How to measure

[Preacherman]

I have a Win. Md 70 liteweight in 243 the best group is 2 inches.I have heard about lenghting the OAL to touch the rifling or a few thousands short.How do you do it without a special tool.
Preacherman

[R.W.Dale]

The eaisest way is to take a fired case from your rifle and dent the case mouth just enough to hold a bullet.  Then take a bullet and cover it with magic marker.  Barley insert this bullet in the case and place this dummy round in the chamber and close the bolt. Extract the case ant knock the bullet from the rifling with a cleaning rod. There should be a scratch in the marker on the bullet corresponding with the case mouth. Line these back up and you have the COL to rifling for that rifle

[41 mag]

Similar to what krochus posted, I have also found that sometimes even with the loose neck tension that the bullet will sometimes simply seat deeper and then come out with the case. When this happens you can remark the ogive of the bullet where the marks of the lands hit, then after measuring, simply seat the bullet a couple thousands deeper measure after each depth change, until you see the bullet come out with no marks on the blackened portion. One thing that you many need to pay attention to when using this method is when extracting the case, if the bullet stays with it, you will want to hold your finger on it to keep it as straight as possible while ejecting it. This will keep it from rubbing the side of the chamber as some extractors Remington especially, will push the case to the side as it is removed. 

Another tip can be found at the link below, just scroll down a couple of tip's and you will see the modified case. This has also worked very well for me on a couple of rifles.
http://www.6mmbr.com/blogmay2005.html

Note it is best to use it with the bullets your wanting to shoot, as different makes will have different ogives and give different results. However I some chambers that I have found are throated long enough that I used a longer flat based bullet simply turned around backward, which effectively put the base at the lands. I have checked this against known measurements of other bullets and found that it is generally only a few thousands off. This is mostly due to the taper of the lead on the lands, and has not shown anything adversely different in accuracy on the rifles I have used it with. In these cases I was wanting to use a light weight bullet and simply needed to know the length away from the lands. Since they were so much shorter than the heavy version they could not be extended out far enough before clearing the case.

If you do not have a set I highly recommend getting one of the Comparrator sets to use for OAL measuring. The best bang for the uck used to be made by Sontey Point, but i believe now they are put out by Hornady. This will get you right back to where you need to be with your handloads with out having to recheck your barrel each time with a new bullet.

[Val]

The bullet seating depth may not be the problem. Have you tried different powders and bullet weights? My .243 likes IMR 4350 in 100 grain pellets and IMR 4064 in 70 grain bullets. I play with the seating depth after I find the load that gives me the best groups. Often I get sub MOA groups with out changing the seating depth. Sub MOA is accurate enough for hunting so I don't need to get more accurate

[Preacherman]

I have tried different powder and bullets 4350 with a 100 gr is most consistant I have some I neck sized have not tried them yet.
Thanks for the help
Preacherman

[Grumulkin]

Seat a bullet in a carse at a length you know will be a little too long and attempt to chamber the cartridge.  Progressively seat the bullet a little deeper until the action just barely closes easily (this would apply to Encores, Contenders or other break action guns).  The bullet will then be seated just off the lands.

If you want the bullet actually touching the lands, also look at the bullet after an attempt at chambering.  You will see a slight scuff around the bullet from where it contacted the lands or throat.  Seat bullets progressively deeper until the scuff mark is very small and to the point where the length before chambering and after chambering don't change (if the bullet is seated out too far, the act of closing the action will push the bullet deeper when you chamber the round).

[wncchester]

Have you tried other 100 gr. bullets too?   Some rifles shoot most anything stuck in them, others are quite picky.  And, sadly, some rifles just won't shoot anything really well.

Seating into the lands is rarely helpful with factory rifles, IMHO.  It's more of a seating method for BR shooters who load with very little bullet tension, for them it helps to get the powder to burn properly. 

Neck sizing a hunting rifle is more of a small tweak for a good load, it won't work miracles.  A 2" rifle sure indicates it may be more than just your reloads that's bad.

Check your bedding.  And the scope mount and ring screws fot tightness.  Or even swap out the scope itself to comfirm that your's is good.   I've seen several 2-3" rifles turn into MOA shooters instantly with a scope change! 

[Preacherman]

Factory RP shells shoot about 3" group. Traded scope mounts got it down to 2". My son had the rifle first tried different scopes bases bullets powders loads .It was a gift from an uncle has to stay in the family.Been thinking about a rebarrel.The current barrel is floated but not bedded.I know it will never cut bullet holes but would like see at least see a 1" group.I like a challenge at my age this is about as intense as it gets.
Preacherman

[Preacherman]

Thanks for all the help spent about 4 hours cleaning the barrel Sat. went to the range after church Sun.shot one to foul the barrel shot three in the 1" ring flinched on the fourth.The shells were neck sized only 100gr Corloks with 41gr H4350. Least got a starting point now.
Preacherman

[Val]

Now you should try playing with the bullet seating. I like to increase the Overall Length (AOL) in 15 thousands increments and shoot them. Some rifles are limited in acceptable OAL by the magazine. Bedding the stock is also likely to improve the accuracy.