You volume shooters; seeking input about the same powder, but different lots.

V

VaniB

New member
Have patience with me guys. I'm not one of you NutriSystem people who burns off the pounds! (........of powder) :D

While I demand accuracy, I don't hunt or do competition shooting, so a 1lb can of powder often lasts me years; I am content with finding a powder that shoots the tight group, and then it's "Mission completed!!...Good job Randall. Next rifle project!" (Sheesh....how long can one go to public range by himself to keep shooting the same rifle into the same tight groups before getting bored.) My question to you precision shooters is how common should it be for me to find a powder that will shoot tight 5/8" groups in my 308 AR for example, but with the next different lot of powder, I find the accuracy has gone to hell......like 4 shots scattered into 1 1/16" groups and a flyer in each group to 1 1/2"! It is because of the errant flyer in each group that I'm suspicious if something else is in play here and I can't blame it all on the new lot of powder. (??)

The load that is frustrating me is the .308 with 168 Hornady BTHP and H4895. After having experienced tight and touching 5 shots in 5/8" groups with my first can of powder, I moved into a 2nd can of powder and that's what I'm finding.
 
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Yes, I'm using flags for my 100 yard groups. The one flyer in each group is vertical.

But, aside from that. I'd like to fucus on the main question about different powder lots, and if it is a common or uncommon cause for accuracy loss.
 
Questions?

What else changed. Primer? Case preparation? Number of times cases loaded?
Shot old loaded cases that sat for a while and now reloading and did the brass change? Depth of seating? different bullet, different lot?
When all else fails get another can of powder and start over with new brass>
Centerfire
 
Lot to lot variation can change accuracy dramatically. Especially with double base powders and ball powders. Combine that with a shooting "machine" with gas ports, buffer springs, and lots of moving parts and you can get much variation in accuracy.

The trick is to buy powder in good quantity and use a chronograph to determine what it's burn rate is.;)

Good luck.
 
goodgrouper said:
Lot to lot variation can change accuracy dramatically. .;)

Good luck.
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Thanks. I guess that answers that. Oh well.

I already made the mistake of buying three $28 1lb cans of it never imagining accuracy would completely disappear. I guess the next 550 rounds of this stuff will have to be my SHTF and casual shooting round at the range.

I guess I'm going to have to try and enjoy being a normal person for a change and try shooting normal ammo off of a normal sand-bag without a notepad, knobs, or flags. :D
 
Lot to lot variation is normal but what your experiencing is generally not. Adjust your powder charge down and then come back up and see if it shoots better. Like mentioned before....is that the only variable that has changed? Are you still shooting the same lot of primers, bullets and cases? All these can cause a change.

Hovis
 
Its fairly simple. Buy powder in at least 8# jugs, primers in 5K batches, brass in quanity, and keep close track of how many times each piece of brass was loaded and when. Oh yea, it helps to buy several thousand match grade bullets from the same production run. Get them from a custom or semi-custom bullet maker that does not mix bullets from several dies. If after a period of work up you with known components, your rifle does not shoot as it should, be prepared to replace the barrel with another match grade barrel that is chambered etc, by a gunsmith, known for producing competition grade rifles. If you cannot do all this, than you may not achieve ultimate accuracy.
 
If you knew what a given volume setting of the previous pound weighed, and what velocity it produced at a particular temperature and humidity, you would have an easier time of making lot to lot adjustments in your load. My advice is to take your loading stuff to the range and fix the load and when you have, record the temp, humidity, velocity, and weight of the charge.
 
Bob's advice might not suit somebody with your usage but when you do buy a few cans at the one time, make sure that they all have the same batch number. Frankly, I would be concerned if my gunshop offered me a spread of batch numbers for any powder on his shelves. It might be indicative of a slow turnover, inappropriate inventory work, opportunist selling or opportunist purchasing habits, none of which would likely assist your search for accuracy.
 
As everyone has said there can be and frequently are variations from lot to lot that may require a load to be worked up all over again. With H4895 I haven't noticed extreme differences from lot to lot in accuracy, but it's sure possible.

When Benchmark first came out I bought several pounds of it and got very good accuracy and velocity/pressure relationship. It came time to buy some more Benchmark a few years later, and fortunately I dropped the charge back some. I still got VERY flat primers, very stiff extraction, and lower velocities. With H335 I've found some lots that worked well with standard primers and gave good accuracy, with other lots magnum primers were needed and velocity was only so-so for live varmint shooting.
 
Everything mentioned previously on this thread is valid, but your comment about getting one vertical flier makes me think the powder charge is a tad too hot (or too low). Have you tried varying the powder charge from the previous lot of powder? Try going down on the powder weight. Try .3 grains less, then .6 grains less, etc. If that doesn't work try going up the same amounts. With a new lot of powder is it highly likely it doesn't burn at exactly the same rate as the old lot, so you have to find a new sweet spot.
 
Just how long ago was this previous batch of powder ?
Years ago I shot H4895 in a 6PPC , the H4895 available these days is so much slower it is totally unsuitable for even consdidering.

Dick
 
It seems that there's merit in everything you guys have mentioned, and I will have to decipher it all to try to figure which factors likely best applies to my situation; Yes, it's differen't batches, yes it's different days with slightly different temperature/humidity. Yes, it's an AR with moving parts that will be easier affected by variations.

The first can of powder was bought about 2 years ago. The 3 new cans of powder I just bought are all of the same lot & same store....on purpose. I pre-weighed the bullets, and am using the same fired Lapua brass. This newer powder is burning the same load a little hotter, and with flatter primers for about 75fps faster more. Yes, I always use wind flags, and admit that it didn't help that it was really blowing that day! But there wasn't the typical horizontal spreads on my target associated with wind .......just crappy loose groups with a high or low shot on each target. It makes no sense and looks more like the reject loads I passed-up during the experimental stages of load development. I'll have to go back and try it again. I had originally found 41.3gr to provide the 5/8" five shot group, and then reduced the load 3/10ths of a grain to 41.0 grain to compensate for this hotter powder. Now the primer is looking somewhat rounded. Maybe I'll try back up to 41.2 grains.


I've got 3 cans of this stuff. Thank goodness it's for a military style black rifle. I suppose having a few magazines of this load will suffice for security purposes if for no other reason. I would never settle for these kinds of groups in my bolt action rifles, and I would be out the $100!! I do prefer to get those 5/8"- 3/4" groups again, but might have to settle for 1" - 1 1/4" with an occassional flyer......yuck.
 
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An AR and it's moving parts should not have that much affect. AR bolts lock up good, and they don't have pistons and operating rods moving around that can affect accuracy as some semi autos do. Don't sell an AR with a good barrel short in the accuracy department.
 
bob harrison said:
An AR and it's moving parts should not have that much affect. AR bolts lock up good, and they don't have pistons and operating rods moving around that can affect accuracy as some semi autos do. Don't sell an AR with a good barrel short in the accuracy department.
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I disagree with you. In comparison to my stationary bolt action rifles, or even my smaller sized 5.56 Colt Rifles, stop a moment and think of how that large 308 bolt is being pushed back far enough by a sudden jolt in order to eject that chubby little case, while the buffer and spring is being compressed back into the collapsible stock with a loud "Boyngggg" sound clearly heard in my right ear. It is combustion with A LOT of mechanical aftermath before the bullet leaves the barrel. Pulling the trigger on that 308 rifle always sounds reminds me of the motion going on in my Maytag washer.

Firing a 308 AR rifle for accuracy clealry requires more of a firm hold and cheeck-weld, with a very careful follow-through..... and way more demanding then my bolt-actons.
 
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