What if you fire a shot with the bolt half closed?

[J_idaho]

Thanks for all the input. It was just a thought that maybe the bolt was not closed all the way. I really feel it’s unlikely that the case was over charged. I load 25-30 rounds at a time for this hunting rifle. There where 19 left, and I just pulled all the bullets and weighed each charge. All of them exactly 49.0 gr. I guess I’ll never really know exactly what caused this but a good lesson to keep diligent in my process.

I measured the neck in the case and it’s .260 slightly larger the the 4 previously fired rounds that measured .252. This batch of brass is neck turned. I shoot non neck turned fire forms and they chamber fine. I don’t think neck turning makes a difference in this chamber so I don’t always do it. The OAL of the case with the blow out is 2.027 while the others are 2.025 and 2.0245

No pics of the bolt. It’s already at the gunsmith being rebuilt. The bore scoped out just fine. Here is a pic of the brass.
View attachment 1528095
Thanks for the help.

No carbon ring?

 

[Burnt Powder]

This is a proof positive method to determine over pressure. Veron Speer did considerable research on this. However, there are some issues one needs to be aware of using this method.

First, you need a baseline measurement before you load a case. Secondly, you need a special micrometer either a ball or knife edge (preferred) to obtain a precise measurement on the head. Third, you need a micrometer accurate to .0001".

The research showed that excessive head expansion will often reveal itself in loose primer pockets. However, the obvious goal is not load anywhere near that kind of pressure situation.

And this technique is only kind of reliably accurate using new, unfired brass. Once it’s been fired it’s a SWAG. Different aloy brass responds differently to the same pressure exposure. Different brands and different lots will react differently. Now if you get a .005 swelling you are in trouble. Actually with large capacity, i. e. Over bore cartridges, and they have typically large quantities of powder in them, with short powder charges you can experience detonation exponentially raising chamber pressure. How do I know? Been there, done that. Those old Ruger 77 actions are a tough SOB!

 

[YBPS]

No carbon ring?

No. I keep it clean. Smith confirmed bore is good.

 

[Pres100]

Do you load for any other calibers/rounds or just this one?

 

[pdog06]

Possible the primers you used had a pistol primer mixed in the batch? Or just a bad primer or a primer not seated properly?

 

[YBPS]

Do you load for any other calibers/rounds or just this one?

I have many others and consider my self pretty experienced hand loader. Been loading for 20 years and I shoot ALOT.

 

[YBPS]

Possible the primers you used had a pistol primer mixed in the batch? Or just a bad primer or a primer not seated properly?

I don’t own any pistol primer and I’m sure it was seated correctly. If it was a “bad” one that could explain some things. Was a CCI BR-2

 

[K22]

And this technique is only kind of reliably accurate using new, unfired brass. Once it’s been fired it’s a SWAG. Different aloy brass responds differently to the same pressure exposure. Different brands and different lots will react differently. Now if you get a .005 swelling you are in trouble. Actually with large capacity, i. e. Over bore cartridges, and they have typically large quantities of powder in them, with short powder charges you can experience detonation exponentially raising chamber pressure. How do I know? Been there, done that. Those old Ruger 77 actions are a tough SOB!

The Speer research was based on virgin cases from the same lot fired from the same rifle. They also confirmed that different results can occur result from different brands and lots of cases.

They began their pressure evaluation based on once fired cases* presumably allowing for the virgin cases to fire form to the rifle chamber. They considered an average expansion of .0003" with no individual reading exceeding .0005" as acceptable (note that is 4 decimal places). They also stated that due to work hardening, they only used this test method for 3 firings to avoid false readings. But that generated enough data to evaluate the pressure of a given load in a given rifle. Also, the readings had to be taken at the same point of the case accomplished by marking the measurement location.

As you can see, this takes more than average skill, equipment and patience to use the method to achieve reliable results. I have found that using a combination of other indicators such as hard bolt lift, ejector marks on the case rim, and primer condition when considered as an aggregate can be a useful indicator of high pressure.

I only ever had one pressure surge condition in 50+ years of reloading and it was using H380 in a 22 250 in 90+ degree weather hunting varmints. It exhibited all three of the aforementioned indicators. It is one of the reasons I stopped using ball powder.

*personally, I like to take a measurement of the virgin case before firing just to give me a baseline of how the case forms to the rifle chamber. As Speer noted, the pressure evaluation starts with a once fired case.

 

[tactserv]

I had an issue today with an explosion in the chamber resulting in a damaged bolt and some ringing ears. It was very loud….even with the suppressor that makes this whisper quiet.

The gun smith told me he would guess there was a barrel obstruction, but I know there was not. I had just shot it 5 minutes before. He scoped the barrel and it’s fine, but my bolt needs work and may need to be replaced.

It’s REM 700 and what I think happened is the bolt was not shut all the way. I looked my neighbors rem 700 and I was extremely surprised how you could still drop the firing pin with the bolt only half closed.

The extractor, broke, and it blew the primer. I didn’t even find a pice of it.

The bullet hit basically perfect on paper at 100 but it was about 150 FPS slower than my 3400 average.

I have shoot 350+ handloaded rounds with this load. Curreny shooting 49 grains and have shot up ro 51.3 with zero issues. Gun shoots so good I want it to last to I’m back at 49grns 3400 fps rather than 3650 with 50-51 grains.

Case is a 22-243AI with 75ELDM

So… let’s just say I didn’t get the bolt closed all the way… not because the round wouldn’t chamber, but I’m just so used to an easy bolt drop I just messed up. Does this sound like what could have happend? Anyone experience this?

"So… let’s just say I didn’t get the bolt closed all the way, and it goes off?" BLAM ! If the cartridge doesn't fully chamber, and the bolt handle does not rotate down fully - don't try to pull the trigger. Doing that invokes the Natural Selection law. Just saying . . .

 

[davidjoe]

I had an issue today with an explosion in the chamber resulting in a damaged bolt and some ringing ears. It was very loud….even with the suppressor that makes this whisper quiet.

The gun smith told me he would guess there was a barrel obstruction, but I know there was not. I had just shot it 5 minutes before. He scoped the barrel and it’s fine, but my bolt needs work and may need to be replaced.

It’s REM 700 and what I think happened is the bolt was not shut all the way. I looked my neighbors rem 700 and I was extremely surprised how you could still drop the firing pin with the bolt only half closed.

The extractor, broke, and it blew the primer. I didn’t even find a pice of it.

The bullet hit basically perfect on paper at 100 but it was about 150 FPS slower than my 3400 average.

I have shoot 350+ handloaded rounds with this load. Curreny shooting 49 grains and have shot up ro 51.3 with zero issues. Gun shoots so good I want it to last to I’m back at 49grns 3400 fps rather than 3650 with 50-51 grains.

Case is a 22-243AI with 75ELDM

So… let’s just say I didn’t get the bolt closed all the way… not because the round wouldn’t chamber, but I’m just so used to an easy bolt drop I just messed up. Does this sound like what could have happend? Anyone experience this?

So, the bolt lugs either stay in front of the receiver lugs when fired, securing the bolt 100%, or they do not.

If the lugs are only partially engaged, and you managed to fire the gun, the contact surfaces will undergo more pressure, but that doesn’t mean the bolt moved back toward you any more than if they were fully engaged. It also does not mean there was more headspace.

If the bolt didn’t move backward forcefully and basically unrestrained, (unmistakable) then it didn’t move at all for all intents and purposes. In theory you might be able to depress tiny triangular indentations of extremely shallow depth into the receiver lugs if you didn’t have a ramp such that your bolt permitted pin fall with almost no closure.

If the loud, damaging round was fully contained, the resulting damage was not because the headspace grew larger than expected. Headspace is all the cartridge can know. How much or little lug contact exists is impossible to discern inside the chamber. This reasoning does put it all on the load or an obstruction.

Bad brass that expanded or ruptured or just plain excessive pressure with good brass, that did that to the brass could explain it.

Are you resizing brass by a very significant amount? There is probably some level of resizing that is so extreme, that the firing pin “will just barely” fire the round, but the headspace is truly too big for the chamber by any standard and the brass cannot handle the stretching permitted.

 

[BoydAllen]

As far as firing on a partially closed bolt goes, it can be tested safely. Prime a case and give it a try. Those that have said that the case will tell the story as far as the pressure of the load are correct. If the diameter of the head of the pictured case is compared to other cases fired with the same load, and the fit of primers, an over pressure should be obvious.

 

[RabbitSlayer]

I had an out of battery discharge on a dirty 1022 with match chamber. It caused the unsupported part of the case to be blown off and the supported part to still be stuck in the chamber. Can't remember for sure, but I think it resulted in a stuck bullet too... I don't actually know, but it seems to me the round would have been not fully in the chamber and that unsupported part would expand under pressure and fail.

 

[wildcatter]

How deep are you seating you bullets, and is there any donut ring in the bottom of the neck?

I don't understand 252 nk then 260, that's a huge differance, also have no idea the nk dimension of the chamber?

 

[wildcatter]

I had an out of battery discharge on a dirty 1022 with match chamber. It caused the unsupported part of the case to be blown off and the supported part to still be stuck in the chamber. Can't remember for sure, but I think it resulted in a stuck bullet too... I don't actually know, but it seems to me the round would have been not fully in the chamber and that unsupported part would expand under pressure and fail.

A blowback breach on a 10 22 is not supported but on a bolt action it is. That is a totally different breach system.

 

[Plumsask]

Iv shot this load +350 times and had zero issues and have shot it ALOT hotter. I really just don’t feel like the load was the issue. But if the bolt question is not possible, I guess it could be. Iv just loaded thousands of rounds and I have a process and never had any problems.

How do you even fire with the bolt not closed ? Everything need to be in place.

 

[Mulligan]

Out of battery detonations do happen. I have seen one example of this happening and know of another. I have one of the rifles in my possession. One a 30-378 Wby. The gentleman really screwed up his hand when the bolt came to the rear. The bolt handle went through the webbing between his thumb and hand.
The setup. He is known to shoot very HOT loads. After examination it was determined the firing pin had NOT touched the primer. So how did it detonate? The case head had 6, count'em 6 ejector pin marks on it. I'm sure the primer pocket was used up and then some being Norma brass. Primers appear benign but really they aren't. My theory and it's only a theory is somewhere between the loading bench and the range the primer had backed out of the primer pocket. Allowing powder to get between the primer and the bottom of the primer pocket. When he ham handed it, trying to force the bolt closed the primer was reseated and the anvil was pushed back into the priming compound. CAAABOOOM. Or the few grains of powder detonated from compression.

The other rifle I didn't see but when it requires a new bolt stop and a trip to the ER something similar probably happened.

Now in this case I think there was something screwy going on with the load.

YBSP,
Just for the hell of it run your finger down the outside of the barrel. If there was an obstruction, even on HV contour barrels, you'll be able to feel the bulge. The ones I've seen still shot surprising fine.

I have read every post on this thread several times.

I did not know out of battery ignition was even possible on a bolt gun.

Dave, thanks for this post.

OP, thanks for asking the question, I learned a LOT.

CW

 

[YBPS]

"So… let’s just say I didn’t get the bolt closed all the way, and it goes off?" BLAM ! If the cartridge doesn't fully chamber, and the bolt handle does not rotate down fully - don't try to pull the trigger. Doing that invokes the Natural Selection law. Just saying . . .

The cartridge chambered just fine. I size all my brass then run each piece through the gun to make sure the bolt drop perfect. If it’s not I measure the brass, to see what’s up and most of the time just toss it. It was just a thought after the”blam” that possibly I didn’t get the bolt all the way shut.

If you have a Remington go close the bolt just so you can barely feel the lugs engage and pull the trigger. It supprised me how little of lug engagement you need to make the firing pin drop.

 

[YBPS]

How deep are you seating you bullets, and is there any donut ring in the bottom of the neck?

I don't understand 252 nk then 260, that's a huge differance, also have no idea the nk dimension of the chamber?

seated the boat tail right at the neck shoulder junction with a K&M arbor press / Wilson die. No noticable doughnut on any of my cases. Most pieces get fire formed then shot 3 times and tossed.

 

[YBPS]

So, the bolt lugs either stay in front of the receiver lugs when fired, securing the bolt 100%, or they do not.

If the lugs are only partially engaged, and you managed to fire the gun, the contact surfaces will undergo more pressure, but that doesn’t mean the bolt moved back toward you any more than if they were fully engaged. It also does not mean there was more headspace.

If the bolt didn’t move backward forcefully and basically unrestrained, (unmistakable) then it didn’t move at all for all intents and purposes. In theory you might be able to depress tiny triangular indentations of extremely shallow depth into the receiver lugs if you didn’t have a ramp such that your bolt permitted pin fall with almost no closure.

If the loud, damaging round was fully contained, the resulting damage was not because the headspace grew larger than expected. Headspace is all the cartridge can know. How much or little lug contact exists is impossible to discern inside the chamber. This reasoning does put it all on the load or an obstruction.

Bad brass that expanded or ruptured or just plain excessive pressure with good brass, that did that to the brass could explain it.

Are you resizing brass by a very significant amount? There is probably some level of resizing that is so extreme, that the firing pin “will just barely” fire the round, but the headspace is truly too big for the chamber by any standard and the brass cannot handle the stretching permitted.

Good info. Thank you sir.

 

[rwj]

If you have a Remington go close the bolt just so you can barely feel the lugs engage and pull the trigger. It supprised me how little of lug engagement you need to make the firing pin drop.

I checked my Rem 700 (2012 vintage short action) and it will release the firing pin once the cocking piece is no longer in its detented position and is being retained by the trigger sear.

However, as noted earlier in this thread by @Alex Wheeler, the firing pin fall is limited by the cocking piece contacting the bolt feed ramp. Until the bolt is rotated to nearly closed, the firing pin does not protrude from the bolt face and can not contact the primer.

To your knowledge, has the bolt in your Remington been modified?