Grease Gunner Posted September 7, 2018 Report Share Posted September 7, 2018 (edited) Greetings Fellow members especially the ones that shoot!! I have been shooting for decades but semi autos and hardly any full autos.And yes I have had squib loadssome of which were my fault when my reloads either were too weak or I missed charging it with the powder drop. In those instances, the slide didnt cycle and I would stop,get a range rod and knock out the bullet. My question is : How does a squib load result in a bulged barrel when the pressuresare not enough to cycle the bolt and strip a new round from the magazine??? If a partial load can do it, I guess I can experiment and download a cartridge,load the magazine with a dummy round and then the "downloaded round" on top of it.Then when I shoot the downloaded round I will be ableto tell if the bolt comes back and chambers the dummy round. Appreciate any input here. Edited September 7, 2018 by Grease Gunner Link to comment Share on other sites More sharing options...
ron_brock Posted September 7, 2018 Report Share Posted September 7, 2018 In full auto mode, especially with an untrained ear/shooter, it is typically the second (plus) subsequent rounds hitting the squib that ruin barrels. Ron Link to comment Share on other sites More sharing options...
johnsonlmg41 Posted September 7, 2018 Report Share Posted September 7, 2018 It's not the squib that bulges the barrel it's the bullet behind it at full pressure. Subguns are mostly open bolt and because the bullet is lodged in the barrel even the backpressure from a squib is enough to cycle the bolt back far enough and you can't let off the trigger fast enough to catch the next round or multiples behind it. When you're shooting a semi either recoil or gas, there isn't enough recoil from a squib and often the bullet never makes it to the gas port either. Those are just a couple scenarios, surely others will chime in with better answers. When you get to 1100-1300rpm things happen very quickly! Ever hear a piston rod break in a motor? before you can turn the key off, the rod is out the side of the block and the engine is still running? Link to comment Share on other sites More sharing options...
lightguy Posted September 7, 2018 Report Share Posted September 7, 2018 Plenty of bulged barrels out there to keep me from shooting my very nice 1921.Its a shame.On the other hand my WW2 Tommies can have cheap replacement parts installed if need be. From what I have witnessed the shooting experience is about the same...No brainer..... shoot the WW2 stuff and oogle the Colt. Link to comment Share on other sites More sharing options...
jim c 351 Posted September 7, 2018 Report Share Posted September 7, 2018 My question is : How does a squib load result in a bulged barrel when the pressures are not enough to cycle the bolt and strip a new round from the magazine??? GG, You almost answered you own question. Many times the bolt doesn't cycle. When the gun stops firing the shooter plus the bolt back and pulls the trigger creating a bulge. So,----if your gun stops firing best check the bore, even if it means loosing a match. Jim C 1 Link to comment Share on other sites More sharing options...
lightguy Posted September 7, 2018 Report Share Posted September 7, 2018 Also remember the primer has enough energy to push the bullet down the barrel. Once lodged the remaining pressure will push the bolt back just as a much more powerful full force round with an open muzzle would do. Link to comment Share on other sites More sharing options...
Grease Gunner Posted September 7, 2018 Author Report Share Posted September 7, 2018 (edited) Also remember the primer has enough energy to push the bullet down the barrel. Once lodged the remaining pressure will push the bolt back just as a much more powerful full force round with an open muzzle would do.The primer only has enough energy to send the bullet from an inch to a few depending on the bullet and the rifling. But that WONT cycle the bolt back.I have seen squib loads in matches and the shooter goes tap rack bang, chanbers a fresh round and BAM!. Two bullets and a ruined barrel and maybe a slide also . Shooter error not gun error Just like Jim c 351 said" Stop and check the bore" There is no way a primed powderless case can detonate and cycle the bolt. Edited September 7, 2018 by Grease Gunner Link to comment Share on other sites More sharing options...
ppgcowboy Posted September 7, 2018 Report Share Posted September 7, 2018 A primer only load will not cycle a Thompson bolt tried it a few times. Link to comment Share on other sites More sharing options...
OldFalGuy Posted September 7, 2018 Report Share Posted September 7, 2018 (edited) I had my Thompson stored and displayed and for some reason said Yeah lets got shoot.Bulged barrels are on the shooter, not the weapon.I failed to properly clear and clean the heavier than normal storage grease. All it took was one normal round to build up too much pressure in that environment and bulge it did...without a another subsequent round fired. Learned my lesson WELL.Praise da Lawd we have PK and all is good in the world (mine) Mark Edited September 7, 2018 by OldFalGuy Link to comment Share on other sites More sharing options...
TSMGguy Posted September 7, 2018 Report Share Posted September 7, 2018 The trigger is pulled on a squb load. It doesn't feel or sound right, and the bolt doesn't lock to the rear. The shooter pulls the bolt handle back and ejects what looks like a normal fired case. The barrel is not checked for an obstruction. The next full power round then bulges the barrel, as stated above. 1 Link to comment Share on other sites More sharing options...
gijive Posted September 7, 2018 Report Share Posted September 7, 2018 A primer only load will not cycle a Thompson bolt tried it a few times.ppgcowboy, You tried firing a primer load with a bullet seated in the case through your Thompson? If so, how far did the bullet travel into the barrel? Link to comment Share on other sites More sharing options...
1921A Posted September 7, 2018 Report Share Posted September 7, 2018 (edited) Jim c 351 is spot on! The majority of bulged barrels happen when a stoppage occurs AND the shooter fails to remove the magazine and check the bore before firing the weapon again. I watched a shooter bulge the barrel on one of my M1 Thompsons. He was shooting surplus steel cased GI ammunition when the gun stopped on a closed bolt. Before I could stop him, he cocked the gun and fired a burst. The result was obvious, even to the untrained shooter. After removing the damaged barrel we did a cut-a-way on the Bridgeport to see how much damage there was - five bullets and 2 rings Edited September 13, 2018 by 1921A Link to comment Share on other sites More sharing options...
ppgcowboy Posted September 7, 2018 Report Share Posted September 7, 2018 A primer only load will not cycle a Thompson bolt tried it a few times.ppgcowboy, You tried firing a primer load with a bullet seated in the case through your Thompson? If so, how far did the bullet travel into the barrel?I loaded a few primer only bullets with no charge. I used Barry's plated bullets, and each time the bullet entered the barrel just a half inch or so into the lands and grooves. The bolt did not budge. Human error of ejecting the spent caseing and shooting a fully loaded round would have indeed bulges the barrel. I even tried weak loads to see how low it would go to cause a squib and my powder check station would catch it. Even 2.7gr of hp38 or winchester231 would not do it and the powder check was sounding off way before that low. Human error is the main cause of a bulge in my limited knowledge point of view. 1 Link to comment Share on other sites More sharing options...
gijive Posted September 7, 2018 Report Share Posted September 7, 2018 A primer only load will not cycle a Thompson bolt tried it a few times.ppgcowboy, You tried firing a primer load with a bullet seated in the case through your Thompson? If so, how far did the bullet travel into the barrel?I loaded a few primer only bullets with no charge. I used Barry's plated bullets, and each time the bullet entered the barrel just a half inch or so into the lands and grooves. The bolt did not budge. Human error of ejecting the spent caseing and shooting a fully loaded round would have indeed bulges the barrel. I even tried weak loads to see how low it would go to cause a squib and my powder check station would catch it. Even 2.7gr of hp38 or winchester231 would not do it and the powder check was sounding off way before that low. Human error is the main cause of a bulge in my limited knowledge point of view.Thanks for the detailed explanation. Link to comment Share on other sites More sharing options...
MauserMatt Posted September 7, 2018 Report Share Posted September 7, 2018 I had a squib once in my Thompson... It was when my uncle still owned it. It was definitely a one in a million shot of luck that the barrel didn't bulge... My uncle used to like to shoot the cheapest ammo he could find. So we were shooting CCI aluminum cased Blazer when my uncle finished up a magazine and then handed me the gun. This was my first time firing it (I was 15 I believe) so I switched it to semi for my first shot. When I squeezed the trigger, we were both sprayed by unburnt powder! Stopped shooting the gun for the day and when we took it in the house to see what was wrong, my uncle pounded 5 bullets out of the barrel with a cleaning rod! I wouldn't have believed it if I hadn't seen it myself.... We both looked it over very carefully, but couldn't find any damage at all! So he took it out back again and dumped a mag of brass cased Federal without a problem! Now I own the gun and it still has the same barrel as when it was manufactured! And I certainly don't shoot aluminum cases through it! Ha! Link to comment Share on other sites More sharing options...
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