MG 42 Semi Owner

The Essentials of Running The MG-42 SA:
Following these steps will help you use this complex system reliably, prevent malfunctions, dangerous operation, and damage.

1) Training: All current or prospective customers are encouraged to make an appointment to come to our shop in Maryland for training. We will show you how to properly use and care for the MG-42 SA. To make an appointment call (301)807-5234.

2) Correct Ammo: (Pages 41 & 42 of the manual) There have been a wide variety of 8mm weapons produced in the 20th Century by numerous countries. Much of this ammunition is not suitable to run in an automatic belt-fed firearm.

3) Correct Belts: During the 20th Century there were dozens of belt-fed machinegun designs that have been produced by numerous countries. Belts designed for one type of machinegun often look a lot like those of another. Many companies in the US sell belts for the MG-34, MG-42, and M-53 that are not actually belts designed for use in these weapons. We have seen numerous VZ, MG-3, and Swiss MG belts in the US market that will not function in firearms designed to run with the German-type MG-34/42 belt. Running an incorrect belt will likely result in damage to the feed mechanism.

4) Lubrication: Use plenty of lubricant such as Ballistol or Break Free on the rails, bolt, feed mechanism, and belts during use. Unless you are in the desert, run the MG-42 SA ‘wet.’ Avoid using WD-40 because it is flammable and may result in excessive chamber pressures.

5) Cleaning: (Pages 38, 39, and 40 of the manual) When cleaning the MG-42 SA, pay special attention to cleaning the bolt head, barrel, entire booster assembly and surrounding receiver area. Pay special attention to the front of the MG-42 DA. This is the exit point for all of the gasses and residue. This includes the flash-hider, booster cone, barrel sleeve, barrel crown, and receiver bushing. These parts must be thoroughly and aggressively cleaned after extended used because the corrosive residue becomes ‘baked-on.’

6) Inspection: (Page 43 of the manual) After cleaning, fully inspect and reassemble the MG-42 SA. Once fully reassembled, load and cycle some dummy rounds through the system to check for proper function.

8mm AMMO in the MG-42 SA

The best surplus ammo to run is Romanian Steel Cased 155 gr. The best commercial ammo to run is Olympic 196 gr. FMJ.

That being said, we have used Portuguese, Yugoslavian, and FN with very good reliability and consistency. One special note: the Yugoslavian Ammo tends to have harder primers usually requiring a heavier firing-pin strike.

ONLY RUN FMJ AMMO. The MG-42 SA, MG-42, MG-34, and XMG will not cycle soft point ammo reliably.

Improper, aged, defective, or weak ammo will not work in the MG-42 SA as well as most other 8mm automatics, and should be considered unsafe to use in all firearms, especially automatics. However, you can get away with running just about anything through a bolt action rifle. The M-48 is certainly the most rugged 8mm bolt action rifle on the market.

Specific Ammo to Avoid:
• Anything made prior to 1950
• Turkish
• German WWII (steel case) - The cases are corroded ON THE INSIDE from the powder. Brass is usually OK but has hard primers. Collect this ammo, DON’T shoot it!
• Ecuadorian
• Nigerian
• Anything south of the border or from a ‘third-world’ nation

Reasons to avoid these types of ammunition:
Primers - Primers harden as ammo ages. Excessive primer hardness will lead to dangerous misfires and hang-fires.
Strength - Much of the 8mm ammo currently available was made for bolt-action rifles. This ammo suffers from thin brass and loosely fitted bullets. Simply, the rounds just fall apart or deform during the harsh chambering and extraction in automatics.
Damage - The last batch of Ecuadorian 8mm we received was green due to corrosion. Don’t trust anything from a ‘third-world’ nation. Most never had to make ammo strong enough to deal with the harsh chambering and extraction of an automatic, especially a ‘pusher-type’ MG-42 versus the ‘puller-type’ 1919.
Corrosion - If the ammo is steel cased, it has a much shorter shelf-life due to the corroding of the INSIDE of the case caused by corrosive powder.
Pressure - All automatic weapons rely on the pressure generated from the round to cycle the weapon. In aged, defective, or poorly made ammo the pressures are often inconsistent and will lead to an unreliable cycle. It will result in jamming, case head separations, primer blowouts, and lots of other nasty malfunctions that can significantly damage the gun and the shooter. Just because the sales person says that it ‘runs in my 1919,’ does not mean it’s good and safe ammo.
Dimensions - There’s a lot of poorly made ammo that will not seat properly in the standard 8mm chamber. Headspace is critical in the MG-42 SA. You will notice this in a bolt action where you sometimes have to force the round into the chamber. Poorly dimensioned ammo results in major headspace issues yielding pressures malfunctions listed above.

Bottom line: If you just bought a Ferrari, don’t expect it to run like Ferrari if you fill it with bad gas.

If you’ve stockpiled some 8mm ammo and want to know if it is going to work in an MG-34, XMG, MG-42, or MG-42 SA, please call 301-807-5234.

TUNE YOUR GUN FOR YOUR AMMO: Our guns come with a heavy hammer spring that will deliver significantly more force to the firing pin. However, you do not want to over-strike soft primered ammo for fear of piercing the primmer. Also, you do not want to under-strike hard primmered ammo due to a potential hang-fire. Also, there are different springs that may be used on the firing pin. You must be careful to find the balance in a spring that will resist slam-fire and allow a proper firing pin strike. Simply, you must have it setup so that it does not overstrike soft-primmer ammo, understrike hard-primmer ammo, or slam fire. Our guns are typically tuned for Romanian and Olypic 8mm FMJ. These makes are the most reliable and share the same setting.

Cleaning After Shooting Corrosive Ammo
Most surplus 8mm ammo is corrosive. This means that the primers and/or powder leave a corrosive (salt) residue on the weapon after firing. These salts mix with other residue and moisture and begin to attack the metal and form rust. However, prompt and thorough cleaning immediately after shooting this ammo makes it no different than shooting non-corrosive ammo.

Oils or solvents will not neutralize the corrosive residue and most shooters do not want to run home to make a warm soapy bath for their gun, especially one as large as the MG-42 SA. Diluted ammonia as found in Windex (with ammonia) and other window cleaners will breakdown and neutralize the corrosive residue.
The window clean with ammonia is your first line of cleaning for the bolt head, chamber, bore, barrel crown, barrel sleeve, booster cone, flash hider, and receiver bushing. Immediately after firing the barrel and booster assemblies will be too hot to clean.

• Remove the bolt from the MG-42 SA, disassemble, and spray the bolt head and internal parts thoroughly. Wipe down until dry, then oil with CLP.
• Remove the barrel and booster assembly with hot barrel mitt.
• Spray and clean the barrel bushing and inside of the forward portion of the receiver, wipe down, and oil with CLP.
• Spray and clean the booster assembly (barrel sleeve, booster cone, and flash hider), wipe down, and oil with CLP. After extended use the corrosive residue will be ‘baked’ on to the booster asembly and barrel crown so you will need to be aggressive with a soft brush when cleaning these parts.
• (Make sure the barrel is not hot). Spray and clean the chamber and bore using a cleaning rod and patch. Run a dry patch through the barrel followed by one impregnated with oil. Spray and clean the barrel crown, wipe down, and oil with CLP.

The rest of the MG-42 SA can be cleaned as specified on pages 38, 39, and 40 of the manual.

Revision: 10/5/04: In the recent batch we just completed last month, we had orders for 2 X 2 cal. guns (e.g. guns with both .308 and 8mm setups). All 11 guns ran perfectly in 8mm, and the primers were perfect round indent. However, we went 0 for 2 on the .308. The same guns that fired perfectly in 8mm, had numerous everted/cratered and pieced primers. The feed mechanisms for the .308 ammo worked fine w/ belts and links, the booster worked fine to cycle the gun... we're nearly certain that it's the barrel. After this .308 debacle, we ordered head-space gauges and finishing chamber reamers for .308 to check and adjust the barrels as needed. I don't believe that it can be any other part given that we held everything else constant during single-shot tests. Our headspace gauges show that the chambers are deep relative to the 8mm counterpart..

Overall .308 performance has varied significantly every time we go to shoot them. This largely depends on ammo. We have found that only Hirtenberger and German Military ammo, currently sold through the Sportsman's Guide on MG-3 belts, will work in our guns. The picture below shows two spent casings from the same gun, one fired after the other during single-shot tests. The RG-84 primmer (right) is pierced and shows signs of case-stress. The FNM/Hirtenberger primmer and case (left) are perfect. We continued to fire a complete belt of FNM in rapid-fire without a single malfunction. The primmers and cases showed no signs of deformation. We also had some Spanish-made .308 that showed severe cratering on the primmers

In the past we have been able to rely on the surplus parts. However, I think the suppliers of .308 barrels may be selling us stuff from the reject pile. After all, the US is the dumping ground for the world's military surplus parts and ammo. It is always suspect to see 'current issue' parts from countries like Germany on the US market. Unlike our WW2 and Yugo parts, the MG-3 top covers and feed trays are usually bent and require repair. As of now, the MG-42 SA is a much better gun in 8mm. However, if the gun is run with Hirtenberger/FNM or German Military ammo, it will run reliably and consistently. From here, we will look for more surplus MG1/3 barrels and make some of our own barrels to test.

Revision: 7/9/04: We have found that the vast majority of .308 barrels are headspaced significantly different from the 8mm setup. The 8mm bolt assembly fails to fully lock into the collar resulting in major pirmer deformation, backout, and piercing. By simply modifying the 8mm striker to engage the rollers more firmly upon lock-up, we were able to remedy this problem.

Many customers have asked about .308, and some owners have had their guns converted and tested to run in both calibers. One customer wanted an MG-3 SA. We built it from our standard MG-42 SA by exchanging our parts for his feed cover, feed tray, buttstock, sights, and barrel. Currently, we are refinishing the receiver with a Manganese Phosphate coating as opposed to the standard black oxide finish to complete the MG-3 'look.'

Converting our 8mm MG-42 SA to .308 is not difficult, but can be confusing. This is a quick conversion that can be done at the range, and is exactly the same as the original MG-42 conversion.

The MG-42 was originally converted to .308 after WWII by modifying existing MG-42 parts, e.g. (barrel and feed tray). These guns were designated MG-1. With this setup you run .308 ammo through your 8mm WWII belts. After the war, dedicated .308 feed covers, trays, boosters, and barrels were made for the post-war-production gun, designated MG-3. This setup can use DM-1 .308 belts or M13 disintegrating links (aka M-60 links) but not the WWII belts. The links will spit out the side of the gun approximately 3 feet. When the belt is finished, two links will remain on the feed tray unejected from the gun. You will need to remove them manually.

You use the original 8mm bolt for both calibers. However, while 8mm bolts will extract both 8mm and .308, dedicated .308 bolts will not extract 8mm cartridges. Be careful, some original bolts have had dedicated .308 extractors installed.

The MG-1 setup is not as common as the MG-3 setup on the US market. We have test fired the MG-42 SA in .308 using British surplus and UMC commercial ammo on both DM-1 belts and M13 links. The gun ran great.

Here are some pictures and descriptions of the MG-42 and MG-3 parts used in this conversion on our semi auto:

These are MG-3 parts. Note the differences between the feed trays. Besides the differences in length they are configured for different assault drums. The MG-42 parts are coated black oxide while the MG-3 parts are phosphate coated.

Close-up of the MG-3 parts: The feed cover functions just like the original but it configured to run only DM-1 belts and M-13 links. It also has a spring that pushed the transfer lever to the right of the gun, a feature not on the original. It's typically a good idea to remove this spring to make loading and unloading this closed-bolt semi auto easier.

8mm (top), .308 (bottom): The opening at the top of the booster cone for 8mm ammo is larger than the .308 booster cone in order to compensate for the weaker .308 round (approx. 13mm vs. 10mm). Since the MG-42 operates using the short-recoil of the barrel (e.g. the barrel is forced back approx. .75 in. unlocking the bolt and cycling the gun), there must be enough pressure put back into the system for the gun to cycle properly. Many early MG-42s were issued with 11.5mm booster cones that we later opened to 13mm in order to reduce the cycle rate. When the .308 booster cones are not available, the early MG-42 booster cones work great.

Middle: M-13 (M-60) .308 disintegrating links, Bottom: DM-1 non-disintegrating .308 belt