Re: 175 gr. SMK and 7mm Allen Magnum
Today I had to head out to the range and test a couple customers rifles so I decided to do a quick load development with the 175 gr SMK in my personal 7mm AM which is based on a trued Rem 700. Most that have been on LRH have seen this rifle many times as its taken a fair amount of big game over the past few years. The barrel is quite long in the tooth and it simply will not shoot the 200 gr ULDs any more, infact it has since before last hunting season.
That is when I switched to the 160 gr Accubond which shot pretty well in the rifle, not steller but plenty good enough for big game hunting out to 800 yards or so. It however is not a real wind beater. I loaded the Accubond to 3350 fps which is relatively mild but still over what the 7mm RUM should be loaded to with this bullet in a 26" barrel length. I have loaded them up to 3500 fps but do not like to push the Rem 700 that hard.
Anyway, after playing with the 175 gr SMK and knowing its jacket is much heavier then the 200 gr ULD or 180 gr Berger which are both based on the J-4 jacket. I decided I would see what it would do in my little green rifle.
I also wanted to work up with Retumbo just to see how this powder performed with this bullet weight.
Remember that I was driving this bullet to nearly 3500 fps in a 28" barrel but this was with a Nesika Bay model M receiver which is extremely strong and rigid. I had no plans on pushing my Rem 700 based 7mm AM this hard.
Anyway, long story short, I worked up to 94.0 gr Retumbo under the 175 gr SMK, Fed-215 and seated to 3.570" OAL which was 10 thou off the lands. This load averaged right at 3320 fps. Being only 30 fps off my 160 gr Accubond load, I was plenty happy with that and there was no real sign of excessive pressure. Loaded some test ammo up and headed out to the range.
The wind was a serious problem, 20-25 mph crosswinds. The customers rifles shot very well inspite of the wind so I was able to get them proven and packed up quickly and then I turned to my 7mm AM to play a bit. The listed BC of the 175 gr SMK is 0.608". In talking with BJ Bailey a couple days ago, he said that it may be closer to 0.677 from some test results he had seen in a reference.
Since my rifle was set up for the 160 gr Accubond, I had to do some quick adjustment. Found a target rock at 650 yards and used the reference line for the accubond load just to see where the bullet would land. It landed about 1 mil high (I am using a TMR reticle 3.5-10x 40mm FFP Leupold on this rifle. Making an adjustment I realized that the 1.5 mil line was pretty much dead on the money to where the 175 gr SMK had landed at 650 yards.
Then I switched to exbal and worked the numbers over and came up with a quick drop chart off 3320 fps, 0.680 BC and the 1.5 mil line dead on at 650 yards
First test, 520 yards, ran the numbers and let one fly. Remember this is with a 20-25 mph wind ranging from my 3:00 to 5:00 depending on different ranges I was shooting at. For the wind, I had the exbal to list drop in mils but windage in moas and I simply dialed in the windage.
First shot at 520 yards landed about 4" low on the left edge of the rock. Made a slight scope adjustment and also made a slight adjustment on exbal. Took a second shot and this one broke the right edge of the 5" diameter target rock.
Found another target rock, this one at 835 yards. Ran the numbers and found the hold and dialed in the wind. First shot landed just on the top edge of the rock. Second shot was about the same impact but a few inches to the left, wind....
Tweaked the drop chart slightly. Took two more shots and these two landed on either side of the rock, which was roughly 6" wide.
Now I moved out to a rock that was 995 yards. Ran the numbers, found the hold dialed for the wind which was around 9 moa. This target rock was the smallest of the three shot at so far, 4" diameter at the largest. Had it not been bright white, I would likely not been able to see it to shoot at it.
First shot broke the right edge of the rock and kicked it to the left about a foot. Shot number two landed just off the left edge, well within 1/2 moa of point of aim. Again, only variations I had seen were windage to be honest, very happy.
Just to fully check drop, I found another target rock at 530 yards. 5" rock. ran numbers, dialed in the wind and took the proper hold, bottom edge of the rock crumbled to the impact.
Then moved to 300 yards which should be a chip shot and again, the bottom edge of the target rock gave way to the 175 gr SMK.
Looking over the notes of the range session it was very clear that 0.680 BC was much closer then 0.608 at least as far as developing an accurate drop chart and predicting the wind. At ranges from 0 to 500 yards it seemed the impacts were running aroun 2" low of point of aim on the drop chart. Well within my requirements as I seldom will be able to shoot that well in the field to see it. Some minor drop chart tweaking will correct for this.
From 500 to 1000, the BC seems to be dead on the money for the most part from where the bullets were impacting compared to point of aim.
I will not say I was suprised by the accuracy of the exbal predictions on the wind because I have come to expect this when you can get an accurate reading on a strong directional wind.
Again, happy with 175 gr SMK and ballistically, it should be far superior to the 160 gr Accubond load. Terminally, I am sure it will not be quite as good as the Accubond but on deer size game it should still perform very well. Hopefully we will see here soon.
I do have the parts for a Nesika Bay based Xtreme Heavy Sporter with a #8 Lilja 1-9, 4 groove, 30" finish length so I may put it together some weekend and see just what this bullet will handle!!!! The more I shoot this bullet the more I like it. More testing to come.
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
Farther, Faster and Flatter then ever before.
Web Page: www.apsrifles.com