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Gunsmithing Case Neck Sealing
- Thread starter Edds
- Start date
It scares me to think this is possible unless it's a Weatherby. I doubt it would happen with a full charge. I have seen shoulder collapse in a 280AI with a fire forming load but the throat wasn't long.
If the throat is that long nothing good can come from it. Some Wbys shoot but they are exceptions to the rule.
I can think of one good thing that could come from it. I have read hundreds of comments about the importance of aligning the bullet with the bore. I can't think of anything that would align it much better than having freebore that was .0003" larger than the bullet diameter and the same length as the bullets bearing surface.
What are some of the bad things?
What are some of the bad things?
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Dang Edds, you're killin' me. I guess a funnel would work. Some wbys do shoot. I am a bad example because I neck size and rely on the case to align the bullet.
The "bad" is the disruption of the jacket when it hits the throat. Not much of a prob with low vel /slow twists.
The "bad" is the disruption of the jacket when it hits the throat. Not much of a prob with low vel /slow twists.
That would probably work well for a little while, but what happens when that throat gets burned out and is now 0-003"-0.005" larger than bullet diameter? Then you have a loose throat that's a mile long.......
I've had exceptional luck with a long throat chamber in magnums with heavy bullets. Trick is using the right bullet.
Berger tend to want some land contact. Sierras and lapua scenars not so much.
Both bore riders and conventional throats have worked well when used with the right projectile.
Berger tend to want some land contact. Sierras and lapua scenars not so much.
Both bore riders and conventional throats have worked well when used with the right projectile.
Blow by is usually a byproduct of a dirty gunked up chamber and/or lube left on the brass. Low chamber pressure by itself shouldn't cause it. How many of us shoot subs with no problem.
Isnt sub-sonic ammo done with a different powder usually a smaller amount of a faster burning powder? If your case neck and shoulder are getting a heavy amount of sooting it is telling you the brass isnt expanding and sealing in the chamber. I believe this causes several problems one of them is its beating the crap out of your bolt lugs as well as having bad effects on the neck of your chamber as this part isnt really supposed to see that kind of heat and fire from powder burn.
My 308 sub load is 9.8 grs. of Trailboss and 170 Gr. Hornady 30-30 bullet @ 1000 FPS That's going have less pressure than a 175 SMK @ 2600 FPS. In 37 years of shooting I have never seen necks seal off completely. If you have soot on the shoulder I would investigate what's going on. The fire and trauma occur in the barrel not on the neck. The only side affect is carbon build up in the neck. A few twists of the bore brush when cleaning usually takes care of that.
Please explain "beating the crap out of your bolt lugs"
Please explain "beating the crap out of your bolt lugs"
Beating the crap out of your bolt lugs is what happens if the case doesnt grip the chamber upon expansion while the powder is burning. Bolt lugs are not intended to that pressure on a regular basis, the brass gripping the sides of the chamber hold it in place during the highest part of the pressure curve is keeps the pressure off the lugs. The reason you get blowby when you leave lube on the case is just for this reason, it allows it to push back in the chamber and not seal. This is also the reason there are minimum loads in books with most powders. This is the reason you are supposed to clean any lube of the brass prior to firing, also the reason you put lube on cases you are fire forming. There are alot of things that happen to a bullet and case from the time the primer is struck to the time the bullet leaves the muzzle and the case is ejected. You are correct in that the neck will always have a bit of carbon and will never seal, but from the shoulder down should be sealed. The load you use for subsonic is just as I said is typical except your using trailboss because of its massive load density as it was designed to shoot light loads in cartridges designed for black powder.
Sorry but I don't buy into the bolt beating thing for several reasons. 1. The bolt is in battery against the action lugs from tension on the firing pin. 2.the ejector is pushing the case forward in the chamber there by pushing the bolt to the rear at the same time. 3. The simple act of the firing pin striking the primer pushes the bolt to the rear. 4. There shouldn't be more than a few thousandths ( 2-5 ) gap between the case head and and bolt face. 5. I can guarantee you that a standard high pressure load is elongating the case to eliminate the gap between the case and bolt face before peak pressure is reached.
Bolt beating I don't think so.
YMMV
I've read speculation about this that suggests the impact is so violent that the lead squirts out the end of the barrel leaving an empty jacket to wobble in the general direction the target but have never seen any actual data of what happens. I've searched everywhere I know to search for information about this. Do you know of any real data?
They are, and they're more than up to the task. Relying on friction (or worse yet, metals that are past their yield point, like brass under pressure) to take load is a bad idea.
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You beat me to it.
The brass yields significantly during each firing event, as is evidenced by its growth. A back-of-a-bar-napkin quantitative analysis appears (at least to my simple mind) to be a bit tricky due to the geometry involved and the difficulty in choosing representative material properties, but a gross evaluation of the situation gives us a cartridge wall cross-section that is substantially less than the area acted upon by combustion gases, and a material yield strength that is not substantially greater than the chamber pressure.
The situation is probably much different with various semi-auto firearms, where friction between the cartridge and the chamber may serve as a means by which to control and moderate the process of unlocking and extraction.
Damn Chad next thing you know we'll be drinking beer together.
I have never seen the lugs sheared off any bolt or even metal displaced on the lugs and I've seen some disastrous stuff. I have seen one Rem where the action abutment was displaced to the point of flowing into the bore of the action. Over time Remington's and even custom actions will have some lug set back. You can't fool Mother nature.
I have never seen the lugs sheared off any bolt or even metal displaced on the lugs and I've seen some disastrous stuff. I have seen one Rem where the action abutment was displaced to the point of flowing into the bore of the action. Over time Remington's and even custom actions will have some lug set back. You can't fool Mother nature.
I will say that friction and the strength/stiffness of the brass will reduce bolt thrust at some point during the firing. It's not clear to me if that happens at peak pressure or not, but I would guess that you could measure a difference in bolt thrust between lubed and dry brass. But that's just a guess.
But it would be madness to rely on that as a matter of design in a bolt gun. Within reason, all that is required to strengthen the bolt lugs is to make them longer - there's a reason they're so thick.
But it would be madness to rely on that as a matter of design in a bolt gun. Within reason, all that is required to strengthen the bolt lugs is to make them longer - there's a reason they're so thick.
Dave and Chad, I respect both of your opinions and I mean no offense and so I will say we just disagree on this. I am sure you both have a vast amount of experience in your trades and I respect that and enjoy reading alot of your posts. If you have the time you may want to look at this link or not but this guy did quite a bit of research on this makes for some interesting stuff to look at, he misses on a few things but gets the right picture in the overall scheme of things. Rifle Chamber Finish & Friction Effects on Bolt Load and Case Head Thinning Calculations done with LS-DYNA and FEA Analysis of a Remington Model 7 action in 243 Winchester Caliber
I have looked at this subject quite a bit and could sit here and discuss it for hrs but I really dont think this is what this thread is about.....thanks for your opinions though.
I have looked at this subject quite a bit and could sit here and discuss it for hrs but I really dont think this is what this thread is about.....thanks for your opinions though.
The only real data I can offer is one instance shooting a 22-6mm 75gr Amax at 3650fps thru an 8 twist at 50 yds. The first 3 or 4 shots put 2 to 4 holes in the paper each shot. After that the jackets stayed on and it started stackin' 'em. I'd credit a rough throat since there was only .010" jump. Back in the late '90s there was an article in FCSA mag about the core loosening in the 750 gr Amax's. I doubt that was jump related either.
Ok, Take your best shooting rifle and punch the throat out a bullet dia. and tell us how it goes;-)
Best case is it will only accelerate throat wear.
Explore duplex or triplex loads. More of a pain but more feasible than trying to cheat physics with a long throat.
