Sand bags or bipod for load development

[ar10ar15man]

reread this part.
"The bullet spends about 0.001-0.002 seconds in the barrel, and in that time before the bullet leaves the muzzle the rifle moves rearward about 1/8 inch. Unless that 1/8 inch movement is EXACTLY the same with each shot, the muzzle won't be in the same place and the bullets can't go in the same hole. Shot-to-shot repeatability is much better with a pedestal front rest than with a bipod, in my experience."

Quote from Benchrest Central:


"Small groups can be shot off a bipod, make no mistake (e.g., http://www.6mmbr.com/TacticalFroggyA1.html). But a bipod on a concrete bench tends to bounce because the rifle pivots around the toe of the stock, and the forend of the stock where the bipod attaches is fairly springy, and there can be a lot of barrel weight in front the bipod. Plus, you generally hold onto a rifle with a bipod, and it takes a lot of practice to hold the same way for each shot.

With a pedestal front rest and rear bag the rifle can be supported where the stock is less springy (closer to the action) and the rifle slides backwards under recoil rather than pivoting on the toe of the stock.

The bullet spends about 0.001-0.002 seconds in the barrel, and in that time before the bullet leaves the muzzle the rifle moves rearward about 1/8 inch. Unless that 1/8 inch movement is EXACTLY the same with each shot, the muzzle won't be in the same place and the bullets can't go in the same hole. Shot-to-shot repeatability is much better with a pedestal front rest than with a bipod, in my experience."

 

[coop2564]

No way i would use LS for load developement. Can change ur vibrations and grouping!

 

[Rick Richard]

No way i would use LS for load developement. Can change ur vibrations and grouping!

Not to mention the possibility of damaging a scope with heavy recoiling rifles when there is no "give" to the recoiling force.

 

[FIGJAM]

No way i would use LS for load developement. Can change ur vibrations and grouping!

I am not advocating the LS - I don't use one and don't own one. But I have used my buddies in the past. How does it change the vibrations? I have seen my buddy shoot some really small groups off of the leadsled while we were doing load developement. They opened up a little once he shot withhout it, but nothing that couldnt be attributed to shooter error

 

[CanardNoir]

I'm asking for load development only. I would hunt, practice and compete with a bipod. I know I should work on my consistency with a bipod, but sometimes I get frustrated during load development, especially group shooting, because I think it's me when that flyer pops out of the group, or the weird impact on the long range ladder happens.
What do you guys do?

After many years of filling sand bags - I'm totally Harris bipod for CF calibers these days.

BTW - at 74 yrs, I know it's "ME"

 

[JGRJR]

The best thing I ever did for load development testing was to by a quality front rest and a quality rear bag and learn some bench rest shooting basics.
I think my rear bag is a Protektor. Money well spent.

You have to follow up and practice with your bipod and full setup.

 

[mountaincarver]

sorry..i do not see how a nonmoving solid hunk of steel caused a bullet to miss.
go to a benchrest match and see how many bipods are in use.
how many sand bags without a rest are used in the front.
there are no facts to back your "questioned the store bought adjustable front rest causing some unexpected impacts".

sometimes when your trying to figure this stuff out on your own you try different things to learn about rifles and how they react with different rests. at the time I questioned the rest I had so I tried something different. cant really say one is better than the other but the particular rifle I was shooting at the time seemed to be picky about how it sat on a rest. ive never been to a benchrest match so I don't know what they use. but... the fact is that the rifle I was shooting at the time seemed to like the bag and I always just kept using it for my others. I think there are some excellent rests other than sand bags out there but I just don't have experience with them.

 

[Eagle eyes 17]

Bags or a good gun rest should be more consistent than a bi pod

 

[Rich Coyle]

Not to mention the possibility of damaging a scope with heavy recoiling rifles when there is no "give" to the recoiling force.

Makes no sense to me. Please explain.

 

[Kiwi Greg]

For the hunting rifles I build where 1/2 moa is golden I use a Harris bi-pod with spikes on a plywood base off a concrete bench with a squeezable soft rear bag, (not the one it the picture it gave me too much inconsistency) as this is closed to how they will be shot in the field, hasn't stopped my shooting plenty of .1-.2 moa groups if the rifle is up to it



For my bench rest rifles I use my of one Seb or Farley rests & rear bag with flags as that's how they are shot.



Can't emphasize enough how important the conditions & flags are to shooting tiny groups, I don't bother with hunting rifles as that level of accuracy is redundant

 

[Jerryrva]

This is what I use. Of interest is the "lab lift" that I use at the rear. Super easy to adjust up or down to line up with targets. The firm bag doesn't settle down too much so I can get back on target easily.

 

[Wallie]

Slightly different topic from consistent tracking during recoil, which seems to be cover pretty well already.
Harmonics matter! They aren't usually addressed directly, because generally harmonics are static rather than variable, but harmonics are exactly what every handloader attempts to optimize!
Specifically, tracking the muzzle as it vibrates around in specific relation to the exact instant the bullet exits. The goal wether we realize it or not is to develop a load that takes advantage of a momentary pause as the muzzle oscillates around. Think of a sine wave, and the flat/horizontal sections of at the tops and bottoms of the wave as pauses ideal for bullet exit, and the steep sections in between as rapid muzzle movement or inaccurate/inconsistent timing for bullet exit.
Everyone takes for granted that heavy rifles and heavy barrels are more accurate, and pencil barrels are harder to dial in, but the reason is harmonics. A heavy tuning fork with lots of mass (and rigidity) vibrates less than a thin light one, and makes the sine wave of muzzle oscillation flat and gentle, while a low mass pencil barrel with low rigidity flexes and oscillates acutely with a steep high frequency sine wave.

Personally, I use a bipod, but you should really be using a lead-sled. The idea of load development is repeatable accuracy. Having YOU or your GRIP or your FLINCH or your headache du jour isn't part of load development. You need a lead-sled and at least a 24x simple crosshair or dot scope. Exact same point of aim, shot to shot, and no other input except the variations in the ammunition you are trying to develop. Anything else risks minute changes from shot to shot that will render your accuracy results completely invalid except by accident. Once the load is developed, then practice shooting from your expected field rest: bipod, tripod, sticks, rucksack, rump of your dead horse or fender of your quad-runner, whatever you expect to use in the field. Then you will know what the load is capable of, and you can practice until you can determine what YOU are capable of.

This is exactly why putting your rifle in a lead sled, and effectively adding its mass to your rifle, is a horrible idea specifically for load development. The whole idea is to optimize the harmonics of your rifle, not a lead sled (unless you ALWAYS shoot with the lead sled attached... then, carry on!)

Unless you get really lucky and your lead sled modified harmonics just happens to coincide with normal/un-modified harmonics, you will get results similar to Deputy819.

You know, I thought that too....and it may have been just me..BUT twice (once with a Rem 700 and once with a Savage 110) I developed loads using a lead-sled and everything looked great on the targets. Afterwards, shot both rifles OUT of the lead-sled/off sandbags and those loads completely fell apart. Was weird......

Of course as CAV2108 and FIGJAM note, consistent shooting ability is a prerequisite for meaningful load development. But developing a load optimized for your 40lb lead slead/rifle assembly is counterproductive.

I am not advocating the LS - I don't use one and don't own one. But I have used my buddies in the past. How does it change the vibrations? I have seen my buddy shoot some really small groups off of the leadsled while we were doing load developement. They opened up a little once he shot withhout it, but nothing that couldnt be attributed to shooter error

 

[FIGJAM]

Slightly different topic from consistent tracking during recoil, which seems to be cover pretty well already.
Harmonics matter! They aren't usually addressed directly, because generally harmonics are static rather than variable, but harmonics are exactly what every handloader attempts to optimize!
Specifically, tracking the muzzle as it vibrates around in specific relation to the exact instant the bullet exits. The goal wether we realize it or not is to develop a load that takes advantage of a momentary pause as the muzzle oscillates around. Think of a sine wave, and the flat/horizontal sections of at the tops and bottoms of the wave as pauses ideal for bullet exit, and the steep sections in between as rapid muzzle movement or inaccurate/inconsistent timing for bullet exit.
Everyone takes for granted that heavy rifles and heavy barrels are more accurate, and pencil barrels are harder to dial in, but the reason is harmonics. A heavy tuning fork with lots of mass (and rigidity) vibrates less than a thin light one, and makes the sine wave of muzzle oscillation flat and gentle, while a low mass pencil barrel with low rigidity flexes and oscillates acutely with a steep high frequency sine wave.

This is exactly why putting your rifle in a lead sled, and effectively adding its mass to your rifle, is a horrible idea specifically for load development. The whole idea is to optimize the harmonics of your rifle, not a lead sled (unless you ALWAYS shoot with the lead sled attached... then, carry on!)

Unless you get really lucky and your lead sled modified harmonics just happens to coincide with normal/un-modified harmonics, you will get results similar to Deputy819.


Of course as CAV2108 and FIGJAM note, consistent shooting ability is a prerequisite for meaningful load development. But developing a load optimized for your 40lb lead slead/rifle assembly is counterproductive.

Your analysis of the leadsled and harmonics makes no sense to me. You aren't adding weight to the rifle, you are adding weight to the platform it sits on reducing felt recoil. Nothing on the leadsled touches or impacts the barrel. If what you are saying is true, shooting from the prone position acting as dead weight behind the rifle and limiting the rifles ability to move backwards would have a large impact on barrel harmonics and cause the rifle to group differently than shooting sitting, kneeling, or standing where the recoil will be absorbed by your body moving backwards.

 

[375fan]

Bipod w/rear bag, prone on the ground (not on concrete, asphalt or gravel). This is what i find to be comfortable, solid and consistent for me. Use to test on bench w/front rest and rear bag but was never really comfortable doing that.