Bolt bounce and Scope shift when dry firing

[L.Sherm]

I have never heard that a scope could take a shot or two to "settle in".
This is good info to have, thanks

Go over to accurateshooter there was some extensive testing done on all kinds of scopes and that's what guys who tested found.

 

[26Reload]

I would check the bolt itself as to the final lockin position...
If you take the stock off...will the bolt go lower into final position before pulling the trigger....maybe the bolt is,resting on the edge of the stock..not fully engaged..when you pull the trigger the bolt bounces because it is not in full lockdown position.....i caught that on my other rem rifle.....very slight..but was there.......

 

[Alex Wheeler]

I was involved in that scope testing. MOST scopes take a couple shots to settle after an adjustment. Ones that are totally rock solid are quite rare, and are keepers. You need a scope checking setup to test scopes, you cant do it with a box test or any of the other common tests.

 

[jdyoung]

Detecting Bolt Bounce, What I do:
Put a piece of masking tape on the stem of the bolt handle, and another piece along the edge of the cut in the stock for the bolt handle.

Cock the rifle making sure the bolt handle is as far down/closed as possible , ( no snap cap, or fired cartridge).

Then using a fine pencil/marker and straight edge, make a witness mark on the applied pieces of tape across the bolt handle and stock. Those aligning marks are one and two and show the bolt position at rest in Battery.

Dry fire the rifle.

Without touching the bolt handle, make a third mark on the stock to intersect with the first mark on the bolt handle. The third mark shows the position of the bolt handle after firing.

You can repeat the cocking and dry firing to see if the first and third marks continue to align after dry firing.

The difference between the second and third marks is how much the bolt moves to align the cocking piece in the cocking cam of the bolt during firing. Finding it's own center as such.

After exhibiting bolt bounce, even if there is a snap cap/ fired cartridge or loaded round in the chamber resulting in no bolt bounce observed, the cocking piece is still out of alignment with the bolt cocking cam. It is rubbing on the cocking cam surfaces where it shouldn't.

A final test is to cock the rifle, (no snap cap or fired cartridge), Important: when rotating the bolt handle down, align the first mark on the bolt handle with the third mark on the stock. With this alignment, when dry firing, the bolt bounce should be minimal indicating the prime resting spot that aligns the cocking piece with the cocking cam in the bolt. A slight adjustment upward will cause the bolt handle to deflect/bounce downward, conversely a slight adjustment downward will cause the bolt handle to deflect/bounce upward.

Remedy? ? ---consult a good smith to see if an attempt to have the bolt body rest slightly tig welded and then resurfaced to bring about proper bolt cocking cam/cocking piece alignment is possible. My preference is to have marks one and three aligned when finished.

 

[Gobears16]

I'm confused... you say you're shooting 3/8 groups all day long. What's the problem?!? I would bet 99% of shooters couldn't shoot a 3/8 group with a capable rifle let alone allll day long. I understand trying to squeeze the last bit of accuracy but I'd go forth and shoot and not worry. I'd have a smile every time I pull the trigger.

 

[Joefrazell]

I haven't seen anyone else make mention of the potential cause of the bolt bounce. I don't see where bolt bounce has anything to do with technique.

Well it does.

 

[CMRHG]

The gun shoots great, but I believe this is what is causing the groups to be always on a horizontal plane. This is the only gun I've built that have had this issue. Sure, it may not shoot any better than it is right now, but sure would be nice to know...and when you have two buddies that shoot the same hole most of the time, there's a little competition there as well. All good and fun tho, thats for sure..lol

 

[26Reload]

Have you checked to see if the bolt is in full lockdown...not touching the angled cutout of the stock....
Like i said...i had simular...touchung the stock..bouncing on firing with or without real load....

 

[CMRHG]

I will check that... thanks

 

[Bang4theBuck]

I think that there is some confusion about what the definition of Bolt Bounce is. My understanding of what the op is describing is a condition where the bolt is rotated all the way down and when you pull the trigger and the firing pin accelerates forward, the bolt handle actually jumps up. Sometimes its only a very very small amount, sometimes it jumps over a quarter inch up. I have a rifle woth this condition and it is not normal and definitely affects accuracy. It also causes a huge shift in your reticle when dry firing, which would usually be indicative of poor shooting/trigger control technique. In this case it is not. It is a problem with the rifle. I can't say for sure that this is what's going on, but it very well could be.

 

[Bang4theBuck]

26Reloads condition is also in line with what I was talking about, and could cause the same condition based on the same theory.

 

[CMRHG]

I think that there is some confusion about what the definition of Bolt Bounce is. My understanding of what the op is describing is a condition where the bolt is rotated all the way down and when you pull the trigger and the firing pin accelerates forward, the bolt handle actually jumps up. Sometimes its only a very very small amount, sometimes it jumps over a quarter inch up. I have a rifle woth this condition and it is not normal and definitely affects accuracy. It also causes a huge shift in your reticle when dry firing, which would usually be indicative of poor shooting/trigger control technique. In this case it is not. It is a problem with the rifle. I can't say for sure that this is what's going on, but it very well could be.

Exactly what is going on...

 

[jd5521]

The gun shoots 3/8"groups all day long. the groups are always a horizontal line. the groups are pretty consistent from the middle then left of center.

Are you shooting off a bipod? I have seen the vertical happen on a bipod and bench and not being loaded that well into the rifle along with a weak rear bag such as one for grab and run in prs.

The following is from Speedy:

Remember that vertical can result from myriad gear issues and gun-handling mistakes. Try to isolate one item at a time as you work to improve your groups.

• Barrel Weight--A lot of rifles are muzzle-heavy. Some rifles have too heavy a barrel and this causes vertical, especially when shooting free recoil. Basically the gun wants to tip forward. The remedy is to trim or flute the barrel, or add weight in the rear (if you can stay within weight limits).

• Unbalanced Rifle--If the rifle is not balanced, it does not recoil straight, and it will jump in the bags. If the rifle is built properly this will not happen. Clay Spencer calls this "recoil balancing", and he uses dual scales (front and rear) to ensure the rifle recoils properly.

• Firing Pin--A number of firing-pin issues can cause vertical. First, a firing pin spring that is either too weak or too strong will induce vertical problems. If you think this is the problem change springs and see what happens. Second, a firing pin that is not seated correctly in the bolt (in the cocked position) will cause poor ignition. Take the bolt out of rifle and look in the firing pin hole. If you cannot see the entire end of firing pin it has come out of the hole. Lastly, a firing pin dragging in bolt or shroud can cause vertical. Listen to the sound when you dry fire. If you don't hear the same sound each shot, something is wrong.

• Trigger--A trigger sear with excessive spring load can cause problems. To diagnose, with an UNLOADED gun, hold the trigger in firing position and push down on sear with your thumb. If it is hard to push down, this will cause vertical problems.

• Stock Flex--Some stocks are very flexible. This can cause vertical. There are ways to stiffen stocks, but sometimes replacement is the best answer.