though only for gov stuff at the time). What you're seeing on the Hunter guns are our newest generation of suppressors. They are additive (3D printed) designs, which allows us to make a baffle matrix that is not constrained by traditional manufacturing processes. These new suppressors are incredibly durable, and have virtually no added blowback effect to the operating system.

So the net result in addressing overgassing is that the gun is able to function properly even if the cyclic rate increases, but with our suppressor suppressor the cyclic rate won't increase. The gun starts off exactly where it should be, and stays there.

 

[Jack_L]

That makes sense. Would some of the potential issues be the greater chance for the barrel to rust or otherwise have durability problems, the harmonics being thrown off possibly affecting accuracy, and increased labor costs?

Every single machining op bears a risk, just to start. All kinds of things that can happen when that high speed tool starts cutting.
Dimpling is not fast, and time is money.
Dimpling requires a machine, and each barrel is a different setup. If a machine goes down, you have to get a backup running and figure out how to catch up.
Time and risk just in making them.
Then comes performance. You can take a great barrel and ruin it with dimpling, or get erratic stringers/fliers as heat grows. It's better than traditional fluting, but it's not a free lunch.

 

[pmclaine]

There's a whole bucket of worms when it comes to assessing "overgassing". To one user group, a gun is overgassed if recoil can be perceived, and to another if the ejection pattern doesn't line up with a clock direction the gun is overgassed. The real story is that some additional force is needed to ensure reliability in extreme environments, under less than optimal conditions, while shooting at extreme upward and downward angles. Most people in the US will never experience those conditions, or have any expectation to have to deal with those environments or conditions or use. To meet the needs of our product-driving customers the first requirement is that the gun must work in the places that they will use them. The problem with that is that once a suppressor is added to a gun that works in those conditions the added backpressure blow-back effect would cause the extraction and ejection phases of the cycle of operations to be accelerated, leading to ejection problems.

KAC approached this issue in a few stages, though some developments were parallel.

The first thing was improving ejection. We did this with dual ejectors in 7.62 rifles first. The dual ejectors allow more ejection force to be applied to the case head, while not requiring longer/stronger springs that could cause other issues. The design and location of those dual ejectors were changed on the 6.5 rifles, and that basic location was used in the 5.56 E3.2. The E3.2 dual ejector bolt will reliably get casing out of the gun even at a pretty high cyclic rate.

The KAC Mod 2 Gas system does a really good job of delivering consistent gas pressure to the bolt carrier, which does prevent the "fouling seal" of loose gas systems which leads to increased operating speeds as the pressure rises due to leaks sealing. Contrary to popular belief it's not really stopping all gas loss, it just makes it more consistent, especially when comparing clean and new to used and fouled. We use our own port locations, places where they make the most sense rather than some arbitrary location based on a front sight post that doesn't exist.

The final piece of the puzzle is the suppressor. We started working on low/no backpressure suppressors several years ago, and that design concept moved into production suppressors (though only for gov stuff at the time). What you're seeing on the Hunter guns are our newest generation of suppressors. They are additive (3D printed) designs, which allows us to make a baffle matrix that is not constrained by traditional manufacturing processes. These new suppressors are incredibly durable, and have virtually no added blowback effect to the operating system.

So the net result in addressing overgassing is that the gun is able to function properly even if the cyclic rate increases, but with our suppressor suppressor the cyclic rate won't increase. The gun starts off exactly where it should be, and stays there.

Thank you for the schooling. Great read.

I know the reasons “why” there is overgassing and don’t object at all……..except when it comes to my precious…….

 

[Jack_L]

Thank you for the schooling. Great read.

I know the reasons “why” there is overgassing and don’t object at all……..except when it comes to my precious…….

Oof, there's something else going on there if you're making contact with the rear of the gas key on the lower.

 

[Happiness Is A Warm Gun]

@Jack_L Thanks for writing such detailed answers to our questions. Would you also mind discussing the history of the relationship kac has with lmt? I only ask because I have seen some intense debates over the years about exactly how much lmt made for kac, who really made the sopmod stocks for who, etc.

It is interesting to me as well because there are obviously a lot of similar design features, not to mention how your companies are widely considered the two most innovative for military grade ARs.

 

[Jack_L]

@Jack_L Thanks for writing such detailed answers to our questions. Would you also mind discussing the history of the relationship kac has with lmt? I only ask because I have seen some intense debates over the years about exactly how much lmt made for kac, who really made the sopmod stocks for who, etc.

It is interesting to me as well because there are obviously a lot of similar design features, not to mention how your companies are widely considered the two most innovative for military grade ARs.

The relationship with LMT dates way back to the SR-25 Match days. I can't recall all of the details, and some aspects are not really shareable without talking to both parties, but I am comfortable with sharing the following:
LMT did make early SR-25 parts for KAC for a short time, but that was well pre-dating the move to Titusville.
KAC licensed some designs to LMT, and we have supplied each other with parts over the years. As product lines diverged, that has dwindled to less and less, and I don't think that either company has used any significant component from the other in quite some time now.
KAC was contracted to produce a decent quantity of SOPMOD stocks for LMT, but that contract was complete several years ago.
We have a friendly competitor relationship with LMT, and I have said on many occasions that I think that they have produced some very nice rifles with innovative features ahead of the curve.

 

[Zoomie]

Years ago, when the M110 was pretty much unobtainable outside .mil, I had a clone custom built. One of the parts impossible to source was the bolt carrier. I was told by someone from KAC the LMT Enhanced would be a really good choice. I recently had that rifle rebarreled, and the person who did it, someone very familiar with the platform said, "how, and where the heck did you get this bolt carrier?"

 

[strikeeagle1]

I know the reasons “why” there is overgassing and don’t object at all…

A few considerations:
Measure your carrier length......should be >6.66". IF it is, the buffer retainer pin location could be out of specification, i.e. drilled too
far rearward.

Make sure that rifle-carbine receiver tubes have correct rifle-carbine buffer lengths.

Gas Key-Lower Receiver Ring Min Gap Go @ 0.1350” No-Go@ 0.125”
U.S. quarter thickness ~0.0650” x 2 = 0.130”
I use this gauge to avoid carrier key-receiver banging each other.

 

[pmclaine]

Oof, there's something else going on there if you're making contact with the rear of the gas key on the lower.

I wasn’t sure if it was doing it when I had the 16 inch barrel on, at least never noted it, and have only a few thou rounds with the 20 inch barrel.

Would have thought the 20 would be conducive to less bolt speed but I probably have it backwards figure as longer barrel equal more bullet speed.

 

[pmclaine]

A few considerations:
Measure your carrier length......should be >6.66". IF it is, the buffer retainer pin location could be out of specification, i.e. drilled too
far rearward.

Gas Key-Lower Receiver Ring Min Gap Go @ 0.1350” No-Go@ 0.125”
U.S. quarter thickness ~0.0650” x 2 = 0.130”
I use this gauge to avoid carrier key-receiver banging each other.

View attachment 8237607

I through a new buffer and spring in from LMT.

I’ll try the quarters gauge and May end up with one or two at the bottom of the tube.

Been kind of thinking of going back to the short barrel at some point but the 20 shoots real nice.

 

[Jack_L]

I wasn’t sure if it was doing it when I had the 16 inch barrel on, at least never noted it, and have only a few thou rounds with the 20 inch barrel.

Would have thought the 20 would be conducive to less bolt speed but I probably have it backwards figure as longer barrel equal more bullet speed.

I don't think your impacts are being caused by excessive carrier speed, I think that something is short. The key should never be able to physically contact the receiver extension thread area. Super simple check is to remove the action spring, drop in the buffer, and then drop in the carrier. Removing the hammer can make this easier, but isn't necessary. You should see a distinct gap between the rear of the key and the arch of the lower receiver. I grabbed a random one from my inventory and measured a 0.167 gap.

 

[Cascade Hemi]

I through a new buffer and spring in from LMT.

I’ll try the quarters gauge and May end up with one or two at the bottom of the tube.

Been kind of thinking of going back to the short barrel at some point but the 20 shoots real nice.

2A Armament sells Delrin spacers that are center drilled for the corresponding receiver extension port. They're a really easy way of adjusting carrier depth. A soft buffer bumper can cause contact as well.

 

[strikeeagle1]

In addition to the above, the buffer tubes are threaded 16 tpi, so every full rotation of the tube is 0.0625" of linear movement, that'd one U.S. quarter thickness per full rotation of the tube.
IF there is available space between the buffer tube edge and its retaining pin for one more spin without binding up the retainer function one can gain some shortening of the parts stacking. Of course OAL of buffer itself should be measured to be in spec, never hurts to check. Carbine buffer mil.spec length should be 3.250", rifle length 5.920".

 

[pmclaine]

This is all good info if off topic.

This is being cataloged to do some checking.

I’d go down and check now but….

 

[HillBilly n TX]

Excellent news Jack hearing the KS-1 uppers should be available. Hopefully some of the 16“ 6.5 uppers start making their way to market. Have a CRS that I’m sure will work great with one.

 

[Jack_L]

Excellent news Jack hearing the KS-1 uppers should be available. Hopefully some of the 16“ 6.5 uppers start making their way to market. Have a CRS that I’m sure will work great with one.

I am a big fan of the 16" 6.5 Creedmoor guns, very excited on them getting out to the market.