When it comes to long range precision matches, velocity is king. Not to say accuracy isn’t paramount because it is, but I’m willing to trade some accuracy for velocity. The faster the bullet travels the less time the wind has to push it off of it’s target. That’s why I switched from the vernable Sierra 175 grain Match King to the Lapua 155 Scenar. It weighs less and has the the same ballistic coefficient as the SMK. Even with my screaming little Scenar my .308 can’t even touch the ultra-fast 6MM or .260. But I degres. My point is you have to get your bullet moving to pay less penalty to the wind, which in turn means higher pressure loads.
Working up a new load with my Remington 700 chambered in .308 I used the Optimum Charge Weight (or OCW) philosophy where I typically have a super accurate cartridge at the lower accuracy nodes and just about the time I should see another accuracy node on the high end I would see the bullet impact all over the place. I tried different components, different charges, different seating depths, etc. to no avail. After checking for things like my barrel hitting the stock or untorqued action hardware I asked a friend who probably knows more about the subject than anyone else I’ve met and he said that he had a pretty good idea what it was once I mentioned my rifle was a Remington 700 and he had a simple test I had to conduct.
I had to pull my bolt and using a Sharpie I colored the backs of the bolt lugs and inserted a spent case back into the camber. Next I closed the bolt on the case and cycled the action a few times. Then I pulled the bolt and inspected the marker on the back of the bolt lugs and much to my surprise the ink had worn off most of one of the lugs and not even make contact on the other lug. After all of the energy spent on load development it turned out that my accuracy problem was actually my rifle.
Under typical load pressures the rigidity of the bolt was enough to keep the bolt face in line and the rifle was sub MOA, but under high pressures the bolt would flex to one side since the lugs weren’t perfectly engaged with the receiver cause the bolt face to be out of line with the chamber, thus causing the mess I was seeing downrange. This explained why only my high pressure loads on what should be an accuracy node were always lackluster when they should have been stellar.
Not to fret, the solution to this issue wasn’t to trash the rifle, cash in the kid’s college fund to send it off for blueprinting, or to live with lower than desired pressure loads. In the end all it took was a dab of lapping compound and some elbow grease to get it shooing sub MOA groups with the high pressures I desired.
Here’s a quick overview of the process it takes to remedy this problem that seems to plague a lot of Remington 700 actions. As already mentioned, using some sort of marking compound, in my case a Sharpie did the trick, color the backs of your bolt’s lugs. Reinsert the bolt on a spent case from the same rifle and work the bolt up and down a few times and remove. If you see the ink removed on one side but not the other it’s time to bust our the lapping compound. Put a very small dab on the lug that IS making contact (the one with the ink removed) and move the bolt up and down while pulling back with a slight pressure. It’ll remove just a small amount of material from the bolt lug and will prevent you from going any further once the shorter lug engages the action. This will be such a small amount of material it shouldn’t affect you head spacing so don’t worry. Once the Sharpie test marks both lugs you’re finished, and you just have to clean all of the grit out and should be good to go. You should also notice a smoother action as well as much improved accuracy down range, especially with your higher pressure loads.
Here are some images and some additional notes from when I went through the process on my rifle.
So, here’s my bolt before the lapping process. Note the valve lapping compound that I picked up from the auto parts store. DO NOT USE THIS COMPOUND! I found out the hard way it is not abrasive enough and I wound up just making a huge mess. What wound up being the perfect compound was the 400 grit silicon carbide general purpose lapping compound from McMaster.com which even in the smallest size (2 oz.) you could probably lap about 10,000 actions.
Here’s the results of my “Sharpie Test” that shows just how uneven my lugs were before lapping them. Note just how little surface area was making contact with the receiver on the right side of the photo below.
So after using the correct lapping compound and working the bolt for a little while, it perfectly passes the “Sharpie Test” and now looks like the photo below. (Note, if you have a “lot” of material to remove you may want to put a wooden dowl down the barrel and apply more pressure on the bolt face while moving the bolt lever up and down). A VERY small amount of compound was also used on the “weak” lug, just to smooth it out once it made contact. A little goes a long way so don’t get carried away here. It was just to smooth out the rough surface and aid in maximizing surface contact. And who hates a silky smooth bolt either?
After you’re happy with the lapping part of the project, it’s time to clean it up. It’ probably best to just pull the action and bolt and go crazy with the mineral spirits and compressed air to get all of the compound out without getting your stock drenched.
So that’s it, pretty easy, eh? It’s certainly been the best $12 dollars ever spent on this rifle. And wow, what a difference it made down range. So if you’ve had accuracy issues with your Remington 700, especially with higher pressure loads, I’d encourage you to get a spent case and a Sharpie and see if your 700’s lugs need some attention.