What direction to go

[doctnj]

Now I may not need to do any changes to this load but I need to do more tests to verify that. This was kind of explained on another thread but I will do a short re cap in a different way. Ive done an ocw for my 260 a few months ago and was shooting very small tight groups at 100 yrds. But the cbto length was too long to use mag. So through a couple attempts and adjustments, Ive come to a good feeding length that doesnt bind in the mag at all. But its about 41 thou. shorter than the length I did the ocw at.

Now with that out of the way, one of my issues is at 100yrds my group went from .4 moa to 1.0 moa. But again I havent ruled out how much of that is me or change in the way I was shooting. The OCW was done on front and rear bags and now I am shooting on bipod and rear bag. So If I go back to front and back bag and the group goes small again problem solved, I will know its me and my set up. BUT,

Lets say I go back to the bags and it stays at 1 moa. Well then Im going to have to do a load adjustment.

Question: What is the general effect on a load when seating the bullet deeper and deeper in to a cartridge? Does the pressure come up and therefore MV also? Im just trying to get an idea of what direction I may have to go to get the load back to equal the the load that had already showed to be a good load for this rifle. In short I was thinking of doing a ladder test a couple load levels lower than the one I am currently using.

Am I going in the right direction with my thinking? The down side is Im not going to have a chance to shoot this for possibly as long as 3 weeks. UGH!!!

[Robinhood]

What bullet?

[doctnj]

260 rem
140 gr berger hyb
lapua brass w normal trim to length
h4350 42.3

[doctnj]

Its my understanding that Hybrids are less sensitive to jump than some but I wanted to see if my thinking is correct about the pressure thing. I know if it went the other way and was up against the lands that the pressure would spike but I dont know what more compression on the powder is doing. Just guessing that maybe it would be a faster ignition due to less air space. I will find out in 2 to 3 weeks its just I have all this time to just THINK about it. Im bad about squirrel caging.

[LongRange]

whats your BTO now?

[doctnj]

My final length that seems to feed very well is 2.171. I had tried two or three spots along the way to this length and I would get a hang up. Mostly on the first round. I have run this length and maybe had one hang up in the last 100 rounds.

[doctnj]

Thats using the 5-26 comparitor (sp)? I have to sit in cheer leading competition for the next two weekends in a row. OMG. well at least after that it will be over for the year and my weekends will be free to just shoot!!

[LongRange]

thats pretty short...id drop to 41-41.5g and start there...the problem is going to be the jump if your combo dont like it...try seating at mag length at 40.5gs and seat .010 deeper until your .060-.070 off the lands and see how it shoots if it dont shoot then you may have to try some different bullets...4350 starts to get a little squirrely if more than slightly compressed so you may also want to try some RL-17 as it will take up less case capacity and give a little more velocity.

[doctnj]

Ok that sounds good. Gives me a plan. That way I can go out with some test rounds. Thanks LR

[LongRange]

if the 140s are not shooting well let me know ill send you a few 130g berger hybrids to try.

[doctnj]

Maybe I need to bend the front tang of my mags a little more. That certainly helped but not sure how far to go with that.

[doctnj]

Sounds good!

[LongRange]

Maybe I need to bend the front tang of my mags a little more. That certainly helped but not sure how far to go with that.

ive done nothing other that polish the mag lips with 2000 grit wet & dry and they feed flawlessly...id only tweak the feed lips as a last resort.

[doctnj]

ok before I leave town I thought I would snag a couple pics and do another measurement. I wrongly measured the chamber space (head space) using the 4-25 comparator. So I put that back on and measured my cartridges to see what the distance is currently from the lands. They are currently .079 from the lands. Here is a pic of the space I have to play with between the tip and the mag. This is hard against the back. I tried to measure the space from the tip to the metal strip in front and came up with .017 ish several times. Any way not a great deal of room especially if they float forward a little. Also a pic from the side. This is in a mag that I stretched out just a tiny bit to allow the tip to sit up nicely. As you see in the picture you can hardly tell at all but it was like pre breaking in a clip otherwise it caught under the feed ramp more often when loading a new mag in.

http://i1075.photobucket.com/albums/w435/doctnj/Mobile%20Uploads/20160415_125613.jpghttp://i1075.photobucket.com/albums/w435/doctnj/Mobile%20Uploads/20160415_125942.jpg

[doctnj]

I can probably come back out 9 thou and put it at the 70 thou off the lands. When I did the ocw they were quite a bit longer than mag length. So yeah if they dont tighten up off of bags Ill just have to re run the ocw and back down or change powder like you suggest. Ill also have my "sniper" wife shoot it and see if its me. This time away from the range is going to feel like an eternity. We sent in and off a lot of parts including the rpr to get fixed since we cant go shoot for a little while. Im getting a tactical handle installed on T's new custom and a brake made and installed also. Mine is all good. I may have to skip a gym day.

[LongRange]

.070 at mag length?? if thats one of your new rifles id suggest you shoot a few 3 shot groups from mag length to about .100 off the lands and if it dont shoot rechamber it or shoot it single shot for the life of that barrel.

[doctnj]

I'll recheck the chamber but I think that's right. I remember pre loading some rounds before I got the rifle to what I thought was fairly long and was planing to seat them deeper after I got it and measured it. I was a little surprised when the rounds went in w/o adjustment. Now I only had the coal to go on so there is some pretty big fudge room with hybrids.
When I originally did the ocw, I did it at what I was sure was .010 off the lands and had to bump it back to get it into the mag. Are you saying the chamber is too long? Should I check it with a go no go Guage?

[m12lrs]

Try this
http://www.bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

It worked for.me

[LongRange]

No I'm saying if you have.079 free bore at mag length that's most likely going to be to much free bore(ogive to lands)to get a bullet to shoot well...I've only had 1 bullet in 1 barrel shoot well past .040 off the lands and most have shot best at .010 to .035 off. Now that's not to say that you might get lucky some where between mag length and.100 to .120 off...I've seen a few guys claim they had or have good luck at .090 off...your best bet is to try what m12 just posted.

[Texas10]

No I'm saying if you have.079 free bore at mag length that's most likely going to be to much free bore(ogive to lands)to get a bullet to shoot well...I've only had 1 bullet in 1 barrel shoot well past .040 off the lands and most have shot best at .010 to .035 off. Now that's not to say that you might get lucky some where between mag length and.100 to .120 off...I've seen a few guys claim they had or have good luck at .090 off...your best bet is to try what m12 just posted.

L.R. is that with factory barrels, or aftermarket custom barrels?