Question in Physics

[Art]

I have a No 4 Mk 2 Lee Enfield I bought new in the wrap.

If I shoot Mk VII ball or cartridges reloaded with Mk VII bullets they hit dead nuts on at 200 yards. The same is true for any other flat base bullet I've shot out of it though elevation might vary.

Sierra 174 gr. Match Kings shoot 1 1/2 to 2 minutes right of the point of hold. This has happened often enough I know it isn't on me. I talked to a three gun competitor who said he has an AR 15 that does something similar if you use 162 gr or heavier bullets instead of 55 gr bullets.

My question is: Has anyone else noticed this phenomenon or is it unique to my rifle?????

Oh, groups are really tight with either type of bullet it's just the deflection is different with Match Kings.

I figure the problem has something to do with gyroscopic forces combined with some other stuff, but heck, I really don't know.

[Tuna]

It's not an unusual thing for military rifles to shoot to different points of impact with the same weight bullets but one being flat based and another with a boat tail. These rifles were all set up to use a flat based bullet the same as USGI rifles were.

[PhillipM]

I think it's simply differences in barrel harmonics in an unfloated barrel.

[emmagee1917]

Correct . Barrels flex and move when fired , usually in a circular or oval path . The Mk VII is leaving at a 9 or 12 Oclock part of the swing of the barrel , the Sierras at a 12 or 3 Oclock position . This also accounts for some up and down as it moves from 6 to 12 and back , but recoil and bullet drop ( or lack of it ) can hide it . A boatail is also more affected by a slight defect in a muzzle , giving it a little gas nudge one way or the other as it departs .
Chris

[Art]

Thanks, I thought it was probably something with barrel movement. I had heard that Lee Enfields can have "issues" with boat tail bullets. This isn't a huge issue and probably wouldn't be one at all if my rifle had sights adjustable for deflection. It's just an irritant.

[PhillipM]

Thanks, I thought it was probably something with barrel movement. I had heard that Lee Enfields can have "issues" with boat tail bullets. This isn't a huge issue and probably wouldn't be one at all if my rifle had sights adjustable for deflection. It's just an irritant.

I'd go .5 + and - on my powder charge and evaluate. I'd also work on seating depth and consider re-crowning the muzzle.

[Art]

I'd go .5 + and - on my powder charge and evaluate. I'd also work on seating depth and consider re-crowning the muzzle.

I'm at 40 gr. of 4064 powder and don't feel comfortable going higher than that, I might back off a little though. The rifle is one of Irish new in the wrap specimens that came in in the 90s and the crown looks absolutely perfect, not a nick or burr anywhere.

If the Brits had just made their back sights adjustable for deflection it wouldn't be a problem, but oh well .

[RED]

Many moons ago (as in 35 years ago) I acquired my first #4 mark 2 complete with cordite powered cartridges. That first day I shot probably 100 rounds and they were quite accurate, grouping 2" high at 100 (probably right on at 250) and I was thrilled. I took the rifle home and being a responsible person I gave it a thorough cleaning. As I was removing all that wood, small slivers fell out along with a couple of pieces of folded paper. Trash I said... big oops that was and I could never again get the rifle to stay in a pie plate at 100 yards.

Fast forward 25 years and I had a M1-A steel bedded into a "Big Red" birch stock. I used to sit on my back porch and shoot beer cans off handed at 100 yards. Then I had a problem that required me to remove the rifle from the stock. When it was put back together, I couldn't hit a gallon water jug at 100. About 200 rounds later the stock resettled and is a 2 MOA gun with cheap milsurp ammo (CAVIM, to be exact).

Never underestimate the value of a properly bedded and fitted stock.