Tracking down the variables

I started a thread recently in Equipment about Powder Measures
https://www.bullseyeforum.net/t14815p25-dillon-powder-measure-issue
Lots of good advice was forthcoming.

I bought some of PhotoEscape's custom powder bar bolts - they are excellent - installed one on the PM I'm currently using for my "Long Line" tool head. I then loaded 100 rounds very carefully, weighed powder drops multiple times, all spot on. Very clean used Winchester brass with Winchester primers. 4.2 of VV N310, Nosler 185 JHP bullets. COAL 1.210. Taper Crimp 0.467. Checked all rounds for uniformity in my Shokbottle.

I shot them through a Caldwell G2 Ballistic Precision Chronograph. I initially had that positioned at about 15' from the bench in front of and in the shadow of the range baffle board. As I've often experienced, I got a lot of ERROR readings amongst the strings. There was another shooter at the range and he suggested that I move the chrono out to about 20' into the bright sunlight the other side of the baffle board. That did seem to reduce the number of ERR readings. The FPS results did not seem to be significantly different between the two chrono positions.

Out of about 80 rounds (fired offhand from a good quality 1911 with a 5" KKM barrel that was pretty clean at the start) I got 53 records:-
 

Average	758
Low	676
High	806
SD	27

According to the USMC tables that are often quoted on this forum, this recipe should produce an average velocity of 822fps.
However, I don't know what method the USMC used to measure velocity - so I am not able to directly compare my results.

More importantly to me is the significant variation in velocity -  130fps Hi-Lo range and an SD of 27.

How can I reduce that variation? Is it significant? 

I'm not able to test for groups at 50 yards at the present time.

Was the brass purchased new by you? How many firings? I more often see .469-.470 crimp for jacketed. I'm not experienced enough to really offer suggestions, just asking the questions in hope they get you an answer! 

Weird suggestion, more related to Hornady LNL loading... If you can tell, do the more extreme values come from either the first 5 or last 5 rounds loaded?

Dave

Mostly range brass which I believe was new when I got it. 2 or 3 times fired.

I have just loaded some with 0.469 crimp. I will test that next.

No idea about loading sequence. They all drop into a bin then get mixed up as I gauge, box and shoot.

#1 you need a better chronograph.
#2 how accurate is it ?
if accurate does it mater?
shot BE for over 20 years ( I made Hi Master) never used a chronograph 
in all those years.

Greetings,

Try no crimp with jacketed bullets. Just iron out the flare. Try to avoid distorting the jacketed bullet.

The interference fit between a Brass case and a Brass/Copper bullet has more pull resistance than Brass/Lead.

Crimping Lead bullets came about as the inertia of recoil and the cartridge being fed out of the magazine resulting in bullets pushed back into the case. (Malfunctions and loud reports, due to increased pressure.) Crimping stops this as the case mouth is forced into the Lead bullet.

Examine quality 45 ACP match ammo loaded with FMJWC bullets. There is no crimp.

Cheers,

Dave

Very interesting.

I had not thought to measure some factory ammo before - too obvious!

Fresh Federal Gold Medal Match 185 FMJ Semi-Wadcutter. Hard to get a really accurate measurement with my digital calipers, but it appears that the brass over the length of the bullet is almost uniformly 0.470", very slight perceptible bulge starts just below the cannelure with the lower part of the brass about 0.468".

OK, so I've just wound out my taper crimp die about a 1/4 turn and am getting 0.469" at the mouth. I will test that and see if I can detect any difference.

Thanks guys.

I believe that loosening the crimp may result in slower velocities. You may have to compensate. I know people go up to 4.5gn of N310 with that bullet.

radjag wrote:Very interesting.

I had not thought to measure some factory ammo before - too obvious!

Fresh Federal Gold Medal Match 185 FMJ Semi-Wadcutter. Hard to get a really accurate measurement with my digital calipers, but it appears that the brass over the length of the bullet is almost uniformly 0.470", very slight perceptible bulge starts just below the cannelure with the lower part of the brass about 0.468".

OK, so I've just wound out my taper crimp die about a 1/4 turn and am getting 0.469" at the mouth. I will test that and see if I can detect any difference.

Thanks guys.

Greetings,

Your research is proving noteworthy.

Back off the taper crimp die until it just straightens out the mouth. Your brass may vary in wall thickness. The finished round should be cylindrical.

Note how the Federal cartridge is smaller below the cannelure. They use about 0.002" interference fit, it would seem.

Fire ten rounds of the Federal ammo for a benchmark velocity. It will be a good reference for load development.

Send me your mailing address, via email, and I will send you a proper micrometer for measuring.

Cheers,

Dave

Just to reassure myself about the intrinsic accuracy of the Chrono I put all of my recent data onto a table to compare against some factory Federal GMM. Note the excellent GMM ammo SD of 5.27, compared to all of my reloads (all with 0.467 taper crimp). Sets 169 to 172 were shot with the Chrono moved out to 20 feet and in bright sunshine.

I would dare to say that, during the current relatively warm weather, 4.2 of N310 is OK. In the spring when it was wet and cold I had to increase my 160 Brazos LSWC 0.467 loads up to 4.4 from 4.3 in order to get 100% reliable function in a dirty wad gun.

fc60 wrote:Send me your mailing address, via email, and I will send you a proper micrometer for measuring.

Cheers,

Dave

What would you consider a proper micrometer for measuring crimp? Blade micrometer?

Christopher

Greetings,

With a little practice, measuring the diameter of the crimp at the mouth of the case can be easily done with a standard 0-1" micrometer.

Blade micrometers have there purpose. I use mine to measure features that a normal 0-1" will not fit.

Cheers,

Dave

Following are two images from a chrono session done last fall.  I was testing 4 powders for velocity and SD.  The gun used is my Contender with a 10 inch barrel.  I had a friend run the loads in “Quickload”  so I could get a “pressure” level as well as to compare velocities.  I reason that “comparable velocities equals comparable pressures” for that recipe.  Note that SD values varied between powder AND  charge weight.  Very roughly speaking 3XSD equals the extreme spread.  I would NOT expect ammo with an SD of 16 or higher to group well at 50.  It might be fine at 25, but not 50.The “Chrono SD” value in the chart is an average for charting purposes to give a expected variance in the chart. Other than that it can be ignored.

Dave,

Thanks for the clarification, didn't know if a better tool existed for the task.

Christopher

Dave, I do have some micrometers, just had not bothered to try them for that task. I will now go find them and try them (and try to remember how to use them - metalwork class at school in UK was just a few moons ago!).

Thanks for the advice.

Newer VV 310 will need to be about 4.4 gr to approximate the original loading years ago with VV310 at 4.2 grains when they used WW brass.  (I assume you are referencing the original pistol team loading in your first post.) 

You are using WW primers, so that will help.  

Not really sure why, but I and a few others have noticed the difference.

CR10X.

Now that is interesting. I will load up some batches with 4.4 to be ready for when I get access to 50 yards and a RR.
Thanks.

I have a Pact model 1 chronograph that I usually use without screens. It performs better on cloudy days but in the sun l have to tilt it so there is no direct light into the sensors. I don't know why that is but it avoids wasting precious test ammo.

So I loaded a few batches according to the various advice in this thread and tested them over the chrono this afternoon.

But the only real conclusion I can come to is that I now know where to locate the chrono in order to get more reliable readings. Positioned at about 20' beyond the baffle board in the bright light - got every shot in 3 sets of 10 Slow Fire offhand. Good.

But the SD result is still not good. Someone has suggested that variations in grip when shooting offhand can significantly affect velocity. I think that I've got a pretty decent grip and all 30 shots fired were pretty good, so I find that a bit hard to believe. The only way to be sure is to test again in a Ransom Rest over a chrono and also see what groups I get at 50 yards. I intend to do that as soon as I can get on the range.

 
Set 175 - I tried opening the crimp to 0.469 - OK, only 10 shots - but no significant difference in average velocity or SD.
Set 174 - No crimp, just smoothed out the flare to produce uniform parallel sided brass. Possibly slightly lower velocity, same SD. Would need to test a lot more to be definitive.
Set 173 - Once fired Starline brass, Federal Match primers, increased to 4.4gr of VV N310. No crimp. Hard to say. SD was better, but still far higher than I want. Again need a lot more testing to get a definitive answer.

Onward & upward!

I’d try 4.2 and 4.5 Bullseye and see what your SD is.... also might want to try 4.0 of 700X.

4.4 VV310 AND WW Large Primers.  (WW LP are for standard and mag loads and are slightly hotter, which seems to help with the low volume loading of VV310.) 

In my opinion there is not really such a thing as  "no crimp".  You need to measure.  You should be .471 or so.  Hold 2 cases side by side and note how they lay against each other at the crimp area.  Perfectly parallel is kinda "no crimp", any taper away from each other will show your crimp for your cases / bullet diameters. 

Check your scale.  Throw 10 charges then weigh to get your charge weight average.

Do not let your press run dry with each batch, keep all shell plate locations full.  Disconnect the powder  measure and   cycle by hand when changing charges and measuring powder drops.  

CR
By the way, I also shake up each powder canister each time before pouring into powder measure.  Probably doesn't mean anything, but its a habit.  

CR

Looking at your chart, both of them, I see Federal Gold Medal Matrch is only 737 av.  I think your chrono is off.   It is printed on the box 778 and my chrony shows that.  SD is good for the GM in both tests, so its reading the shots. but velocity is off.

Your starline brass is showing the best SD.  It has been proven on this board many times Starline is good brass. 

Range brass can be once fired or 20x fired.  You don't know.   Also, your Starline brass almost duplicates AV as the Gold Medal.

David