reloading for an auto-loader

[coyote315]

Ladies and Gentlemen:
Submitted for your consideration-
I am reloading .280 remington for my standby 7400 auto-loader. I am preferring the 162grain Hornady for now. Here is my question: basically no matter which powder i try, no matter whether it is a reliable cartridge load for functioning the rifle and shooting consistently accurate, or a screwball, I am chronographing the same average speed of 2450 fps.. is this is characteristic of having a gas-action bleeding off pressure when the bullet crosses the port hole?
This is about 200- 300 FPS slower than the average bolt action long barrel speed for the chart, which with consistent loads like Varget I am comfortable with and not complaining a bit, just wanting to understand the mechanics of what is happening. Basically, despite having a 22" barrel for guiding the bullet, I get only the pressure of a 12" or wherever the gas port is along the barrel.
Right?

 

[rcmodel]

No.

You might lose a slight amount of velocity to the gas system.
But not enough to measure.

By the time pressure drops and the bolt unlocks, the bullet has already crossed the sky-screens and probably reached the target.

no matter whether it is a reliable cartridge load for functioning the rifle and shooting consistently accurate, or a screwball, I am chronographing the same average speed of 2450 fps..

If you are saying whatever load you try is giving the same 2,450 velocity?

Your cronograph is screwed up.

There is no way any two loads could give the same velocity, let alone several different loads.

What powder & charge weight have you tried??

rc

 

[coyote315]

agreed

Ok, I agree with your assesment. To clarify, no, the chrono is not posting EXACTLY the same speed- that was an average. But it was also reporting variances of +/- 80FPS, which seemed really bad to me. Now I'm no expert on handloading, but I would like to hope that i can keep a better-than 160fps gap in between my rounds (?) Also, I would "think" that if they were that far off, I wouldn't be getting 2" groups at 200 yards out of my ol' deer rifle. SO, I agree, the chrono itself seems suspect.:banghead:
I shot my .35 remington loads through it, and got results i could expect: 2150fps, with a 50 fps spread between 6 loads. I'll take that.
To be fair, the chronograph i am using is the one from work we use to test paintball markers and such, with two metal Vs you shoot through. Mayhaps putting a 162gr bullet through it at somewhere faster than the speed of sound is just a bit too much to ask of the old girl. It may be more successful picking up the slow fat beer keg of my 35 but not so much on this needlegun.

As for loads: Right now I'm using Varget and 4138SC behind the 162gr Hornady Amax, but I'll gladly try other recommendations if you have a good heavy-ish pet load (150grain bullet or so; trying to work up something for distances over 400 yards) I want something to reliably kill the maurading paper plates, milk jugs refilled with water, and occasional coyote on my farm in the river bottoms.

 

[rcmodel]

What charge weight with each powder have you tried??

rc

 

[coyote315]

charge weight

Forgive me, but my log book is at home so I am working from memory. I went from 50 to 53 grains of the 4831 short cut in .5 grain increments, and nothing really impressed me. I messed around with Superformance (no, not on the load sheet from Hodgdon, I know I know...) but only validated their assessment that it was good but not great for the 162gr bullet. I did spend about 20 minutes on the phone with their customer service getting an education which helped understand some things.

I am taking some 39.5-43 grain increment loads of Varget to the range tonight, will let you know how that goes, and then my local gun shoppe has a guy who reloads and claims to love IMR 3031 so if the Varget doesn't do the trick, I will try that next.

I also gave in and spent the money on a scope that i do not hate, which I had been too cheap to replace, and maybe that will tighten my own groups just because of shooter comfort. I'd love to say I'm immune to the physiological effects of that sort of thing, but none of us truly are.

On the bright side, I haven't blown out a primer or put significant wear in the permatex buffer bead I put in ahead of the barrel nut, so at least I am not beating up the rifle (yet) and haven't gotten discouraged. I checked the chrono and replaced the battery with a fresh one just in case- will let you know how it goes!

 

[coyote315]

well here's the update, ballistic chrono freshly reconditioned and new battery: using Varget didn't change much either. Basically no matter what I run through this rifle, I'm getting about 2400- 2450 FPS solutions for a 162gr hornady amax. That is about 100-150 FPS slower than what the Hodgdon references for their data, which is based on a bolt gun with a barrel 4in longer, so I will buy that as logical. The fastest yield is supposed to be the H1000, which I will try next and see if it gets anywhere near the 2700 FPS they're claiming.
I guess my rifle just doesn't like the 4831 or superformance. Anyway, the Varget results are encouraging.

 

[chris in va]

My Lyman manual shows 4831 with a max charge of 56.5 compressed at 2784fps. I don't think you're loading it enough.

Max charge of Varget at 43gr shows 2526fps.

 

[KansasSasquatch]

I wouldn't trust a paintball chronograph to measure bullet speeds. Most of them are designed to be most accurate at speeds of less than 600fps. The good paintball chronographs also have to be tuned from time to time and in my 15+ years of playing I know that tuning doesn't happen as often as it should. There are a few that are marketed for testing speeds of 5000+ fps but I wouldn't trust them much unless I knew it were properly tuned.

 

[helotaxi]

Max charge of Varget at 43gr shows 2526fps.

That seems to me to indicate that Varget is way too fast a powder for that cartridge and that bullet. Consider that 46gn is the max load for a .308 with a 168gn Amax and the .280 case is MUCH larger. The .308 load is also faster. A good deal faster in fact. I'd be looking for a powder that does a better job of filling the case for a more consistent result.

 

[helotaxi]

I wouldn't trust a paintball chronograph to measure bullet speeds.

Where did you get the idea that he was using a paintball chrono?

 

[KansasSasquatch]

Post #3. I guess to be fair, he did say they use the chronograph to test paintball markers. That doesn't necessarily mean it is a chronograph designed for paintball.

 

[helotaxi]

Copy. Missed that part.

 

[tahoe2]

loading for the .280

I also have a 7400 in .280 and my best load for accuracy was 45 grns IMR 3031 with a 150 grn Rem Core Lokt bullet (7/8" for 4 shots @ 100), not sure of speed (2770fps posted in manual) as I don't have a chrony, and you will have to check if that is a max load. (I can't recall). I have reloaded the 162 A-max & 160 Sierra's with good results also, but will have to go back and check my records. Good Luck!

 

[jmorris]

Basically no matterwhat I run through this rifle, I'm getting about 2400- 2450 FPS

I would say your chronograph is broken. Despite what powder you are using you should be able to lower you charge all the way down to 0 fps (aka bullet stuck in the barrel). If you get 2400 fps at 30 grains and 2400 at 40 grains, you don't need us to tell you that your tool for collecting data is wrong.

 

[coyote315]

clarification

the chrony is indeed a ballistic chronograph. When the big Army supply system authorized us to buy one, we went all out. As for the loads not being heavy enough; hmmmmmmm. I'm going by the hodgdon online reloader's guide, (so maybe they're shorting it much more than necessary for their own protection?)

 

[coyote315]

Tahoe, you're the second guy to recommend IMR 3031 to me, and it is next on the list to try. As for my FPS, I seem to be losing about 350 off what the load sheet says i should get, which seems more acceptable when I consider having a 6" shorter barrel than their 28" testers.
the bottom line is, if I can wring good groups out of it at the range, I will adjust to the drop and let the bullet do it's work. I suppose I should let that .6+ BC do it's magic to flatten out the trajectory.
Tahoe, did you do anything else to your 7400 to get that out of it?

 

[tahoe2]

Coyote....I bought the rifle for $250 bucks from a private party about 10 years ago.
It had a cracked stock, so I threw it into a Ram-Line camo synthetic stock,
and hunkered down on the reloading bench, that gun is a shooter.
Most loads hover around 1-1/2" to 2-1/4", a couple are exceptional and under 1".
That gun also likes 130 grn Speer spitzers @ 2900 fps(49 grns IMR 4007ssc).
I topped it with a Pentax 3-9x40 Gameseeker with a ballistic plex reticle.
Because of the gas operation recoil is like a 30-30. Love that gun!!
I took two Pronghorns in Wyoming last October with that 130 grn load.
I would try another chrony before condemning your loads.
170726170727

 

[coyote315]

PRETTY!!!
Yeah I completely agree that the 7400 is the most under-rated autoloader out there; ten years ago i had one built in 30-06 and this is an attempt to improve upon that old girl.
Tomorrow morning I'm taking some 130 sierras loaded w/ superformance to the range and chrono it. Will let you know

 

[coyote315]

I am jack's raging success

2950 FPS average out of the 130gr sierras so, we're on the right track. Thanks for all the input, gents! Load seemed about right, now to start tweaking +/- half-grain increments til I find that magic number. Gonna try the 139 hornady Amax next.

 

[coyote315]

IMR 3031 to B'mark conversion

Never got the accuracy out of Varget I hoped for. Well, I couldn't find IMR 3031 but I have 8 lbs of benchmark and I'm pretty happy w/ it in everything else. Since they're close on the burn chart, I'm going to 'speriment. Now according to my math:
in 30-06, starting load for a 150gr bullet w/ IMR3031 is 43 grains and with b'mark it's 45 grains +/-depending on the bullet profile.
SO, that means benchmark is by-volume of powder less pressure than the 3031.
Acknowledging that the slightly smaller 7mm bore of the .280 will produce higher pressure, I think if I start working up the benchmark at 40 grains (better safe than sorry- worst it can do is not cycle the girl) then, I might be able to find a load that works.
The idea of benchmark's all-temp accuracy appeals to me because deer season is cool, hog "season" is warm, and coyotes season is crazy.