barrel and twist vs bullet

[slamb750]

I have a RRA varmint a4 with the 18 inch barrel and 1/8 twist. Doesnt look like the gun likes the 55 grain bullet. With this barrel do i need to go with a heavier or lighter round. I some 52 grain and it grouped great. I thought with the faster twist I should be shooting the heavier a bullet.

[AR15barrels]

Faster twists will show better accuracy with longer bullets.
Longer bullets are usually heavier as well.

The difference between the 55gr and 52gr bullets you were using is probably in the QUALITY of the bullets.

The better the quality of the bullet, the better they are going to group as long as they are the appropriate length/weight for the twist rate of barrel you are using.

Your 1:8 barrel should be excellent with 77's and 80's, but your pocketbook probably prefers 55's.

[Grin Reaper]

Doesnt look like the gun likes the 55 grain bullet.

I take it this is a problem with groups, and not reliability?
I've not encountered this in a 1-8 bbl (haven't fired a 1-7 enough to have an opinion, yet). It's even stranger that you found the 52gr a better performer in this twist rate, since it typically performs very well with heavier bullets. To be frank, I'm as confused by this as I imagine you are.

Was this problem with a single type/brand of ammo? 'Cause if so, I'd try another brand & see what happens.

[slamb750]

Im asking this because I would like to start reloading. The 55 grain ammo i was shooting was partisan paruvian. Im sure the spelling is wrong but anyway, my bolt rifle loved it. My AR wont group well with it. Wonce I figure out this reloading concept I'll have to try out a few different bullet grains .

[gunny]

www.ammo-oracle.com

[slamb750]

link is not working.

[AR15barrels]

The 55 grain ammo i was shooting was partisan paruvian.

I'll post it again because you seem to have missed it...

The difference between the 55gr and 52gr bullets you were using is probably in the QUALITY of the bullets.

Privi Partizan ammo is not going to have high quality bullets.
Get some black hills ammo with sierra matchkings.

[Robb Jensen]

I have a RRA varmint a4 with the 18 inch barrel and 1/8 twist. Doesnt look like the gun likes the 55 grain bullet. With this barrel do i need to go with a heavier or lighter round. I some 52 grain and it grouped great. I thought with the faster twist I should be shooting the heavier a bullet.

Generally faster twists work best with longer bullets. BUT that's not a concrete rule. A friend of mine has a 1x7 twist 20" barrel that shoots 52gr MATCH bullets more accurately than any other load tried in that gun (like 1/4MOA or smaller).

[M193 BALL]

I have 2 LMT M4`s 14.5 barrels 1/7 twist

I shoot very tight groups with CHEAP White box WIN 45grHP

[AR15barrels]

I have 2 LMT M4`s 14.5 barrels 1/7 twist

I shoot very tight groups with CHEAP White box WIN 45grHP

Winchester's 45gr white box loads shoot great in almost every gun.
There's something about that ammo that I wish they could figure out for all their other ammo.

If I had to pick an off-the-shelf ammo to use as an accuracy standard for testing of multiple rifles, I would use that 45gr ammo as it's been consistently accurate for many many years.