Guessing its my chronograph???

[jgh4445]

Loaded up some .223 Sierra 65 gr GK BTSP and 64 gr Win PSP's today. I used H335, 400 primers, LC Brass. My rifle is a Sig M400, 16" bbl enhanced with the only mods being a free floating handguard, a POF trigger and a JP adjustable gas block. I loaded 5 rounds each of 25.2 gr and 25.6 gr of the 335 for each of the bullets. The rounds are seated to 2.250.
My chronograph, a CED Millenium II showed velocities that ranged from a low of 2528 to a high of 2620. All of the rounds fell into this grouping. The Sierra manual I used shows a minimum velocity of 2600 achieved and a max of 2950 which was with the 25.6 load that I had 10 rounds loaded with. I never got over 2650. Does anyone use any of these loads? Shouldn't the velocity be up around the 27-2800 fps mark? Is my chronograph calibratable ( if that's a word)? A friend shout his revolver thru it and before he shot he said he thought his round was about 700 fps. He shot 5 rounds and averaged 688 fps with a high of just over 700 and a low of about 620. He said he thought the chrono was reading correctly. What do you guys think?

 

[Jim Watson]

The chronograph is right, your barrel is short, the manual exaggerates because they use a P&V barrel which is minimum in all dimensions.

 

[jgh4445]

Yeah, but I'm getting velocities well below what the book says is a minimum? Hard to believe that is right. Tried a few HDY 55 gr SP loads with 26.5 gr of Win 748. Got about the same velocities..

 

[matrem]

Done a lot of chronographin (I know that can't be a word either) since the nineties.

Virtually everything you actually test will fall far short of what you'd expect, if you're only reading how fast it should be going with such and such load.

 

[jgh4445]

Did the math ( or I let Strelok do the math) The come up in MRADS, zero'd at 50 yds, is 1.0 at 300 yds for the 65 gr Sierra at 2900fps. At 2600 fps its 1.5. Not a whole lotta difference at 300. At 600 its 4.4 at 2900 and 6.0 at 2600, much more as it gets farther away.
Gonna clean the rifle tonight, load both those bullets with some CFE223 and try the chrono out again tomorrow.

 

[cfullgraf]

Chronograph data from your firearms will rarely match the data published in the manuals.

Lots of reasons for the differences.

Having said that, Sierra used a Colt Match Target (20" barrel AR-15) to develop their Service Rifle Loads a while back. My Colt match Target pretty closely matched their data for the 69 grain Sierra Match King and powder I was using. Then, I got a Compass Lake Service Rifle match rifle, a 20" barrel AR-15, and the velocities with the same bullet and powder load was 10% higher than both Sierra's data and my data from the Colt.

I'm sure there is some way to calibrate a chronograph but I suspect it is beyond the equipment/tool capabilities of the average enthusiast. The manufacturer of the chronograph would be the place to start.

Shooting the same load over two chronographs side by side on the same day would give some data for comparison. Do your best to make conditions identical for each shot.

While there will be some shot to shot variations, the average and extreme spreads between the two should be very similar for statistically significant sample sizes.

If not, one or the other chronograph is out of calibration but unfortunately you will not know which one.

 

[ArchAngelCD]

I know it's hard to believe but 300fps is not out of line. The data on the Hodgdon site was produced using a 24" barrel, you are shooting a 16" barrel.

In my AR here is what I got:

Loading a 55gr bullet Hodgdon reports 3174fps with a charge of 25.5gr Varget.
I charged 26.0gr Varget and got an AV of only 2965fps and that's with .5gr more powder. With a charge of 25.0gr the AV was 2797.

As you see, the velocity difference is considerable.

 

[TBJK]

I know it's hard to believe but 300fps is not out of line. The data on the Hodgdon site was produced using a 24" barrel, you are shooting a 16" barrel.

Bingo. You really have to get to design/laboratoracal (just wanted to say that cause everyone else gets to have fun). I see stuff like this all the time. Different industry but concept is the same. The customer complains to say they are not making design, at non-design conditions. If I'd have a wild guess I'd say your likely not going to get the velocity without the extra length of the barrel & without exceeding the Max charge.

 

[hdwhit]

jgh4445 wrote:

My rifle is a Sig M400, 16" bbl

And what was the barrel length of the test rifle used in the Sierra manual?

You cannot expect to get the same results as are published in the manual unless you duplicate the rifle used in the manual. Shorter barrels will experience significant deviations from published data based on longer barrels as the powder burn rate increases.

 

[Steve C]

The manuals give you the velocity they got with their mix of gun, barrel length, bullet, powder lot, primer, and case likely under both temperature and elevation difference than what existed when you did your measuring. The chrono tells you what velocity you are getting with your mix. You just need to accept the readings of the instruments. If they where way off then one can suspect the placement of the chrono too close to the barrel muzzle where the powder smoke will give a vastly higher velocity or ambient flashes from passing cars, lightning, or just poor lighting conditions.

 

[Blue68f100]

I just ran the same load last week for my AR. I have an 24" Bull Match barrel with a min spec chamber, 1:10 twist. Here are my results. LC-15 Brass, CCI #41 primers, 2.260" OAL. Crony was at 12'.

25.2gr H335 3094 fps
25.4gr H335 3171 fps
25.6gr H335 (Max) 3185 fps

 

[jgh4445]

Thank you all for the replies. They are all spot on. I haven't used the chrono much and never with a .223 before. I usually use it for 45 Colt and 45 ACP and the like. I also use it for centerfire rifles in calibers of .308, .260 .280, etc.. Since my barrels usually closely match the test equipment, the differences are not so apparent or drastic.

 

[sugarmaker]

High velocities sell powder, bullets, and manuals. Long barrels are commonly used in development.

 

[jmorris]

Yeah, but I'm getting velocities well below what the book says is a minimum? Hard to believe that is right.

Think of it like they are trying to sell a car. When is the last time you achieved the mileage on the window sticker?

 

[spitballer]

I concur with first response, barrel length for data testing purposes is generally 24".

 

[FROGO207]

I usually use a Crony to tune in my accurate on paper loads to achieve a low velocity deviation. This helps my overall accuracy I feel. I pay more attention to the actual VEL if it is over the published results as the pressure could be over max then. Otherwise I just chalk it up to must be a difference in components and/or equipment used in their test. As noted above barrel length (and twist rate) can make a huge difference at times. If your other loads with different rifles were reasonably accurate according to book data your Crony and how you set it up should give accurate results.

 

[jgh4445]

Went back to the range yesterday with some loads using CFE223. Same thing, velocity was around the 2600 to 2650 range. Shot the same load from my 20 inch LTR and the speed jumped up to the 2900 range.
Then I shot some loads using AA2230 and in the AR 16 inch. These were loaded with the book max or 24.9gr. I was at 2989, 3009, 2998, 2991, 3012 for 5 shots. Didn't try it out of the LTR. Then I shot some Hornady 35 grain, advertised on the box at 4000 fps, out of the AR and it read 3700+.Next I tried some Hornady Superformance and got to within 300 fps of the advertised speed. The chrono seemed to be correct when tested at known velocities.
I was really happy with the AA2230 as far as velocity and accuracy was concerned. Gotta get some more of that stuff.

 

[ArchAngelCD]

.Next I tried some Hornady Superformance and got to within 300 fps of the advertised speed. The chrono seemed to be correct when tested at known velocities.

Probably just a typo but Superformance is distributed by Hodgdon, not Hornady.

I would not waste the components on trying Superform in the .223. According to Hodgdon the increased velocities are only seen in a very limited group of cartridges, the .223 not being one of them. Same goes for their Leverevolution powder, it only increases performance in a narrow band of cartridges.

 

[jgh4445]

Hornady Superformance Varmint. Ammunition, not powder. Velocity is posted on the box.

 

[ArchAngelCD]

Hornady Superformance Varmint. Ammunition, not powder. Velocity is posted on the box.

Sorry, my mistake.

 

[hdwhit]

I still have a Hornady Manual, 4th Edition and a Speer Manual, 11th Edition, both of which were published in the 1980's.

The Hornady loads were developed using a rifle with a 24 inch barrel, while the Speer loads were developed using a rifle with an 18 inch barrel.

The difference in presentation between the two manuals makes direct comparisons difficult as Hornady lists loads at velocities 100 fps apart while Speer lists loads as fixed intervals and corresponding velocities. I looked to me as if faster burning powder resulted in differences in velocity on the order of 200 fps while slower burning powders showed the differences on the order of 300 fps. Since the progression of the change appears to correspond with burn rates, I assume the majority of the difference is attributable to the difference in barrel length.

 

[Blue68f100]

Thank you all for the replies. They are all spot on. I haven't used the chrono much and never with a .223 before. I usually use it for 45 Colt and 45 ACP and the like. I also use it for centerfire rifles in calibers of .308, .260 .280, etc.. Since my barrels usually closely match the test equipment, the differences are not so apparent or drastic.

I should add that when shot out of my cheap Anderson 18", 223 Wylde Chamber with a 1:8 twist barrel the velocities are over 400 fps slower than book values on the H335 powder data by Hornady. I have not shot these 65gr SBT GK with this powder (h335) combo. This barrel only like 65gr + bullet weights. ALL 55gr bullets look more like a shotgun pattern than a rifle. So I gave up on any thing lighter than 65 gr. I probably shot the barrel out trying to find some 55gr bullet/powder combo it likes before giving up. The best I could get was 1.5"-2". The 65 and 69gr would hold 1/2 moa.

 

[RainDodger]

Jim spoke the truth in post #2. The only time I've ever gotten close to published values has been with the 26" barrel on my .308. Actually, I was slightly OVER the published FPS value, which surprised the heck out of me.

Your chrono is just fine.

 

[macgrumpy]

Read the beginning of the 223 AR-15 section in the Sierra manual and you will find that you aren't using the same kind of barrel nor are you using the same primer, case, or cartridge overall length. Additionally you don't know if Sierra's velocities are adjusted for true muzzle speed or the readings they got some distance away from the muzzle. And finally, the ambient weather and light conditions, different lots of powder, primers, bullets, cases, and battery strength will cause variations in the chronograph's numbers.

My copy of QuickLoad estimates that Sierra's 2950 FPS for the 20" barreled Colt HBAR that they used to develop their load data is right on the money for a high capacity cartridge case (around 31.8 grains of water capacity). Using those same numbers for your barrel length drops the estimated muzzle velocity to 2765 FPS. I assume that you had your chronograph several feet from the muzzle, let's say 15 feet, so your bullet is actually going slightly faster than the numbers that the chronograph showed, you state you got no higher than 2650 FPS, compensated for distance from the muzzle that would be around 2675 FPS at the muzzle. Then you can add slight errors in the chronograph, the cartridges, and my software and I'd say that your bullets are within 50 FPS of the expected velocity that a 16" barrel should produce. That's still a bit more variation than I'd prefer but without being able to see your setup I couldn't estimate any closer than that and it's a reasonable difference in calculated approximations.

 

[jmr40]

A barrel 8" shorter than the one used to test the loads will account for the speed differences you get. That works out to about 37 fps slower for each inch difference. A little more than I think you'd get if you started with a 24" barrel and cut it back to 16". But I've seen over 100 fps difference with barrels of the same length. Combine the shorter barrel and the real possibility of a "slow" barrel and you're in the ballpark.

Virtually everything you actually test will fall far short of what you'd expect,

This is not my experience. Virtually all of my loads have been pretty much in line with expected speeds when shorter barrels are accounted for. And right on the money when my barrels matched the tested barrel length. Most of my hunting bolt guns have 22" barrels. Most of my loads are less than 50fps slower than published numbers. Which is from the 2" shorter barrel. I have 1 rifle with a "slow" 22" barrel that is consistently 100+ fps slower than published numbers. But it is the exception, not the rule.