Front sight "bounces" when prone shooting

[ptf18]

Did some smallbore shooting the other day with my H&R M12 at both 50 and 100 yards.

I noticed that when I fired the round the front sight aperture "bounces" around the black bull. The front sight and its apertures are secure.

The "bounce" isnt much.....perhaps more of a light shake. BUT I do notice it and I'm wondering if the bullet POI reflects this "slight shaking/wiggling/bouncing that I see. I dont shoot SB much but if i remember correctly I've had this issue forever.

I shoot Federal 711b ammo and did notice that when I tried some Geco standard velocity this "bouncing" was noticeably lessen.

I've tightened my position to some degree but that hasn't helped to reduce/eliminate this "bouncing".

Any ideas?

[Modena]

Sounds like recoil to me ????

[jenrick]

To clarify the "bounce" is seen after recoil, or are you saying the sights move as the gun fires?

If it's the first, verify that the butt of the rifle isn't slipping in your shoulder a bit under recoil. Depending on you jacket that may mean tightening up the shoulder on your jacket. You can see the same if your sling is slipping a little bit down your glove or your arm. Might verify that's all set and tight as well.

If it's the later I'd say that's recoil and to be expected.

-Jenrick

[ptf18]

Thanks Fellows. Perhaps "bounce" isnt the correct term. I shoot NRA HighPower so I'm familiar with the recoil we face with the "big" guns. This front sight movement is more of a "wiggle".

The bull will stay inside of the front aperture its just that the front ap sort of "wiggles" maybe "vibrate" is a word I could use, around the bull when the round is fired.

As I mentioned I thought that I had a "loose" position but tightening things didn't reduce/eliminate this "wiggle".

What I did notice is that shooting standard velocity 22rf ammo DID reduce/eliminate this "wiggle".

Thanks for any ideas you may have.

[Tim S]

The gun has to move under the recoil; exactly how it moves will depend on the position sling tension, body-counter-weight) and the shape of the stock. The recoil impulse is ideally a tiny and quick flick up and down. Is your wobble consistent? In my experience muscular tension in the body will produce an erratic wobbly impulse.

The H&R is a copy of the Winchester 52D, and the stock is a pretty basic. The handstop/swivel is adjustable, but that's it. So you may have to fit yourself around it, and only the top of the butt may make contact with your shoulder.

[Modena]

recoil will see the target wobble around inside the aperture, are you saying you're seeing some other sort of wobble in addition to standard recoil movement?

[ptf18]

Thanks again Fellows. As Tim S mentions about recoil being a quick flip up then down....its not that. Nor is it muscular tension as this "wiggle"... vibration ONLY occurs when the gun is fired.

Its as if the front aperture is loose.... I just check and found it and the aperture tight.

Perhaps Im seeing barrel vibration as the bullet passes thru and out the bore?

Any other thoughts?

[Tim S]

I wouldn't be so sure it's not muscular tension. If you don't have proper NPA, and are pushing the gun onto the target, those muscles will relax when your fire. You may be seeing the rifle wobble as it drifts back to its natural alignment.

It's not a bad idea to check the sights are properly mounted. The tunnel may be clamped tight, but is the mounting block tight on the barrel?

I doubt you're seeing the barrel vibrations. If these are visible, the barrel action is loose; either the bedding bolts are loose, or the bedding itself is faulty.

[ptf18]

Tim S. Thanks. Im thinking about getting to the range this Friday if the weather is... nice. I'll look at my position again. Perhaps your on to something.

I've got 2 more m12 rifles that are bone stock original. I might try them out and see if this sight "issue" carries thru to them.

Seems odd that when I shot standard velocity ammo I dont notice this.... "wiggle"..."vibration"... as much

[Tim S]

So you only notice the wiggle with subsonic target ammo, but not faster standard velocity? I'd stick with the target ammo, as it likely to be more accurate and much more consistent from batch to batch.

[Modena]

put the rifle on a benchrest and see if it does it

[ptf18]

Fellows: A update. Nothing "exciting". I pulled the barreled action from the stock. When doing so I found that the receiver screws were a bit loose. Um......

I removed the oily film I found on the bedding and the area that the receiver contacts the bedding and reassembled the rifle.

I torqued the larger front receiver screw to 30" pounds and the smaller rear screw was snug tight as my torque wrench only goes down to 20" pounds.

Still had that barrel vibration when I "flicked" the end of the barrel with my finger but it wasn't as pronounced.

Went shooting this AM as the wind was....low... less than 6,7,8 mph. I shot a variety of ammo to see what grouped the best at 100 yards.

Didn't notice the "vibrating" aperture issue I posted about.

I'm going to post a question about ammo.


Thanks Fellows.

[Tim S]

You aren't the first to find loose bedding bolts don't help.

However it's unusual that the bolts need different torque. Normally the same tension is applied to both, so the receiver isn't placed under stress. Some shooters have different settings for 50 and 100, and for iron sights and scope, but those settings are applied equally. Are the bolts both the same diameter?

[ptf18]

No sir. The forward screw is 1/4" diameter and the rear is smaller.... perhaps 10/32". I'm not sure what the torque should be on those screws. I chose 30" pounds out of the air.

[Tim S]

No sir. The forward screw is 1/4" diameter and the rear is smaller.... perhaps 10/32". I'm not sure what the torque should be on those screws. I chose 30" pounds out of the air.

It might be time to seek a professional opinion. One bolt needing much more force to tighten suggests the wood underneath it has compressed.

Are you sure the larger screw is 1/4in and the smaller is 10/32in? 1/4 is only 8/32.

[beye]

Quite sure he means 10-32 screw, which is about 3/16" in diameter.