velocity and groups

[Axis II]

I have kind of a dumb question for you guys...

I'm reloading 223-55gr v max with 23.3gr of benchmark and cci450 primers with LC brass out of a savage axis 1-9 twist-22inch barrel as my most accurate load. According to hodgdons I'm below their 24gr start and 24gr puts me at 3k fps which now I'm below the 3k fps i would like for shooting flatter at longer ranges.

Why when i go up in charge which I'm sure factory ammo is hotter than my reloads and shoots fine does the reloads open up from touching to 1 inch or worse at 100yards when i get around the 23.8gr mark? I'm trying to develop a good flat shooting 250-300yard round for varmints and don't think my 23.3grs is going to cut it for that far.

any tips on going higher in charge but still keeping good accuracy?

 

[Grumulkin]

For each powder in a particular cartridge, there is an optimal load at which accuracy will be the best. Some powders have a wider range of weights at which accuracy will be good. You have no idea what powder factory ammo is loaded with so you can't compare your reloads with it. If you must have higher velocity with acceptable accuracy, you'll need to go to a different powder.

That said, your load doesn't have to be all that flat shooting for 250 to 300 yard shots. I would MUCH rather have a load that gave me all shots touching with a little loss of velocity over a load with worse accuracy and more velocity.

 

[otrman]

Ok, first off, it can sometimes be a bad idea to start below the listed start charge. That is one of the ways you can end up with a squib load. Most rifles will have 2 accuracy nodes, one at the lower end of the load and another towards the upper end. Work up toward max and you may find another accurate load that gives you the velocity that you are seeking.

 

[Blue68f100]

Like said there are normally 2 accuracy nodes, low and high. There is nothing wrong in using your existing load for longer distance. You just have to work with the drop and wind drift till your comfortable with it. I've had many 3 shot wonders till I fire the 4th round

I would just continue to work up your charge toward max.

 

[wally]

I'd suggest actually using it for your intended purpose for a while and only worry about "working up" if it proves inadequate. Its not like there is a season you need to be ready for with varmints.

 

[Axis II]

Ok, first off, it can sometimes be a bad idea to start below the listed start charge. That is one of the ways you can end up with a squib load. Most rifles will have 2 accuracy nodes, one at the lower end of the load and another towards the upper end. Work up toward max and you may find another accurate load that gives you the velocity that you are seeking.

starting load in the hornady manual is like 21gr. hodgdon site says 24gr start. I always start at the book min and workup to hodgdon max. would have never found the 23.3gr sweet spot if I started at 24.

 

[Bart B.]

I often read there's 2, sometimes 3 accuracy "nodes" for a given cartridge. Virtually all are with commercial barrels from rifle companies. They're typically based on one or two few-shot groups at different charge weights.

All the sporter and match barrels I've checked for this thing have all had a 3 to 4 grain spread in charge weight below maximum where accuracy was very good. The most accurate load has been closer to max. Going more either side of that band degraded accuracy. The difference won't be observed by 90%+ of all shooters. It's a waste of ammo and barrel life to resolve it any finer.

I concluded that there's one charge +/- 1/5 grain that gives best accuracy. Up to 2 or 3 grains below that, accuracy doesn't change enough to matter unless you can detect a 1/10th MOA. change.

 

[Grumulkin]

Sometime I'd like to see targets with the mythical 2 accuracy nodes demonstrated.

Some powders do have a 2 or 3 grain spread with good accuracy but I've found the spread for optimal accuracy to be usually less; sometimes a lot less.

 

[Bart B.]

In an early '70's conversation with a ballistics guy at Lake City arsenal about a bad lot of M118 match ammo, he mentioned some stuff about their accuracy tests. They typically see a few grain bandwidth for best accuracy. Then adjust charge weight in that range to meet pressure and velocity specs. Velocity specs were +/- 30 fps about 2550 fps at 26 yards.

I shot a couple hundred rounds of 308 Win with 168's over 41 to 44 grains of IMR4064 at 200 and 300 yards. Same accuracy about 2/3 MOA.

I think the concept of 2 or 3 accuracy nodes for a given component comes from shooting one few-shot group with each setting. If it is small, that's an accurate one; otherwise a bad one in the eyes of its shooter. Had the test for each setting been made with a 20-shot group, the first few shots have a 10% chance of being a larger group or a smaller one than average, but all 20 shots include both as well as a few other groups closer to their average size. Should a test of a few shots for two component settings be small and each setting is at their extremes, the common conclusion is "Ah ha; two accuracy nodes!"

 

[witchhunter]

Try another powder if your groups are opening up with velocity, but don't give up too soon, sometimes you can get a node at near max. It all depends where you are comfortable with the pressure you are developing. Pressure will decrease brass and barrel life. I am also of the opinion that an accurate load is king, no matter the velocity, unless it is extremely low. just shoot it at all ranges and learn your drops and windages. Give me an 1/2 minute load at 3000 fps rather than a 1 minute load at 3400 any day.