Cryogenic treatment vs wear rate

[3mctoledo]

I was looking for any input on cryogenic treatment of barrels for enfields. I have an extra 1941 Lithgow with a headspace of 066 (like new). I want to use it in vintage shoots. My one friend swears by the process. The one thing I can say is the rifle he has is easlier to clean after a long day of shooting. It also seems to disipate heat better.
The one plus, if it is true, is that you may be able to maintain a rifle shooting longer or not damage a collectable rifle you want to shoot with having the lower wear rate. I have not really priced it out yet.

1. Increased wear resistance for easier cleaning
2. Reduced friction, heat, and wear for an improved barrel life
3. Improved shot groupings resulting in improved accuracy
4. Increased velocity of about 50-60 feet per second

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[dp4]

I know they do that to chainsaw chains, and they do last longer and stay sharper.

[muffett.2008]

My sons played with this 35 years ago, quite upsetting for the wife to find the cat stuffed in the freezer and very solid.

[jmoore]

I would surely like to see a scientific paper of the process and it's benefits at the atomic/crystalline structure level. Snakeoil to me.

[Frederick303]

It was very much in vogue in the competitive high power circuit back in the mid to late 1990s. For a time great benefits were claimed, until a metallurgical engineer took the time to post a very detailed paper on it around 1998~1999 in precision shooting. In short if the barrel was properly made, the effect was minimal at least according to theory.

I believe the American rifleman also ran an article around this time, though it might have been in the 1999-2001 time frame. In any case they gist of their article was they took some match barrels made from identical steel and ran one through cryo treatment. Testing the untreated barrel against the treated barrel in ammunition tests, with a large number of groups on each barrel they found no real difference in wear or accuracy.

Around this time or shortly after Kevin Thomas of Sierra bullets did a similar test but he ran either 4 barrels or 6 .308 barrels in his test group (some cryo and some not) and ran the barrels until their accuracy was on the down hill stretch. I do not recall the exact results but one of the cryo treated barrels did last a little bit longer, but not by much, maybe 2 to 300 rounds. None made it to 4000 rounds before the peak accuracy was past. Note that the test was with high BC bullets with short bearing surfaces, and that is what one can expect with such bullets, peak accuracy is not that long. All were sub MOA at the start.

That said Krieger barrels , which makes some of the very best barrels in the US does in fact cryo treat their barrels after drilling and reaming, prior to the final cut rifling. So the benefit is likely small, but at least one barrel manufacturer thinks the effort is worth while. Given that barrel manufacturer is very much connected to the AMU and used by the very best marksman in the US, there is some small advantage.

I seem to recall that with barrels that were already made, the supposed advantage of Cryo was to stress relieve the barrel, which would in theory allow for less shift in the point of impact when the barrel heats up. That being the case, trying it out on a Lithgow heavy barrel might not be a bad idea, just do not expect a massive difference.

[303Nut]

I used to do the cryogenic treatment to our small textile parts. It did change the structure of the metal and a lot of our customers praised the extra wear that they got from it. I've read the articles on it being done on gun barrels but it seems the results are mixed and may not be much of any help on wear.

[Bruce_in_Oz]

Most barrel makers are very cagey about exactly what they do to achieve the desired results. And this starts with their choice of steel.

Modern barrels are generally made by processes utterly different and from very different materials from the old SMLE barrels. For starter, SMLE barrels had an early forging stage, during which the breech end was heated and the barrel hammered axially, to bump up the diameter for the "Knox Form". This also meant that there was quite a different crystal structure in the chamber area and the bore in general.

Note also the amount of detail given to the bore size and finish and the almost complete lack of notes on the depth and surface grade of the grooves.

Steel for SMLE barrel is "DD8"

Process: from S.A. 462 P, 14 December 1938:

12. Barrel(a) Forged. - An Inspector will, at any time, select barrel forgings for testing, put his stamp on them, and direct manufacturers to make test pieces therefrom, These pieces will be tested in the Royal Ordnance Factories in the presence of an Inspector, and must comply with the terms of the Specification.

(b) Fine bored stage. - The barrel will be viewed in the finished bored stage, when it must receive a plug .3025 inch, and reject one of .305-inch diameter. The bore must shade straight from end to end. The exterior will be tested for concentricity with the bore by being spun on plugs entering the bore when a toleration of .003-inch from the centre of the bore will be allowed. The exterior, in this stage, will be gauged in three places; the limits between receiving and rejecting being marked upon a bed plate above which the barrel is supported

(c) Rifled. - The barrel, in this stage, will be gauged with plain plugs .303-inch or .304-inch receiving and .305-inch rejecting. The bore must be parallel from end to end; to ensure this the receiving plug, according; to the diameter of the bore, must run. The depth of the rifling to be gauged with wing plugs receiving and rejecting, the stem, of the plugs being .303-inch and .304-inch, receiving and rejecting, to be used respectively according to the diameter of the bore. The pitch will be tested, and the rifling and bore examined to see that it is smooth throughout and free from greys, scratches and other injuries.

(d) Screwed. - The barrel, in this stage, will be gauged for size and position of thread from the end of the barrel, and also for position from flat.

(e) Chambered. first. - The chamber will be gauged with gauges smaller in diameter than the finished size, and the extractor way gauged for depth and position from flat; also the position of the key for slot for block, band, foresight, will be gauged.

The bore will be examined and the barrel spun,

(f) Sights, fitted. - The barrel will be submitted with the sight bed assembled, and the block, band, foresight, fitted. It will be examined for fit, and gauged for the position of block, band, foresight; bed, back sight; and sight axis pin hole; and size and depth of fixing screw hole, also for height of block, band, foresight, and figure of dovetail. The exterior will be gauged at the muzzle, radius, and breech end, also for the figure of the reinforce.

(g) Proof. - The barrel will be submitted with the action attached for proof. The distance from end of bolt to face of barrel will be tested with a cartridge head gauge .067-inch. The proof will then be carried out with a proof cartridge, the charge being about 33 grains of No. 9 cordite, having a Service bullet of 215 grains, giving a mean pressure not below 24 tons per square inch, after which the action will be examined; and the barrel, body, bolt, and bolt head will be marked with the proof mark.

(h) Browned and finished chambered. - The barrel will be examined for browning and bore (which should be burnished with wire gauze), and to see that the entrance to chamber is rounded, chiefly at bottom, The bore will be tested far straightness by being spun in the testing machine on a rod with two bearing points, one at the breech end and the other at the centre of the bore; the muzzle end will be allowed a total lateral movement of .006-inch. The chamber and bore will again be gauged. The bore must be parallel from end to end, and take a .303-inch or .304-inch plug, and reject a .305-inch plug; the receiving: plug, according to the diameter of the bore to run, The barrel will also be gauged for length.

(i) Barrel with body (breeched up). - The barrel will be submitted for view assembled to the body, the latter being examined for browning and for polishing of the bullet lead. The barrel must be well bedded down into the body. The barrel will then be gripped in a breeching-up vice, and the position of the flat on the barrel gauged from the body. The breeching-up will be tested by means of a hand-operated spring wrench, which, when pulled to completely depress the spring, should not unscrew the body. A pull of about 30-lbs. applied 12-inches from the axis of the movable arm of the wrench being required to move it, and about 55-lbs. to completely compress the spring; the axis of the movable arm being 2,32-inches from the axis of the body. The position of the flat on the barrel will again be gauged, and the barrel and body spun.

etc, etc and thus on to the fitting of sights etc.

Notice also how many times the chamber is cut / adjusted.

The internal stresses in barrels made by forging (buttoning, hammer forging), or cutting (gang-broaching or hook-cutting) are different. The principal difference is that forging processes generally involve rifling a parallel blank first, stress-relieving and then profiling; as against rough profiling, stress relieving and then boring and rifling. Interestingly, the TRW M-14 barrels, highly regarded by keen shooters, were made by the latter process.

You just cannot successfully button a light-profile blank; it just bulges. The clever folk at Steyr seem to have perfected making a hammer-forged barrel, complete to final profile, in one pass. Also their AUG barrels, almost completely parallel in profile, go the next step and use a mandrel that forms the rifling, throat and chamber in one pass. The trick there is to travel this mandrel rearwards at the twist rate as the metal flows rearwards under the hammers and then stop it and let the rotary hammers traverse along the chamber area. Hammer forging machines are big, noisy and impressive to watch.

And then there is EDM (Electro Discharge Machining) Some of the big pistol manufacturers are "cutting" their rifling this way now: surface grade is mind-bogglingly fine.