Types of Brass and Accuracy

[PhillySoldier]

How much does the type of bass used affect accuracy?

 

Over the last month I’ve been doing some 9mm load testing; shooting 10 rnd groups @ 25 yards from a ransom rest.  A couple weeks ago I happened to switch the brand of brass I was using (from starline to blazer brass) and saw a pretty large difference in my average shot group sizes. Avg sizes increased 0.8” from 1.3” to 2.1” so it was a pretty significant difference. Though without the rest I probably would’ve never noticed it and just chalked it up to my shooting being off. Last weekend I went back to the starline brass and the shot groups went back to previous averages.

 

I gotta say I was pretty surprised at the difference. I always figured as long as I didn’t mix different brands of brass together, it shouldn’t make much of a difference. Now it has me wondering how much attention I need to start applying to pistol brass. Anyway I figured I would mention it to discuss with others.

 

Now I have a crap load of blazer brass casing to get rid off grrrr

[glassblower]

When you switched over the brass, did you adjust your crimp? If the crimp is too loose or tight it will affect accuracy. Too tight and it peels the coating or deforms the projectile. Too loose and the projectile can shift OAL, both of which will cause a change in accuracy.  Starline is a higher quality brass than Blazer and their case walls are thicker than others. I’d also do a plunk test and ensure that a case length diff isn’t a cause.

[PhillySoldier]

Yes, crimp and seating were both adjusted. I was actually running a seating depth test that day. So I had a pretty big variety; running 20 rnds each (two 10 rnd shot groups) from 1.06" to 1.15". All groups were consistently up that 3/4's of an inch. And I agree about the case wall thickness but again I didnt figure Id see much of a difference unless I was mixing different brands together and not adjusting. 

Edited July 2, 2018 by PhillySoldier

[Dwbsig]

What was the difference in oal and wt of starline vs blazer brass ?

[PhillySoldier]

I didnt weigh or measure the COAL just the OAL after bullet seating. I can do so later though. 

[Hi-Power Jack]

1.3" groups at 25 yards is excellent    

 

What is the gun ?

 

I'm surprised that brass would have that much impact on group size (1.3" -  2.1"

is 50+% wider group).

 

I use range brass in my TruBor and get pretty good accuracy, but I guess I might

get better accuracy from a particular type of brass - have to give it a try one day  

[PhillySoldier]

Thank you, Im pretty happy w the current results. The best single 10 rnd shot group from last weekend came in at 0.9". I got the ransom rest about 2 months ago and my reloads at the time were shooting 5.5" from it at 25 yards. It has led me down a dark path with a testing obsession ever since. I have learned a lot since getting it though.

 

Im using an Sig P226 9mm with fitted match barrel. How do you like your TruBor? Ive been researching the different STI models online trying to find a model I might like to get. 

 

With everything separated and the dies adjusted to compensate; I didnt expect any differences at all. Im pretty stumped to see how much this actually has an impact. Also pretty annoyed since I have like 12 gallons worth of the blazer brass saved up for reloading. 

 

 

 

Edited July 3, 2018 by PhillySoldier

[HI5-O]

Could it be the difference in velocity between the two different cases? 

[PhillySoldier]

Between the three different tests, I have 8 different shot groups that match as apples to apples (same OAL and charge weights); except the brass. With that and looking at the overall even with the differences in velocity, all show a rather large jump in the group sizes. 

[lgh]

I've measured all the once shot brass I shoot with. 10 measurements each brand. Length, case thickness at mouth, and one other parameter I can't recall. They vary and I consider that a factor in COAL variation but I didn't know of such an effect on accuracy. A Ransom rest might be interesting and I've always wanted one. Do you have to shoot them from a more-or-less permanent bench?

[PhillySoldier]

I was definitely surprised by it. I was doing a seating depth test and figured it wouldnt matter if I changed the brands of brass as long as I was readjusting my dies for the different casings. I wouldnt have even used anything different if I thought it would affect accuracy. Im specially surprised Ive never even read about anyone mentioning that brass affects accuracy. 

 

From what Ive read the other ransom rest users seem to go overboard with columns of steel pillars and tons of concrete poured around it. I just take mine to the range w me. They have a pretty sturdy bench and I got the portable 40 lb bast plate to go with it. Seems to work fine. Oh and I put c-clamps on it as the manual suggests but ive also read it may not be necessary w the baseplate

 

Edited July 3, 2018 by PhillySoldier

[Hi-Power Jack]

"seems to work fine".    BOY, that's an understatement with a 0.9" group at 25 yards  

 

I'd LOVE to get one ….

[usmc1974]

What am I missing? It is a 9mm pistol. I use range brass a 92fs berett and A Dillon square deal, I can hit a 6 inch steel and keep'em in the A zone of a IPSC target at 25 yards  with out a red dot sight. I am just B class limited...Just asking.

Edited July 3, 2018 by usmc1974

[mlmiller1]

If youre really chasing accuracy, check your h2o volume in starline vs volume in blazer brass.  If they vary considerbly, you likely need to do ladder test with blazer brass & find an accuracy node.  Then check accuracy..... IOW, optimize your load in the blazer brass.  I suspect with tinkering around, you can achieve similar accuracy.

[PhillySoldier]

The h20 thing is a bit further than i ever wanted to test pistol brass (so dont ye be putting thought in me already obssesive head) and again i just came across this by accident and figured id mention it.

 

If it wasnt for the ransom rest, i woulda chalked the differences up to my shooting for the day. But i figured a 60 some percent increase was pretty significant for something i didn't expect to have any impact

[PhillySoldier]

Completely off topic but something else ive learned in the last month w the RR that i never expected to make a difference is the first and last round in the mag.

 

Apparently manually closing the slide causes a different POI by about an inch then a fired round auto cyling the slide. Something similar occurs on the last round and slide lock. Ive since learned to add two burner rounds to each mag and direct the rest off target

[mlmiller1]

Come on now..... eyedropper testing is pretty simple.... hahaha.  Now Ive planted that worm in your head.  Set your ocd free.  Let it run.....

[RH45]

Yup, brass makes a big difference in accuracy.

Most of my "game" guns will shoot under an inch at 25 yards, with brass, and loads they like.

If I use loads they don't like, or mixed brass, I've seen my groups open up to 4".

Like rifles, every gun seems to have it's own preferences, for best accuracy.

My Sig, Xfive prefers once-fired, Blazer brass.

Some of my pistols don't seem to care what brand, but, all shoot best with same headstamp, once-fired brass.

[IHAVEGAS]

On 7/3/2018 at 11:57 AM, usmc1974 said:

What am I missing?

 

Therin lies the rub for many of us. 

 

It would be nice to know. Worthwhile considering the cost of the rest & other issues, I do not know, but nice. 

 

Have toyed with the idea of buying the rest & offering it as a rental tool to try & recoup some of the investment. 

[zombywoof]

On 7/3/2018 at 4:07 PM, PhillySoldier said:

Completely off topic but something else ive learned in the last month w the RR that i never expected to make a difference is the first and last round in the mag.

 

Apparently manually closing the slide causes a different POI by about an inch then a fired round auto cyling the slide. Something similar occurs on the last round and slide lock. Ive since learned to add two burner rounds to each mag and direct the rest off target

 

 

I started my competitive shooting decades ago as a Bullseye shooter. We were fortunate to have a former State champion at our club. He spent lots of time time behind a Ranson Rest. He told me that exact thing about the first and last round. 

 

[Hi-Power Jack]

Massad Ayoob used to mention this effect of the first round - I've never heard about the last

round being a problem also.

 

When I test loads, I always fire the first round into the berm, shoot about 15 shots, and

then discard the 2-3 flyers - measure the other 12-13 shots     

[IDescribe]

It's clumped powder and powder position.

 

When you chrono, two things you can do to improve SD:  

• Tap the loaded mag back side down against the table a few times to make sure any clumped up powder breaks up. 
• When you chamber the first round, slingshot the slide.  Don't let it forward easy.  Don't start with the slide locked back, then use the slide stop lever to drop the slide.  Start with the slide forward, then yank it back all the way and let it go, letting the recoil spring slam it home so the the powder will experience as close as possible the same forces as it will under the subsequent shots and recoil cycles. 

 

These two things work together.  The forces sent through the pistol on the first shot plus that first recoil cycle will break up any clumped powder for every round after the first, and set the powder position similarly for every shot after the first, so your manually breaking up the clumps for the first shot and setting the powder position by slingshotting will go a long way to improve your chrono results relative to the first shot.

 

 

SOME PEOPLE go the extra distance of pointing the muzzle straight up before each shot, then lowering it back down to firing position slowly before firing the shot, so as to get powder position as consistent as possible, but personally I have seen negligible results with this as long as I'm tapping and slingshotting the first shot of each string.

I've never heard anything about the last round in the mag.

[PhillySoldier]

It doesn't seem to be as bad on the last round for me but is a slight diff in poi. Both though ive heard will vary depending on the load itself