When it comes to precision rifle accuracy, ammunition quality can make a significant difference. While modern factory ammunition can offer remarkable performance when paired with Criterion barrels, most precision rifles will not perform to their true potential without developing a handload recipe tailored to the individual barrel.
While one barrel may prefer one particular load, a barrel designed to the same specifications may have a completely different load preference. While working up a load there are four different components that need to be considered:
During our load development process we had already pre-selected the case and primer (PRIME once fired brass and CCI BR2 Large Rifle Bench Rest Primers). These were selected largely due to positive past experience and availability. Much like the bullet and powder, switching primers can have a noticeable impact on velocity numbers and consistency, and may be worth experimenting with during the load development process.
We utilized a new rifle build designed with PRS-type competition in mind. This build offered us a fair bit of flexibility over the course of testing, as it could be evaluated both off of a bipod and in a benchrest assembly. As the author is a .5 MOA capable bipod shooter on a good day, this added support capability came in handy in evaluating the rifle once the shooter’s skill level had been exceeded. While efforts could have been made to decrease group size further from what was experienced during testing, the intent of this article is to showcase the different variables that come into play when accurizing a practical precision rifle.
The rifle selected for this load development test was built off of a Bighorn/Zermatt Arms Inc. TL3 custom action seated in a Grayboe Ridgeback composite stock with a Grayboe DBM. The optic selected for this build was a Nightforce ATACR 5-25×56 F1 with a Tremor 3 reticle mounted in Nightforce rings. A Timney 510 trigger with a wide trigger shoe was also used.
Topping off this precision rifle build is a Criterion Savage pre-fit barrel locked in place with a Bighorn Arms 12 point nut. While most Criterion pre-fits feature a standard Savage style barrel nut, this new prototype nut is torqued into place with a standard 31mm box wrench.
The barrel itself is 22” long, chambered in 6.5 Creedmoor, and features an MTU contour with a threaded muzzle. Installed on the barrel is a Griffin Armament Taper Mount brake, designed to be cross compatible with a Recce 7 suppressor (not used in this article).
Both the barrel and the barrel nut have been salt bath nitrided to maximize barrel life and enhance corrosion resistance. The TL3 action has been cerakoted graphite black to match the optic and barrel in coloration.
The old saying “there is more than one way to skin a cat” applies to load development as well. Ladder testing, optimal charge weight testing, and countless other solutions exist that all serve to accomplish the same goal: Finding the ideal handload recipe in as expedient a manner as possible.
On the other extreme is a thorough scientific analysis. It’s possible to invest countless hours and dollars researching each independent variable, monitoring velocity numbers for each course of fire, collecting larger sample sizes of each load recipe, and retesting to confirm results after adjusting each individual variable.
Unfortunately we have neither an infinite supply of time, labor, or barrel life (this barrel is supposed to last the author through the upcoming 2019 shooting season) to allocate a few thousand rounds working on load development. We decided to take a middle-of-the-road approach between the two extremes instead.
This approach revolves around three key variables in load development:
• Bullet selection
• Charge weight
• Seating depth
By taking known quality components and tweaking these three variables, a shooter can typically find a fairly optimal load recipe. If desired results are not obtained by tweaking these three variables, then additional powders and primers should be tested as well.
Aside from these three factors, we also incorporated two other major variables in load development:
• Handload quality
• Rest/Support quality
Over the course of this test we incrementally increased the quality of the handloads. During the initial bullet selection tests the handloads were fairly casually loaded, using looser tolerances and production methods. During charge weight testing more attention was paid toward refining loading processes, reflective of the quality of loads we would typically utilize during PRS match preparation. The loads used during the seating depth portion of the review begin to approach “benchrest quality” with extreme attention to detail paid toward each component and how it is loaded.
The final variable explored during this load development test was the quality of the rest or support used. During the initial bullet selection the rifle was fired from a standard “field configuration” supporting the rifle with a simple bipod (Harris BRMS) and Tab Gear rear bag.
During the charge weight testing the rifle was fired off a Sinclair benchrest with Edgewood front and rear bags. While this offered a more stable shooting platform, the fore-end of the stock was not ideally contoured for the inlet of the front bag.
On the final seating depth test the same Sinclair benchrest assembly and Edgewood front and rear bags were utilized, but a Sinclair benchrest adapter was installed beneath the stock, offering an extremely stable and repeatable position. During this last test the trigger pull weight was also reduced to 2.25 lbs from its slightly heavier factory weight.
Test 1: Bullet Selection
We started our load development testing by testing three different bullet designs. Normally we recommend evaluating a few different bullet types during any load development attempts, as each individual barrel (even those in a similar configuration) will have their own individual preference.
The three bullets evaluated were drawn from some of the most renown manufacturers in the industry.
Sierra 142gr. MatchKing:
One of our favorite bullets found in a variety of factory loads. We have encountered solid results from Creedmoor Sports 142gr. 6.5 Creedmoor load featuring this particular bullet.
|Group Fired||Five Round Group Size (MOA)|
Hornady 140gr. ELD-M:
Hornady ELD-M’s (in the 140 and 147gr. designs) have been reported by many Criterion customers to offer excellent performance with our chamber design. One benefit to this particular bullet is it’s ability to be seated at or near the lands in most AICS magazine designs.
|Group Fired||Five Round Group Size (MOA)|
140 gr. Berger Hybrid Target
This is typically our go-to bullet design for our 6.5×284 F-Class rifles, so we had a number of these on hand for testing and evaluation. The Berger Hybrid bullets feature a blended secant/tangent ogive, which offers combined benefits of reduced drag and easier tunability.
|Group Fired||Five Round Group Size (MOA)|
During the initial loading session we assembled the loads into what we would consider “practice quality handloads”. While the brass was still resized, trimmed, and chamfered, loads were simply metered by an RCBS Chargemaster. Primer pockets were not uniformed or cleaned, and the other components were not weighed or sorted. Occasionally the charge weights would vary +/- .1 gr (for an extreme spread of .4gr when factoring in the Chargemaster’s variation tolerance), but all were accepted. All three loads used a 40.0gr. starting charge of Hodgdon H4350. The Hornady and Sierra loads were seated to 2.800 cartridge overall length (COAL), while the Berger load was seated to 2.850.
With 15 rounds of each bullet type loaded, we proceeded to head to the range. This barrel had previously been broken in and had approximately 100 rounds put through it. This is normally the point where I feel comfortable beginning load development, as velocities generally tend to settle on a barrel at this point in its life.
The rifle had been cleaned prior to this outing, so we fired an initial five round group of factory PRIME ammunition to foul the bore. From that point we proceeded to fire (3) five round groups with each load. Care was taken to allow the barrel to cool between groups, ensuring surface temperatures were roughly the same for all three bullet types.
Both the 140gr. ELD-M and the 140 Berger Hybrid Target bullets performed quite well. The Sierra 142gr. MatchKing generated a pair of sub-MOA groups, but seemed to experience a bit more horizontal stringing than its competitors. The results from each bullet fired can be found in the below chart:
Test 2: Charge Weight
It was at this point in the testing process when it was decided that this load development process was going to be employed in an article. As such, we decided to up the ante a bit to see how much tighter we could shrink the groups generated with this particular rifle build.
For the second test we elected to use our standard PRS match load procedure. While still metered by an RCBS Chargemaster, charges were tossed out if they didn’t match the desired grain weight. While the Chargemaster still incorporates a tolerance of +/- .1 grain, it’s typically within the acceptable margin of error for the type of performance required by PRS competitors.
Cases were resized, hand primed, and trimmed/chamfered with a Giraud case trimmer. During this step case length and chamfer uniformity was inspected upon removal from the trimmer. Any deviation from the prescribed ideal led to the brass to be added to the “seconds” bin for use in a future barricade practice session.
We began our charge weight testing 40.0 gr. of H4350 as the baseline for the load workup. A comparatively light load, this recipe produced an average velocity of 2609 FPS. As our local and regional match series both max out at 1,000 yards, this recipe should be sufficient for the purposes of this build. A suppressor could easily be added for a slight velocity boost as well.
Five rounds were loaded for each charge weight tested. Each charge weight was metered in .3 grain increments, from 40.0 to 41.5gr.
The following test results were generated during the second course of fire:
|Charge Weight (Gr.)||Five Round Group Size (MOA)|
(During the seating depth test we mounted a Sinclair benchrest adapter to the base of the Grayboe stock to more efficiently ride the front bag under recoil)
Test 3: Seating Depth
During the final stage of load development a great deal more care was taken to ensure consistency from one cartridge to the other. All cases and bullets were sorted according to weight, primer pockets were cleaned and uniformed. While charges were still metered with the RCBS Chargemaster, they were also inspected with a beam scale to confirm uniformity to within +/- .05 grain.
Each of these inspection measures required twice the amount of time allocated toward setup, sorting, and production of each round. While meticulous care can be taken to ensure a significant amount of consistency from round to round, the opportunity cost is less time spent at the range training on different barricades or engaging targets from awkward shooting positions.
With all of the rounds loaded, the final test was upon us. Using the 2.850 COAL as the baseline (all rounds were measured using a comparator rather than a base to tip measurement for additional consistency) we bumped the seating depth out in increments of .005 for each five-round course of fire. The maximum overall length tested came out to 2.875, as longer cartridge lengths would have approached the limits of the Magpul AICS pattern magazines used during testing. Even at 2.875 the distance remaining to the lands measured out to .055, indicative that a fair bit of jump is inherent when feeding this bullet design from a magazine length load while using a SAAMI spec reamer.
(The end result of our load development testing)
Over the course of this third test we discovered what would be considered a fairly distinct accuracy node. While the group size remained fairly small seated to 2.865, bumping the COAL below or beyond that point led to a noticeable increase in group size. The tightest five round group evaluated during Test 3 measured out at .351 MOA, proving itself to be the preferred recipe for this individual pre-fit barrel.
|COAL||Five Round Group Size (MOA)|
Accuracy requirements vary considerably depending on the intended marksmanship discipline the shooter is competing in. The criteria for an accurate 3-Gun rifle normally falls in the 1 MOA range. PRS and F-Class competitors typically require consistent .5 MOA performance to bring home a trophy or to set a national record.
Benchrest competitors hold their rifles to an even higher standard, typically requiring sub-.25 MOA rifles to compete, frequently shooting group sizes in the low .1’s to win matches. Unlimited Class benchrest railguns typically weight upwards of 50 lbs and are built to maximize the efficiency of each rifle component used.
It is quite logical to assume a pre-fit barrel mounted on such a rifle could likely generate tighter groups than the rifle configuration described in this article. Testing would also be carried out inside a climate controlled enviroment where wind reading would not be required. While the author is admittedly a fairly average shooter, a more accomplished marksman would likely be able to consistently produce smaller groups.
Additional variables that also may have improved overall rifle precision when compared to what was encountered during testing include the following:
• Glass bedding the stock (the Grayboe Ridgeback has aluminum bedding pillars, but the action was not glass bedded during assembly).
• A stock optimized for shooting off of a benchrest.
• A higher magnification optic with a finer reticle design.
• Further reduced trigger pull weight and takeup.
• A heavier rifle designed to further mitigate recoil impulse.
• Seating closer to the lands (between .000 and .035) likely would have further reduced group size.
Through this load development testing we can confirm that Criterion Savage and Rem/Age pre-fit system should have no problem generating consistent sub-.5 MOA groups utilizing a quality handload recipe on a well-built practical precision rifle. Pre-fit barrels are quick and easy to install, simple to maintain, and a relatively affordable solution for a top tier competitive rifle build.