Help with POI shift!!!

[misterc01]

Screws- Yu said tight. Are they tight by hand or torqued? Minute variations in pressure can do strange things. I learned this with a Ruger 10/22 - Under or over tightening the screw caused POI shifts. So I used a torque wrench using inch-pounds and torqued until my shots grouped the best. I believe Ruger says 110 inch pounds, but other forums have used up to 30 inch-pounds. On my longer range rifles, I use the factory setting to start, and try a +/- variation test. Just another thought on variables.

 

[Mrhounddog]

Hey Ninja,
A few questions:
- How many times have you shot this rifle...total?
- Have you thoroughly cleaned the chamber, specifically the neck and throat area?
- Have you checked the neck thickness on the brass you are using?

What you are describing sounds like pressure differences between shots, which could be related to inconsistent bullet release. The neck tension has to be the same for all shots...obviously. If one round has a thicker neck, with increased tension before release, then the pressure is higher and it will not group. Excess carbon in the neck/throat area can do this too.
Of course, you have to be reloading very consistently to eliminate that as a variable. All of this to give you one or two more things to look at. Hat tip to Kiwi Nate for accuracy stuff.

 

[T3ninja]

The brass used is once fired, I'm using a Redding body die, and neck sizing. Using 215M primers. During load development I increased charge weight by .3 gr, 73.6 and 74.2 shot pretty much identical with the charges lower than .6 not shooting as good. I ran this a total of 3 times (27 rounds) before settling on 73.9.


Screws are torqued in IN. Lbs but I can't temper to what, I'll check when I get home from work. I think it was 65 inlbs.

I've never heard of bedding the chamber area of a stock, only the receiver. How many of you have done this? What was the result?

I will run some rounds over the chrono to see if there is any change in velocity from shots 1-3 maybe 1-5. I'll try to do this tonight, and when I get back from camping on Monday.

Thanks all for the replies, if I can in fact get this thing shooting well when heating up it would give me a lot more confidence!

 

[cohunt]

all your shots and poi will be different in CO-- you are going from 900ish msl to probably around 10000msl (where most elk hunting takes place-- you will need to not only site in your rifle at altitude when you get here, but all your drop chart info will change due to the higher altitude/less pressure and most likely less humidity too. best to find a range to check your zero and drops when you get here (dont forget to bring extra ammo)

as others have said, if the poi shift is due to a barrel heat/harmonics issue, it may be repeatable, if its from higher velocity then the extra altitude will extrapolate the problem

best best, since you are using RL26, is to just send all the rest of your reloder 26 powder to me here in CO and I can use it for testing purposes

 

[T3ninja]

Mrhounddog
Not sure on exact number of firings but I'll see when I get home. Top of my head I'm saying 150 max. For the first 20 rounds, I cleaned every shot 1-5 then every 5 until I hit 20 rounds. Then a thorough cleaning. I tried H-1000 with terrible accuracy (2moa at best) no matter the charge weight. Then a cleaning again before switching powders (this was right around the 50-60 round mark). So it's running right around 60 round or so on this cleaning cycle.


I have not checked thickness on the necks but I did weight sort the brass, and am loading/shooting them in "batches".

 

[T3ninja]

all your shots and poi will be different in CO-- you are going from 900ish msl to probably around 10000msl (where most elk hunting takes place-- you will need to not only site in your rifle at altitude when you get here, but all your drop chart info will change due to the higher altitude/less pressure and most likely less humidity too. best to find a range to check your zero and drops when you get here (dont forget to bring extra ammo)

as others have said, if the poi shift is due to a barrel heat/harmonics issue, it may be repeatable, if its from higher velocity then the extra altitude will extrapolate the problem

best best, since you are using RL26, is to just send all the rest of your reloder 26 powder to me here in CO and I can use it for testing purposes

I'm aware that the altitude will effect my drops. The area I'm looking at has elevation right around the 9k mark. So it will be a pretty significant change. Ammo is one thing I don't think I've ever forgotten or been short on( knock on wood) .. as for RL26, well I'm already looking at other powders because I've had 10Lbs on backorder for about 3 months and there seems to be no hope in sight.

 

[skipglo]

The rifle is factory bedded, pretty nicely done in fact. It's not so much that I can't cope with the shift. It's more about the elevation change. I can compensate for this at my altitude, but I have a CO elk hunt planned this year and the area in scouting and planning to hunt is 8500-9500 FT. My main question is, right now, it gives me a .4 mil change. Would this still be .4 mil at the higher elevation? Not sure I'm wording my questions right.[/QUO

Hey all,

Here's the story. I just picked up a Browning Max LR in .300 Win. I'm not new to reloading, but this is my first belted Mag. I'm somewhat familiar with some POI shift due to heat, stock contact etc.

So as of now I'm still working to fine tune this load for my rifle which is 215 Berger 73.9 RL-26 .010 from lands. This is giving me consistent 1" groups @ 175 yards. Acceptable to me for a hunting rifle.

Here's my problem. I've shot this rifle 4 times (12 rounds) @ 450 yards. The first 2 rounds of each 3 shot group are perfect, within 1.5-2" of each other, the 3rd is ALWAYS 6.5" high! Approx .4 MIL. I'm not happy about this but since it's consistent I can compensate for it. My question is, at my altitude 950' I'm hitting .4 mil high, will this correlate to the same thing at say 9k' elevation? I'm going to be running this load at everything from 100 to 1k, so I'll have info for everything in between. I understand these will be useless at elevation, and will need to be updated accordingly.

Being RL 26, Do you think that the 3rd round heats up enough in the chamber to cause part of this vertical? I have a magneto to put on but it changes my POI so much I don't do any accuracy testing with it, especially at distance since it will probably cause me to miss the target completely.

Thanks in advance

On my ballistic calculator the change to 9000' is negligable but a 6.5" shift is unacceptable. Put 60 seconds between shots and see what happens and check all your scope and base screws. What rail or mounts are you using? Do you have a 20 MOA rail by chance?

 

[crkckr]

First thing I think of is, are you positive it's the 3rd shot going rogue? Getting the 1&2 group is bad but keeping track of order can be a real pain. But is necessary.

If you're certain about the order, the first thing I would check are the scope mounts. This does not sound like a heating or bedding problem to me (reality may be completely different!). I have experienced the exact same thing and found the base tight but a ring actually eating up a Pic mount (obviously a cheap one). First shot loosens it up, second makes it jump, third shot goes... somewhere! If you have another scope, that too would be on the list of possibilities (shake the thing & see if it rattles!). Try a known good scope & see if it repeats. Lastly, what about a 4th shot? In the group or are you maybe getting a 2 & 2 group? So many possibilities! So many possible fixes! Just make sure you do just one thing at a time or you may never kniw what actually fixes the problem. And that really sux!
Cheers,
crkckr

 

[LoneTraveler]

First I would find a friend and borrow a free standing chronograph. I like to shoot every round through a chronograph when working a new rifle. Heat causing powder change, or bad lot of primers will show up quick.
If the scope is good, mounting good, torqued proper. If the action screws are torqued proper. And it is the 3rd shot is going high.

Is the stock a hand laid stock or a molded stock?

Since you state you are using a Bipod and back bag. I would suggest you have a buddy check the barrel channel relief when you get the rifle in position to fire. Shoot shell 1 and 2, load the 3rd shell and have them check the barrel channel relief again.

Could it be that as you fire shots 1 & 2 the bipod is stressing the stock and heat from the chamber softening the stock right at the edge of the bedding of the action. The bipod has a mechanical advantage of the legs length to stress and move the forearm at the action/barrel point, Or stress the end of the stock from the bipod mounting stud to the front of the barrel.
Good Luck in finding the cause and solution.

 

[T3ninja]

So, camping for the weekend and have bad service. Trying to respond before i lose signal again

I have a 20 MOA rail bedded to the action, I've checked rings, then the rail, re torqued rings. It is a known good scope. Steiner 4-16 I took it off my .260 rem and it was flawless on there.

As for being sure of order of rounds fired. I color the bullets with sharpie, RED BLUE GREEN... it leaves color on the target

 

[entoptics]

So, camping for the weekend and have bad service. Trying to respond before i lose signal again

I have a 20 MOA rail bedded to the action, I've checked rings, then the rail, re torqued rings. It is a known good scope. Steiner 4-16 I took it off my .260 rem and it was flawless on there.

As for being sure of order of rounds fired. I color the bullets with sharpie, RED BLUE GREEN... it leaves color on the target

Ahhhh. There's your problem! Green ink known to cause accuracy issues...

 

[Gary kittelson]

Spacing your shots one minute apart will not solve your problem, elk don't hang around while your rifle cools lol. Good news is if you practice enough you will not need a third shot

Ahhhh. There's your problem! Green ink known to cause accuracy issues...

 

[Doug Herold]

Sounds like your over-riding concern right now is accuracy for your upcoming elk hunt. Count on your POI changing at 9000 ft.
When you get out there, find a rock at 400 - 600 yds and rezero your come-up.
Right now, track POI on all first shots out of a cold bore. Thats the shot that counts !!!! Elk don't care about groups.

 

[Rhett Crider]

I see that this rifle on Browning's site is 8 twist. Pretty hard twist for 308 cal.. Different opinions here on over stabilization. Berger calls for 10 twist. Might try some Hammer Hunters-227HH. Every post I've seen on the Hammers has been excellent.