Load development group problems

[Toydy]

So I'm shooting groups at near maximum load and seem to be noticing a pattern.
I'm shooting a 270 wsm with 130 gn ttsx at around 3220fps and testing by shooting 3 shot groups.
The first 2 shots of the group are nearly touching but the 3rd is high by around 3/4 to an inch.
Could the barrel (sporter profile around 17mm at the muzzle ) be heating up by the 3rd shot and be the problem or could it be something else ??

 

[Rich Coyle]

It could be. When Mine was doing that someone suggested I change the overall length. It worked for me.

 

[Toydy]

Thanks for getting back to me so quickly.
That's what I was trying, I have shot 10 different seating depths and am out to .13 inches off the lands, just wondering if this sort of thing is common.

 

[Buffalobob]

If the sequence is always the first two are together and the third is out then its is probably either the barrel expansion or else you are leaving the third round in the hot chamber too long before firing and heating up the powder.

 

[Rich Coyle]

One of my rifles came in at.180".

 

[LeftyWilbury]

I generally bring 2-4 rifles to the range. That way I'm always resting rifles between shots. I try to make sure I'm giving each rifle a 10 minute break before I chamber the next shot in it to let the barrel cool substantially (well, at least when it's cool out...).

Of course this also leads to groups opening up at the end due to fatigue. By that point I have 4-5 shots in each rifle from a cool bore though. Enough to narrow down which load I want to focus on.

 

[Toydy]

One of my rifles came in at.180".

Wow that's a lot.
I'm already starting to get the crunch when seating and I am at around I think .12, should I push on or drop back half a grain and keep going?
Would outside neck turning reduce neck tension, maybe that's it ?

 

[RockyMtnMT]

I think before you burn a bunch more resources I would try shoot a cold bore group. Most sporter rifles for us have shot the 1st 2 great then open up if not cooled.

Steve

 

[bpcrshooter]

just out of curiosity have you ever shot a 4th round after the "bad" 3rd?? as it may be other things (you, wind, blah blah). I would say most "hunting rifles should be able to take 3 rounds but, I dont shoot 270. In my 7mmRm I can do 5 and it starts to move.

 

[N2TRKYS]

My 1st and 3rd shot will be touching. The 2nd shot is my flyier. Very aggravating.

Good luck with yours.

 

[Bullet bumper]

Probably a barrel heating and bedding issue . I agree on trying a cold bore group and see if the group is better . That narrows the problem area down somewhat , possibly heating and bedding issues. I don't even try to work up a load or even shoot the gun until I fully pillar bed a stock or other such bedding system as is suitable to the rifle .
Make sure the barrel is floated and the actions screws are tight but not over tight .
If it's a factory built rifle and never been bedded then that is a good place to start before you burn a lot of components . That's my guess .

 

[Toydy]

Thanks for all the help so far.
It is a steyr pro hunter stainless with a synthetic stock and I bedded it with devcon putty as well.
I think the bedding job is pretty good and I also filled up the front of the stock with some epoxy I got from work as it was pretty flimsy.
Am I way off with the neck tension thing or do I just shoot a cold bore group and see ?
Maybe neck size half neck to reduce the neck tension ?
Do I need to drop the powder charge down half a grain and keep seating it deeper by .01 a charge.

 

[Joefrazell]

Do a 5 shot group and wait 5 min. Between shots. In my own experience a 3 shot group can lie to ya. Id say if your trying different oal with no avail then maybe try a diff primer just for fun.