Advice on changing zero and group size...

[laylandad]

Last September I thought that I had found the best load combo for my Remignton 700 30-06. After checking the zero and group size a couple of times to confirm that it was not a fluke, I settled on the load. Fast forward to now, I went Friday to confirm zeros on my hunting rifles. The loads are from the same lot number of powder, brass, primers, and bullets. I can't replicate the same accuracy nor zero from last year! The load is straight from Nosler #6.

30-06
180 gr Nosler Partition
55.0gr IMR 4350
WLR primer
Nosler case (new)
COAL 3.340"

What should my first course of action be to remedy this? The barrel is free of copper fouling (although it has been fouled prior to shooting groups and verifying zero), the action is bedded in MarineTex and the barrel is floated. The action has not been removed from the stock.

Here is a target from last year, I am too embarrassed to post a new target. Let's just say that MOA is not even close!

 

[DrMike]

Just a query. How many trials did you conduct to verify your load last year? Many times we get a good group, but it isn't representative of the accuracy potential of that load. At a minimum, you should shoot the load three times to verify the accuracy. If the group centre is impacting approximately the same place that it did last year, it is quite possible that you require more work on the load itself. Also, be aware that scopes do fail and action screws do loosen. If the rifle is wood stocked, did it get wet or has oil soaked into the wood in the barrel channel? Before I did too much, I would check the action screws and the scope rings to verify that nothing has come loose. If the action screws are properly tightened and the scope is secured, verify that the scope itself has not received a knock unbeknownst to you. Shoot a known load or shoot a box to verify that it is tracking properly. Then, and only then, would I begin to play with seating depth if the standard deviation is low.

 

[laylandad]

Thanks, Dr. Mike!

I shot this load several times to verify. Sometimes it opened just a tad, but not much. I figured that was me. I am really bummed over this because I have just under 150 loaded! I started out with 250. I was hoping that this would be the last hunting round that I would ever need for this rifle. Guess not!

The load is averaging 2683 fps (5 shot) from my 24" factory barrel. The standard deviation was 14.67. I will revisit the range and verify the load over my chronograph. I will check the action and mount screws.

 

[joelkdouglas]

How hot is it there? Could be groups opened up due to higher ambient temps causing more pressure? Was it cooler last September when you tested?

 

[laylandad]

This month is about the same temp as last September. We've had a really mild summer compared to years past.

 

[gerry]

After checking out the gun like Mike suggested I would take a good look at the scope and mounts, even good scopes can go bonkers and it is amazing how screws on rings can loosen off putting a known good scope on it would tell you if yours needs repair. I have had both situatons happen before.

 

[cloverleaf]

Couple thoughts....are these loads you made up last year? Or did your role them "fresh" just recently. Is your seating depth exactly the same? Ambient temp or temp of the rounds (ie did they lay on the dask last fall and gt a little warmer...) acn make a difference. Ive had the same troubles but in my case usually attributed it to operator error :roll: Good luck! Let us now what you figure out. CL

 

[usmc 89]

Is this the first time you have shot in awhile? could be a rusty shooter problem??? I know if i dont shoot for a week or so i notice a difference in my performance.

 

[Wondermutt]

My -06 did the same thing this year. I checked everything and come to find out it was the scope. That was confirmed when I got the feedback from Leupold. Somehow, someway something broke in the scope.

I was bummed and glad at the same time. This is the first time since '83 I have had a Leupold fail.

Good luck

 

[laylandad]

To answer everyone's inquiries....

These were loaded last year at the time of load confirmation with the same components used in workups.

The stock is a Laminate wood, so I don't think that moisture is a problem. The action area was bedded and then the remaining areas were given a good coat of BLO.

I shoot often, though not as often as I would like. It could be me, but shouldn't I have the same problem on my other rifles?

I checked the action screws, and the mounts and rings. Everything is tight. I will change scopes with a different one. It may be time to send this one back to Leupold. I will keep you informed.

Thanks again for the advice.

 

[kraky]

Try seating one of your bullets a little deeper in the case...see if it moves easily or if it takes some pressure and it sort of "cracks" loose.
Certain neck lubes can sort of bond w/the bullet during storage...this can cause more pressure just like adding powder...in other words the recipe has changed. Before I got good at getting all the lube out of necks I had this happen during storage...although it was longer storage than you have. Might be worth a check.

 

[ElmerThud]

You mention in your OP, when you arrived at what you believe your 'final zero' was, the barrel was fouled.

Once you clean the barrel, particularly if you remove the copper fouling, it is known that a load having previously shot well, may take a few rounds before the barrel and ammunition begin to deliver the performance you were satisfied with.
The number of rounds required to restore the previous performance may be five or six, but could easily run to a dozen or so until you have a similar 'copper bedding' once again.

I am comfortable in the knowledge that when I copper strip my barrel, it will take a few rounds to bring my load/rifle back to satisfactory performance and then I just 'carbon clean' the barrel with a couple of patches until after fifty or sixty rounds/end of season (whatever comes sooner) I then fully copper strip the barrel again.

Don't lose heart in the load just yet, unless you've 'proved' the load just doesn't work. Get some more rounds down the barrel first, then check again.
I hope it works out for you, but there are of course so many variables with rifle ammunition combinations. Best of luck. ATB ET

 

[wildgene]

...first thing I would check is the focus on the scope, a very small change in our eyes, which happens faster & faster as we get older, or just a little bit of a movement of the focus objective can cause havoc, parallax that wasn't there before, & alot of "chasing the bull", while being hardly noticeable...

 

[laylandad]

Ok, I changed scopes with a known "good" one. Same problem. I guess I will pull these rounds that are loaded and start over.

 

[Oldtrader3]

For your edification I have used these very same loads (55.0 gr 4350) with 180 grains bullets in (6) .30-06's that I have owned since 1963. They shot MOA or close to it in models including: a Beretta 502 (1983), a 1903 A3 sporter, a Winchester Carbine (circa 1936 model), a Mannlicher Model 70, 20 inch bbl (circa 1970), a Featherweight (circa 1956) and Model 70 USRAC (circa 1995).

You did not say what scope you are using?

 

[Wondermutt]

Let us know what you find out. I have the same bullet & powder but with 55g of IMR for a mid '80's Rem 700 30-06 that I love. Not sure what happened, but the 100 yd groups are now over 2". So off to the bench I went and came up with a 180g AccuBond with 53.5G of IMR powder combo and now its grouping again. Weird.

Sure hope the barrel is not going south.

 

[Oldtrader3]

I would take 5 or so of your .30-06 loads from last year and put them through the seater-die again, adding .005 to the seater length to break the Dielectric bonding of the case to the bullet skin. This may explain your pressure rise. Try it and see. I have used that load for 50 years in the .30-06 with several 180 grain bullets (Partitions mostly) and have had no issues with ammo, new or old.

 

[laylandad]

The rifle in question had a Leupold Vari-XII 3-9x40 on it. I switched it out for a Nikon 3-9x40 to recheck the groups.

I will seat a few in a little deeper and see what that does. What should I do to the necks to prevent the "bonding"? This was new Nosler brass straight out of the box.

 

[laylandad]

I was getting an average of 1.75-3.5" groups today. I fired 5 fouling shots and let the barrel completely cool before trying for groups. I only shot 3 round groups today.

 

[Oldtrader3]

So, it did not help you very much to break the dielectric bonding? Try using Imperial dry neck lube for sizing necks. It lightly coats the neck with graphite and may retard the bonding issue?