Gas port safety on bolt action rifles?

[MCMXI]

A work-related issue came up this morning that had me rummaging through my gun safes this afternoon to see which of my centerfire rifles have gas port safeties in the receiver. If they did have one, I checked to see where it's located relative to the bolt face. Interestingly enough, my AI AW that came in .308 Win doesn't have a gas port in the receiver whereas my AI AWMs in .300 Win Mag and .338 Lapua Mag do have a plugged gas ports. The AI AWMs share the same receiver so if it's needed for the .338 LM it might not be needed for the .300 Win Mag but not sure. None of my AR15s or AR308 have gas ports in the receiver but my Kimbers, Lee-Enfield No4 Mk2, Savage 16 and Remington 700 all do.

So is this a feature that has been added just because or is it an essential safety feature for some designs? Was the Mauser '98 the first receiver with a gas port safety? Do you know of other designs that don't have a gas port safety in the receiver, particularly bolt action rifles?

Thanks.

 

[Goosey]

SAKO 75 and 85 dosn't have a gas port in the side of the receiver. Weatherby Mark V also lacks one. Browning A Bolt and X Bolt lack it as well IIRC. Just to name some. Most have some other way of venting or containing gas, for example down the magazine well, etc.

 

[LoonWulf]

Abolt 2s dont have them. The rest of the rifles I have do.

 

[sage5907]

I have had and witnessed some experiences with gas ports in bolt action rifles. One of the most important features of the Mauser 98, FN Mauser de luxe, and FN Mauser supreme actions is that there is a large ring on the front of the bolt shroud that deflects gas sideways and away from the shooters face. What happens is when a primer ruptures or a case fails most of the gas from the chamber is directed rearward through the bolt channel. The Model 70 Winchesters do not have this ring so gas does get into the shooters face which reinforces the need for the shooter to wear glasses when shooting. To me there is a question about how much the gas port on the side of the receiver helps but it surely helps some. A friend was shooting a Remington 700 type rifle recently with a detachable box magazine. A case failure directed most of the escaping gas rearward and downward through the magazine box. The magazine box was blown out of the bottom of the rifle with damage to the surrounding area. These problems reinforce the need to use safe reloading practices.

 

[edwardware]

A work-related issue came up this morning. . .

If you can elaborate, we're interested (at least I am)!

I've had 4-5 failed primers in bolt guns, but none were any more than a slightly odd 'ppfft' sound on top of the usual boom. All my bolt guns have ported receivers and bolts.

 

[MCMXI]

If you can elaborate, we're interested (at least I am)!

I can't go into specifics but if you've worked as an engineer in an industry where you're in a constant struggle with product managers, sales, industrial engineering, CEOs, CFOs, operations and others, you'll be familiar with the push for faster and cheaper. One issue is when there's an initiative within IE to make a part using a different process in order to reduce cost and increase output. The problem is when the new process can't create key features as designed and there's pressure to change those features to accommodate the new process without any regard or understanding of the implications of those changes.

Thanks for the feedback, it's very helpful.

 

[edwardware]

I can't go into specifics but. . . there's pressure to change those features to accommodate the new process without any regard or understanding of the implications of those changes.

Nearly every week. . . I understand perfectly.

 

[Nature Boy]

if you've worked as an engineer in an industry where you're in a constant struggle with product managers, sales, industrial engineering, CEOs, CFOs, operations and others, you'll be familiar with the push for faster and cheaper. One issue is when there's an initiative within IE to make a part using a different process in order to reduce cost and increase output. The problem is when the new process can't create key features as designed and there's pressure to change those features to accommodate the new process without any regard or understanding of the implications of those changes.

It's what I do for a living

 

[CarJunkieLS1]

I agree gas ports are essential in bolt action rifles. The gas will go path of least resistance so if there isn't a "relief" somewhere where will it go and what are the implications.

I've had a pierced primer before and I feel like the gas port definitely helped in not making the damage any worse than a slightly etched bolt face and a change of underwear lol. If that gas relief hadn't been there my guess is possibly the bolt may have came rearward hitting me in the eye/cheek area. That particular rifle doesn't have a 1 piece bolt.

 

[Walkalong]

I read about them when I was a youth, so the idea has been around awhile. What all actions did and didn't have them I don't know. I mentioned it here once and was told there was no such thing.

Tell them it's a freaking safety issue, just do it.

My FN SPR.

 

[Walkalong]

Sako L579 .308

 

[NIGHTLORD40K]

SAKO 75 and 85 dosn't have a gas port in the side of the receiver. Weatherby Mark V also lacks one. Browning A Bolt and X Bolt lack it as well IIRC. Just to name some. Most have some other way of venting or containing gas, for example down the magazine well, etc.

I believe the Weatherby is supposed to direct gas down the firing pin channel and out through those holes in the bolt. Also the reason they use the fully shrouded striker.

 

[MCMXI]

@Walkalong , thanks for the great photos, and feedback from everyone. I have to wonder if some companies added gas ports in the receiver without any testing and merely because some other company had them. I also wonder if the diameter and location of the port or ports is a best guess or based on actual test data or even aesthetics. As I mentioned in my first post, my AI AW that came in .308 Win doesn't have a gas port in the receiver. Most bolts that I've seen have one or more ports to help direct gas away from the shooter as it enters the bolt body. You can see two ports in the Kimber 84M bolt below. With the cocking piece threading into the bolt body the way it does there's a fairly good seal at the rear, and combined with the ports in the bolt, gas shouldn't get back to the shooter via the inside of the bolt.

 

[kozak6]

The Mosin Nagant lacks gas relief holes. Apparently, the multi-piece bolt helps disperse some of the gasses, but some of it still gets channeled back into the shooter's face.

 

[Slamfire]

o is this a feature that has been added just because or is it an essential safety feature for some designs?

In my opinion, the so called "Hatcher Hole", the larger receiver hole on the left side of the receiver, in addition to the small extractor hole on the right, are there mainly for show. Based on the size, location, and gas pressure, they are too small to effectively vent a gas burst.

The Hatcher hole did not prevent this receiver from rupturing.



Nor did the small extractor gas port hole keep this receiver ring together.




These "vestigial" holes are there to make you feel better. Sort of like the Door Close buttons on elevators:

As mentioned above, the Door Close button is there mostly to give passengers the illusion of control. In elevators built since the early '90s. The button is only enabled in emergency situations with a key held by an authority.
https://gizmodo.com/380741/things-you-dont-know-about-modern-elevators

By the way, mirrors next to elevator doors are there so you can admire yourself, and thus, gazing at your perfection, take your mind off how slowly the elevators are traveling.

I think this would have made a better gas vent, though not a gas block, in the M1903 action:



In terms of gas venting, the M1903 is horrible, you can tell examining a 03 receiver that it really was not a consideration. And there are a number of modern actions which you can examine and come to the conclusion that they are no better.

I examined my FN Deluxe Mauser, it does not have any of these illusory receiver gas vent holes. Mauser designed real gas venting features in this design. The gas vent holes in the M98 bolt are real and will work. Firstly, they are rather large. Gas goes down the firing pin shaft, and pushes the firing pin back into the cocking piece. You can see the flats and the functions of those firing pin flats in these pictures:



Firing pin bottomed out.



You can more or less see the firing pin here, though it is not fully back, but gas will vent down into these bolt vent holes and go down the magazine.



There are more gas blocking feature on the M98. The safety lug goes beneath the bolt and blocks gas flow under the bolt.

The bolt shroud blocks gas going down the left receiver rail, exactly as this late model M70 bolt shroud.



This feature is not in pre 64 and most push feed M70's. You can more or less see the bolt shroud on the M1903, and that it is inside the receiver ring. It will not block gas. Gas , powder particles, brass particles, will go straight down the firing pin shaft and down the left receiver rail, right into your eyes.



Always wear shooting glasses! Always.

I really like the gas baffling of the Savage M110, I don't have any pictures, but you can examine the action and see how the designer, Nicholas Brewer, blocked off gas flow around the bolt and firing pin shaft.

Stuart Ottesen did an outstanding job of looking at gas handling in his books:
The Bolt Action: A Design Analysis, Volumes I and II (1 & 2)

https://www.amazon.com/Bolt-Action-Design-Analysis-Volumes/dp/B005KCQOW6/ref=sr_1_2?s=books&ie=UTF8&qid=1519228827&sr=1-2&keywords=The+Bolt+Action:+A+Design+Analysis

I need to mention that the Mike Walker or Remington Arms, built a very strong and safe action that effectively blocks gas at that source. One feature that was altered, somewhere in the 1990's, was that Remington made the firing pin hole larger, so primers would cup around the firing pin tip, at normal pressures. A number of shooters thought their loads were too hot, because they were cupping the primer, but, in actuality Remington did this to make the primer a better gas seal.

John Garand's design does a good job of protecting shooters from gas release. His action blows gas up, well away from the shooter's face, and down into the magazine well.



The receiver heel is a gas block. This is for those who like to bed the entire receiver, don't. Leave an air gag under the rear sight knobs. This is a gas vent port.

 

[MCMXI]

@Slamfire , thanks for your excellent post.

You can more or less see the firing pin here, though it is not fully back, but gas will vent down into these bolt vent holes and go down the magazine.

I wondered about this too, but when the bolt is closed the gas ports vent to the 3 o'clock position relative to the shooter. I would have thought that the bolt vent holes would be pointing straight down into the magazine when the bolt is closed. The Kimber bolt above does the same thing with the gas ports blowing gas into the left bolt raceway rather than down into the magazine.

 

[Slamfire]

@Slamfire , thanks for your excellent post.



I wondered about this too, but when the bolt is closed the gas ports vent to the 3 o'clock position relative to the shooter. I would have thought that the bolt vent holes would be pointing straight down into the magazine when the bolt is closed. The Kimber bolt above does the same thing with the gas ports blowing gas into the left bolt raceway rather than down into the magazine.

You are right! Just checked a Yugo M48. The gas ports blow gas on the left receiver rail. Actually, not bad as all military Mausers have a clip slot hole, should make a good gas vent just due to size. Then, by not blowing out the right side, you are less likely to blow the extractor off. I do think the floor plate is coming off if the case head fails. Mauser lost an eye, don't remember if it was M96 era, or automatic rifle era, but it was due to a gas blowback.

Before I knew that ammunition pressures increased with age, I had lots of pierced primers with surplus 8mm. Lots of gas release down the firing pin shaft. The cocking piece would pop out and strike my thumb, also blocking gas flow.

 

[dieselchief]

slamfire, my m70 win has the lip on the cocking piece as previously shown in your pics, also has a hole in the receiver in line with the bolt head like walkalongs, and two huge holes in the bottom of the bolt body.....

 

[Slamfire]

This is a pre 64 bolt. Actually it is a Widner's pre 64, my recollection it is close enough. Not much in terms of gas vent ports.


This is a FN PBR, gas ports in line with the magazine box.



I have had pierced primers in a M70 Classic, USAR rifle, gas goes right down the firing pin shaft into your eye. Don't know if the PBR will actually be all that much better even though it has gas ports.

Some late model M70 blow up pictures. Something split the stock.



Gas did go down the magazine box





Almost blew the extractor off



At some pressure level, even steel can't hold together.

 

[LoonWulf]

My 6x47rem 700 will pierce primers if any of the softer ones are used on loads over about 50kpsi (i NEED to get that bolt bushed). When it does youll feel a puff of gas on your face i assume is coming straight out the back of the bolt. Ive had my hand right infront of exhaust ports on the side when its done it and never felt anything.

 

[Hummer70]

As OP pointed out there is no ports in the AR. When an AR has a case failure the case head turns plastic and the gas escapes from all the way around the bolt and back into the upper/lower receivers.
We had them come in about every five months. Strangely enough they never came in with the case that caused the failure which was a red flag that something was amiss. My most memorable one was one let go bowing out the upper and lower receiver and the report said the magazine was inserted into the shooter's forearm.

Initial examination showed all the lugs on the bolt were intact with no deformation. Same for barrel extension. A look down the barrel indicated barrel was obstructed but there was no bulge anywhere on the barrel. It was a M16A1 and had the small thin barrel.


Along with the rifle was a nastygram from a Maj who accused us of fielding a POS to his people and inferred we did not care.

I took the rifle to industrial X ray and it took about three trys before the power as adjusted to only look as far as the center bore line. There is was, a cleaning rod jag with a patch on it had been inserted into the muzzle at the range and upon removal the jag/patch and stayed in bore back adjacent to the throat area. There was a 55 gr. M193 projectile stopped nose to nose with the jag.

Obviously when the round fired it moved a short distance and engaged the jag/patch combo and all the while the pressure was building in the case to the point that the case failed at the rear below the web area. Cases do this about the 110,000> lb range and it let go.

I took the rifle and X ray back to the office and showed it to the Chief and he immediately wrote the major a letter saying in effect, "we appreciate your concern for getting the best weapon possible for your people which is what we strive to do however in this case we feel that had your people been instructed properly in weapons inspection this failure/injury could have been avoided--see attached X Ray."

That was the worst M16 failure I observed as all the others were similar ( bowing of upper and lower receiver) to a much lesser degree. To my knowledge there has never been a catastrophic (lug failure) on any M16 or barrel socket failure as the case heads fail first. Most are charged to case failures as everything else checked out fine .

I have never heard the discussions you outlined at the Army Small Cal Lab but am not surprised to learn they are likely to happen in the industry. I had a senior engineer at a vendor plant in the New England area express the same concerns/complaints to me.

It is not so much a design problem because you can have the best design and the gorillas on the production floor will mess it up for you. CIP I was walking around a vendor plant as management knew my background and gave me free walkabout privileges and the guy that trained me had warned me that the folks on production floor are not direct descendants on John Browning, Sam Colt, Smith and Wesson, the Mauser brothers etc.
.

I stopped and asked this guy what he was making and he had no clue. It was a major part and that is all I need to say as if I identified the part it would be evident who the vendor was.

Then there was a vendor who was making M14 barrels and first article inspection series was performed at Rock Island and they were Rockwell dinged and came up dead soft way out of range on like five out of a hundred. That led to DECAS notification and the FBI got involved. Bottom line was a couple of production floor types were shooters and they wanted extra barrels for their M1As so they substituted cold rolled stock for 4140 and of course the CNC tooling went along it merry program and turned them out and you had the old "a barrel is a barrel is a barrel" logic. Fortunately none of those barrels were fielded so no injuries.

I have seen a M1911A1 barrel with no rifling. I have seen a M1911A1 slide certified proof fired that had never had the striker opening fabricated.

I have seen a Mosin Nagant that was never rifled.

I was on a malfunction investigation at a vendor plant with four others and we were led on a tour of the facility and I got lost quickly and started walking down the lines and observed the workers and this one guy was taking a part to a 4" belt sander to remove a burr left from stamping. I made a mental note of it and we found out the cause of what we were sent for and left. Two weeks later we got reports that there was another failure in the same assembly that had a crack form and I was able to identify the cause without leaving my desk.

I also served as a Contracting Officer Tech Rep on a contract and caught the vendor making short cuts and not proofing correctly and no MP following. My management covered it up along with other things and I was not going to be part of that. Things happened and I left and I wound up testifying before Congress.

Springfield and Enfield barrel failures are not unique. There is a warning in Hatcher's notebook about Springfields and P O Ackley when he taught at Trinidad told his students to never rechamber a gov't barrel for a magnum and one of his students thought he knew more than Ackey and opened a 1917 Enfield barrel into a 300 Win mag. The barrel had a classic failure and sheared all four fingers on students left hand. The guy I worked with at Picatinny in Product Engineering told me about it. He was in the same class.

All the Pattern 14 barrels are suspect and all productions were known to crack starting at the muzzle and moving backwards.

I reviewed test results of a number of 95 mausers that were purposely fired with issue cleaning rods in bore. It was amazing of how well the receivers held together.

We also had incidents of troops dropping M14 cleaning rod sections down the barrel and launched them with blanks. Not advisable haha.

I feel for your situation but if it is any consolation you are not alone.

 

[Slamfire]

Springfield and Enfield barrel failures are not unique. There is a warning in Hatcher's notebook about Springfields and P O Ackley when he taught at Trinidad told his students to never rechamber a gov't barrel for a magnum and one of his students thought he knew more than Ackey and opened a 1917 Enfield barrel into a 300 Win mag. The barrel had a classic failure and sheared all four fingers on students left hand. The guy I worked with at Picatinny in Product Engineering told me about it. He was in the same class

You are da man!

James Howe, The Modern Gunsmith, Vol II, 1941 Supplement, "Gun Barrels, Their Steels and a Safety Analysis" gives a warning that the M1917 Enfield barrels were not appropriate to 300 H&H conversions. He calls it "the caliber 300 magnum"

People today assume the process technology of WW1 is the same as today. It was not. Steels, especially war time steels, were full of slag and inclusions.

 

[792mauser]

I love the gas handing of the 98 mauser.
Just saw a greyish cloud come out of the wrong end of the receiver.
The head of the steel case had completely removed itself from the body.
I barely got any gas anywhere near my face.