Target shooting grouping gets worse as I move to a heavier bullet

grntrkguy1964 - September 12, 2021

I had something interesting happen today. I was shooting 7.62mm 150 grain bullets and this happened…so, I switched ammo to match grade 178 grain and the groups were horrible. Anyone else have a rifle that doesn’t seem to like “the good stuff?”

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So what is wrong with that group?   Or maybe you aren’t showing the group with the 178 grains?

IMO, 178 grains is getting pretty heavy.  If you have a 1:12 twist barrel, that is at about the max it can handle.  I’m certainly no expert in these matters, but from what I’ve read, you might just need lighter bullets to shoot better thru your gun.  I’d try some different “good stuff” that is lighter.

 

that was the group that i shot with the 150 grain. the 178’s were about 3″ group. It just seemed strange thats all.

thanks!

 

What was your shooting setup like? Were these just free hand or was the gun in a vice/sandbagged? I’m just wondering if anticipating for the additional recoil was affecting the grouping. 

You could go full out scientific here and sandbag it and have someone else place in an unknown round so you aren’t biased by which load is in there. Taking out human error is important to know if there is something up with your gun and it doesn’t like a particular round. Good job though on noticing this and figuring out before your life may depend on it.

Hope you don’t mind me editing the title of this post to make it more clear on what the topic is about. Feel free to edit it further if you want.

 

Completely shot from a good rest, open sights. So, very little human error. Im gonna try the 168 grain to see if there is a difference.

 

I reload my own ammo, and now am wondering if I should try multiple grains of ammo and see if one is more accurate than the other. 

I’m mostly just a paper target slayer, so going with the lightest grain of ammo is my go to, because I can use less powder and it’s cheaper. 

Give us an update on the 168 grain when you can, I’m interested in your results.

 

Lots of factors could be at play, but if you manage to isolate the differences to just grain weight, there is a very good chance that the twist of the rifling in your barrel just prefers the lighter bullets.

Example: My friend’s 5.56 is a 1-in-7 twist and does not care for the 45-grain or even 55-grain bullets, but it likes 62-grain bullets and loves 77-grain.

 

In addition to all the questions, advice listed here already… different grain weight from the same manufacturer or different grain weight from different manufacturers?  Also, are they different grain weights within the same line? The grain weight might not be the only difference even if caliber is the same – sometimes there are differences in the lines (hunting versus target, match versus everyday) and manufacturers differ quite a bit from each other.

Your grouping on the 150gr looks good!

 

What distance were you shooting at? If at 100 yards or more, that group looks to be at 1 MOA or less, which is the gold standard. Do you have a certain MOA that you are trying to achieve?