velocity spread!

S

stenger

Guest
i am currenlty shooting a 6.5-284. i purchased the gun from a benchrest shooter that came into financial problems. the gun shoots really well i have shot groups in the .0 range. my question is i am getting a 40 fps velocity spread from this load and want to know how i could reduce this, or should i just leave it alone since it shoots so well. The load is 49 grains of 4350, Lapua brass, SMK 142, and federal 215M primers. i think that the problem is with the primers. also it is shooting a an average speed of 2930fps. what do you all think?

Thanks!
 
Last edited by a moderator:
2930 fps

If your load is shooting at 2930-fps and shooting that well, leave it alone. The more I shoot a 6.5-284 the more I like a load at 2930 to 2940 rather than faster. Shoot it and enjoy it.
 
If your barrel is around 30" long, then there is a good accuraccy node around the 2920-2950 fps. The big velocity spreads might be OK at 100 yds, but I would say that at 1000yds verticle would suffer. I know that 100yds BR shooters dont weight their charges as it doesnt matter at short range, while serious 1000yd BR shooters weigh everything.
Some guns like dfferent primers, I would say most likely due to firing pin/spring differences, but my target guns shoot least verticle with PMC primers, while other people dont like them. I dont think anyone has had much luck using 215 magnum primers in a case that size with H4350 powder, I would go to 210 primers, not 215s. Maybe a primer change or different neck tension might help get the spread down.
 
Last edited:
40 fps deviation is likely to eat your lunch at long range.
 
spread

thats what i am thinking. i am currently at .002 under loaded round for neck tension. i think i will try different primers. Hope the groups stay the same.

thanks
 
49 grains of H4350 behind the Sie 142 is a bit hot, particurlarly with the newer lots of powder. I suggest you back down to 48grs. then try 48.2, 48.5,48.7 and 49.0 looking at 3.8 fps for each .1 grain increase. Somewhere before 49.0 grains you will see the vel/powder charge linear, but as you go up velosity will become erratic and thus explain your high extreme spread. 48.0 to 48.3 will most likely have a lower extreme spread. Once you get the powder charge that produces the better extreme vel. spread, try weigh sorting the brass and sorting the bullets by bearing surface for yet even lower vel spread.
 
I shoot the same round (6..5 x 284 Shehane) and I weigh and sort the cases and bullets.

My load:
Case: Lapua. Neck: .288 (loaded) rifle has .290 neck.
Powder: 51.5 H4831SC (new cases are fired using 50 grns) 3030 fps.
Primer: Fed 210M
Bullet: 142SMK (measured and weight sorted) 13 tho. in to the lands.

My spread was off when I first started shooting as well but I found the problem to be measuring the powder more than anything else.
I use two separate scales to measure the powder, it seems ridiculous but I will take out or put in 1 grain of stick powder to get the desired amount.

The spread is usually under 10 fps.
 
The first thing to do to get better ES/SD numbers is to stop using magnum primers, not only are they not needed in a 6.5 X 284, they are too hot for a 6.5 X 284 and likely the main culprit behind those larger velocity spreads. Strt using either the Federal or CCI match standard large rifle primers.

Once you've done that you may have to alter your load slightly to make up for the less hot primer, but what you should get is more consistant ignition.

After that it's the quest for uniformity. Uniform brass, uniform neck tension (occasional annealing as required helps here), uniform powder charge weights, uniform seating depth (after you've ascertained what seating depth your rifle likes best) and that should get you towards single digit ES/SDs.
 
You must log in or register to reply here.
Back
Top