accuracy between long or short AOL of cartridge

[turtlezx]

have a 740 remington .308
for the shells to feed thru the magazine the length of the shell
needs to be .140" off the rifling!!
what difference in accuracy might this cause??
gun is capable of 5 shot groups @ 100yds of 2"
loaded thru the mag
what would the group size to be expected with the boolits
seated long .005" off the rifling??

turtle

[runfiverun]

does the nose engage the rifling?
or is it the jump you mention?
might not matter either way,i have boolits that engage the rifling,and ones that don't.
i have different degrees success and failures both way's.

[44man]

I had the same problem with an old Rem bolt gun. I worked loads to under 1/2" at 100 to find none would fit the magazine. If seated to fit, nothing would shoot so he has to load single shot. He does not hunt so he is OK with it.

[Willbird]

You could seek out a bullet with a shorter ogive and see, some such as the Amax have a tangent ogive instead of a secant ogive, thus you might end up with a round that both fits the mag and comes closer to touching the rifling.

[bobthenailer]

ive allways seated the J bullet about 0.020 from touching the rifleing and have gotten excellent accuracy in every senairo.
Once i had a rifle and seated the bullet as stated , with the new at the time nosler BT J bullets when set up as above it was to long to feed through its magazine , i tried them @0.020 and they shot 3/4' at 100 yards which is normal for that rifle with other bullets then i seated them shorter to feed through the magazine and the groups opened up to 2"
JUST REMEMBER you will probley have to use a few grs less powder than the stated max to keep pressure safe , but you should get the same velocity with less powder because the pressure starts sooner as the bullet has lees freebore and in reality has the same pressure.
both loads with the same powder charge, only difference was seating depth

[felix]

The difference is in the pressure-time curves generated when fired. The gun likes to have one that mates to itself well, no matter how obtained. Absolutely nothing more to it. ... felix

[Doc_Stihl]

The difference is in the pressure-time curves generated when fired. The gun likes to have one that mates to itself well, no matter how obtained. Absolutely nothing more to it. ... felix

I agree 100%.

I have some loads in my bench gun that want a specific bullet jammed into the lands with a lighter charge, other bullets want a .020 jump and a near max load of the same powder.

A bullet of the same weight and different brand/design often shoot differently. Bergers and Barnes often prove to shoot much different than sierras.

[madsenshooter]

You could seek out a bullet with a shorter ogive and see, some such as the Amax have a tangent ogive instead of a secant ogive, thus you might end up with a round that both fits the mag and comes closer to touching the rifling.

Hornadys have a secant ogive don't they?

[Willbird]

Hornadys have a secant ogive don't they? Well I have read they are tangent, maybe they are just a shorter secant ??. I know for sure in my 6-284 that a 107 sierra seated to touch the lands is too long for the magazine, but a 105 amax fits with room to spare. Here is a 105 amax next to a berger 105 vld, the berger and the 107 sierra have a similar shape in my experience. The line you see I sort of scribed with a fired 223 case to show a point on both ogives at a given dia. I have seen numbers assigned to secant ogives, so maybe it is just a shorter secant ?? The amax has been impact plated with Danzac.
http://i.imgur.com/17vnn.jpg

[Larry Gibson]

Odds are that with a 740 Rem you won't find any difference in bullet distance off the lands. Frankly the 740 just doesn't have the accuracy potential to know the difference. Where you may find a difference in accuracy is if the GC is below the case neck with the shorter seating. Several variables involved so only way to know is to test fire with sufficient shots (7-10).

Larry Gibson

[Dthunter]

"Chances" are The boolet will shoot better either close or slightly engraved into the rifling.

The best Thing To do is to try these different seating depths to "PROVE" what your rifle likes/prefers.

Shooting rounds that are too long for a magazine is a pain. But if a shooter wants target accuracy from a rifle that prefers that seating arrangement, do it.

I shoot a .308 win that shoots about .600" or better when BERGER VLD's are seated .150" away from the rifling lands! Unusual yes, but it will feed through my magazine! Bonus!
If This rifle did not shoot this way, I would have set the barrel back, and rechamberd the rifle with a throat .150" shorter. Then the bergers would more than likely shoot very well very close to the lands. Bullet ogive style often dictates this tendancy.

If the rifle was a cast only rifle, I would throat the chamber so that the boolet was touching the lands when the base of the boolet Is even with the bottom of the case neck.
Thats why I normally like long necked case styles for cast shooting.

[Lloyd Smale]

Not allways true larry. My buddy called me one day and told me you have to get over here right now. I drove to his house and he was out at his range with a 742 06. It had tape around the forearm because it rattled. A tasco 4x scope on a see through mount and looked like it had been dragged behind a truck and if anything thats an understatement. He showed me a 5 shot group that went 7/8s of an inch he had just shot with it. I told him he got lucky and he said you try. I sat down and shot 5 shots. Figured with that terrible trigger id be lucky if they went 2 inch. You couldnt see well enough through that cheap scope to tell while shooting so i walked up with him to check the target and was about floored to see a 5 shot group that went 15/16s. That gun would have been scary with a good trigger! No doubt there typicaly 2 inch guns but never say never i guess.
Odds are that with a 740 Rem you won't find any difference in bullet distance off the lands. Frankly the 740 just doesn't have the accuracy potential to know the difference. Where you may find a difference in accuracy is if the GC is below the case neck with the shorter seating. Several variables involved so only way to know is to test fire with sufficient shots (7-10).

Larry Gibson

[44man]

I have seen them shoot very well but the 760 was deadly. Something to do with the forearm hanger system. I had a few 760's that went to pot only to find the tube came loose. After tightening it they came right in and would put most bolt guns to shame.
Now seating depth can make or break. Working the .308 for my friend, he only gave me so many bullets so I used seating depth instead of powder charge work. It is eye opening to see the same powder charge go from a shotgun to a tack driver. Sad they made the magazine so short.
I have never seen these changes with a revolver.

[pdawg_shooter]

I have a Savage 112 in .223 that loves Remington 50gr SPs. If I loaded to engage the rifling the base of the bullet would be about 1/8" past the end of the case. These will shoot under .5 all day long. Sometimes a long jump doesent hurt anything. A tight throat helps a bunch.

[williamwaco]

I agree 100%.

I have some loads in my bench gun that want a specific bullet jammed into the lands with a lighter charge, other bullets want a .020 jump and a near max load of the same powder.

A bullet of the same weight and different brand/design often shoot differently. Bergers and Barnes often prove to shoot much different than sierras.

DITTO:

Every rifle is a different beast!