COLD STEEL ACCURACY
Can cryogenic technology be used for major gains in accuracy?
By Jim Gosnell

As with just about any trade show of any kind, there were many new and interesting things to see at the NRA convention in Phoenix last spring. We writers have to keep the buyer's motto of caveat emptor well in mind when searching out new products or services to write about. And I don't mind telling you that when I heard about "freezing" gun barrels, I was skeptical about the possibilities of any benefit. I read the literature on cryotechnology, which was well written and very convincing. It talked about advancements in metal items, ranging from aircraft parts to tubas. Tools, gears, engine blocks, cutters, transmissions, drill bits, pistons, crankshafts, punch dies and just about anything metal that is affected by heat and stress has been reported to have been amazingly improved. These improvements include durability, reduced wear and enhanced performance, and these all lead to reduced cost and improved production. This process has been used extensively in the machine industry, and the newest benefactor of cryotechnology is NASA.

I decided to chat with the folks who published the literature and stopped by the 300 BELOW booth. There, I met Peter Paulin, the company president. I explained my skepticism, and he was most understanding, stating that such skepticism was a tough obstacle for his company to overcome in the gun industry. We talked about some of the results of cryogenics, and I told him that I might give him a call a bit later and try the process.

I am by no means a metallurgist or engineer, so as far as I am concerned, most of what happens to the metal as it is frozen might just as well be written in a foreign language. I did spend some time studying the material and talking to some people who really are metallurgists in an attempt to gain a layman's understanding of the process and the changes that take place. Things do happen and changes do occur, but attempting to show them is almost impossible and gaining an understanding of them is nearly as difficult until the process is translated into simpler terms.

I had hoped to do some sort of non-destructive test to obtain hardness both before and after the cryogenic process but was told that this was not possible. The change in Rockwell hardness would be insignificant, and if I were to conduct any real scientific tests, I would have no barrel left. Performance, therefore, was going to be the only measure that I had available to me.

After the show, I had considerable difficulty getting this new process out of my head, so I gave Peter a call and told him that I had a tough test in mind. I had a Ruger Target chambered for .22-250, and I felt that it would be most interesting to see if we could improve its performance. Peter thought it was a good test and told me to send the barrel on when I was ready.

There are other cryogenic processes available using dry ice to obtain a temperature of about -120°F, but 300 BELOW uses a process that takes the metal below -300°F. The process, known as deep cryogenics, involves a slow computer-controlled temperature drop of a few degrees per hour until the temperature reached is -317°F. Control is so precise that temperatures can be maintained to within one-half degree.

Liquid nitrogen is used as a refrigerant, but the metal is not submerged in it. Submergence can cause unwanted stress. The temperature is held for at least 10 hours and then slowly brought up to 300° above zero, then slowly returned to room temperature.

The freezing process is an extension of heat tempering, and there are actually some changes that take place in the metal as a result. Most of us know that heat tempering does harden steel, but this process goes way beyond that and does a more complete job. So what really does happen?

In simple terms, there is austenite, a soft metal, in the steel and marten-site, which is much harder. Martensite is the "good stuff," and that is what we want. The deep cryogenic tempering process turns most of the austenite into martensite. Additionally, the molecular structure is changed to a refined microstructure with greater density. Voids in this structure are filled with micro-fine carbide "fillers" that are formed during the process, further increasing the density. This change is a permanent and irreversible.

Stress is an inherent property of steel and will lead to accuracy problems in rifle barrels. Stress is induced by the random heating and cooling of the barrel when firing and is unavoidable. As it is heated, the metal expands, then it contracts as it cools. You may think this is a gradual heating and cooling; however, it is not.

All of this can and will cause warpage. Though microscopic, this warpage will be most evident at the target. The deep cryogenic tempering process reduces much of this stress by an overall strengthening of the steel. The bottom line is a barrel that is denser and more resistant to warpage, which, in turn, results in smaller groups, as long as the shooter is doing his job.

My Ruger is not quite in out-of-the-box condition, but I have not made any radical changes to it. First, I had Charlie Robertson of Score High Gunsmithing install a muzzle brake of his design. I know, you are wondering why a brake on a .22-250, and up to this point I would have been asking the same question. For starters, a .22¬250 does have recoil, and with Charlie's brake, it is much like shooting a .22 LR. I can now watch my targets in the scope and see the bullet impact as it happens—really neat. Another reason is that even the low recoil of a .22-250 can get to a person after expending a few hundred rounds. I cannot say that it has improved the accuracy of the gun, but it has helped the consistency of the shooter—me—and therefore is a definite improvement.

Next, I spent an evening with a few chisels and a dremel tool and opened up the stock a bit. I used Brownell's Glassbed Kit to bed the action and the first inch of the barrel. This was to en¬sure that the rifle had a solid bed and would not move around. The Brownell's kit is one of the handiest things I have ever used for glass bedding—everything you need (except tools), and there is no mixing required.

I suppose this might be a touch of overkill, as the Ruger has a wonderful wood laminate stock, but I just wanted to be sure there would be no variables—or at least as few as possible. The last thing I did was to mount a Leupold Vari X III 6.5-20X Target scope. This turned out to be an excellent combination.

The Ruger was, for all intents and purposes, new, having had less than 10 rounds through it. My thoughts were to get several different kinds of ammunition together, factory and handloads alike. I would shoot a couple of "before" groups from each box and reserve the remainder of the box for the "after" part of the comparison.

I used Winchester, Federal and Remington for the factory loads and ordered some custom loads from Superior Ammunition. The Superior loads were loaded with-52 grain Sierra BTHP Match King Bullets, and the cases were primed with CCI Bench Rest Primers. Aside from that, I do not know what the load was, but they shot incredibly well, so well, in fact, that I will be shooting a lot more of them.

For the handloads, I chose some once-fired Federal cases that I prepared on my RCBS Trim Pro and Trim Mate to ensure uniformity. Once they were ready, I primed them with CCI Bench Rest Primers and started to work. I did not have time to check out as many loads as I had hoped, so I picked two that have proved to do well in the past for me. One was Hodgen's Varget powder, driving a Nosier Ballistic Tip bullet, and the other was Norma 202, pushing a Speer 50-grain TNT bullet. These handloads were assembled on a ROBS Ammomaster Press using ROBS Competition dies.

Bullet depth was determined using a Stoney Point Overall Length Gauge, ensuring a clearance of .020 inch off the lands. Both of these combinations have proven extremely accurate and provide incredible speed with no pressure problems, tripping the clocks at speeds of over 3,800 fps.

With sight-in and break-in out of the way, I started to shoot some groups with the selected ammo. I chose to shoot three-shot groups and put up targets at 100 and 200 yards. The figures in the attached table are an average of three three-shot groups. I actually shot a couple of groups both before and after that I have not been able to duplicate. Who knows why? No matter what I do I just couldn't seem to equal them. For that reason, I have left those numbers out of the averages in the table.

Now to set the record straight, the folks at Speer put a note in each box of 50-grain TNT bullets advising not to use them at speeds over 3,300 fps. However, I have been driving them at speeds of over 3,800 fps for years and have yet to have one come apart.

I am not promising that you will not experience bullet disintegration, so attempt this at your own risk. My original intent was to have a bullet that would enter a coyote and explode inside without exiting. There is also little chance of ricochet when hunting varmints. This works quite well, and the incredible accuracy I have found is a fringe benefit.

The stage was set for the "before" part of this comparison test, so I set up my Bench Master rest at the range. The Bench Master is one of the handiest rests that I have used in a long time, and it provides a very solid platform for the gun. As with most tests, I like to eliminate as many variables as possible and thus get the true performance of the gun.

Since my gun was new, I spent some time shooting targets for sight-in and break-in. I cleaned the interior of the barrel after each five shots, and by the time I had put about 70 rounds through the gun, I was ready to start. This was a long process, as the heat of a New Mexico summer will allow a barrel to heat up rather quickly, and it seems as if it took forever to cool.

Some things that I noticed on the "before" test that seem to be significant are:

1)            As the barrel heated up, the groups began to increase at a noticeable rate.

2)            The Ruger showed a definite preference for certain types of ammo. Those that it did not like had groups that were near double those of the preferred brands.

3)            Cleaning was not easy. Even after five shots, it took as many as eight patches to get a clean bore.

4)            Consistency was poor. Though the gun was still very accurate, it would vary from group to group with the same brand of ammo.

None of the above are problems that would cause undue alarm, and the cleaning would probably get better with time. In fact, this gun is a good shooter for a varmint rifle, which is why I purchased it in the first place.

To be honest, I was a bit worried that anything I did at that point might make things worse, but I was committed. I took the barreled action down to Charlie Robertson, and he pulled the barrel. I also had Charlie pull the barrel on a Remington XP-100 that I had been working with, and I carefully cleaned both, then sent them to 300 BELOW.

The XP-100 is chambered for .223 Remington and has a Burris 7X EER scope mounted on it. The stock is a factory reject that I made fit some time ago and coated with red paint. It may look a bit wild, but it works. I had been working with this gun on another project and thought it might be a good subject for this test. Just about anything I fed this gun would group between .80 and one inch at 100 yards—okay, but I had always hoped for better.

The folks at 300 BELOW really prefer barrels and not the actions. This is mainly due to the fact that neither you nor they have to mess with an FFL. In addition, they are metallurgists, not gunsmiths. To make it easy on all parties, it is best simply to send barrels. When the barrels came back, I could not see a bit of difference. I am not sure what I was looking for, but there was absolutely nothing new on the outside. Curiously enough, the bore on Ruger barrel seemed dirty, and I ran a few patches through it. Sure enough, it had a fair amount of dirt in it that must have been dislodged by the cryogenic tempering process even though I had cleaned it well. I do not think this means anything: it's just an observation.

I was most anxious to see some results, so I headed down to Score High Gunsmithing, and Charlie put my toys back together for me. With both guns back in the stocks and their scopes remounted, I set sail for the range.

When I arrived at the range, I noticed a slight breeze but set up anyway. I had decided to run 25 shots through the Ruger before I got down to business in order to sight in and "season" the barrel. The point of impact had changed slightly, up and to the left, but that can be explained as a result of barrel removal or the remounting of the scope—nothing serious at all.

My first shots were grouping at just under an inch, and I could feel a knot in my stomach developing. I forced myself to ignore this, as I was not into my actual shooting test as yet, but that in itself was a chore. With the first 25 shots out of the way and my gut feeling like an overworked pretzel, I started the accuracy test.

The end result was a clear improvement in average groups as shown in the table. I began to feel better, and the Ruger seemed to settle down a bit. The groups in the table are each an average of three groups. A few single groups were considerably smaller. This particular test showed a 30-per¬cent improvement in accuracy—most notable. With time, I am confident that I will be able to shrink these group sizes by adjusting my handloads.

The XP-100 turned an improvement as well. It now groups a consistent .62 inch with all of the loads that I use in it. This, too, is a 30-percent improvement. Again, this is quite gratifying, and I will work on further improvement through handloading.

One brand of ammunition that my XP-100 really likes is Black Hills. My other .223s seem to favor it as well. What makes this so unique is the fact that the Black Hills .223 is remanufactured ammo that is produced with once-fired military brass. The brass lots are mixed, but the quality is outstanding. This stuff is amazing, and as good as it is, accuracy improved with the freeze.

Some observations that I have made with regard to the Ruger during the "after" part of the accuracy test are:

1)            The gun doesn't seem as picky about ammo as it was before. It is very consistent, shooting under one-half inch.

2)            Cleaning seems to be less of a chore. Fewer patches are necessary to get the bore clean.

3)            The gun does not like a "squeaky clean" barrel. At least two or three "fouling" shots are required to get it to settle down after cleaning.

4)            Where I used to clean after 10 shots, I now go 30

5)            Impact change when the barrel heats up is now minimal. In fact, I do not see it as a factor when small-varmint hunting.

6)            The gun is more accurate.

7)            Velocities have increased about 50 fps across the board for all loads. The Federal Premium 40-grain loads are now averaging 4,313 fps from my gun!

Okay, I am convinced that this process has a definite application in the gun industry. I know many people who have spent hundreds of dollars to get less of an improvement in accuracy. If the claims of extended life are true, I will benefit from that as well. The Ruger is a varmint rifle and will see many thousands of rounds in a few short years. My next barrel that is going to the deep freeze will be one of mediocre accuracy, as I think it will be interesting to see just how much improvement there will be.

It is interesting to note that there were two records set recently in 1,000-yard matches. The only thing that the two recordholders had in common were barrels that had been frozen in the deep-cryogenic tempering process. The more I see of this process and the more I hear about it, the more impressed I become.

It seems to me that competition shooters, such as those in IPSO, would also benefit from the cryogenic tempering process. Those guns can get mighty warm during a shoot, and the cryogenic treatment might extend barrel life. It would also be interesting to see if there would be any reduction in leading as a result. The price is right and the results seem to be there. I can tell you that I will be sending several more barrels to 300 BELOW in the near future.

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