I have been searching high and low without success for information pertaining to crosshair movement when dry firing a rifle on rests. It seems to me that I once read that there should be no movement of the crosshairs when you dry fire. Well, I tried it on two different rifles and there is crosshair jump on both when the firing pin falls. When the guns are in the rests, they are solid enough that I can lightly thump the bolt handle and there is no crosshair movement. I would never have suspected that the firing pin falling could jar the rifle enough to move it (both are heavy varmint barrels). One of the rifles is shooting consistent 1/4 to 3/8 inch five shot groups (my Savage LRPV 6BR). The custom 6BR with the Krieger barrel is not doing as well. It won't consistently do 1/2 inch groups and it should do as well as the Savage. That's what got me to looking into whether the problem might be the scope, but I tried three different scopes and it didn't help. Then I thought I would try the dry firing thing. When the crosshair jumped every time, I changed the scope and that one jumped too, so then I tried the Savage. The Savage has a Weaver fixed 36X target scope on it, and the crosshairs on that gun jumped the most. Now, I know the gun shoots, so it seems to me that this crosshairs jumping when dry firing thing is not a very good diagnostic. Comments Please!
Dry firing and crosshair movement
- Thread starter lrgoodger
- Start date
I haven't tried this... it sounds like I don't want to! I might be disappointed! 
This post is really a 'tag' as I'm interested in the responses that come about...
This post is really a 'tag' as I'm interested in the responses that come about...
drumcorpschamp
Silver $$ Contributor
My observations with 2 different front rest tops.....
On dry firing while using the rest top from manufacturer "A", my crosshairs would jump about 1/4" m.o.a. up and to the left. Repeating the same routine with the rest top from manufacturer "B" showed the crosshairs jumping a little less than 1/8" m.o.a. in the same direction.
Until I have the time to do some experimenting and problem solving, I'll be using the top from manufacturer "B". The rifle is a 17 lb. .260 Rem. with a Nightforce BR scope. Funny thing is.....last summer when the gun was mostly stock and I mounted a Weaver 36X and dry-fired from a $100 front rest......I observed NO crosshair movement.
Sorry....I have nothing to offer in the form of help, just sharing some frustration.
Good luck,
Jerry
On dry firing while using the rest top from manufacturer "A", my crosshairs would jump about 1/4" m.o.a. up and to the left. Repeating the same routine with the rest top from manufacturer "B" showed the crosshairs jumping a little less than 1/8" m.o.a. in the same direction.
Until I have the time to do some experimenting and problem solving, I'll be using the top from manufacturer "B". The rifle is a 17 lb. .260 Rem. with a Nightforce BR scope. Funny thing is.....last summer when the gun was mostly stock and I mounted a Weaver 36X and dry-fired from a $100 front rest......I observed NO crosshair movement.
Sorry....I have nothing to offer in the form of help, just sharing some frustration.
Good luck,
Jerry
The gunsmith I was dealing with told me that vibration from the fireing pin and spring will make your crosshairs move and that a speedlock fireing pin and spring would remedy that and improve accuracy.I didn't notice crosshair movement before in my two guns but when I changed the pin and spring the vibration was reduced drastically.
BoydAllen
Gold $$ Contributor
Lighter firing pin softer bags less jump. It's a momentum/damping thing. Try it with a fired case in the chamber (with the fired primer in place). I have seen different amounts of jump with different rear bags. It is not why your custom 6BR is shooting like it is. I would look elsewhere. How have you checked the bedding?
I've done a great deal of research on bedding. I pillar bed my own varminter stocks (which the gun in question is). I use Devcon plastic steel for bedding compound and measure the results with a dial indicator at the forend. Movement between stock and barrel is less than two thousandths on this gun when loosening and tightening the action screws. It shot very well with the Bartlein .243 barrel on it (record PD distance - 692 yards), but since I wore that barrel out and switched to Krieger barrels with 6BR chambers, I have not been able to get it to shoot consistently. It has always had heavy varmint contour barrels on it.
I've built several excellent shooters in the last 3 years, but this one has got me stumped. It used to shoot and now it won't, and the only thing that has changed is the barrel. The very first five shots out of this barrel went into .28" at 100 yds and I have not been able to repeat it since (well, I guess I did once with a .50" at 200 with a different bullet). I have a bore-scope and good cleaning technique. My Savage shoots superbly. I'm actually thinking about using it in both factory and custom class at the next local shoot. Another Savage shooter got a perfect score at the last varmint shoot (200 - 4X at 200 yards on 3/4 inch bulls) and beat all the custom guns.
I've built several excellent shooters in the last 3 years, but this one has got me stumped. It used to shoot and now it won't, and the only thing that has changed is the barrel. The very first five shots out of this barrel went into .28" at 100 yds and I have not been able to repeat it since (well, I guess I did once with a .50" at 200 with a different bullet). I have a bore-scope and good cleaning technique. My Savage shoots superbly. I'm actually thinking about using it in both factory and custom class at the next local shoot. Another Savage shooter got a perfect score at the last varmint shoot (200 - 4X at 200 yards on 3/4 inch bulls) and beat all the custom guns.
I had quite noticeable reticle movement on my Rem 700 when the original Xmark pro trigger was in it.
I had come off of years of shooting the GI trigger in the AR15... so I THOUGHT the xmark wasn't THAT bad....
Once I sat on the bench and dry fired while aiming at a 200 yard paper target, I realized it was time to replace that trigger. I put a Timney in the rifle and the reticle movement was gone.
I had come off of years of shooting the GI trigger in the AR15... so I THOUGHT the xmark wasn't THAT bad....
Once I sat on the bench and dry fired while aiming at a 200 yard paper target, I realized it was time to replace that trigger. I put a Timney in the rifle and the reticle movement was gone.
Bradley Walker
Very interesting thread.
You can see jump in the scope on the AR-15 if the lower is not bedded to the upper. The hammer "lifts" the upper at the strike.
You can see jump in the scope on the AR-15 if the lower is not bedded to the upper. The hammer "lifts" the upper at the strike.
Yes, I know about Krieger. That's why I got one. You may remember the post a little over a year ago about a chipmunk sized PD shot at 1071 yards with a gun I built using a Krieger barrel. That gun was not finnicky. It shot every load I put in it under 1/2". I got the best result from 31.0g Varget using the 105g Amax (consistent low 3s). That bullet has shot well in every gun except this one. I have varied the loads, tried different powders and different bullets (all from the 6br favorite loads for heavy bullets). I will say that my experimentation did improve my SD and ES when I discovered that using the K&M expander on the necks after partial neck sizing with a Lee collet die resulted in less neck tension. I can actually seat the bullets with the Wilson micrometer seater by hand if I push hard enough. SDs are in the 3 to 9 range now, and I know that is not enough to affect short range groups.
By the way, there is one thing that keeps nagging me that the bedding job might be responsible for the flyers. I've shot groups with different torques on the action screws and there is a marked reduction in vertical as I lighten torque. I wound up leaving it at 15 in-lbs since that's where the groups were tightest. Also, the Krieger barrel measures 1.250 at the shoulder wheras the original Bartlein I bedded into this stock measured 1.255. I had bedded about an inch of the barrel, but with the Krieger being a tad bigger, I removed that inch of bedding. The dial indicator says it did not affect stock to barrel movement.
I have attached a couple of targets. I keep good records and keep ALL my targets. The first was shot about 3 weeks ago when I first discovered the 107g SMK was outshooting the Amax. This is a 200 yard target and you can see from the top 3 groups that the gun wants to shoot, but will throw a couple of flyers each time. After shooting the second group, I zeroed the crosshair on the 2-3-5 cluster and it moved the center of the group right where I wanted it as shown by cluster 1-2-4 in the 3rd group. The bottom group is out of the Savage (the 7 shot group was sight in). The .51", 200 yard group is typical for my Savage 6BR, and you will note that it was with the 87 grain vmax, which many claim will not shoot in a 12 twist.
The second target was shot yesterday with sorted 95g SMKs. You can see the same type of pattern I was getting from the 107s. Note that I was varying powder load on these groups. The last two groups were the 105 Amax, which still refuses to shoot.
Oh, before I forget, you asked about seating depth. I have been putting the SMKs .008" back from seated with the bolt. With the light neck tension, they don't go into the lands very far, so I should be into the lands about .005".
I think I'm going to re-bed the stock just to make sure that it's OK. If that doesn't help, the only conclusion I can reach is that the barrel is not doing the job.
By the way, there is one thing that keeps nagging me that the bedding job might be responsible for the flyers. I've shot groups with different torques on the action screws and there is a marked reduction in vertical as I lighten torque. I wound up leaving it at 15 in-lbs since that's where the groups were tightest. Also, the Krieger barrel measures 1.250 at the shoulder wheras the original Bartlein I bedded into this stock measured 1.255. I had bedded about an inch of the barrel, but with the Krieger being a tad bigger, I removed that inch of bedding. The dial indicator says it did not affect stock to barrel movement.
I have attached a couple of targets. I keep good records and keep ALL my targets. The first was shot about 3 weeks ago when I first discovered the 107g SMK was outshooting the Amax. This is a 200 yard target and you can see from the top 3 groups that the gun wants to shoot, but will throw a couple of flyers each time. After shooting the second group, I zeroed the crosshair on the 2-3-5 cluster and it moved the center of the group right where I wanted it as shown by cluster 1-2-4 in the 3rd group. The bottom group is out of the Savage (the 7 shot group was sight in). The .51", 200 yard group is typical for my Savage 6BR, and you will note that it was with the 87 grain vmax, which many claim will not shoot in a 12 twist.
The second target was shot yesterday with sorted 95g SMKs. You can see the same type of pattern I was getting from the 107s. Note that I was varying powder load on these groups. The last two groups were the 105 Amax, which still refuses to shoot.
Oh, before I forget, you asked about seating depth. I have been putting the SMKs .008" back from seated with the bolt. With the light neck tension, they don't go into the lands very far, so I should be into the lands about .005".
I think I'm going to re-bed the stock just to make sure that it's OK. If that doesn't help, the only conclusion I can reach is that the barrel is not doing the job.
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