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"Jamming" bullet into the lands?

 
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  #1  
Old 12-03-2010, 07:30 PM
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"Jamming" bullet into the lands?

I often read that so and so shoots a what ever and gets excellent results with no jump even seating a bullet .010" into the lands.

How do you do that without damaging the jacket How do you do that without pushing the bullet back into the case when closing the bolt? Granted the jacket gets damaged (maybe not the right choice of words) as soon as its fired regardless but by seating the bullet .010 into the lands, is the bullets actually imbedded into the lands?

High pressures for sure but it doesn't seem like something uncommonly done.

would someone clear this up>>
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Old 12-04-2010, 03:05 AM
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Re: "Jamming" bullet into the lands?

Benchresters and others may use this so-called "jam fit" for best accuracy, but do not use it in a hunting rifle. The bullet may stick in the lands and pull out of the case when you exract a live round, leaving a receiver full of powder.

"Been there, done that."
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Old 12-04-2010, 04:53 AM
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Re: "Jamming" bullet into the lands?

I too have "been there done that", left a bullet in the throat and filled every little crevice of the action with powder. Bolt wouldn't even close till I cleaned it all out, and it took alot of time to do that.

Seating them long may be just fine if you know for sure the round will be fired, but IMO that is not the case in a hunting rifle. Even if we don't load a round until we're ready to fire, the target may decide to step behind something or lay down or turn or who knows what.
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Old 12-04-2010, 08:24 AM
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Re: "Jamming" bullet into the lands?

I hunt with a couple of rifles that have the bullets jammed. It gives me good accuracy and that is important. I was hunting with one of them yesterday but nothing showed up to shoot at. Most of my rifles are single shot and I seldom have a round in the chamber. However the possibility of a round getting stuck is real and you should have a cleaning rod available if it happens.

I do not understand your assertion that there is some damage from the bullet being jammed.

As far as pressure increases, that is simply caused by how much powder you put in the case. If you are unwilling to hunt with jammed bullets then there is no point in testing them jammed. If you are willing to hunt with jammed bullets then when you begin load development you test your loads with the bullets jammed and once a load is found you then can test shorter COLs with no problem because you are already know that the pressure at jam is OK.
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Old 12-04-2010, 10:00 AM
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Re: "Jamming" bullet into the lands?

Umm, it's "Seat the bullets .010" AWAY from the Lands of the rifling".

The idea is to have as small a gap as possible for the bullet to jump before it hits the rifling.

Those who "Crush Fit" their ammo into their chambers are asking for trouble, IMO.
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Old 12-04-2010, 10:33 AM
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Re: "Jamming" bullet into the lands?

The way I do all of my rifles with respect to process is the same. Jamming is not smart esp on a hunting rifle but people do it and still really do not understand why they may or may not get smaller groups.

Using a 700 style action---remove firing pin assy---remove extractor---(this is also how I judge sizing of brass by resistance to the bolt closing then back off .02 to .03) then mark the bullet with a black marker from the ogive back. Place round carefully and close bolt then look at the bullet. What you are looking for is the point where each land makes a complete line (not 2 lines and 1 dot and nothing for example on a 4 grove tube) that will cause the copper to show. Then back off what you feel is appropriate for the purpose of the rifle as obviously a BR rifle is going to be different than a hunting rifle.

When you do this you have established the shortest distance for the bullet to travel and engage all of the lands as close to the same time as possible.

This is the way my smith does it and he is a HOF shooter. Have never had anything but success doing this on around 20 or so rifles and 30 tubes when working up loads.

Also when you have the firing pin assy out check the bolt shroud to ensure no contact----any contact there is bad ju ju for accuracy!!
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Last edited by Boss Hoss; 12-04-2010 at 10:45 AM.
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Old 12-04-2010, 11:07 AM
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Re: "Jamming" bullet into the lands?

"Benchresters and others may use this so-called "jam fit" for best accuracy,"

That's correct...but only for some of the BR crowd. Not all of them do it and the primary benefit isn't to gain "better bullet alignment" as it's often stated. They seat bullets to the lands to retard movement until the pressure curve is steep enough to get a good burn.

Most, if not all, serious BR shooters have very tight necked chambers that demand their case necks be thinned quite a bit to even chamber. Bullets seated "normally" in thin necks may have too little start resistance for the powder burn rate to build properly for best accuracy. Few sporting rifles with normal (thick) necked cases need that start resistance and most factory (SAAMI) chambered sporting rifles shoot best from .020" off the lands to as much as 5 -6 times that much.

Bottom line, BR shooters load for their rifles. But we don't have BR rifles or components so attempting to duplicate their methods without understanding why the he77 we're doing it not only may not help, it may actually hurt our results.

That said, the light ogive surface marks at lands contact mean nothing to the bullets so jamming into the lands isn't likely to do anymore meaningful "damage" to the jacket than the die seating plug does.

Last edited by boomtube; 12-04-2010 at 11:13 AM.
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