Load Development Inconsistency

[fasteddie911]

Hi,
I have a 30-30 lever action that I'm trying to work up some loads for. This is my first lever action that I'm developing a load for and I have been seeing some stuff that I really haven't seen before and I was wondering if someone could help me understand whats going on. Basically I have been playing around with remington core-lokts RN, 150gr & 170gr, along with IMR4895 and IMR3031, and a Federal 210 primer. Here's what I've been seeing:

1. I noticed that .5gr difference would sometimes shrink a group considerably, but another .5gr opens it right back up. For example, 29gr. of powder gives 3" group, but 29.5gr gives 1", then 30gr gives a 3" group.

2. Another thing I noticed is that when I get a good group, I try to replicate that load for my next range session, only to have the group open up.

3. The last thing I noticed is that when I would replicate a load, the POI would shift a few inches even though the rifle hasn't been touched.

I've seen some of these things happen before, but not as frequently as I am now, and I was wondering if anyone has some insight or general explanation as to why these things occur and what it could mean. What do you suggest my next steps be? Should I try another powder? Change bullets? or both?

Thanks!

 

[justgoto]

I load develop with my Winchester 94 in 30-30 a lot so this is right up my ally.

.5gr difference would sometimes shrink a group considerably, but another .5gr opens it right back up

Exactly what I experience, when I ladder test I increase grains by .1 increments.

2. Another thing I noticed is that when I get a good group, I try to replicate that load for my next range session, only to have the group open up.

That could be due to the powders used. I noticed an 8 inch difference in POI height at 300 yards with only a 10 degree F temperature change. In some loads that would also open the groups up considerably.
I now use Varget to get around the velocity issue due to temperature changes. Varget burns a bit slower than the powders you have listed. H4895 is a bit slower than IMR 4895 but I bet it isn't by much. H4895 is an "Extreme Powder" which is temperature insensitive, give that a try.

3. The last thing I noticed is that when I would replicate a load, the POI would shift a few inches even though the rifle hasn't been touched.

Ballistic inefficient bullets are very sensitive to wind; just a 5mph wind can account for 2 or so inches at 100 yards. I've used the Hornady FTX bullets to cut the wind better.

 

[boomtube]

Your group changes following charge changes are typical, that's why we must experiment to find the best shooting charge.

You may be expecting too much. Win 94s typically shoot 3 MOA groups no matter the load, while a really good Marlin 336 might shot 1.5 MOA groups. Bad load choices will make that worse.

You tell us what powder and bullets you are using but not what rifle; that matters! Marlins do tend to be a bit more accurate than Winchesters but consistant 1" groups are virtually impossible with either. Shakey benches and rests, wind, poor triggers, inexpensive scopes in "see-through" mounts and unskilled shooters combine to make it quite difficult to obtain high accuracy!

Occasional small groups of a few rounds are statistical anomolies with no value. All that really matters are groups with a lot of holes, say twenty or more, only that will actually let us know what our rig is capabile of. For instance, say your rig and load is a 4" shooter. You fire and put three rounds into an inch cluster high and right and later put three more low and left but the outside shots are within 4"; you really don't have two tight groups with two POI, you have six shots inside the expected range.

 

[bigngreen]

One thing to make sure of with the lever actions is to make sure the tube is in place properly and make sure the wood is secured, if things get loose they will change. The FTX bullets seems to be a great bullet in these from what I've seen.

 

[fasteddie911]

Thanks for the suggestions. It is a marlin 336, and it sounds like I may be expecting too much from it. I was hoping for 1moa, but maybe that's too high of an expectation. I have seen 2moa more consistently and possibly that's as good as it will get. I have a few more loads I'm going to try and I'll try to pay attention to those things you guys have mentioned. Thanks!