Model 12 BVSS .223 Rem - Unpredictable Accuracy

[TnTom]

I did a lot of process improvement activities during my working years and sample size always became a very important issue. With shooting we're trying to combine a lot of variables into a single result. When making a statistical evaluation the practice is to throw out or disregard the extreme but that doesn't work so well in shooting but is more applicable to calculating S.D and process capability indices and really that should be based on a sample of 15 or greater.

I'm going to make it a point today to shoot 10 shot groups at 1 minute interval and do that 4 times and track the barrel temp at the chamber and find out what length of time it takes for the temp to drop to ambient. At some point in process I think there will be a correlation between temp and where the bullet prints. Its just something to observe. The last couple of times at the range I noticed more shimmer than usual and I knew I wasn't paying much attention to it.

If every round were fired with the barrel at ambient temp it could take a long time to fire 40 rounds but the results would be far more reflective of the overall picture and what would be the difference between one 40 round group, four 10 round groups, eight 5 five round groups or thirteen 3 round groups. :-\

I'll report back.

[jsteag]

Mine likes Berger 70 gr VLD in front of 24gr Varget and cci benchrest primer. Bullet jamed .001 into lands. Shoots 10 shot .5 at 300 yards.

[fatdaddy]

"Shoots 10 shot .5 at 300 yards." WOW... thats a real shooter. I'd surely be entering that gun in some competitions... Bill

[racinready300ex]

"Shoots 10 shot .5 at 300 yards." WOW... thats a real shooter. I'd surely be entering that gun in some competitions... Bill


If my savage shot like that, I'd stop shooting in the factory class at IBS shoot, and shoot with the customs.

[borg]

Were barrel heating not an issue, I would agree that 10-shot groups are more statistically relevant. However, considering that POI changes when the barrel is heated, I would advise either to shoot multiple 5-shot groups and find the average or allow the barrel to cool for longer periods between shots. As I enjoy the time I spend at the range shooting more than I enjoy the time spent staring at my rifle, I opt for the former.

Someone is going to suggest rotating group shooting between multiple guns. That, in this case, would require multiple rests.

P.S. As far as I can recall, for determining the value of a single data point 3 samples is considered quite sufficient.

[TnTom]

Well so much for the temperature thing. I dropped the thermometer. I did shoot at one to minute and a half minute intervals. 55gr hpbt 53gr hp H335
5-10 rd groups .5 to .6 horizontal and .25 to .9 vertical. I'd call it 5 groups .5-.9, the best group was the .25 x .5

I began a 6th group and it was obvious the barrel went foul and stopped after five. I'll clean and begin my next session with the last 5.

I met another shooter today who no doubt had a lot of bench experience he was shooting a new Shielen barrel on a 110 action and when we finished shooting I asked him to look at my set up and he thought the front rest was still to hard and too tall or high on the bench which he felt was playing into the vertical stringing. He looked at the crown on mine his crown did not have sharp edges, there was about a .003 -.005 radius. He felt if it were his gun he wouldn't hesitate to re-crown at the same time take it back an inch. We're going to meet again next week and he offered to shoot my gun in his rest. I have never seen prettier 10 shot groups than he shot today. .3's and 4's. It was also suggested that I set up lower to the bench. My front rest is tall. Anyway I felt it went better today and I'm going to get things more settled on the rest and load up some more.

I do feel the sierras 53s and 55's both did better than the 69's sierras and the Lapua bullets are simply not an option. To dang expensive anyway.

Again thanks for so much great feedback. I really wanted to see how much the barrel temp changed over 10 rounds. Next time. I had found a dozen lab thermometers on Ebay for $12.00 man I have them hanging in the garden in the chicken coop from my truck mirror all over the place. :D

[sha-ul]

you might try a touch-less infrared thermometer.

[Tozguy]

Just curious about why you should cut the muzzle back an inch.

[racinready300ex]

I shoot 3 shot groups some, if it wont shoot three it sure as hell wont shoot 10. My thought on it.

Once I get it close to where I want it I move up to mulitple 5 shot groups and average them together. I have similar trouble to Tom, I can't seem to get the groups I think it should do. I keep getting a random shot off here or there. Average .5-.7, but I'm looking for closer to a .5 average. There's so many things to try it's hard to narrow it down.

I plan to get to the range this weekend with my 223 and hope to average under 6" at 600 yards. That's my current goal, it pretty much alway under .7" at 100 so if I do my part it should be able to do it.

[TnTom]

Just curious about why you should cut the muzzle back an inch.


Didn't ask why but I would need a pretty valid reason to cut it back. I could speculate a little but wouldn't run out and do it. I'll ask him a more about it when I see him at the range next week.

I agree my lab thermometers really are not the tool of choice. If I slide one in the chamber it would reflect an idea how much it heated up and how long it took to return to ambient, somewhat.

[4runnerman]

I shot 75 Hornady A-Max behind 24 gn RL-17. I can consitantly shoot 3/4 groups at 300 yards. Mine is kinda finiky though
Once i clean it i have to shoot about 5 rounds before it comes back to the tight groups. Love it. One very nice shooting rifle. Mine is a 1 in 9 twist too and it does not like 55 gn bullets at all. I had real good luck with Berger 70 vld also,but wanted to find a cheaper bullet as i shoot a lot.

[King Ghidora]

I think I understand why you have a problem with .7 groups when you can shoot .3 groups at times. I have a similar problem with my rimfire MkIIBTV. I can shoot groups under .2 (at 50 yards) frequently but then my groups will open up to .7 with no apparent reason. I've been trying to track down this problem for a year now. It drives me crazy because I know the rifle is capable of shooting much smaller groups than I get sometimes. But with mine I'll be shooting a very nice set then the POI will just jump to another spot and it will shoot to that spot consistently. Believe me I've tried every scope remedy I could think of too. I've used so many scopes and mounts it just ain't funny and it always ends up being the same thing. My gunsmith says it's the gun itself causing the problem. He says there is a barrel issue of some kind. He's very good at what he does so I tend to take his word for it.

BTW I have a 12 LRPV in .223 and it shoots the .69 gr bullets and even higher (I've shot some 75 gr. stuff and it worked ok but not quite as well as stuff below 70) very consistently. I don't really shoot it at 100 yards very often but I can shoot 5" groups at 440 yards which considering I'm new to shooting longer ranges is not bad I think. I don't notice a lot of difference between the heavier bullets and the 55 gr. stuff.

[borg]

It does sound like a barrel issue. It sounds just like barrel heating.

[dsculley]

I agree with using an infrared thermometer. Track the temp change and record barrel temp prior to each shot. Compare barrel temp to impact point and see if there is any correlation. Just an idea. This is something I have been considering with my rifle, track temp to see how much change is required to change impact point.