OAL Question

[Howitzer1987]

So I decided that I wanted to try and improve accuracy on my PTR 91 AND PWS MK220 Rifles by finding the ideal bullet seating depth. I went out and bought the Hornady curved OAL length gauge along with the modified 308 cartridge. I am using Prvi 168 gr match bullets for the depth gauge but I keep getting highly inconsistent measurements. I cleaned the bore and put in a bore scope to make sure there was nothing that could affect the measurements but still the measurements are off. I was wondering if anyone has had this issue and how to remedy it? TIA

[highpower790]

Measure oal to the ojive ,not the tip of bullet.

[knucklehead0202]

Measure oal to the ojive ,not the tip of bullet.

^^^This. You'll never get that consistent measuring to the tip unless you make the bullets yourself in a CNC machine out of solid copper. Even then, tools wear out...

[Howitzer1987]

Thank you gents. I have to find my comparator in my toolbox

[baih777]

it could be your bullets also. use the compaarter and measure 10 bullets.

[OpenSightsOnly]

OP are you trying to load longer than magazine length?

Or are you trying to figure out why bullet seating is inconsistent?

If latter, then you may need to sort your bullets based on ogive to base length. If that's too much work, buy 168 grain Sierra Match Kings, Hornady 168 BTHP, or Nosler CC 168 grain.

[Howitzer1987]

Well bullet seating is slightly inconsistent but nothing too crazy. More than anything I was trying to improve the accuracy of both rifles and try to get the best accuracy possible. I figured by tweaking a few minor things like bullet seating depth and even playing around with the maximum cartridge length I can squeeze a tiny bit more accuracy out and get smaller groups.

[baih777]

Maybe try a different bullet. I use hornaday match. And sierra smk.

The reason we suggested to compare the bullets , Is to verify the ogive to base.
This is the reason i quit buying PRVI 62 gr bullets. The variance was .004.

[OpenSightsOnly]

FWIW, you can make gains with match-grade bullets, quality powder, and a consistent powder charge.

Don't know if seating depth will matter (maybe or maybe not) because you are bound to mag length ammo.

Have you tried the 168 grain FGMM?

[Howitzer1987]

Just finished measuring the the bullets and it looks like I am going to be using the last 100 or so that I have for plinking. The variance was pretty significant measuring as much as .006 on one bullet.

[baih777]

Just finished measuring the the bullets and it looks like I am going to be using the last 100 or so that I have for plinking. The variance was pretty significant measuring as much as .006 on one bullet.

The Hornaday 168gr match goes on sale more than the sierra smk.
Midway has a free shipping offer right now. Thats when i order bullets.

[LynnJr]

Bullet variance comes about because the manufacturers use more than one die to make the same bullet.
I have seen 0.023 variation in a box of 100 bullets.
To improve your accuracy start at the longest length that will function properly out of your particular gun.
Work back from that length in 0.005 increments until best accuracy is found and don't be afraid to shorten them up an 1/8 inch!!!!!!!!!!!
The comparator should be used because as you have already seen variations are very common.
There are also different types of seating dies.
The standard dies will push on the bullets meplat so any variation in bullet overall length will also affect your seating depth.
The second type of seater dies use a collar to push on the ogive of the bullet rather than the tip or meplat of the bullet and your seating depths are way more consistent.
Seating depth is the second most important step to accuracy so keep on track with it.

[desert dog]

With your PTR-91, you will likely be loading to a reliable magazine length rather than chasing the lands.

Also, you will absolutely need to crimp with the PTR-91, as that HK91 action puts a tremendous recoil pulse down through the reciever and strips rounds from the mag onto the feed ramp with authority. I would worry about bullet set-back. Get a Lee Factory Crimp Die for 308 to solve that issue.

Also, my two PTR-91s absolutely destroy brass. I just shoot cheap ball ammo through it now. Reloading rifle ammo isn't a good investment if you can't reuse your brass.

[Howitzer1987]

Thank you all for the replies. You were absolutely right about PTR with bullet length and magazine allowance. I honestly just want to see what the rifle is capable of by taking as many variables into account. Thank you guys for all the tips and advice

[boyguan]

So if you size the first one to ogive. How do you seat the rest to match? Doesn't the seating die push on the tip of the bullet? Isn't that the variation we try to avoid by using the ogive?

I see that they place a case with a loose mouth and a bullet into the chamber and close the bolt. Then measure oal and push it in another .002-.005. How is this repeated on the press?