Low ES Proves Elusive

[CamTheBam]

Hi Guys,

I thought I might ask you if you had any thoughts on the following.

I've been struggling to get two 6.5 Creedmoor Ruger Precision Rifles to play ball.

No matter what I try, they refuse to yield low ES figures with any degree of repeatability.

I regularly develop loads for rifles, and ESs of 3 or 4 are common for me, with the odd 1 or 2.

However these two rifles regularly produce ESs of 40-50, and very rarely, 15.

I'm tearing my hair out trying to figure out where I'm going wrong.

Brass:
I've tried Lapua SRP (approx 500 pcs), Norma LRP (approx 200pcs) and Hornady LRP (approx 500pcs).

Primers:
I've tried Federal GMM in SR and LR, and CCI SRM.

Bullets:
Hornady ELD-Match 140gr, Sierra TMK 130gr, Sierra TMK 107gr, Sierra SMK 120gr, Sierra SMK 140gr, Sierra ProHunter 120gr, Lapua Scenar-L 136gr, Lapua Scenar 139gr.

Powders:
VV N150, VV N160, VV N550, H4350, RS62.

Process:
I set the F/L dies up so that they are bumping the F/F shoulder back 0.001" (chamber specific for each rifle). The pieces or brass are then run through a RCBS Pro Trim with a 3-way cutter head. The flash holes are then deburred, and the cases are then sorted by headspace, weight and fire count. I then load up a window of approx 4.0gr in 0.2gr increments, three cartridges per weight, and then shoot them over a Magnetospeed chronograph which is double-checked against a LabRadar regularly. I'm looking for plateaus on the curve (as per the Scott Satterlee method), and also tight ES brackets. From there I test seating depth in order to achieve the tightest group sizes.

Whilst both rifles are exceptionally accurate at 100-500yds, their high ES figures make them trixie at 800-1,400yds.

I love the thinking behind in the in-line recoil path on the RPRs, and the fact that they make proper use of the Magpul PRS rear stock. I've found that the scopes exit pupil varies minutely on the vertical axis as you dial from 100-1,400yds, and the PRS allows you to make micro adjustments unlike the stock on say a Tikka T3x Tac A1. In saying that, I developed a load for a Tac A1 which repeatedly produced ESs of 3 or 4.

So as much as I love the design and functionality of the RPR, and as much as my ego is desperate to prove that with enough effort I can develop a load for any rifle, I'm at the point where I'm considering calling it a day and switching back to a Tikka T3x Tac A1.

Have you guys ever encountered rifles which just refuse to yield a low ES?

Thanks,

Cam.

 

[ngb1787]

neck tension? Have u turned necks, maybe chrono is bad

 

[Dusty Stevens]

Ignition man. You aint got it with that rifle.

 

[CamTheBam]

neck tension? Have u turned necks, maybe chrono is bad

A neck tension of -0.002". I haven't turned the necks (I never do). I've run the Magnetospeed and the LabRadar concurrently, and they both show the same results.

 

[Straightshooter1]

Hi Guys,

I thought I might ask you if you had any thoughts on the following.

I've been struggling to get two 6.5 Creedmoor Ruger Precision Rifles to play ball.

No matter what I try, they refuse to yield low ES figures with any degree of repeatability.

I regularly develop loads for rifles, and ESs of 3 or 4 are common for me, with the odd 1 or 2.

However these two rifles regularly produce ESs of 40-50, and very rarely, 15.

I'm tearing my hair out trying to figure out where I'm going wrong.

Brass:
I've tried Lapua SRP (approx 500 pcs), Norma LRP (approx 200pcs) and Hornady LRP (approx 500pcs).

Primers:
I've tried Federal GMM in SR and LR, and CCI SRM.

Bullets:
Hornady ELD-Match 140gr, Sierra TMK 130gr, Sierra TMK 107gr, Sierra SMK 120gr, Sierra SMK 140gr, Sierra ProHunter 120gr, Lapua Scenar-L 136gr, Lapua Scenar 139gr.

Powders:
VV N150, VV N160, VV N550, H4350, RS62.

Process:
I set the F/L dies up so that they are bumping the F/F shoulder back 0.001" (chamber specific for each rifle). The pieces or brass are then run through a RCBS Pro Trim with a 3-way cutter head. The flash holes are then deburred, and the cases are then sorted by headspace, weight and fire count. I then load up a window of approx 4.0gr in 0.2gr increments, three cartridges per weight, and then shoot them over a Magnetospeed chronograph which is double-checked against a LabRadar regularly. I'm looking for plateaus on the curve (as per the Scott Satterlee method), and also tight ES brackets. From there I test seating depth in order to achieve the tightest group sizes.

Whilst both rifles are exceptionally accurate at 100-500yds, their high ES figures make them trixie at 800-1,400yds.

I love the thinking behind in the in-line recoil path on the RPRs, and the fact that they make proper use of the Magpul PRS rear stock. I've found that the scopes exit pupil varies minutely on the vertical axis as you dial from 100-1,400yds, and the PRS allows you to make micro adjustments unlike the stock on say a Tikka T3x Tac A1. In saying that, I developed a load for a Tac A1 which repeatedly produced ESs of 3 or 4.

So as much as I love the design and functionality of the RPR, and as much as my ego is desperate to prove that with enough effort I can develop a load for any rifle, I'm at the point where I'm considering calling it a day and switching back to a Tikka T3x Tac A1.

Have you guys ever encountered rifles which just refuse to yield a low ES?

Thanks,

Cam.

You didn't say whether or not you turn the necks or how often you anneal. Turning the necks was the first thing that made a significant difference with my RPR (mine is in .308) in getting my ES's consistently down. And along with that I anneal my cases after every firing now and that too has made a significant difference. Now am getting ES's that are running 10 - 24 and SD's running 3 - 9. I feel like that's pretty good for a .308 considering they're not as apt to get the lower numbers like 6.5's or 6mm's can do more easily. So, if you're not doing those two steps, you sure should give it a go as it tends to give much more consistent neck tension.

 

[CamTheBam]

Ignition man. You aint got it with that rifle.

Sorry, I don't follow?

 

[CamTheBam]

You didn't say whether or not you turn the necks or how often you anneal. Turning the necks was the first thing that made a significant difference with my RPR (mine is in .308) in getting my ES's consistently down. And along with that I anneal my cases after every firing now and that too has made a significant difference. Now am getting ES's that are running 10 - 24 and SD's running 3 - 9. I feel like that's pretty good for a .308 considering they're not as apt to get the lower numbers like 6.5's or 6mm's can do more easily. So, if you're not doing those two steps, you sure should give it a go as it tends to give much more consistent neck tension.

OK, that's interesting. I'll give those a go. A friend has recently purchased an AMP, and has offered to try a test batch for me.

 

[ngb1787]

A neck tension of -0.002". I haven't turned the necks (I never do). I've run the Magnetospeed and the LabRadar concurrently, and they both show the same results.

Only other thought, take a fired case, drop a bullet inside, if the bullet goes in ur good, if not u need to turn necks, btw, h4350 and fed210m works wonders, i am on my 6th barrel, 20 off the lands, 142smk,

 

[Dusty Stevens]

Sorry, I don't follow?

Consistent and strong ignition is key. Its hard to get low numbers with a factory action

 

[Sandstorm]

My Tikka T3X Tac A1 Gets silly low ES and SD numbers With N150, However shoots much better with the RL16
and slightly higher ES and SD numbers at 500 and up for a Factory Action rifle.....my 2c

 

[Tomo999]

I too own a RPR in 6.5mm Creedmoor, and have put approx 1800 rounds through it at this point. I average a SD of 6 and an ES of 16; no matter what I do I cannot get the ES to consistantly drop into single digits.

I shoot 139gr Lapua Scenar bullets with Lapua SR brass.
44.80gr RS62

I've come to the conclusion after LOTS of testing that I need to try a different primer (using Murom primers at present) or try a different neck tension (am using a Redding Competition neck sizing die with varying collet sizes - .288, 289, .291 & .292.)

 

[carlsbad]

One thing you can do to possibly improve the ignition is to bush the bolt and turn down the firing pin. It is inconclusive if a smaller firing pin gives more consistent ignition but it takes less force to push a smaller diameter firing pin into the primer. It can't hurt. I've been bushing 6.5 Creedmoor RPRs lately for cratering. PM me if you'd like it bushed. 2 day turnaround right now. --Jerry

 

[Evan]

One thing you can do to possibly improve the ignition is to bush the bolt and turn down the firing pin. It is inconclusive if a smaller firing pin gives more consistent ignition but it takes less force to push a smaller diameter firing pin into the primer. It can't hurt. I've been bushing 6.5 Creedmoor RPRs lately for cratering. PM me if you'd like it bushed. 2 day turnaround right now. --Jerry

I haven't taken a look at my RPR. Jerry, have you noticed how much pin fall they have? Is that something that could or should be tuned up?

 

[Evan]

To the OP, is it the original barrel? Mine has a mile to jump to the lands with 147eldm and I think that hurts ES a little too. I'm also suspicious that good custom barrels, chambered well, produce lower ES because they are more consistent, uniform, and straight. Factory barrels are cut with the dullest, sloppiest reamers spinning true to only within 0.0005 on good days in comparison.

 

[carlsbad]

evan,
It is easier to measure the pinfall when you have the bolt in the action. I don't own one but next time I get one in I will look at it.

--Jerry

 

[CamTheBam]

Thanks for all the replies guys... food for thought!

 

[mauser284]

Consistent and strong ignition is key. Its hard to get low numbers with a factory action

I wanted to add that a lot of people think lighter firing pins are better because they might reduce lock time. The problem with lighter firing pins is that they do not reliably strike consistently shot after shot. You really want a heavier pin not a lighter pin. Smaller diameter pin and bushed for sure if it is a mass produce action. Most firing pins have very little bearing surface inside the bolt normally at the very front and near the rear. In a perfect world you would want to more precisely control the movement of the pin inside the bolt body. Consistency is more important than lock time especialy when you want to punch holes in paper not a running animal.

Just because something be it an idea or a practice is in common use does not mean it is best practice or even needed. I find that things people did with old rifle designs often to military surplus action when sportizing them 20, 30, 50 years ago that seem to make sense might not be best practice today!

 

[boogerruger]

One thing you also might look at is the inside of the neck. The pilot bushing on the trimmer can tear up the inside of your neck and can do it on just one side. That's easy to eliminate as a possible problem and some polishing can fix it.

 

[R.Morehouse]

Leave the carbon in the necks, I just run a nylon brush in and out a few times. I run some fine steel wool around the case mouth while it still turns in the Benchrite to smooth out things I can't feel or see. Pay VERY close attention to the seating force. I have found a little more neck clearance helps a LR, 2K per side. I would consider neck-turning, but many seem to be getting away from that. I neck turn and anneal......Best Of Luck

Regards
Rick

 

[Webster]

One thing you also might look at is the inside of the neck. The pilot bushing on the trimmer can tear up the inside of your neck and can do it on just one side. That's easy to eliminate as a possible problem and some polishing can fix it.

The OP posted the question 5 years ago. He probably doesn't have the rifle now.