ol mike
Well-Known Member
Jamming the bullets into the lands when loading virgin brass - is this something you believe in ?
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Fire forming new brass -do you do it ?
- Thread starter ol mike
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FearNoWind
Well-Known Member
No - the whole idea that such a practice offers any advantage is utterly ridiculous
MudRunner2005
Well-Known Member
Not necessarily... If he is talking about forming into an AI or improved chamber, then that is considered standard practice, along with using a reduced load of powder to eliminiate pressure spikes.
Now, if he is asking about doing so with standard brass in a standard chamber, then yes, I agree that is a waste of components and not necessary, unless it is a competition rifle.
I agree! For my .270 AI, I develop accuracy loads for both pre-fireformed (.270 Win) and fireformed (.270 AI).
ol mike
Well-Known Member
A benchrest shooter was saying he always shot his new brass with bullets into the lands.
I explained that I had read what happens when a round is fired -firing pin hits primer -round fires -bullet seated off lands now hits lands -brass slams backwards -bullet then goes down barrel . It all happens in a millisecond , but benchrest guy insist on fire forming .
I'm not going to worry about it -going to load some 180 hybrids the way Brian Litz says to -15K off lands.
I explained that I had read what happens when a round is fired -firing pin hits primer -round fires -bullet seated off lands now hits lands -brass slams backwards -bullet then goes down barrel . It all happens in a millisecond , but benchrest guy insist on fire forming .
I'm not going to worry about it -going to load some 180 hybrids the way Brian Litz says to -15K off lands.
FearNoWind
Well-Known Member
Looks like you just about said it all there, Mike. The round is in an enclosed chamber. When it is fired the pressure begins moving things around, including the outer walls of the case. Whether the bullet is "jammed" into the lands or .020 off the lands the case walls don't know about it. They move the same regardless of where the bullet is seated. Now, if you want to distort the shape of the case, it is possible to put in enough powder and jam it far enough into the lands to cause the case to break up into small pieces and pollute the shooting bench. But that ain't a good idea.
MudRunner2005
Well-Known Member
Looks like you just about said it all there, Mike. The round is in an enclosed chamber. When it is fired the pressure begins moving things around, including the outer walls of the case. Whether the bullet is "jammed" into the lands or .020 off the lands the case walls don't know about it. They move the same regardless of where the bullet is seated. Now, if you want to distort the shape of the case, it is possible to put in enough powder and jam it far enough into the lands to cause the case to break up into small pieces and pollute the shooting bench. But that ain't a good idea.
Jamming the bullet into the lands for fire-forming has a more legit purpose. It keeps the case properly seated against the bolt face and against the lands, because when the primer is struck by the firing pin, if the chamber was not cut 100% perfect and the headspacing is off (which is known to happen alot on factory barrels), it can push the whole case forward, and when the powder burns and the case expands to the chamber, it will create a false shoulder on the case, and the case will form slightly short of the length it needs to be. Therefore it will be an improperly formed case.
If you keep the case head seated up against the bolt face, and the bullet jammed into the lands, then it keeps the cartridge planted firmly in-place for when it forms to the chamber, so it will form properly, by forming the shoulder in the correct place.
Belted cartridges this is not important, because they headspace off of the belt, and not the shoulder. Non-belted cases, this is important, because they DO headspace off of the shoulder.
112Savage
Well-Known Member
I will say that I have a sloppily chambered 264 Winchester Magnum that fire formed brass comes out 0.03" longer to the shoulder than virgin brass. In this rifle, cartridge, case combination I can see some advantage to "fire forming" because it saved my brass from stretching right above the belt.
I fireform for my 7mm wsm. I cannot find 7mm wsm brass so I use norma 300 wsm. I have done both Cream of wheat style and into the lands. Both work fine. Normally, I stick to just using a bullet because the cream of wheat is boring and you have to make sure you do not get the barrel hot.
My head space is also tight. Virgin 7mm wsm brass will probably not fit without a little force from the bolt. This prevents someone from loading a factory round into my short free bore.
I have started neck turning to start with and annealing between every reload. 7 reloads and still going, expecting to get 15 to 20 out of them.
My head space is also tight. Virgin 7mm wsm brass will probably not fit without a little force from the bolt. This prevents someone from loading a factory round into my short free bore.
I have started neck turning to start with and annealing between every reload. 7 reloads and still going, expecting to get 15 to 20 out of them.
el matador
Well-Known Member
- Joined
- Jul 30, 2008
- Messages
- 647
This is exactly right.
Are you saying the case head will just be floating out away from the bolt face, so the case will end up too short? I don't think you realize what 10,000 lbs of force will do to a case head.
With the pressure generated by a rifle your brass WILL expand to fit the chamber. You're not going to see any cases coming out short or with the shoulder in the wrong place. Jamming into the lands merely helps ensure that the brass will stretch and expand at the shoulder rather than near the case head.
Belted cases are very susceptible to case head separation, so this type of fire forming is well suited to them. I think their reputation for case head separation comes from excessive shoulder movement during resizing, but that's a separate discussion. Most precision reloaders will treat belted cases just like any other case, and headspace off the shoulder after fire forming.
I don't feel that this process is worth it for me so I don't do it. A little extra stretching on the first firing isn't going to make a huge difference in case life.
MudRunner2005
Well-Known Member
I do agree with you that forming brass for a standardized caliber using standardized brass is not necessarily necessary.
However, I was primarily referring to fire-forming brass for wildcat calibers, froming one caliber out of another, or with a non-belted caliber that has excess headspace issues. Alot of factory chambers are out of spec.azsugarbear
Well-Known Member
When fire-forming brass for my 6.5-06 or 277 AM, I never found it necessary to jam the bullets into the lands. However, when fire-forming my 338 Lapua AI (very similar to Kirby's 338 AX), I found nearly half my virgin brass was showing signs of advanced case head separation. In speaking with my gunsmith, he suggested jamming the bullet into the lands. It worked for me. I fire-formed another 75 rounds without the problem reoccurring.
MagnumManiac
Well-Known Member
I agree with most said here, but this is my take, especially on belted cases, but also for improved cases.
I fireform my comp belted cases and improved cases with Clays and a twist of TP.
On my belted cases, this ensures that on the first full pressure load, the belt is in no way influencing headspace negatively, so to speak. My cases are headspacing off the shoulder, and I don't get any case stretch near the web/belt. The only time I don't do this is if the chamber isn't overly long in the head to shoulder dimension, as it normally is in most factory rifles, but my 338WM is fairly tight in this area. I have also found it beneficial if the belt headspace is overly generous. Even my 338 Edge gets fireformed with a low pressure load first, it ensures it is concentric on the first firing, which is where I do initial load work up, my 375 Weatherby gets the same treatment.
As to my improved cases, the AI's should never need to have a bullet jam to fireform correctly without stretching excessively at the web, if the chamber is cut correctly, the juncture at the shoulder/neck should be .005" shorter than the parent case, this is negative headspace that holds the case firmly against the bolt face, however, I prefer to fire form as above, with a low pressure load and no bullet. I have never seen the point in using any improved rifle for hunting with the factory/parent round in use because the velocity is significantly reduced and the idea of an improved case is for higher performance.
I have NEVER had a case head separation because of this method. Previous to doing this, my 375 Weatherby would separate after 4-5 firings, the reason was due to the case being short from head to front of belt, compared to my chamber, it has generous belt headspace, by fireforming this way, the cases no longer stretch excessively near the web. I have sectioned cases after 6 sizings, and no stretching is evident.
Cheers.
lightbulb
I fireform my comp belted cases and improved cases with Clays and a twist of TP.
On my belted cases, this ensures that on the first full pressure load, the belt is in no way influencing headspace negatively, so to speak. My cases are headspacing off the shoulder, and I don't get any case stretch near the web/belt. The only time I don't do this is if the chamber isn't overly long in the head to shoulder dimension, as it normally is in most factory rifles, but my 338WM is fairly tight in this area. I have also found it beneficial if the belt headspace is overly generous. Even my 338 Edge gets fireformed with a low pressure load first, it ensures it is concentric on the first firing, which is where I do initial load work up, my 375 Weatherby gets the same treatment.
As to my improved cases, the AI's should never need to have a bullet jam to fireform correctly without stretching excessively at the web, if the chamber is cut correctly, the juncture at the shoulder/neck should be .005" shorter than the parent case, this is negative headspace that holds the case firmly against the bolt face, however, I prefer to fire form as above, with a low pressure load and no bullet. I have never seen the point in using any improved rifle for hunting with the factory/parent round in use because the velocity is significantly reduced and the idea of an improved case is for higher performance.
I have NEVER had a case head separation because of this method. Previous to doing this, my 375 Weatherby would separate after 4-5 firings, the reason was due to the case being short from head to front of belt, compared to my chamber, it has generous belt headspace, by fireforming this way, the cases no longer stretch excessively near the web. I have sectioned cases after 6 sizings, and no stretching is evident.
Cheers.
lightbulb
