Changing Brass = Changing Accuracy?

[hugo121175]

I have been reloading .277 135gr SMK's with 60gr IMR-4350, Fed GM215M primes, and Win brass for my 270WSM. I have been getting .6 to .3 MOA from this load. I had some Federal once fired brass laying around, so I thought I'd use the same load as above to see what accuray I can get. I know what you guys are going to say "If it ain't broke, don't fix it", but I figured what the heck

What happened shocked me. I went from shooting sub MOA groups to shooting 2.876 MOA! Holy heck Batman! I just can't get my head wrapped around how far apart the group sizes are from just changing brass. Why is the accuracy sooo different?

The brass was all prepped the same way:
Cleaned
Trimmed
Deburred
Primer Pocket Uniformed
Flash Hole Deburred
Annealed
FL Sized

All Load were loaded the same:
Primed with GM215M using Lee Auto Hand Priming Tool
Charged with IMR-4350 from the same 8lbs container to < .1gr tolerance
Topped with sorted 135gr SMK to the same COAL using a Redding Competition Seater



Hugo

 

[ChadTRG42]

Re: Changing Brass = Changing Accuracy?

Correct. When you switch brands of brass, you get different thicknesses, which create different pressures from another case, and can change up your neck tension. This will all effect you load and pressures. And if you run a hot load and switch cases, you can start blowing primers and causing major problems. Once you have a load for a set of components, stick with it. If you change components, then re-work the load. For my 270 Win ammo, I use 3 different brands of brass, one for each bullet I shoot. So when I clean and size it all, I look to see which headstamp (or brand) I need for a certain bullet I want to load.

 

[craigp40]

Re: Changing Brass = Changing Accuracy?

Chad is spot on. Internal case volume and neck tension could vary significantly between brands, thus affecting pressures. I'm sure you could find another load with the new brass, but you'll have to play with it a little. Best to just stick with your original brand.

 

[mwroseberry]

Re: Changing Brass = Changing Accuracy?

Correct, actually you can even head space your rifle spacifically for the brass you're going to be using. I knew I was going to be going with winchestor brass so I headspaced it using winchestor brass instead of the sami gauge. Alot of guys might frown on that because I won't be able to switch brass manufactures without changing headspace but I know I was going to stick with one manufacture.

Good luck,
Merritt

 

[aggiesig]

Re: Changing Brass = Changing Accuracy?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mwroseberry</div><div class="ubbcode-body">Correct, actually you can even head space your rifle spacifically for the brass you're going to be using. I knew I was going to be going with winchestor brass so I headspaced it using winchestor brass instead of the sami gauge. Alot of guys might frown on that because I won't be able to switch brass manufactures without changing headspace but I know I was going to stick with one manufacture.

Good luck,
Merritt </div></div>

Why couldn't you just trim the other brass manufacturers to winchester specs or if it's too short fireform it to your chamber?

 

[hugo121175]

Re: Changing Brass = Changing Accuracy?

Thanx guys..... I'm going to stop trying fix my anvil, and just stick with Winchester brass until I can afford to switch completely to Norma....


Hugo

 

[mwroseberry]

Re: Changing Brass = Changing Accuracy?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: aggiesig</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mwroseberry</div><div class="ubbcode-body">Correct, actually you can even head space your rifle spacifically for the brass you're going to be using. I knew I was going to be going with winchestor brass so I headspaced it using winchestor brass instead of the sami gauge. Alot of guys might frown on that because I won't be able to switch brass manufactures without changing headspace but I know I was going to stick with one manufacture.

Good luck,
Merritt </div></div>

Why couldn't you just trim the other brass manufacturers to winchester specs or if it's too short fireform it to your chamber? </div></div>

Because brass wall thickness can not be trimmed out. Well it can't I just wouldn't recommend it.

 

[armymedic.2]

Re: Changing Brass = Changing Accuracy?

your loads fine, it is the rifle that shit the bed.

bring it over again so i can shoot it in for ya and get her back to were she needs to be :}

 

[hugo121175]

Re: Changing Brass = Changing Accuracy?

Hahahaha..... Medic, you can watch my trace for me this week-end.....