It seems like in the last few months we are having many, many new 1919 owners and also seeing more accidents with out-of-chamber ignitions causing injury and/or heavily damaging guns.
Often, with much over-confidence, I hear a new guy say how many 100's of other guns they have and have built and it comes across that a 1919 is just another gun. I know of few other home builds or semi conversions where you have to worry about critical adjustments and parts "everytime" you go to the range. Also, if you build an FNFal it usually will stay in 308 caliber the rest of it's life or if you build a Garand chances are it will be 30-06 for generations to come. With the 1919 so convertible to 3 different calibers it's easy to mismatch critical conversion parts.
The exact causes of explosions cannot always be determined, but for the new guys here's some potentially injury saving and/or life-saving tips. I'll go ahead and apologize now because it may come across as harsh, but you will probably have innocent folks all around you if you blow up a 1919 so it won't be just you that is endangered...sorry. These guns produce approx 60,000 pounds per square inch of pressure...a 308 round has an approximate surface area of 3.92 square inches so multiply those two numbers and you get a total pressure of 235,200 pounds or roughly 117.6 tons of total pressure. These guns are extremely fun, but they are not toys so listen up...please:
1. If you don't understand the feed and function of the 1919, don't know how to properly load belts or links and can't proficiently disassemble and reassemble it before you go to the range the first time then don't go until you can. See the disassembly tutorial on the home page.
2. If you don't know how to recognize a 308 booster VS a 30-06/8mm booster then don't shoot your gun until you can. Don't trust that your brand new factory made gun has the correct booster. Don't trust that your parts set has the correct booster. See the converting tutorial on the home page.
3. If you're not sure what "headspace" is then do not in any way attempt to fire your 1919. The gun does not come already properly headspaced...even if it was test fired...it may not be correct headspacing for your ammo. Do not use a headspace gage, follow Method 2 of the headspacing tutorial on the home page with one exception; with surplus ammo of every caliber varying so much in quality, whether you're shooting 308, 8mm or 30-06, start at zero headspace or with only one click out from bolt lockup...if the gun runs fine leave it alone. If it gets sluggish or the bolt won't quite close when the gun gets hot then go out one click at a time until it runs good, but never more than 3 or 4 clicks out from bolt lockup. If you change ammo mfgr or lot/date number then re-headspace. Don't mix ammo of different lot/date numbers or mfgr on the same belt. Headspacing is only to compensate for heat building up in the gun so it's best to start with a tight headspace...you can always work out from there. See the * section below taken from another thread for more detailed explanation.
4. While shooting, if the gun "misfires" and you have to manually cycle the bolt, check the cartridge that ejects to make sure it isn't separated. If it is separted then use a broken shell extractor or tap to remove the piece remaining in the chamber.
5. While shooting, if the gun "misfires" and you have to manually cycle the bolt, check the cartridge that ejects to make sure it still has a slug in the casing. If you manually eject a casing with no slug then that means the round didn't produce enough gas pressure to automatically cycle the gun and chances are there's a slug wedged in the chamber or barrel. Take one minute and lock the bolt open and run a cleaning rod down the barrel.
6. While shooting and you find that the bolt won't lock up, don't assume it's headspacing. If a round will not seat there's a good chance that the previous round separated and a piece is still in the chamber. If you keep manually cycling the bolt and putting new rounds into the chamber you may eventually smash the brass remnant flat enough to chamber a live round and lock up the bolt...which will have catastriphic results if you pull the trigger. If the bolt will not close and you're sure the headspace is correct then DO NOT KEEP INCREASING HEADSPACE UNTIL IT WILL CLOSE, check the chamber with a broken shell extractor.
7. When you buy a parts set ensure the barrel and booster are for the caliber you asked for.
If you don't understand any of the terms I just used then study the tutorials on the home page and/or ask questions on this website...you won't find any better source for info and help.
When I first started tinkering with these guns I already had over 60 guns in my collection and I found out real quick that this was an animal of a different breed. I had no clue what a booster was, buffer disks, headspacing, breach block cam, accelerator, lockframe, etc. I also found very quickly that there were plenty of patient guys and gals on this website to help me thru every step of building, owning and operating a 1919...take advantage of this and don't assume anything.
Do you know why the FAA does not regulate home-built ultra-lights too heavily...you don't even need a pilots license? It's because they don't have a high and catastrophic crash/injury rate. Let's keep it that way with semi 1919s and stay below the radar screen by minimizing avoidable incidences.
*XXX, please read that thread I posted for you above and toss the headspace gage and follow method two in the headspacing tutorial with the modifications I mention in the warning thread. You might want to print it out, along with this post, and have your smitty study it before you two decide on how you're going to set up your gun. Even if he is extremely familliar with a GI 1919, the headspacing method using a gage is not reliable due to our semi mods and mix-match of parts and especially using 8mm ammo.
Just so you and he understand my reasoning I'd like to take a moment and explain it. These guns come with two different bolts; 308 (7.62 stamped on top of the bolt) or original 30-06. The primary difference is that the T slot in the front of the bolt that the round slides down is deeper on a 308 bolt because the case rim is slightly thicker than a 30-06 round. A 308 round is a bit too snug in most 30-06 bolts and due to the thicker rim the rounds tend to hang up in the T slot. The ideal would be to have two bolts and use an '06 bolt to feed '06 and 8mm rounds and a 308 bolt to feed 308. Most all of us use a 308 bolt because it will feed all three rounds.
However, here's the down side and it only takes a little care and understanding to shoot crap 8mm with a 308 bolt. Because the 308 T slot is deeper the 8mm rounds have "slop" in the slot which screws up trying to use a gage to headspace it. Because the 8mm round has a gap in the T slot there is automatically some unintentional headspace built into the arrangement. Just to clarify here, headspace on a 1919 is not like any other weapon and it is defined as the distance from the rear of the barrel to the face of the bolt...not the face of the T slot ears, but the face of the bolt where the firing pin hole is located. The reason for adjustable headspace on a 1919 is to allow for heat expansion as the gun gets hot. After the bolt has picked up the round and moved forwards into the chamber if the case head is seated back against the bolt face there will be slop in front of the case rim which means the round is probably not quite seated against the shoulder in the chamber...especially on a cold gun. There is quite a few thousandths of slop where an 8mm case will move in the T slot and that equates to a click or two on the headspace. Unfortunately, the front of the T slot ears hit the rear of the barrel and not the true bolt face that the cartridge head rests on. Because of this you can't truly measure and start at a point where the round is properly and firmly seated in the chamber and firmly in place back against the bolt face like on a bolt action gun....due to the slop the round may be seated or it may not be by a few thousandths.
Typically you would go 2 to 4 clicks out on the headspace adjustment after the bolt is locked up using 308 ammo in a 308 bolt. Because of the gap in the T slot with 8mm I only go one click out and see how the gun runs. One click is usually very tight, but with the slop it has proven in my guns to be dead on. If after the gun gets hot it starts to slow down or the bolt won't quite close then go out one or more clicks until it runs right.
At this point, with the 8mm Yugo I'm going to start running it at 0 clicks to start with just to see if it will run okay...there might be enough slop in the T slot for it to run good at 0. The tighter the headspace you can run the better.
Others may disagree with my opinion on using gages, but I've set them with a gage and then without and have found the gage to produce too loose of a headspace. I love to go "by the book", but in this case "the book" isn't applcable with the way we're using a 308 bolt as a universal caliber bolt. If I were shooting 30-06 with a 30-06 bolt or 308 with a 308 bolt I would use the gage because that is the combination the gage was designd for and not for shooting 30-06 and 8mm that slop around in a 308 bolt.
I guess I'm on a crusade to try and prevent any more blown top covers using 8mm and the above headspacing practice is the means to my madness. Please forgive my pontificating.