How far over maximum?

[therifleman556]

I've been reloading for about 18 years now. When I started out, I was in my teens and did everything by the book because I didn't have a chronograph. How fast my loads were didn't matter; I was shooting 200 yards tops. It wasn't until about three years ago that I finally broke down and bought a chrony. That was an eye-opener seeing just how far off my loads were.

Having a chronograph was a useful addition, but so were Nathan Foster's books (and later this forum). It wasn't until reading about how generous chambers and throat lengths can have a very negative effect on the speeds and pressures achieved that I began creeping over published maximum charges.

I'm not advocating anyone doing this, and most certainly not if they don't own a chronograph!

Here's my question to some of you professional (or hell even amateur) ballisticians: what's the most you've had to venture over maximum to achieve an expected speed? I understand some rifles simply cannot reach what the manual says is possible, while others can get there comfortably.

I'll pose a few examples.

1. A Browning A-Bolt 270 WSM. Using RL 19 and the 110 TTSX, this rifle will exceed published speeds by almost 100 fps but I cannot get close to the max charge listed. I have to stay 0.9 grain under listed max (which puts me a few fps over their max speed).

2. A new to me Remington 788 in 243. This rifle a tried various charge weights of Varget under the 75 grain V-MAX. I did not have my chronograph with me when testing but accuracy was good and I did not get any stop signs up to book max. It shot good so I loaded 40 of them up. That was a mistake; I checked it later and it's about 300 fps slow.

3. A 25-06 with a 24" barrel. I'm intending this to be my 400 yard coyote hammer. This time I'm using the chronograph to find this rifle's maximum. Nosler says RL 19 should propel the 85 grain Ballistic Tip to 3600 fps. I loaded up 10 rounds in half grain increments (at their coal) and ran them over the screens. At book maximum I got 3200 fps, and primers that looked like I'd been shooting starting loads. A 2.5 grain over max charge netted 3399, and still no pressure. I should add that this rifle is my guinea pig for trying HBN, and the bullets are coated. I know this causes a drop in pressure and a need to add more powder but still, 400 fps low?

What say you?

 

[Barrelnut]

Well, I'll jump in. Good question. IMO load data books have gotten more conservative over the years. Lots of book loads are tested in 26" barrels or 24". Powder speed can vary some lot to lot. The altitude your are shooting at can affect the velocity see at the chrony (especially an optical one). Throat lengths can vary based on the reamer used. etc, etc, etc.... I think this is why they say each rifles is an individual.

Now days, I set the bullet .010~.020 off the lands. I start going up in .3 gr. increments until I hit pressure signs. ( pancaked primers and ejector marks). Also, once a rifle hits pressure it is easy to feel in recoil amounts too. Recoil will really start to increase with additional powder. All the while watching on the chrony. What I got is what I got at that point. I have seen it faster than the book, with a shorter barrel. I have found it slower with a longer barrel. Have seen it a couple grains over book max and even not quite being able to get there.

That chrony really opened up a whole new world didn't it?

 

[memtb]

As mentioned above....most manuals are "very" conservative compared to the '60's/'70's! But as you stated, there will be differences in barrels....some faster, some slower. Unless you own a "strain-gauge", about all you can do is slowly work up your charge, constantly monitoring pressure indications. Often you will get a fairly steady increase in velocities with the increase of charges. If you step-up the powder, and do not see a velocity increase, this "may" indicate you've reached maximum!

For what is worth, I do my load development on hot days....making sure that I am within safe pressures on hot days. Though many of our modern powders are fairly temperature stable....I err on the side of caution! memtb

 

[therifleman556]

That chrony really opened up a whole new world didn't it?

It did! I've got a friend at work who just got into reloading and has gotten quite serious at it. Still, he's shooting blind without a chronograph. Now and again he'll tell me about how he found a good load that shoots good and "according to the manual should be doing xxxx fps". I can't help but laugh when that line comes out.

 

[therifleman556]

. Often you will get a fairly steady increase in velocities with the increase of charges. If you step-up the powder, and do not see a velocity increase, this "may" indicate you've reached maximum!

Right, another good point. But we're also told that this stabilizing velocity can be a node. I noticed this too at around 56-57.5 grains. I actually dropped a couple fps at 56.5, and 57.5 was only about 30 fps over 56.0 (going off of memory, it's written down but i could be off a bit). Primers are still quite round at this point so I press on and find that the next shots are getting a higher spread in velocity.

 

[Trnelson]

A reliable Chronograph is nearly required equipment for a reloader, just like go and no-go gauges. When I start a new rig I always start with the minimum published charge and measure what that yields with my magnetospeed, back in the old days a shooting Chrony had to fit the bill. That gives me a solid, safe baseline that I can work up from. I've had a couple of rifles over the years that have yielded a surprising velocity that didn't make it any place close to the published charge weight data maximums.
Modern manufacturing techniques have done a lot to capitalize on repeatability much better precision in production rifles. A smart guy realizes that it doesn't matter much what the XXXXX manual lists as a maximum charge if you are getting that velocity with two grains less powder and stops while he is ahead. It isn't fashionable to wear any part of your rifle in or on your face. Listen to what your chronograph is telling you.

 

[Barrelnut]

Another thought on this is the brass being used. Different brands have significant capacity differences because of the wall thickness. Example is Nolsler or Lapua vs Winchester or Hornady. The latter have thinner walls and therefore higher capacity. It affects pressure and velocity.

 

[therifleman556]

I almost always wind up using Hornady or Winchester, I'm to cheap for anything else. I'll have to check Nosler's data again to see if they list water capacity. I've always liked their data because it's the least conservative I've found.

 

[just country]

morning, 40yrs. ago when others and myself started slinging bullets
there were very few graphs to check the performance of powders,
bullets, brass and primers. I bought every book I found on reloading
rifle and pistol ammo. no computers for storing reloading info.
had sticky tabs on the top of pages denoting calibers and
loading info on every caliber, I was reloading. we read, loaded,
shot until we found the magic sweet spot and info.
I have enough different powders, primers, and bullets
to start my own store. brass I am very selective. I bought
a very good chronograph, now out dated. my dedication
to research reading reloading books still is my major
go to--plus the knowledgeable folks on this forum and
others. we I have said before r the scientist of the reloading
culture. what is printed in the reloading world
is a starting reference. we love the science of R&D.
very senior participant. justme gbot tum

 

[Gord0]

I laugh when I see people on reloading groups saying a reloading manual is like the Bible... There are way too many variables between your rifle and the test barrel used by whoever's data you're looking at.