Lower sd and extreme spread?

[Furtaker21]

I have Redding T7 and RCBS rockchucker presses. I use Redding competition bushing dies and sometimes lee collet dies for neck sizing. I use a RCBS chargemaster lite powder dispenser. Using hornady brass I cannot seem to achieve any consistently good extreme spreads or SDs. Sometimes 30-50 FPS. Sometimes more. This is bolt gun. With .204 ar15 today I was shooting three shot groups. First two shots were within 10-15 FPS, third shot would be like 70-80 FPS slower. My groups are always sub moa (commonly 0.5” ) at 100. The extreme spreads are frustrating though. I do not turn the necks though. I do not weigh brass. I haven’t went to that extent to see if that’s the missing variable. I also haven’t used lapua brass yet. I’ve used some norma and starline but haven’t really had a large sample size with those two makers yet. Mainly I’ve had hornady and federal I’ve kept from factory ammo. If my weak link is neck tension, I’ll probably just live with the results I’m getting as my ammo is accurate enough size game I hunt and the ranges would encounter them. I almost forgot to add that I’m using a Caldwell chronograph and I’m questioning whether or not the chronograph is reliable. So many variables. Just wanted to check and see how critical neck tension is from folks who are more experienced than I with reloading. If there’s something I should be paying attention to other than turning necks I would appreciate any input.

 

[zr600]

Neck tension is very important for es, are you annealing your brass? Also what is your procedure for finding a good powder charge? There is lots that go into this. It could be the chrono graph possibly too. Do you know anyone with a Labrador or megneto speed I would trust them a lot more. Also if not you could shoot at distance on a big target and figure out your drop too, and compare it to the ballistic calculator for velocity that would ha e you right in the ball park. If it shoots good at the furthest distances that you shoot I wouldn’t worry about the numbers.

 

[AWS]

If the groups your rifle work for you why bother chasing something that isn't important.

I have a chronograph and the only time it comes out is when I'm loading for cartridges with No data available to. If I have data available I just find a load that will do what I need be it killing coyotes or punching tiny groups on paper. Sometimes we let technologies drive us too much.

 

[spotstalkshoot]

Load for minimum vertical dispersion, one caliber(.204 in your case) or less @ 100 yards. You are shooting a gas gun, not a sealed bore. Even 100 fps means very little at 300 yards. Your chronograph will have a +,- error %, faster the round more fps of error.

 

[arlaunch]

I have found changing primer brands can reduce extreme spreads by a long shot some times.

Certain powder types just flat out shoot more consistent than others types also.

Certain brands of brass

Weak or inconsistent firing pin spring

Case fill also plays a large part in this.

+/- .1 grain during the powder charging process really means a .3 grain powder charge spread. That can easily be 25+ fps spreads depending on the caliber.

If you are firing some brass with 2 firings mixed with brass with 6 firings, that will make a difference also.

Bullet release with perfect necks and annealing is when you are trying to get E.S. down from 20 fps to 10fps

 

[pyscodog]

Originally Posted By: AWSIf the groups your rifle work for you why bother chasing something that isn't important.


Sometimes we let technologies drive us too much.


I couldn't agree more.

 

[mbaysinger89]

ES really doesnt matter inside 400 yards. If you are long range target shooting it makes a huge difference. I like to do load development at the max distance for the rifle youre loading for. Good brass does make a difference.

 

[BrianID]

If your 204 is consistently shooting 1/2 MOA, I wouldn't worry about ES.

ES doesn't become a significant factor unless you are shooting long range. A 204 isn't a long range cartridge. Wind drift is going to be a bigger problem for your 204 at 500+ yards more than your ES. There are so many things that can affect ES and getting a low ES requires everything to be correct. The barrel temperature is likely a factor in your ES.

I do think it is possible that your chronograph numbers are not accurate. My Labradar provides me data that I believe more than my old chronograph.

 

[Dholsapple]

I’m not completely convinced my Caldwell chronograph is completely accurate. A load I was working on the other day was within 15fps for about 6 out of 10 and read 2 around 40 FPS lower than that average and had 2 about 40 FPS higher than the average but they all grouped together and hit the 10” plate at 650. With the reading of almost 100 FPS difference I would’ve expected there to be more than an inch of difference in height at that distance. I don’t neckturn but use a bushing die to size the outside of the neck. I wondered if that caused the irregularities in the brass to be pushing against the bullet on the inside with uneven neck tension so I got a mandrel die. Now after resizing I run the cases thru that and size the inside. I can’t say it helped the es for sure but I can say it definitely helped the concentricity. It was not uncommon to have some bullets .004 or .006 of variance and now I’ve checked about 30 rounds and only had 1 that had .001 of difference with the rest having half that. My next step is to order a magnetospeed as they seem to be reliable. Until then I guess if it groups it doesn’t really matter. I know I didn’t give you any help on getting the es and sd down but your not alone haha.

 

[Kpuck08]

I use Hornady brass in my .223 reloads and Starline brass in my .243 reloads.

If I remember correctly the Starline brass weighs about 168 gr and has a spread of about 2 gr over the lot. my Hornady brass is somewhere in the 90's and ranges from 90-100 gr.

So the Starline has a 1.1% variation and the Hornady has about a 10.5% variation. I'd imagine the brass weight variation in your Hornady brass is your culprit.