6.5-284 Tube Gun

07/20/13

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6.5-284 on a BAT Model MB Action Long Range Target Rifle

 

Completed 7/10/08

This rifle project was conceived right after the 2007 F-Class national Championships in September, 2007. After the 2007 competition season, I had come to the conclusion that the MAK TubeGun, while an excellent shooting rifle, was not optimum for prone F-Class use. I had also found that the LowRider stock on the 6 Dasher was a near perfect fit for me and provided a very stable and repeatable platform for precision shooting from the prone position.

I therefore decided to build a 6.5-284 on a LowRider stock, and chose a BAT model MB action as the heart of the new rifle. I ordered a 1.250" OD Broughton 5C barrel to complete the main suite of components. The build up started during April of 2008, with all the work done by myself, as usual.

The specifications are as follows:

Caliber

 6.5-284 Lapua Match

Barrel

Broughton 5C, 1:8 twist, stainless, 31.5" finished length, contour 1.250" straight cylinder

Reamer

Dave Kiff of Pacific Tool and Gauge 6.5 X 284 Lapua Match, 0.297 neck, 0.120 freebore

Receiver

BAT Model MB MultiFlat. This action has an extra 1" of action extending past the barrel to action shoulder to provide additional bedding area for long heavy barrels.

Sight Rail

BAT 20 MOA

Trigger

Jewel HVR
Stock West Custom Rifles Lowrider in Black Rutland laminate, with polished BAT triggerguard. Stock has a Limbsaver pad. Pillars are stainless, made by me for this action and stock. Greg supplied me with a polished escutcheon for the front action screw. It is finished with WaterLox Original Sealer and Finish. The barrel action is bedded with Devcon 10110  epoxy.

Scope

Nightforce NXS 12-42X56 with NP-1RR reticle

Rings

Leupold QRW high, 30MM

Weight 20.5 pounds. I may add 1.0 pounds to the buttstock after testing it for a while.

Break-in showed real promise, with a couple 5 shot groups under 0.5" at 200 yards using left over TubeGun ammo.

7/13/08

Testing some standard accuracy loads for my other 6.5-284 today, it was very obvious that the rifle shoots very well indeed. Three loads were tried, from the standard F-Class prone position:

Moly 142 grain Sierra MatchKing, seated 0.010" back from a hard jam, 49.5 grains H4350, GM215M primer, Lapua brass

Moly 140 grain Berger VLD, seated 0.020" past the hard jam (bolt seats the bullet when chambering), 49.5 grains H4350, GM215M primer, Lapua brass

Moly 130 grain Berger VLD, seated 0.020" past the hard jam (bolt seats the bullet when chambering), 51.5 grains H4350, GM215M primer, Lapua brass

Conditions were not great - switching fishtail wind at about 5 MPH, and a ton of mirage in the prone position. I couldn't even see all the bullet holes with my Alpen 88mm spotting scope. I also observed at least 1 MOA point of impact variation over a few minutes from the mirage. Shooting fast groups to try and get five off in a constant condition, I was able to get a couple 0.7" groups, but some were over 1.25".

I moved off the concrete and sent to a shooting bench, and got rid of a large portion of the mirage. The groups tightened up considerably. All these loads were shooting about 0.5" to 0.7" at 200 yards. The edge went to the 130 Berger load, which was also my best load in the TubeGun. I will be doing a formal re-tuning of this load for the new barrel, and will post chronograph and on-target results.

You can see that the crown is cut square and true from the perfectly symmetrical "star" formed from combustion by products on the 11 degree target crown:

6/12/09 - Reloder 17 and 140 grain Berger VLD Load Test Results!

After months of searching, I finally received some Reloder 17, and today worked up some loads for the 140 Berger VLD (moly). Folks on the internet had reported 100+ FPS velocity increases over H4350 in the 6.5-284, so I was itching to try this powder to see for myself how it performed. My standard H4350 load (140 Berger VLD moly, 49.5 grains H4350,GM215M primer, Lapua brass, bullet seated 0.010" past a hard jam so that the bullet seats the final distance when the bolt is closed) ran 2940 FPS to hit the accuracy node (1.435 mS for a 31.5" barrel). Getting the 140's up over 3000 FPS would help a lot at the extreme ranges (1500+ yards) that I plan to shoot this summer.

After some QuickLoad work, and a bit of testing at the range, I settled in on 49.4 grains RL-17,140 Berger VLD moly, GM215M primer, Lapua brass, OAL of 3.090. This OAL puts the bullets 0.010" past a hard jam as usual. The results were spectacular. The velocity averaged out to 3066 FPS, with an SD of about 13, and an ES of about 29. This matched the QuickLoad predictions exactly, with a barrel time of 1.428 mS, right on an OBT. The rumored 100 FPS velocity increase with RL-17 is real, and it is very accurate to boot. It also looks like RL-17 will be easier on the barrel than H4350, as the powder has a lower, but broader pressure curve. In addition, the ballistic efficiency of the load (from QuickLoad) is over 31%, two percent better than the H4350 load.

The powder did not like to run much below max pressures, as it got very dirty at the lower loading densities. In this respect it behaves exactly like RL-15 in the 6 Dasher. It likes to run hot. There were zero signs of excessive pressure, even with a load 1 grain over the optimum at 50.4 grains. The groups started to diverge at about 50 grains, but there were no pressure signs. The temperatures were in the mid 70s, and the barrel was getting warm later in the session. I have no doubt that this will be a stable load on the Highpower range, as well as the prairie dog towns.

It should be noted that this is the original Broughton barrel, with about 900 rounds downrange. I set back the barrel by two threads just before this test, so at least it had a new throat. Very good performance for a nearly shot out 6.5-284 barrel.

The conditions were terrible for testing at 200 yards, with heavy mirage, and fishtailing winds of about 8 to 10 MPH. I used wind flags even at 100 yards to help judge the conditions when shooting the test groups, but it was very difficult (at least for me!) to get all the shots off in the same conditions. I have a lot of respect for the short range benchrest folks, this was not easy! Even so, the load was shooting in the 2's at 100 yards when the conditions co-operated, and I didn't mess up. Here was the screamer group for today:

I missed a wind pick-up on this group. It should have been in the 2's:

Needless to say I am very pleased with RL-17 in this cartridge. This will be one very nice PDog load for next months hunt out on the Wyoming prairie. It will be supersonic well past 1500 yards. F-Class results should be just as good. I am going to try and shoot it in a match in a couple of weeks to see how it does at 600 yards.

12/19/09 - Reloder 17 and 140 grain Berger VLD Field Test Results!

The optimum load above (49.4 grains RL-17,140 Berger VLD moly, GM215M primer, Lapua brass, OAL of 3.090) was shot extensively this last summer and fall both at F-Class matches as well as on the prairie dog towns of Northeast Wyoming.  In summary, it is the best long range load for this caliber that I have yet found.

Performance at 600 yards, both in F-Class matches, as well as informal group shooting, was excellent, with a number of sub 1.5" 5 shot groups. During a 20 round F-Class string, the total elevation spread would typically be less than 2". This elevation performance essentially matches the 6mm Dasher at 600 yards, which is saying something. No unexplained flyers were observed.

This last July, the rifle was used to great effect on the prairie dog towns in Northeastern Wyoming. As usual, Ralph at Trophy Ridge Outfitters set us up with some excellent long range prairie dog shooting, and the rifle and load acquitted itself well. Hits were made out to and a bit past 1200 yards. The elevation variation at these ranges was excellent, less than the height of a small standing pup. I did shoot some of the older H4350 loads (~2950 FPS) at ranges of about 800 to 1000 yards, and the RL-17 loads did seem to have a bit of an edge regarding wind deflection, as the velocity increase provided by RL-17 would predict. It was fairly hot at times (90's), and there were no observed temperature related issues: - sticky bolt lifts, flattened primers, or unexplained flyers. This load was just plain solid. I also noticed a slightly different recoil feel to the rifle with RL-17 versus the H4350. The Rl-17 seemed a bit "smoother" and not as sharp. The rifle is un-braked, so this might be due to the smoother acceleration provided by the RL-17. No matter what the reason, it was a bit easier to shoot and keep the sight picture on the target for shot spotting with the RL-17 over the H4350.

In October, I shot a Palma course F-Class match (15 shots each at 800, 900, and 1000 yards) out at the Rattlesnake Mountain range near Richland, Washington. The performance was again excellent, with less than 6" total vertical (under reasonably calm conditions) apparent at all ranges. Now, "reasonably calm conditions" at The Snake can mean that you actually kept it in the black, as anyone who has shot there can attest. The winds at The Snake can be, shall we say, a bit challenging, and it is not uncommon for even very experienced shooters to miss a change and end up in the 6 ring, or worse. Even with that, the elevation held right in there. I was extremely pleased with the performance as I did nothing to tune the load for the much lower temperatures; it was still set at 49.4 grains. The static temperatures were in the low to mid 30's for much of this match, with winds running past 20 MPH at times. It was cold, much colder than out on the Wyoming prairie, which was usually in the 80's to 90's. Again, no pressure signs or other evidence of the load not being tuned correctly.

My summary conclusions are that this RL-17 load is definitely a significant improvement over my standard H4350 load, yielding superior velocity and accuracy. Velocity variations are low, and the load yields very low elevation variances even at extreme ranges. Flyers are not present, and I have a very high confidence that when I point the rifle at the target, the bullet will hit where it is aimed. I never had this complete confidence with H4350 due to infrequent unexplained flyers. I have made the switch to RL-17 for this caliber a permanent thing, and am planning on testing it in the 260AI as soon as the local weather conditions improve. It should be a very good match for that cartridge with the 140 grain bullets.

 

 

 

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