OAL vs. Accuracy

waynewjw

waynewjw

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So how much does OAL affect accuracy. I'm working on a load for my 30-06 Weatherby 1:10, 24" barrel. IMR4350, 56 grains powder behind a Sierra 180 BT. So I start with 3.32 OAL and 3-shots of 55.9 and 56 grains powder, and I work down from there 3.31, 3.30..... (I'm at this point from the previous weekend of shooting in 0.5 grain increments).

Anyway the net result wasn't all that encouraging. The Lyman manual says I can go up to 3.34 which is what I'm going to try this coming week assuming I can load it into the rifle and then back off 0.01 for subsequent loads.

And thoughts or suggestions? Groups in the 1st batch were around 3/4" at 56 grains, so I thought I'd do the 0.1 increment to fine tune. Now the groups at 55.9 and 56 are just over an inch. Whats up with that? Other than it might be the shooter.
 
If you are changing depth by .001" and hope to see any real change, you are bound to be disappointed! [Plus you burn a lot of powder unnecessarily]
Change by .005" increments, and if you see a significant difference, you can try around that length by changing in smaller increments [I usually use .002-.003"]
Do not seat a bullet out to 3.340" until you are sure that such length will not "jam" the bullet into the rifling.
Using a "dummy" round, You could mark a bullet seated out there with smoke from a candle or with a black marker and chamber it to see if it is touchimg the rifling.
I would seat the bullet .005" off the rifling, and move back in .005" increments to see if my rifle preferred a certain length.
Regards, Eagleye.
 
Also, the berger bullet page has a good read on OAL testing. May be a worthwhile read.

IME, Jumping 10-60 thou with hunting bullets (non VLD) has proven very well over the years. Your barrel will tell you what it likes best.

Consider temp changes to fall conditions with the IMR powder. Your load will definitely fluctuate with IMR. Max or near max loads with hotter temps will possibly knock you out of your node or worse popped primers etc.

A bit of jump will allow for normal pressure to develop. You may want to consider the next lower node and test again to provide some options if you want to look for some flexibility around differing conditions. My two bits.
 
i usually measure the max coal my riffle will accept then make sure it will fit in my mag and cycle. i then start my load .015 off the lands and adjust .005 at a time after that if i i think i can tighten it up. i also use berger VLD's in basically everything and they do tend to like next to no jump. so that method has worked good for me but every bullet and barrel are different.
 
I experimented with OAL and my Tikka 7mm mag. I found that a OAL of 3.345 made a big difference in accuracy. Most books list a OAL of 3.29 for the 7mm mag. It took some experimenting and work but was worth it. I am currently doing the same for my 7X57.
 
jacky said:
I experimented with OAL and my Tikka 7mm mag. I found that a OAL of 3.345 made a big difference in accuracy. Most books list a OAL of 3.29 for the 7mm mag. It took some experimenting and work but was worth it. I am currently doing the same for my 7X57.
Click to expand...

in my Sako 7MM Mag i use a oal of 3.460 with berger VLD's
 
So, you have found your most accurate powder charge??

I ran into an issue playing with charge and seating depth.I was going like a fool changing everything.

I was told by a very experienced and respected shooter to pick a depth and stay with it(length to fit magazine for hunting or a recommended one from the manufacturer for target).

The reasoning behind this was that you will get your pressure changes from both charge weight and seating depth and that it is much easier to play with charge weights and leave OAL alone.

After his advice I had better luck, I found a bullet that worked better also.

What I did find is that my rifle preferred tangent ogive vs secant.

Keep it simple applied for me on this as well.
 
A good friend who is a NRA master in F-class and has done well in one mile shoots taught me that you should fart around with seating depth first and then change the powder load up and down. Guess what, he's right. So now I pick a reasonable load and alter the seating depth from on the lands and then off the lands by .005 increments till I get the best group size and then alter charge wt by 0.3 gr increments to hone in on the sweet spot. Highest pressures are always going to be on the lands or jammed in.
 
Well - Bear in mind its a hunting rifle, and you intend to use the rifle/load for hunting. As stated above, diddling around with 1/100 inch increments is a waste of money and time. From my experience, a good load shows promise right from the get go, and that usually starts with a given bullet weight and the correct speed of powder.
Taking the bullet closer than 10 - 20 thou to the lands can cause problems in a hunting load, as there exists natural variation in ogive profile from box to box of bullets, and from your reloading process. Who wants to jam a bullet in the field?
FWIW, for my hunting rifles I stick with 30 thou across the board.
 
waynewjw said:
So how much does OAL affect accuracy. I'm working on a load for my 30-06 Weatherby 1:10, 24" barrel. IMR4350, 56 grains powder behind a Sierra 180 BT. So I start with 3.32 OAL and 3-shots of 55.9 and 56 grains powder, and I work down from there 3.31, 3.30..... (I'm at this point from the previous weekend of shooting in 0.5 grain increments).

Anyway the net result wasn't all that encouraging. The Lyman manual says I can go up to 3.34 which is what I'm going to try this coming week assuming I can load it into the rifle and then back off 0.01 for subsequent loads.

And thoughts or suggestions? Groups in the 1st batch were around 3/4" at 56 grains, so I thought I'd do the 0.1 increment to fine tune. Now the groups at 55.9 and 56 are just over an inch. Whats up with that? Other than it might be the shooter.
Click to expand...

If you've got a load that shoots into three quarters of an inch on demand from a Weatherby's pencil thin barrel, how much better do you expect it to get? That would be my "go to" load in second, provided that when I shot it at 300 it still performed and stayed close to MOA.
 
My Tighter

I had 56 grains IMR4350 for the 3/4" group, felt I could get this down to 3/4" or the 3-leaf clover shots as I have done in my .270. However, I am using a different rifle, load, bullet, etc. in the .270.

So this weekend, I think I will load 5 rounds and back of just enough so the bullet isn't touching the lands and see what that brings. On Weatherby Nation, quite a few of the fellows are saying that the Weatherby rifles tend to have a longer throat that other brands, hence the longer OAL.

Anyone else out there loading 30-06 into a Weatherby?
 
Kelly Timoffee said:
So, you have found your most accurate powder charge??

I ran into an issue playing with charge and seating depth.I was going like a fool changing everything.

I was told by a very experienced and respected shooter to pick a depth and stay with it(length to fit magazine for hunting or a recommended one from the manufacturer for target).

The reasoning behind this was that you will get your pressure changes from both charge weight and seating depth and that it is much easier to play with charge weights and leave OAL alone.

After his advice I had better luck, I found a bullet that worked better also.

What I did find is that my rifle preferred tangent ogive vs secant.

Keep it simple applied for me on this as well.
Click to expand...

This can work for alot of people but the truth is your selling your rifle short of what can be achieved with it for many bullets like the amax and vld seating depth is often more important then the powder charge. If your only. Shooting 100-200 yards the difference is very small but beyond that it can be the difference between 1 Moa and 1/2 Moa very easily
 
waynewjw said:
So I've been changing by 1/100" increments. Based on what you guys are telling me that to big a change??
Click to expand...

If this rifle is a hunting rifle load it to whatever length you need to feed properly from the mag. If you are looking for benchrest accuracy and you are single loading(not from the mag) find the powder charge that works best with the bullets touching the lands.
Once the load is found shoot a group with the bullets seated .005 deeper into the case. Then try .010" deeper, .015" deeper etc. up to .050"-.060" deeper.

I tested 5 types of 155 gr bullets out of my .308 target rifle and found every bullet shot the best groups .020" off the lands. Every rifle and barrel are different.
 
With the particular rifle I am referring I could not get the results I wanted out of AMAX or VLD's , once I switched to SMK's my overall results improved as well as fine tuning, it worked this time for me, next time who knows.That was for a target rifle, for my hunting stuff I don't put near the hours into load tuning.

ripitup911 said:
This can work for alot of people but the truth is your selling your rifle short of what can be achieved with it for many bullets like the amax and vld seating depth is often more important then the powder charge. If your only. Shooting 100-200 yards the difference is very small but beyond that it can be the difference between 1 Moa and 1/2 Moa very easily
Click to expand...
 
It may be a good idea to purchase the proper tools for measuring the bullet seating depth from the ogive. Measuring OAL to the tip of he bullet is a waste of time and will never give consistent results.

Without the proper measuring equipment you might as well be trying to measure the top speed of a Ferrari using a bucket of water.
 
Sharpie marker and bullet comparators are your friends!!:D

Suputin said:
It may be a good idea to purchase the proper tools for measuring the bullet seating depth from the ogive. Measuring OAL to the tip of he bullet is a waste of time and will never give consistent results.

Without the proper measuring equipment you might as well be trying to measure the top speed of a Ferrari using a bucket of water.
Click to expand...
 
Suputin said:
It may be a good idea to purchase the proper tools for measuring the bullet seating depth from the ogive. Measuring OAL to the tip of he bullet is a waste of time and will never give consistent results.

Without the proper measuring equipment you might as well be trying to measure the top speed of a Ferrari using a bucket of water.
Click to expand...


^^^

First step, I like to establish the seating depth to touch the lands. The RCBS Precision Mic works well for this "baseline" reading.

Some throats are too deep to securely hold the bullet in the neck, and/or mag feed, when seated to touch. Some throats are quite short, and easy to jam too hard, if not carefull.

Some bullets (like Amax) have longer shanks, and so have more flexibility in the longer throated chambers.

As Heddok said, I too like to find the sweet seating depth first, then tweak the powder charge into the center of that accuracy node.
Two or three thou. are added to the seated length every hundred rounds to cover throat erosion.

One change at a time works best in the long run.

It's soo easy to mix up the load variables, when trying to get more results from each range visit.

If the rifle is a hunter, feeds reliably, and consistently shoots 3/4MOA, I'd be :D, and happily spending my time/$ shooting that same load under field conditions. What can be learned of drop and wind, trigger and hold, out past 200yds or so, will have far more effect than another 1/4 MOA of grouping ability. IMO.
:cheers:
 
I have stopped messing around with seating depth unless I can't quickly find a sub-1.25 inch load with the bullet I want.

I load to SAAMI length and with a good barrel/chamber combination it doesn't seem to make any difference. I would say over half the rifles I've loaded for have produced 1 inchish groups with messing with OAL.

I have had a few exceptionally accurate rifles where it made a difference( and a few that really weren't accurate), but in most the differences are minimal.
 
martinbns said:
I have stopped messing around with seating depth unless I can't quickly find a sub-1.25 inch load with the bullet I want.

I load to SAAMI length and with a good barrel/chamber combination it doesn't seem to make any difference. I would say over half the rifles I've loaded for have produced 1 inchish groups with messing with OAL.

I have had a few exceptionally accurate rifles where it made a difference( and a few that really weren't accurate), but in most the differences are minimal.
Click to expand...

I do likewise with loads for my hunting rifles simply because any gain in accuracy I might achieve through tweaking the seating depth I would not be able to exploit under field conditions. Therefore I seat to SAAMI, or seat to the cannelure if the bullet has one. When making up loads for my target rifle, I'll seat long, but I single load that rifle, which pretty much takes the need for reliable cycling off the table.

Having said that, pulling out all the stops to achieve the very best accuracy possible from your hunting rifle can be an interesting exercise. Providing that using these accuracy enhancing techniques doesn't negatively impact the reliability of the rifle, improving accuracy should increase your confidence.

Sometimes though, our desire for accuracy becomes unrealistic. I recall a young fellow who thought he had to have a hunting rifle built on a 40X and topped with a big power scope. That is until I realized there was no realistic big game target I could hit with a rifle like that, that I couldn't hit with any properly outfitted, good quality, hunting rifle over normal hunting ranges. After all, the big game tends to be large and the range tens to be close. Under such conditions an accurate fast shot is more likely to succeed than a deliberate shot, particularly if our hunter practices that type of shooting. Of course if you want to knock down game cleanly at ranges approaching or exceeding the half mile mark, that's another problem, which requires a different answer.
 
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