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Reducing SD and ES

13K views 43 replies 14 participants last post by  mamalukino 
#1 ·
Hi folks,
I want to thank everyone for their help with my continued pursuit of that elusive temptress known as consistency....

As you may recall I shot a OCW test last week, using BL-C(2), 70 grain Berger VLD's and virgin Lapua match brass, and after some awesome input in my other thread, I selected 25.4 grains for further development.

So I started to play with seating depth and found that I got the best grouping when seated the rounds somewhere between .010-.015 off the lands. (Varying neck tension affects my seating depth)

Today I had the opportunity to have someone fire these across a chrono for me, and my results are deplorable.

Using once fired lapua brass, CCI Benchrest primers, 25.4 gr Bl-C(2) and the VLD's at .010 off the lands I got a spread of 118 and SD of 42
This the specific order
1 2841
2 2928
3 2881
4 2890
5 2871
6 2948
7 2959
8 2919
9 2861
10 2844

The mean is 2894.

Is this anything other than a neck tension issue? An annealing setup is my next big purchase, which I hope will allow me better control as I move forward.

I'm sure there is some variation in terms of charging, but given that I'm using a RCBS charge master, that I have "tuned" as recommended and anything better is beyond my means theres not a whole lot I can do about it at this time.

I'm using an unmodified forester FL die for shoulder bump (I got about .003 this batch, aiming for .002 or so)
I also use it to decap and expand.

Thanks again for the input
 
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#3 · (Edited)
Switch to a "hotter" primer or a magnum primer with ball powder, it is a double base powder with nitroglycerin and uses more deterrent coatings than single base powders. And it needs a hotter and longer spark to get it going, * see the Speer reloading manuals



And the funny part is the Remington 7 1/2 primer boxes are labeled bench rest primers.



Now guess what primer Remington used when it ran Lake City Army Ammunition Plant to light off Winchester ball powder in their 5.56 ammunition.
 
#6 ·
Somehow I thought a benchrest primer simply meant it was more consistent.

I'm going to retry it agin tomorrow if I can find some 7-1/2s. I have some CCI "normal" primers, so I'll give that a shot too.

Any thoughts as to how much a primer will affect my results this far? (about 1/2 moa) I'm pretty stoked on my results.
 
#8 ·
I can't find the original article associated with the pictures above. It was written by a rifleman named German Salazar. {It's too bad his shoulder won't let him shoot anymore.}

His (GS) conclusion was that one wanted to use as light/soft/little a primer as would ignite the whole stack of powder to get the best ES and SD.

This is in contrast with the advice above.
 
#18 ·
While I don't own a Garand, and its not applicable to rifles of similar design, I worry that it'll throw off point of impact on free floated barrels.
I suppose you simply fire for groups first, and then again for speed, but that burns barrel life and ammo.
 
#20 ·
I would like one of these if they are consistently accurate; would eliminate the harmonic change introduced by the magnetospeed.
SuperChrono Acoustic Shooting Chronograph ? Steinert Sensing Systems
Thats pretty slick. Being able to detect things down range would be nice. Thats similar to the system Litz used in Applied Ballistics, isn't it?

I'm sure you've seen these, but I like that I don't have to move down range at all to set up or get reading. Which is a big plus for me having to share range time.

LabRadar - My Personal Radar
LabRadar Ballistic Velocity Doppler Radar Chronograph
 
#21 ·
Back to the issue
I just loaded forty rounds, with four different types of primers.
They're going to get shot through the chrono tomorrow

Then I simply select the best primer with the lowest ES/SD, correct? as I've already determined the best combination of powder/brass/bullet and seating depth
Or will all this be thrown off?

How much will the primer affect my other results?
 
#23 ·
Changing any component can have consequences either good or bad.
Different primers can definitely effect the MV and may need a powder adjustment.
Your original load may pleasantly surprise you with the chrono moved out to 10 feet.
 
#25 ·
Back to the question of how to lower ES/SD, among the anal retentive crowd known as Benchrest Shooters, the holy grail of consistent ammo is Case Preparation.

They spend more time on case prep than any other aspect of their "sport".

Matching case capacities in batches by using water fill or actual case weights, Annealing, neck turning not only to fit their custom chambers but also to achieve consistency that factories won't produce in neck wall thickness. Couple all that with the proper amount of neck tension by selecting the right bushing for neck sizing or having the die maker hone one to their specs.

Neck tension is so important to consistency they often use none at all. Some shooters, that aren't under a time constraint in their competition, will merely "stuff" a bullet into the lands using a separate tool that inserts the bullet into the lands with micrometer accuracy. They then use a case that's been primed, charged, and capped with some green florist's foam--just something to hold the powder in place.

For those that have a time constraint and can't breech load their bullets as described, will use only enough neck tension to keep the bullet from sliding all the way into the case on it's own. The final seating is done when the bolt is closed on this "minimal neck tension" cartridge.

For my case prep I merely clean in SS Pins, Anneal, Neck size with a bushing and then in a final step make sure all neck ID's are the same by using a mandrel type expander. The cases, when new, were fired once, F/L sized, then the necks were "skim cut" to just true them people used to do with tires. Not necessarily cut all the way around the circumference but enough to insure that at least 3/4 of the way around the neck is uniform in thickness.

This gives me cartridges that I don't have to be ultra careful when handling and can load from a magazine if I so choose.


As for the Chrono Readings? When I see groups that are measuring sub .250 MOA on a regular basis, the only reading I care about from the chrono is the average speed. I use that to fill one of the "boxes" in my Ballistic's program for use in multiple distance calculations.:cool: Unless your chronograph uses the old "shoot through" contact sheets (one use per) the sensors can be triggered by different parts of the bullet as it passes "through". The most accurate method if you can afford it is Ulta High Speed Video with a distance measuring background like used on Mythbusters and in a lot of labs. Unfortunately those cameras can run easily from the low 5 figures up into the low 6 figures. Everything else is "value engineered" for the intended user.
 
#27 · (Edited)
Orkan, no worries. She actually gets mad at me when I assume she knows what I'm saying when I start talking to her about this stuff. But some of the guys she works with are jokes, and these are the ones that are actual "gun experts."
As I'm sure you know, theres a huge gap between practical knowledge and book knowledge when it comes to this stuff.

Regarding my ES/SD issue

I actually ran the math on the values I got from the too close chrono tests and at 500 yards theres only a 5-1/2 inch drop between the fastest and the slowest value. Using the average value thats still close enough to kill ground squirrels at that range.

However theres good news. Mrs. Ragnarnar was kind enough to re-chrono the rounds I loaded last night. This time at an appropriate range of 8-1/2 feet.

A few of the values didn't get recorded, but I got what I needed.

Again the load is 25.4gr BL-C(2), 70gr Berger VLD Target, in Lapua brass.

CCI BR-4: Mean 2925 SD 11.56
CCI No.41 (for 5.56) Mean 2931 SD 12.6
CCI No. 450 (SRMP) Mean 2923 SD 9.1
CCI No. 400 (SRP) Mean 2892 SD 28.6

(I wasn't able to find any 7-1/2's)

Obviously I'm going with the magnum primers, a SD of 9 fps is better than I could have hoped for this early on.....
I'm really interested to see what happens if/when I get around to annealing, neck turning and anything else I do.

Thanks for the help with this one folks, I don't know why it didn't occur to me to me that muzzle blast would affect the chrono readings

edit: just found this
http://precisionrifleblog.com/2015/12/27/best-bullets-brass-primers-powder/
take a look at the primers part.
 
#29 ·
Orkan, no worries. She actually gets mad at me when I assume she knows what I'm saying when I start talking to her about this stuff. But some of the guys she works with are jokes, and these are the ones that are actual "gun experts."
As I'm sure you know, theres a huge gap between practical knowledge and book knowledge when it comes to this stuff.

Regarding my ES/SD issue

I actually ran the math on the values I got from the too close chrono tests and at 500 yards theres only a 5-1/2 inch drop between the fastest and the slowest value. Using the average value thats still close enough to kill ground squirrels at that range.

However theres good news. Mrs. Ragnarnar was kind enough to re-chrono the rounds I loaded last night. This time at an appropriate range of 8-1/2 feet.

A few of the values didn't get recorded, but I got what I needed.

Again the load is 25.4gr BL-C(2), 70gr Berger VLD Target, in Lapua brass.

CCI BR-4: Mean 2925 SD 11.56
CCI No.41 (for 5.56) Mean 2931 SD 12.6
CCI No. 450 (SRMP) Mean 2923 SD 9.1
CCI No. 400 (SRP) Mean 2892 SD 28.6

(I wasn't able to find any 7-1/2's)

Obviously I'm going with the magnum primers, a SD of 9 fps is better than I could have hoped for this early on.....
I'm really interested to see what happens if/when I get around to annealing, neck turning and anything else I do.

Thanks for the help with this one folks, I don't know why it didn't occur to me to me that muzzle blast would affect the chrono readings

edit: just found this
Top Bullets, Brass, Primers & Powder - What The Pros Use - PrecisionRifleBlog.com
take a look at the primers part.
I have to say... thank you.

You have no idea how refreshing it is for me to see someone doing testing themselves, getting advice here, and then going to do real world testing of their own and working through these issues. Someone ACTUALLY shooting, rather than just talking about it. More amazing still is the fact that you are remaining objective and data-oriented in your approach. You have absolutely no idea how refreshing it is to have an opportunity to help someone such as yourself. Bravo sir, and I look forward to seeing more of your work.
 
#31 ·
Second (or third0 the comments about your chronograph being too close - I believe Oehler recommends 10 feet from muzzle to middle screen. As close as you have it, muzzle blast can induce inconsistent readings.
 
#33 ·
So a little side question regarding primers..... Back in the 'great shortage'. When we couldn't get primers or powder .... I got some magnum primers (Winchester LRM) and I have been using them in 308 and 30-06 with imr 4064 and imr4895 respectively. I started low and worked up looking for pressure and found none at me current loads, but would a see a diff using regular LR primers?
 
#34 ·
In a word, possibly.

I looked into it and found a couple people who said the only difference between a CCI 200 and CCI 250 (small rifle and small rifle mag, respectively) is the cup thickness and that they're alike in all other regards. While I can't speak to that or your situation, I don't see why the same might not be true for you.

Try it out. Thats the only way to know for sure.
 
#41 · (Edited)
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