257 Allen Mag long range testing.....
I finally was able to get out this morning for an hour or so to try the 257 Allen Mag out at some longer ranges. Let me work up to this though by letting you know how it has been performing at 100 and 500 yard ranges.
After some load development I got the rifle to consistantly print three shot groups in the 3/4" range at 100 yards. Nothing amazing but with a 156 gr ULD RBBT at 3300 fps in a 30" #5, heavy fluted barrel with a very fast 1-7 twist, I think very respectible.
I was expecting to get groups in the 2" to 3" range at 500 yards but when I tested at this range my tinkeritous kicked in and I lengthened the seating length by 0.010" to get a bit closer to the lands. Bad idea. This rifle has proven pretty sensitive to seating depth in both pressure and accuracy.
Anyway, with the longer loaded rounds I tested at 500 yards. First three shot group, 4" ctc. Not bad but not what I wanted. Second three shot group, 7" ctc!!! Again not want I was looking for.
I began to think maybe I had crossed the limits of barrel mass and length with this long, light barrel. I packed her up and headed to the 100 yard range as I had some customers rifles to test before shipping. On the way I remembered the longer seating depth. I had three rounds left of the original length loads so when I set up at 100 yards I shot three of the long seated loads and they cut a 1.75" ctc group at 100 yards. I then fired the three original length loads, 0.010" shorter and they cut a .201" cloverleaf!!!
I felt confident I had found my problem. That was a week ago and I have not had a chance to get back out and test so this morning at 6:30 I packed the rifles up and headed out to my long range shooting area and set the rifle up with the original length loads.
This was a very imformal range test, just wanted to see how consistant the rifle would be at longer ranges. Found a small white rock(8" diameter) laying in a clean dirt bank on the side hill 745 yards away, perfect for seeing bullet impacts. The rifle was impacting right at 13" low at 500 yards so I used the third mil dot down from center as a reference hold and let one of the big coated 156 gr ULDs go down range. Dust flew almost instantly as the trigger broke, even at this range they flat out get there almost instantly!!
The shot landed high, basically right under the second mil dot down. Seeing that I then moved over to a slightly larger rock, around 15" in diameter with a clean flat face. I placed the second mil dot down on the top 1/4 of the rock dead center and pulled the trigger.
A large cloud of white smoke boiled off the rock face at the break of the trigger, and then the dramatic WHACK drifted back to my shooting position.
Shot three more shots and all four clusted in a 4 to 5" group on the rock, I was very happy [img]/ubbthreads/images/graemlins/grin.gif[/img]!!
After testing at 500 yards I was thinking that may be the limit of my shooting at my pronghorn in October but after this range test, it is clear the rifle will easily reach 800 yards with 1/2 moa consistancy so we are back in business.
I also tested the 7mm Allen Mag with the 200 gr ULD RBBT and the 270 AM with the 169.5 gr ULD. Once dialed in the 7mm went five in a row on the rock as fast as I could pull the trigger. THis was the first time I shot this rifle past 300 yards so I was very happy.
I though the 257 and 270 were fast on target, the 7mm is flat out crazy fast to get on target and the impact even more impressive.
The 270 AM was, as usual boringly consistant. Making hits on this size targets at this range is simply to easy for what is really a heavy sporter rifle. TO be honest they all had 100% hit ratios at this range once dialed in on the smaller target rock.
Now its time to develope the drop charts from 0 to 1000 yards and get ready for daddy big buck pronghorn to make his appearance!!!
I have learned one thing though, I feel for a 30" barrel, one is best served keeping barrel mass to a #6 contour as a minimum.
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
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