SITKA Gear

Handloading a .280 AI

Brian in Montana

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Well, it will be hard to improve on this:

IMG_20210129_121802717.jpg

I don't know why pics always wind up sideways when I post them. Anyway, that's 59.7gn of H4831sc pushing a 150gn ABLR. Velocity data could be a little better. ES is a bit of a concern, but it was mostly my last shot that skewed the data. Avg - 2886fps. ES - 40. SD - 15. Of course that's based on only 5 shots.

I lined up my 3 shot group with the one I shot last week and couldn't help notice the last 7 shots of that load all printed within .5". That's pretty accurate.
 

std7mag

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I usually do my load testing with the Hornady's. Due exclusively to their low cost. They perform good enough to get a sense of how a load is going to go.
I'll fine tune with the Noslers afterwards.
Groups only seem to get smaller changing from the Hornady's.

And yeah, Brian, if your not happy with the size of group 3 bullets made, adding 2 more isn't going to shrink it.
You may want to try the RL23 with the ABLR.
RL23 is a bulky powder, but you have enough case volume to handle it.
When you true your ballistics at longer range, you may need to adjust the BC on the ABLR. They like to fly. Ended up bumping my G7 up some to get to match.
 

Brian in Montana

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OK, moving on. Since my last post I've done some experimentation with H4831 and 154gn Hornady Interbonds. I started with my standard 12 round ladder test ranging from 59gn increasing each round by .2gns, maxing at 61.2gn. from the velocity data, pretty much everything between 59.6gn and 60.6gn looked pretty stable and even with the Magnetospeed on the barrel, all shots were within about 1.5".

From the data gleaned, I loaded 6 three-round test loads. I shot them today and came away with 4 of the 6 group less than .7" so I'm going to go out on a limb here and say the rifle seems to like this combination. But the standout was 60.3gn, with the 3-shot group measuring just .25".

IMG_20210219_194659510.jpg

Next step is going to be a 5shot string of this load and another 5 with the Magnetospeed to get an average muzzle velocity. I anticipate it will be around 2950fps, probably a little more.

Unless I can't duplicate the group, or there's something really screwy going on with the MVs, I'll probably stick with this for bear season this spring.

Funny thing, as an aside, I know they aren't as popular as a lot of other bullets out there, but I have found the Hornady Interbonds to be the most accurate in every rifle I load for. And I can generally push them faster than others without sacrificing accuracy. If you've never tried them, I do recommend.
 

ImBillT

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Glad to see that you added powder to the Jan 29th group. I was going to suggest a change of powder charge. I would focus more on the velocity that your best group came at than the powder charge. It’s possible that a future lot of powder or batch of brass would give you a different velocity and take you off your node. You’re using a pretty temperature stable powder, but if the temp was wildly different, you could experience a similar issue.

If your velocity spreads remain bad(and if that bothers you) I’d weigh each of your cases and measure the base to ogive measurement on a whole box of bullets. I don’t think the velocity spread was related to you powder or load. Winchester brass tends to be fairly inconsistent in terms of internal capacity.

Also, if a batch of bullets has substantial variation in base to ogive measurements, you basically end up with significant differences in jump or jam from shot to shot even though your dies were setup the same. Because most of the manufacturers that put out massive quantities of ammunition use more than one die to form each bullet, you’ll usually find that instead of the bullets having a normal distribution of BTO measurements spanning a very tight or very wide range, what you actually find is a number of groups of bullets(from a single box) with very distinct BTO measurements. Each bullet making die is making very consistent bullets, but not each die produces bullets exactly the same as the die beside it. One of the big advantages of custom bullets in the past was that a guy making bullets in his garage could only afford one set of bullet making dies for each type of bullet he made. That meant that every bullet of a specific type he ever put out was made on the same die. The big manufacturers have made changes to their processes in the past decade or so that have made their bullets much better, but BTO measurements can still cause issues from time to time.

Most likely it’s your cases. If you don’t want to scrap them, you can weigh them all and put them in order by weight, then shoot them in that order. Your velocity spread will likely go down. That will be more effective if you uniform the depth of primer pockets and trim them all to the same length before you weigh them.

Again, that’s only if your velocity spreads bothers you. At 100yds, getting on a node will negate the effects of a large velocity spread. I would only concern myself with it if I was trying to tighten up groups at much longer ranges.
 
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Brian in Montana

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Most likely it’s your cases. If you don’t want to scrap them, you can weigh them all and put them in order by weight, then shoot them in that order. Your velocity spread will likely go down. That will be more effective if you uniform the depth of primer pockets and trim them all to the same length before you weigh them.
I do think the brass I'm using is contributing to the inconsistencies, not that the numbers are really all that bad, just I've done better. I have a couple loads, .308 and .270, both using Win brass that consistently show an SD of 6 or 7. In the 280AI, I'm just using repurposed, fire-formed .280 Rem brass because I couldn't get anything else. Most of it turned out a little shorter than SAAMI specs, so there's that. When loading a string of test loads I measure the casings and even though they're a little short and not uniform, I choose ones all within a .002 of each other. It works out OK for now, but I have some Peterson brass on backorder.

Anyway, I did get out to the range the other evening for some follow up on the 60.3gn load. A 5-shot group came out to .73". I'm pretty happy with that - usually my goal for a new load is consistently .75MOA or better. The velocity data wasn't bad either. Average MV was 2949fps, with an ES of 29 and an SD of 13.

I'm fully comfortable working with this load and hunting with it in the Spring, but I still have other combos to play with. I'm leaning towards the 160gn Federal TBTs and probably RL22.

You guys feel free to post your own 280 adventures. I started this thread out of being excited about my own 280AI build, but I don't have to dominate it. 👍
 

BucksnDucks

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Looking good Brian. I picked up some RL26 and am giving it a try with 162 ELD X. I only have 1 pound so I'm gonna be in a pickle if it's the magic dust.
 

Jbotto

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You guys feel free to post your own 280 adventures. I started this thread out of being excited about my own 280AI build, but I don't have to dominate it. 👍
I wish I could contribute to this, as my brother and I rebarreled a rifle in .280AI. He’s two states away and doesn’t have huge confidence in his reloading ability so he did a basic load work up using steps of .5grains. Found one that shot “good enough” and has stuck with it. I keep telling him to come visit and we can go through it a bit more in-depth but it hasn’t happened yet. I do know he is shooting H4831SC behind a 150gr TTSX. He has sent me pictures of his groups that are really pretty good for as much time as he has behind a rifle, and they only get better with every visit to the range. I have enjoyed following this thread as it’s a very interesting cartridge!
 

6mm Remington

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160 accubond and 7828 ssc shoot very well in one of my 280ai with fed 210 match primers.
I use IMR7828SSC and have great results with it also. I have only been shooting either 140 gr. Partitions or 140 gr. Accubonds. 3230 fps and 3186 fps. Used the Accubond on my grizzly bear fall of 2019. One shot at 158 yards. Hit him tight behind the right shoulder. He spun 180 degrees into the shot, did two tight somersaults, and was dead. He never even twitched again. Bullet exited out his left side behind the shoulder. My bear was an arctic grizzly that squares out at 7' 6" and I was told he's huge for an arctic bear. We estimated his live weight at about 400 pounds plus.

Guide Mike Lettis with my bear. Best of luck with your 280AI. You will love that cartridge. Ovis Outfitters was the outfitter for my hunt. Great folks.

Peterson Cartridge Company brass! You must get some of this. I have 100 cases so far and it sure looks to be great stuff.
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ImBillT

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I do think the brass I'm using is contributing to the inconsistencies, not that the numbers are really all that bad, just I've done better. I have a couple loads, .308 and .270, both using Win brass that consistently show an SD of 6 or 7. In the 280AI, I'm just using repurposed, fire-formed .280 Rem brass because I couldn't get anything else. Most of it turned out a little shorter than SAAMI specs, so there's that. When loading a string of test loads I measure the casings and even though they're a little short and not uniform, I choose ones all within a .002 of each other. It works out OK for now, but I have some Peterson brass on backorder.

Anyway, I did get out to the range the other evening for some follow up on the 60.3gn load. A 5-shot group came out to .73". I'm pretty happy with that - usually my goal for a new load is consistently .75MOA or better. The velocity data wasn't bad either. Average MV was 2949fps, with an ES of 29 and an SD of 13.

I'm fully comfortable working with this load and hunting with it in the Spring, but I still have other combos to play with. I'm leaning towards the 160gn Federal TBTs and probably RL22.

You guys feel free to post your own 280 adventures. I started this thread out of being excited about my own 280AI build, but I don't have to dominate it. 👍
I’m on the same page that your SD/ES is perfectly adequate for hunting, so I wouldn’t worry about it unless you just wanted to. It would probably improve long range groups slightly.

Don’t worry that it is fireformed from .280Rem. I’ll be fireforming mine. My other AIs have to be fireformed, and believe me, they shoot.

Don’t worry that they are a little short. That’s not really hurting anything.

Very different neck lengths can be an issue. .002” is quite good though. You’ll find that it’s nearly impossible to trim them better than plus or minus .001”, which gives you a .003” spread. What I would do though, is set up your timer to trim .001” longer than your shortest case, and trim them all to that length. That way you won’t have a bunch of different length cases.

I would consider sorting by weight. I have 40 pieces of old “white box” Winchester Western 6mm Rem, all from the same lot. They span a weight range of over 10gr. I also have 140pcs of RWS 7x57...the lightest case is 181.9gr and the heaviest is 183.4gr. A 1.5gr extreme spread. I also frequently get single-digit velocity extreme spread over the chrono. I have a few rigs that give single-digit SD, and occasionally single-digit ES. All are using brass that has been sorted by weight, or is good enough that sorting by weight would have been a waste of time. If you were just able to sort your brass into two lots that were within 3-4gr of each other you would probably see an improvement. If you’re mixing brands, you’ll probably get an improvement just by sorting headstamps.

Again, I wouldn’t bother with it unless you just wanted to. Growing up shooting at a benchrest club, I have trouble not doing certain things. Unfortunately, I could have killed a giant elk in AZ in Dec. with an out of the box Savage .308 using factory Core-Lokts and iron sights if I had just put the sights in the right place. Instead I came home empty handed in spite of a very good rifle and very good ammo.
 
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Brian in Montana

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Well, I'm at the range now shooting some test loads based on a ladder test I recently did with 150gn Nosler ABLRs and RL22. First load was nothing to write home about. Got 4 more. I'll update.

Man, it's a beautiful sunny day in SW Montana.
 

Brian in Montana

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Results were not too bueno. Best group was about 1.5". There was something of a pattern, though. In several 3-shot groups I'd have 2 about 1/4" apart or touching and a third almost 2" high. Seems to be some significant inconsistency for some reason. I've seen this kind of thing before, but probably not quite this pronounced. Anyway, I'm inclined to move on to a different combination.
 

ImBillT

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4 of 7 groups were very similar to this. Anything to be read into this other than just the load is inconsistent?

View attachment 176364

Most likely gun handling. Could be a loose screw on a scope base or ring. Could be something touching the barrel. Ammo doesn’t usually get that bad.

Most hunting style stocks have some slope in the fore end and a lot of slope in the butt stock. If you shoot something that has a fair bit of recoil with a stock like that, from a front rest, the back of the stock will tend to drop as the rifle recoils. If the position on the front rest changes or if the pressure on your shoulder changes, the amount that the stock drops(and the barrel raises) during recoil(and before the bullet leaves the barrel) will change. Usually the more fore end that hangs over the rest, and the harder you pin the butt to your shoulder, the lower the bullet will impact(and this is usually close to where it would impact in a machine rest). The closer the front rest is to the end of the fore end, and the looser the stock is held against the shoulder, the higher the bullet will impact. It’s not uncommon to start a group with the rifle forward on the rest, and a firm hold, but by the end of the group, the rifle has shifted rearward to the point that it’s about to fall off the rest, and the shooter has become comfortable enough to loosen his hold. A good test for this is to shoot prone from a very stout bipod. F-class style bipods are easier to shoot than collapsible bipods, but it’s possible to shoot well with collapsible bipods.

It could also be from the front bag touching the barrel. It’s not uncommon, for the bags to settle enough at the end of a group to have one touch the barrel. Even worse would be if you’re using a hard front bag in a front rest, and the stock came off the bag and the barrel was just resting on it. I’d think you’d have noticed that though.

You’re not using a Tupperware stock are you? I’m assuming it’s a very rigid FRP stock.
 

Brian in Montana

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I'm using a Bell and Carlson stock. Its pillar bedded, very ridgid, and the barrel is floated. I'm shooting off a bipod attached at the forend with a sandbag supporting the butt end, nothing touches the barrel. I'm pretty meticulous about scope installation, use a Fatwrench and make sure the torque is equal on all the screws. Same with the action screws.

This is my 3rd load to try in the rifle, the other two didn't do this. It was the usual process you'd expect, narrow down the charge, seating depth, ect., until it groups. This particular combination is hotter and recoils more than the others; that as well as the odd pattern I'm seeing with 2 shots touching and one 2" high, does make me wonder if something is moving around. I'm pretty sure it isn't the scope, but being a RemAge barrel it has a pretty sizeable barrel nut snugged up to the receiver. The thought occurred that maybe with the heavier recoil, and the extra size and mass of the barrel nut, maybe the recoil lug is shifting around in the stock. But even if that happened to be the case, I doubt it would cause flyers that pronounced. In any case, it's strange. Like I said, I have seen this kind of pattern before when developing a load, but not this pronounced or repeatable. I've always just determined the load was not going to be consistent and moved on to something else.

I think my next step is to go back and shoot a string of that last load I developed (154gn Interbond/H4831) and make sure it's still doing the same as last week.
 

ImBillT

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I'm using a Bell and Carlson stock. Its pillar bedded, very ridgid, and the barrel is floated. I'm shooting off a bipod attached at the forend with a sandbag supporting the butt end, nothing touches the barrel. I'm pretty meticulous about scope installation, use a Fatwrench and make sure the torque is equal on all the screws. Same with the action screws.

This is my 3rd load to try in the rifle, the other two didn't do this. It was the usual process you'd expect, narrow down the charge, seating depth, ect., until it groups. This particular combination is hotter and recoils more than the others; that as well as the odd pattern I'm seeing with 2 shots touching and one 2" high, does make me wonder if something is moving around. I'm pretty sure it isn't the scope, but being a RemAge barrel it has a pretty sizeable barrel nut snugged up to the receiver. The thought occurred that maybe with the heavier recoil, and the extra size and mass of the barrel nut, maybe the recoil lug is shifting around in the stock. But even if that happened to be the case, I doubt it would cause flyers that pronounced. In any case, it's strange. Like I said, I have seen this kind of pattern before when developing a load, but not this pronounced or repeatable. I've always just determined the load was not going to be consistent and moved on to something else.

I think my next step is to go back and shoot a string of that last load I developed (154gn Interbond/H4831) and make sure it's still doing the same as last week.

Did you bed the lug? I usually put two pieces of tape on the bottom of the lug and bed it front, back and sides. While I don’t know what kind of problems can happen, the massive open are for the lug on a B&C always made me nervous.

That B&C isn’t bending and touching the barrel, so that’s out.

Using a bipod, inconsistent placement of the front rest isn’t the problem, and neither is a bag touching the barrel.

Are you using a rear bag?
 
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