Chronograph... anyone seen anything like this?

[tahunua001]

today I went to my local gun range to test out some 6.5x50 loads I've been developing for black bear season and rather than run over and get my crono from my brother in law I decided to just use the range chronograph.

first I started out with hornady factory loads which according to them, should be loaded to approximately 2600 FPS. the chrono graph read them out to be 1850 FPS give or take. we traded out to a 22lr which read at little over 1200 which is right about where a 22 should be but I can't figure out why my Arisaka would be over 800 FPS off from the mark... and to further complicate things I tried my new loads which should be on the weaker end of 2500 FPS and they chrono'd out to 2175... more than 300 FPS faster than the ammo that should be 2600FPS...

has anyone ever had this happen before?

[ligonierbill]

Not exactly your situation, but I have generally found factory ammo to be slower than advertised in real hunting rifles. Not as much as you have observed, however. How long is your barrel? The ammo company probably tested in something like a 29" tube. They probably are selling "lawyer loads" as well, so I'm not surprised your handloads are quicker. My loads in various calibers vary from slightly faster than manual to 300 fps slower. Every rifle is different, especially older military rifles. Are your rounds accurate?

[tahunua001]

mines a carbine so it's quite a bit shorter than the standed 6.5 barrel, I think about 9 inches shorter. however I don't think that barrel length would be more than 100 FPS different between long and short barrel. given the accuracy of this gun I am not inclined to think that the barrel is worn to any extent that would cause such a loss of velocity.

[ligonierbill]

What load are you testing? My Hornady Seventh has several loads for 140's at 2,600, but their test rifle was an Arisaka Type 38 with a 30" barrel. I get an honest 2,600 from a M70 6.5x55 with a 22" barrel (140 SGK over 45.5 gr Reloder 22), but it has a slightly greater case capacity than the Japanese round.

[tahunua001]

I believe I settled on 32.5gr of 4064 behind 140gr nosler accubonds.

[I.R.Chevy]

I had a similar experience with my 300WSM and building hand loads. I was coming in 3-400 fps short on my recipes. Granted I was using a 22" barrel but again that shouldn't make up such a substantial difference.

After weeks of reloading and testing for accuracy and safety trying to attain something resembling a hot load I decided for gits and shiggles to buy some cheap-o federal 180's for testing against my home loads.

I set up the same way I always do on my table and leadsled set the target at 100 yards. Home loads are slow(2650fps) and punch a 1/2 hole. Stock Federal loads rock out at 3001fps and spray a 1 1/2 inch group.

At first I didn't believe the chrony but the truth hurts I guess....

I have since been slowly working up some hotties and have managed to match the factory loads for performance but I do see some signs of pressure after loading them multiple times.

I think guns have personalities and act all kinds of ways with all kinds of bullets. There is really no way to know before trying.

[Brian Pfleuger]

How far was the muzzle from the chrony?

[tahunua001]

about 4 feet.

[Brian Pfleuger]

Yeah, that's waaaaay too close. The muzzle blast is giving you false reading. 15 feet is the standard. My Glock 33 will almost tip over my tripod at 5 feet.

[tahunua001]

interesting, we've gotten decent readings with other rifles before, it's a fixed chronograph so it never moves...

I don't rightly know what the issue is... the muzzle blast sounds like a reasonable explanation which would be why the 22lr looked about right but then again that doesn't explain why on other days a 300 weatherby mag and 7mm rem mag gave accurate readings.

[Brian Pfleuger]

I don't know but I guarantee the problem is muzzle blast.

[SSA]

After checking a couple of manuals, it looks like your chronograph works, your handloads are right where they should be, and the factory loads are a bit slow.

[chris in va]

Wow yeah, 4 feet.

Back that gun up and don't shoot the chrony!

[zeke]

too close back it up. likely a short barreled 6.5 has different pressure wave. Sun angle or un burned powder can also throw off readings, but 5 feet is too close.

[SSA]

6.5X50mm Arisaka carbine, 140 grain bullet, 32.5 grains 4064, 2175 fps.

Sierra second edition reloading manual:
6.5X50mm Arisaka carbine, 140 grain bullet, 32.2 grains 4064, 2200 fps.

[tahunua001]

interesting my 5th edition has about the same data. I wonder why hornady lists it so much higher and why their factory ammo that they state is 2600 FPS is 300 FPS slower?

[Brian Pfleuger]

You really need to back up that chrony. I don't know if the numbers you're getting are right or not but 4 feet is WAY too close. The data published in manuals is almost always from 15 feet. It is pretty much the standard distance.

I'd be shocked if you could get reliable numbers from anything besides a 22 at 4 feet. I've never been able to get good readings from less than about 10 feet with my Beta Chrony, even with a .204Ruger.

My Glock literally rocks the tripod from 5 feet or so. Not just wiggles, it rocks the thing, almost tips it over.

Back it up to 15 feet and THEN we can discuss your velocities, good, bad or indifferent.

[tahunua001]

it's a fixed position chronograph owned by the club. I have no way of backing it off and no right to do so even if I could. it appears that Hornady uses a very long test barrel which is why their data is so different from Sierra's which is right about in line with what I was reading. the hornady factory data is severely flawed though it does seem as if my rounds felt quite a bit hotter and were supposed to be lighter loads.

[cvc944]

So the gun club moved it close enough to hopefully keep it from being shot. Good idea to keep it in one piece, I suppose, but bad idea for accurate readings.
I used to set mine up at about 10 feet, but found the readings were much closer to each other out at 15 feet.

[Unclenick]

The club probably set it up for IPSC shooters trying to see if their ammo made Major for a match. For most semi-auto pistol loads you can get away with close screens, though 6 feet is the more commonly recommended first screen distance even for pistol.

The SAAMI standard setup uses 15 feet as the midpoint between screens.

We had a board member a year or so back who discovered his .338 Lapua Magnum had so much muzzle blast that he'd get false triggering even at 15 feet and had to go back to 18 feet.

The Sierra manual notes the barrel length of the carbine as 19", which makes it 11" shorter than the 30" rifle. I get about 260 fps difference between those barrel lengths with the 4064 load in QuickLOAD.

[tahunua001]

yeah I think that's what's going on, my carbine has a 19 inch barrel and hornady uses a 32 inch test barrel so that accounts for some of the inconsistencies but not all with them.

as for why they chose the range they did I don't know, we don't have ISPA here, there is USPSA but they share their range with the local PDs and this is pretty much the general public rifle range.

[steve4102]

Yup distance is to close, the 22lr has much less MB, that's why their readings were more in line with reality.