Strange issue...advice wanted.

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EduardoVincente

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So I had my most inaccurate day of shooting in quite a long while. A little background...

Back in January I started load development on my 7mm again...starting to wonder why? I thought I was on track with the new load as I had some really good groups and my best group ever. Today it all unwound...so I had never shot this load in the heat and I realize that causes pressure to increase, as evidenced by the magneto speed results. I was averaging 3080 fps with a 162gr ELD-M, and exceeded 3100 on a couple shots out of 10 chronied. This is out of a 24" barrel...so it does seem a little high. No obvious signs of pressure though, so I carried on with the session. I couldn't hit the broad side of a barn! I average sub moa and on a good day a good deal less than that but today was crazy! After the chrony shots I went to 730 yrs and was making very sporadic hits...couldnt figure it out. Winds definitely sucked but i have shot in wind and haven't had this poor of results in a long time. I was about 22 degrees hotter than I ever shot this load. Here is where it gets really strange...i bring it back to 220 yrs, my zero, and shot 2 groups that were about 2 to 2-1/2 moa. Ok what gives? I am also shooting my .22 so I decide to take a couple of shots at 25 yds. First one where it should be...second one couldn't find it on the paper I was shooting at...what??? Look at another target beside and I have an almost perfect vertical keyhole. Third shot I never did find...checked the scope and action screws...dialed back out to 730...sporadic hits again. Called it a day.

Experienced guys please chime in, can over pressure cause a bullet to keyhole and that kind of crazy accuracy issues?

Learned a valuable lesson and will spin up some of my old load to see how that goes...i was trying a high velocity load to make a mile but my old load should be able to do it...just go subsonic a little sooner.

I welcome some input or insight. Thanks in advance.

view


Picture of the key hole. Another note is that the hits on the plate at 730 yds were normal round indentations.
 
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A bit of pressure shouldn't make that much difference. I don't know about the keyhole, but the one time I had wacky results like that I realized my scope mounts had come a bit loose. Could it be something that simple for you?
 
Back off your load about a full grain and try again or enough to lower velocity to where you had your good groups
you are too fast for your load combination
bullet length/ twist/ speed combination

if it gets even hotter it will do it more so (enlarged group size)
 
Sounds to me like your rifle is NOT stabilizing those long bullets. Most newer 7mm mags have a 1in 9 or 1 in9 1/4 inch twist but there are some rifles out there with 1 in 10 and even 1 in 12 inch twist. The slower twist will shoot lighter bullets (140 and lighter) but groups really open up with heavier bullets. I would suggest you go back to a shorter bullet, possibly one that shoot well in the past and retry it.
 
I would agree with that except the same bullet, rifle, powder combination at a lower charge never gave me any issues. Successfully shot to a 1000m sub moa and all ranges in between. Weird for sure....

Reply to Rokoro....will use the reply with quote button next time.
 
shotgunjoe said:
You don't state what powder you are using and it has been shown that some powders are not good with temperature changes. It could also be your scope is pooched.
Click to expand...

IMR 7977...sure hope the scope isn't pooched but unfortunately that wouldn't explain the key holed bullet. I will try and add a pic of that in my first post.
 
diopter said:
Did you check your action screws?
Click to expand...

I checked them out tonight...if anything they were probably too tight as I had almost 60 inlbs on them. I didn't have a torque driver when I installed them originally but the rifle has shot very well excepting this last outing. I removed the action and cleaned all the aluminum bedding surfaces and followed the 10 inlbs per screw alternating front to rear up to 45 inlbs. Ring screws were tight and in spec at about 22 inlbs and 32 inlbs respectively. All seemed alright in the screw department...need to look elsewhere.

As suggested above I will try to inspect the crown though that would be difficult with the brake on...

In the end I may chock the keyhole up to a twig or bug...and the rest of the ordeal may have simply been the change in temperature moving me out of the sweet spot. I will revert to my proven load that I have shot with great success in all weather conditions. Thanks for everyone's help!
 
EduardoVincente said:
So I had my most inaccurate day of shooting in quite a long while. A little background...

Back in January I started load development on my 7mm again...starting to wonder why? I thought I was on track with the new load as I had some really good groups and my best group ever. Today it all unwound...so I had never shot this load in the heat and I realize that causes pressure to increase, as evidenced by the magneto speed results. I was averaging 3080 fps with a 162gr ELD-M, and exceeded 3100 on a couple shots out of 10 chronied. This is out of a 24" barrel...so it does seem a little high. No obvious signs of pressure though, so I carried on with the session. I couldn't hit the broad side of a barn! I average sub moa and on a good day a good deal less than that but today was crazy! After the chrony shots I went to 730 yrs and was making very sporadic hits...couldnt figure it out. Winds definitely sucked but i have shot in wind and haven't had this poor of results in a long time. I was about 22 degrees hotter than I ever shot this load. Here is where it gets really strange...i bring it back to 220 yrs, my zero, and shot 2 groups that were about 2 to 2-1/2 moa. Ok what gives? I am also shooting my .22 so I decide to take a couple of shots at 25 yds. First one where it should be...second one couldn't find it on the paper I was shooting at...what??? Look at another target beside and I have an almost perfect vertical keyhole. Third shot I never did find...checked the scope and action screws...dialed back out to 730...sporadic hits again. Called it a day.

Experienced guys please chime in, can over pressure cause a bullet to keyhole and that kind of crazy accuracy issues?

Learned a valuable lesson and will spin up some of my old load to see how that goes...i was trying a high velocity load to make a mile but my old load should be able to do it...just go subsonic a little sooner.

I welcome some input or insight. Thanks in advance.

view


Picture of the key hole. Another note is that the hits on the plate at 730 yds were normal round indentations.
Click to expand...

Even though 7977 is an Enduron powder, it does still experience variances due to temperature. You're probably shooting 60-70 fps over what it was shooting at when you developed your loads, and are probably now missing the node on your barrel. Back your load off by about a grain or two and try again.
 
I just worked up some loads with those bullets in my Rem 700 (9.25 twist) and measuring a dozen of them randomly, OAL was all over the map, very inconsistent ogives to bullet length. You are on the line for stabilizing them at a 9.5 twist, and possibly hit a few extra long bullets in the batch that wouldn't stabilize.
I won't be buying anymore of them, sticking with the traditional match bullet makers. I never found Hornady to be that great in the match bullet department before...these looked promising, but they seem to be pumping them out faster then they can QC them.
 
I believe they are also designed for a 1/8.5 twist. I was told by Hornady they will work in 9.5" twists but so far I haven't found the "load" for them in my 7mm STW yet. They do sit very deep in the case.
 
Here are some potential issues that may be causing your large groups:
1) Savage is notorious for using crappy stock to receiver fitting stocks. If it is a synthetic stock, check clearance around the barrel to ensure it isn't touching. As the gun heats up the stock puts pressure on different parts of the barrel and/or action. This will cause erratic shots. Remove the stock from your rifle and file down any spots that are touching then re-install stock to check clearance. Typical torque on the retaining screws is 40"# on the back and around 28"# on the front. You can adjust these ratings up or down 10% to refine your groups when you get this problem sorted out. Tighten the rear one first then the front.
2) Measure the length of your bullet and find out what the rate of twist is of your rifle. use this greenhill formula to see if your rate of twist is sufficient to stabilize the bullet. (http://ebrammo.com/info-tools/greenhill-formula-for-rifling-twists)
3) Make sure your barrel is clean! Use a copper fouling remover like Sweets 7.62 or Wipe-Out overnight. Sweets is very potent and should only be left in the barrel for 15 minutes max but it is the best in my opinion for removing copper fouling. If your barrel is full of copper your groups will reflect it pretty quick.
4) Set up a video camera of you shooting your rifle. Look at it in slow motion to see if your flinching or changing your hold. This will effect groups even in a rest.
5) This one is a given, make sure you are using the same powder and components listed in a "current" reloading manual. I've been doing this for over 35 years and have older manuals that suggest start loads that far exceed max loads of newer current manuals. I always cross reference two or three manuals to see if they are all in the ballpark before I sit down for a session.
6) I would also remove the scope and make sure the mounts are tight. Use a touch of lok-tite on the threads for the mounts and make sure everything is clean before re-assembling. I use a tiny dot of Auto-Goop on the rings face then tighten the rings around the scope to 18 - 20"#.

If you've done all of this and still have unacceptable groups I would say there is either a problem with the scope, the muzzle of the gun has been dinged or there is a problem with the rifle. Hope this helps.

Fellow GunNutz - Andy
 
8x68 said:
I believe they are also designed for a 1/8.5 twist. I was told by Hornady they will work in 9.5" twists but so far I haven't found the "load" for them in my 7mm STW yet. They do sit very deep in the case.
Click to expand...

palle%20hornady%20edl%20match%20cal%207%20mm%20gr%20162.jpg

I'm able to seat them to 3.410" in my 7mm Rem-mag, they don't need to be seated deep unless you have mag length restrictions.
 
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