Gun tuning with springs and oil

I got down to finally replacing the Heavy Buffers Modified AR10 Buffer Spring on my AR-10. I’ve been having some cycling issues that have outlasted the break in period on the gun and I want to get that resolved. I had initially wanted to put a DPMS LR-308 Rifle Buffer Spring (#308-BS-10B) into the gun but they were out of stock at the suppliers I’ve been using until recently. It’s a lot nicer of a spring as it’s ends are properly flat instead of just chopped coil. The Heavy Buffers spring was mad of 0.070″ wire, 28 coils, and 290mm long. The DPMS spring is made of 0.080″ wire, 38 coils, and 323mm long. The action feels a lot better with the new spring.

An issue did come up though even after changing the spring… short-stroking.  This could have been a result of having the adjustable gas block too restricted but that was opened entirely and didn’t resolve the problem. This morning I went through the gun and found that using grease to lube the BCG had been a poor choice. As time has gone by the grease has caked and has slowed the movement of the BCG. I cleaned it up and lubed it with CLP. It’s far more free now. Hopefully this will solve the issue.

For additional insurance against friction I ordered up a POF-USA Roller Cam Pin .308 For AR/10 Piston Driven and Gas Impingement Rifles (PN# RCPA308). This may help reduce some of the drag during cycling. By letting the bolt cam roll instead of drag, considerable friction can be eliminated from the system. Let’s hope.

I also bought a Timney Trigger Tension Scale (8oz -10lbs). Using this on the AR-10 I measured 4 lbs exactly every time. Very very consistent, it has a Timney 4lb trigger installed. My Ruger 77/22 was letting go between 4.25 and 4.5lbs randomly. Ok, but not excellent.

On the theme of triggers, I ordered a new hammer spring for my Berretta 92FS. The trigger pull stock is very smooth and 5.5lbs. I swapped in a Wolff 28616 (16lb) spring for the stock 20lb spring. This reduced the trigger pull to 4lbs. Nice.

I changed the recoil spring in the Berretta as well. Since I shoot a lighter 115gr. round I should be able to smooth things a bit with a lighter spring. Replacing the stock 13lb spring with a Wolff 11lb (40611) spring was simple enough. The gun felt better than ever and I’ll be ordering a 9lb (40609) spring on my next order.

The best thing about all of this spring tuning is how cheap it is. Spring cost so little and the difference is really noticeable. Nice.