Moving An Inch

Carteach0 put up a post where he asked the question, “How far (in thousandths of an inch) must the muzzle deflect to change the point of impact 1moa at 100 yards?” I answered in text in his comments, but it seemed like such an interesting question I wanted to explore it here.

He was considering the full length of the rifle, but I think you could consider the problem from the rear sight forward, as it would be the same whether there is a stock mounted on the rifle or not. On most rifles the rear sight sits over the chamber, the front sight is close to the muzzle. To eliminate all other variables, assume no wind and that perfect ammo is being used, so that if the rifle doesn’t move, every round would impact the same hole. With that, here goes my thoughts on the topic.

Imagine a line that begins at the center of the rear sight, passes over the tip of the front sight, and impacts the target in the center. How much does the front sight move to move the impact point one inch? In my calculation, I assumed my rifle had a sight radius of 16 inches. I used this on-line calculator to solve the angles. Essentially you are solving for a long skinny triangle. Two sides are 3600 inches, the third side is one inch. That makes the small angle 0.0159 degrees. A movement of 0.0159 degrees moves the bullet impact 1 inch. If your sight radius is 16 inches, that means your front sight has to move 0.0044 inches to move the bullet impact 1 inch.

It puts the whole “sight picture / sight alignment” issue in a new light.

A Rainy Saturday

clean_benchRange plans cancelled. Too wet to cut firewood. Set up in the shop, talking about old guns and old shooters we have known, special times at the range, and the power of memory.


Range Day

Saturday, sunny, high 70s. I met my son Joe and my friend Dan at the range. Dan brought a Garand. Joe brought a Mauser. I brought TRNOW and a 1903A3. Here they are side by side.
Ammo was consumed. Noise was made. Holes were made in targets. Here’s a 5 shot group shot prone with a sling. Not quite one ragged hole in the X, but I’m improving.
And here I am, slung up. Rifle built on old military receiver, old military blanket, old military shooting blouse, old cotton military sling. There’s some sort of theme here. springfield1

The Rifle No One Wanted

I have a friend that is selling out his collection. He is older, has had two heart attacks, and has a wife with disabilities. He has seen it happen before. An older shooter dies, his wife and family have no idea, and all his “best friends” show up to help the widow with the collection. So he decided to sell them now, before they were in the safe for his family to deal with.

I’m not involved, another club member with a lot more experience is helping him. I’m not buying, either. This stuff was out of my price range. Colt Python, O/U shotguns, custom 1911s, Tubbs rifle in 6mm-br, lots of other rifles, everything in good shape, with excellent scopes, and so on.

Anyway, there was one that didn’t sell. An orphan rifle. Too modified to interest a military collector, and not modern or custom enough for the guys in the arms race that “F” Class has become.

It’s a 1903A3 from 1943, taken when they sold for about $25.00 and modified to be a long range rifle. Laminated stock, heavy barrel, aftermarket trigger, Redfield sights, and so on. It was a project gun, something to do to see what could be done with 30.06.

He brought it over and offered it to me as a surprise. I installed the sights last night, took it to the range this afternoon with some reloads. Here’s my first 100 yard group. 1st_100yd_tgt_sm

And here’s the rifle no wanted.Old_rifle1_sm

By the end of the afternoon my face hurt from grinning.