Range Report Bullets not stabilizing?

[m1ajunkie]

I'm having some issues with a bullet in a rifle I have a lot of time shooting, and can shoot very well with my known loads (175smk). When trying out the 178 amax and shooting for groups, I can occasionally get some sub 1" 5rd groups at 100yds, but usually 3-4 of the rounds are well under an inch with 1-2 fliers 1-2" out making almost all the groups 1.5-2" total. 10 round groups usually have 7 rds under 1" with 3 fliers opening the group up to the same 1.5-2" size.

Is this a sign that my rifle is not completely stabilizing the bullets, or would it show no kind of group if that was the case? How can I tell if I am having stabilization issues? Am I just overlooking something here?

FWIW, my rifle is a 16" .308 gas gun, 1/11.25" twist rate. I've almost always shot the 175smk, but decided to try the 178amax and got these results. I am almost 100% confident that the issue is not me because I can swap to my good 175 load, or drop in my 6.5cm barrel and easily shoot sub moa groups.

 

[One-Eyed Jack]

You've proved it's not you, but accept the fact that your rifle doesn't like 178AMAX bullets. The "barrel harmonic" theory could explain why the Hornady bullets work differently in your rifle. Anyone who shoots 22LR a lot knows that rifles may like particular ammo and hate other ammo. Unless you see keyholes in your target, it's not stabilization. Forget the AMAXs and stick with 175SMKs.

 

[damoncali]

To put it bluntly, the 178's are shooting 2" groups for you. If 175's do better, use them.

 

[roggom]

I am sure you worked up the 178 Amax and did not just use your old formula. Even then try to vary seating depth and see if that shrinks the groups. Amax's are usually very forgiving because of the ogive type. You will be surprised how much a few thou can effect flyers.

 

[melloyello]

The biggest question here is, did you work up a load or just use what you were using for the smk? I mean, did you do any OCW testing, ladder testing, grouping or just load the same powder charge and seat a 178amax?

 

[m1ajunkie]

Thanks for the info so far. I didn't think it was a stabilization issue since the 175gr bullet is only 3grs lighter and shoots great. The current situation is forcing me to try other bullets than I normally shoot because I am running low on the 175smk.

I did work up a load, and even experienced the fliers during this process. At that point I was thinking maybe I was just having a rough day at the range. It wasn't until this weekend that I got out to really test the amax that I figured out I was shooting fine, it was just throwing fliers.

I'll play with seating depth and see what happens. Hopefully that is a fix because the rounds that group well in a group are roughly 3/4" which is well within my expectations.

 

[wvlapua]

Definetly play with seating depth. I had this problem with berger 155.5 fullbores. They had to be loaded way closer to the lands and needed a slightly faster powder than the 175smk and 168 berger. So long they have to be single fed.

 

[lanwickum]

My DTA covert 308 shoot some bullets so bad I was getting 4-5" groups at 100. I can shoot others under .5moa. My other 308 with rock barrel shoots everything I put through it at or under 1moa. Sometimes you have to figure out what works and use it.

Seating depth can make big difference I recently fully discovered. Was trying 210 bergers in the DTA. At 2.8" OAL they shoot horrible. Seated them into the lands roughly .010". It was under .5moa. First group was .25moa. Because of the horrible accuracy at first I just gave up on it. Working up loads I can tune them into .5moa from 1moa or such. I have never seen 2-3moa to under .5moa with the same bullet until then.

 

[melloyello]

Are you shooting over a chrono? Have you noticed any velocity swings on the fliers? I have used the same brass, primer, powder, bullet length, seating depth, etc and have seen 80fps difference on 1 or 2 out of 20rds fired. Thought it might be the chrono giving the bad numbers. I try to keep everything the same everytime I reload but it happens sometimes.
I have a load for 178 amax that has proven to shoot .4-.5"@100yds several times and just yesterday I got these numbers:
2458 2510 2432 2456 2424 (1.355"@100yds)
Where did the 2510fps come from? It should take at least 1gr more of Varget for me to get that velocity per my load work up notes in my book. And looking back at my pic of that target 1gr and 1.5gr more shifted my POI to the right almost an inch at that velocity. That was the flier that opened my group way up and I almost guarantee that the change in velocity changed the wave of my barrel which changed the POI. It's right there in my noted history so I can't deny it. This load normally has an average of 2423fps and a spread of 32fps. Take out the 2510 and you get an average of 2442fps and spread of 34fps. That's pretty close to my past results. Not the fastest load but it is something I was planning on using if I ever wanted to use this gun to hunt and it would get the job done out to 300yds for me.

 

[m1ajunkie]

I haven't ran the 178's over a chronograph yet. I'm going back out this weekend so ill work with seating depth and try to get some velocities. I'm also getting some 168smk bullets to start working with.

I'm hoping things will go back to normal and ill be able to just shoot the 175's like I always have, but I guess this is a way to try other bullets out.