Target comparisons

[SCHUETZENBOOMER]

Though it’s not black, I am posting here as I think it most relevant to my situation.

Interested in hearing thoughts on the following groups shot yesterday. I lay in bed last night studying 12 groups that were shot….this comparison really intrigues me.

The larger group was with Unique and crimped. Though it says “WAD” it was .5gr Dacron against the powder. Bullet was seated at 2.620”OAL. Notice the E (Extreme velocity spread) was 11.48fps and std deviation was only 5.00. Boolit was crimped.

The smaller group was same bullet, not crimped, diff powder and seated 2.660”OAL. This is the part that confuses me……. Look at the “E”, it’s 82.96 fps and std deviation is 31.06. By the numbers this group should have been in the toilet!

All other variables were as consistent as I could possibly hold: rest location, sight picture, release, both groups shot within 10 minutes of each other.

[dubber123]

I don't know how to explain it, other than the pressure curve resulted in possibly a smoother start down the tube? I have gotten loads with single digit spreads that were regualrly outshot by loads with 30 or 40 fps. spreads. Dunno, always bugged me too.

[rhbrink]

I have had the same thing happen myself, can't explain it and no one else has either that I have knowledge of at least to my satisfaction. I don't spend all that much time anymore with the chrony other than maybe to check what the ball park velocity is the real proof is the size and to be able to consistantly shoot nice small round groups.

[1874Sharps]

Schuetzenboomer,

May I first say congratulations on your good group on target #2. Very interesting and puzzling topic you pose. I wish I could offer a clear answer as to why the difference between the two targets, but I cannot. The answer likely lies not with just one factor, but several. Now for short and mid range the ES in velocity will likely not show up very much. At long range you will likely get vertical stringing. I think the longer COL on the second target helped out the group size and I speculate that a decent roll crimp may shrink the ES. At least you have a good starting place from which you can start experimenting! Good luck with it and let us know how it goes.

[Old Grump]

To much reliance placed on the numbers on paper. Proof is in the pudding or in the holes in the target paper.

[405]

Yep a puzzler everytime it happens. Really drives engineers crazy :veryconfu. If you look at many reloading manuals that list such things for individual loads such as "Most accurate tested" or "Potentially most accurate" I think they are looking at ESs/SDs of pressure and velocity.... not group sizes. That's why so many folks poo poo those manuals when their group sizes on target don't match the manuals quote of "Most accurate". There is no way for labs to shoot on target each load. And no way to guarantee two guns would be the same anyway.

In reality it is of little consequence at the shorter ranges but can become more critical at longer ranges where the velocity ESs/SDs would really start showing up in vertical stringing on target.

Since at least three or more variables are involved, would be hard to isolate culprits or pursue attributes within the loads. Crimp, powder, seating depth (others?) would be the variables.

That second group is a winner! If I could do similar to that each time, I'd stick to that load. Might shoot it at say 200-300 yards and see if the SD "rears" up and shows itself on the target.

I just noticed after enlarging the 2nd target. 5744!!! one of my pets for loading smokeless cast in 45-70. I use it a lot in bullet weights ranging from 425-510. I do use it with a very low density dacron filler of .5-.7 gr. Also, I don't crimp those loads for the single shot and seat the bullet out so the tapered edge of the front drive band is touching the lands (bullets are Mountain Mold). The velocity SDs in those loads almost always stay between 5-15. And, accuracy is outstanding.

[HPT]

The problem I think is that 5 shots is not statistically significant (approx 30 shots would be "statistically significant). I would make 2 targets and alternate 1 shot of load #1 on target #1, then 1 shot of load #2 on target #2 until there was at least 10 shots on each target (15 ea would be better) if you really want to see the difference. This would ensure both groups would be made with the same conditions

Then I would not only measure the size of group, but measure & record the distance from each hole to the centre of group to "score" each target using the average distance of each hole to the centre of the group. Another way to "score" your group would be to take a clear piece of plastic & draw circles (centre is X, next 10,9, & so on) and place it over your target to get the best score and compare them that way.

[garandsrus]

How far were you shooting? At 100 yds or less 100 fps probably doesn't amount to much vertical spread. I did the math and the 100 yd drop difference from 1164fps and 1247 is 1.6"

John

[SCHUETZENBOOMER]

Tribe,

I very much appreciate all the suggestions and tidbit's of wisdom! I am in data collection mode for this whole BPCR game and am soaking it up like a sponge! I am not confident enough in the rifle to just switch to black. If and when I have confidence that it(and I) can shoot <MOA groups I will make the switch and never look back.

Here is another one of the groups shot at the same time. This is the sister load to the 2nd pic above. Same load, except boolit crimped and seated out to 2.740" vs the 2.660. As 1874Sharps speculated, the crimp cut the ES and std deviation almost exactly in half. Of interest to me was the point of impact change between these loads, nearly 3" with the same sighting point.

The second pic is another one that shows promise. This one using Lymans 490gr. tapered 457677 which allows me to seat it out to just engrave the 2nd band(my bore is .451). Std deviation on this load was 5.3. Using only 13 grains of Unique, its fun to shoot too!

Fyi...all shooting at 75 yards( the bench is frozen in). Anxious to load some more revs and shoot but heading to SHOT Show next week.

[John Boy]

Interested in hearing thoughts on the following groups shot yesterday
Boomer, offering 2 items:
1. Burn rate: Unique has a RQ of 36 and 5744 RQ is 91. The key to shooting these heavier bullets is to emulate the pressure curve and velocity as if you were shooting black powder which has a slow burn rate compared to nitro based powders.
2. Stabilization of Bullet: Obviously with the slower burn rate using your 5744 powder charge, even though the SD sucks, emulated a good BP average velocity of 1158fps for stabilizing the Gould HP bullet

You might want to try some 3031 (RQ 116) or 4895 (RQ 125), in an average 1158 fps range, to determine if you get good groups with these powders also

[stubshaft]

When I started to compete in silly wett in the early 80's I religiously chrono'd my loads and shot ALOT of groups. I was suprised to see that the SD of the velocity did not correspond to the size of the groups. I have had SD variations that were in excess of 85fps that shot great. One of the boolit shooting mysteries...

[NickSS]

Its a mystery to me that two loads can shoot so differently but it happens. Right now I am experimenting with my 40-65 rifle trying to get a new case of black to work. I started out with 5 shot groups and they went to a silhouette shoot and did poorly. The reason I found out when I used the same ammo to shoot a 15 shot group at 200 yards. There were flyers high and low. I am reloading that ammo right now and plan to load several batches of 20 rounds increasing the charge by a grain each batch. My last batch was at 51 gr of FFG Shutzen with a 400 gr snover bullet. Hopefully, more compression will prove better consistency. Oh by the way the load that shot so lousy has a sd of 12.

[SCHUETZENBOOMER]

Thanx again for all the help and suggestions. As an engineer, these unknowns are driving me nuts. Glad to hear some of you with much more experience than I, experience the same concerns. Waiting for a decapper to arrive so I can continue to load without full length sizing. Made up some expanders in .001" increments to vary neck tension.

[Boz330]

I'm not trying to rain on your parade but smokeless loads are not going to make switching to BP any easier. The burn rate and pressure curves are hard to duplicate even when the velocities match up. My experience is that smokeless is fairly forgiving in a BPCR. Just get some BP and get your feet wet. You have to start sometime so why waste time developing data just to throw it out the window.
Every rifle is a little different and you are crimping boolits now but when you change to BP you might find that your rifle likes no neck tension what so ever. Even though you there is only one powder, all of the other variables can keep you busy for a long time. My BPCRs will just about shoot a large ragged hole at 100yd but 300 is a different story altogether. I don't shoot at anything less that 200yd for group or less that 10 rounds. I have also figured out that one good group doesn't make a load, it has to be repeatable.
Again I'm not trying to be critical just encouraging you to come over to the DARK side sooner than later, "you'll like it I promise".

Bob

[Doc Highwall]

All of those statistics of ES, SD, MAD, do not take into account barrel vibrations. I learned that the hard way myself.

[montana_charlie]

I am not confident enough in the rifle to just switch to black. If and when I have confidence that it(and I) can shoot <MOA groups I will make the switch and never look back.I'm not trying to rain on your parade but smokeless loads are not going to make switching to BP any easier. The burn rate and pressure curves are hard to duplicate even when the velocities match up. My experience is that smokeless is fairly forgiving in a BPCR.
I tend to agree with Boz.
Shooting smokless is useful for familiarization with the new rifle, and it is enjoyable. But, it does little to prepare you for the challenges that shooting black will force upon you.

The rifle recoils differently under BP, so the recoil management you are learning now will need modification after the switch.

You are not required to deal with fouling, now. That alone has a learning curve which involves new skills. It can't be seen as a 'bad idea' to begin that 'education' at the same time you are getting to know the gun.

If you are using smokeless-compatible lube right now, you may need to change later...and that can affect the leading possibilities.

You have found how a crimp on the bullet establishes bullet engagement with the lands...and how it can improve SD. But, that improvement is a smokeless characteristic. It needs some retardation of the bullet in order to burn correctly.
With black, seating depth will be regulated by the powder column, and 'crimp' (per se) will no longer be in your list of tools.

Your published targets show an ability by you (and the rifle) to hold a group.
To continue to shoot smokeless loads (unless you simply want to) is only valuable if you are using it to fireform all of your cases...in preparation for loading the dark stuff.

CM

[SCHUETZENBOOMER]

Boz,
I lived in Washington State for a year.....I fear not rain. If anything, living there gave me a new appreciation for how we easterners can and will cancel anything if a few drops darken the horizon. I chased elk for 2mos straight in the rain and loved every second of it....sigh!

I completely understand how useless these loads will be once I start loading black. If anything I am re-familiarizing myself with some loading disciplines that I have gotten sloppy with over the last 25 years. It's not the loads but the disipline that I seek. I have been peddling surplus "stuff" lately to shore up an account should a nice Rolling Block taunt me. I hope to get my hands on an "ofisheel" BPCR soon, and with that said, I will grab my new rifle and jump headlong into that swirling black vortex you all beckon from.

[Boz330]

Boz,
I lived in Washington State for a year.....I fear not rain. If anything, living there gave me a new appreciation for how we easterners can and will cancel anything if a few drops darken the horizon. I chased elk for 2mos straight in the rain and loved every second of it....sigh!


I don't hunt in the rain anymore, a product of age. I guided elk hunters in NM for 10 years and just because it was NM doesn't mean there is no rain. I spent more than my fair share of time being way to wet.

Bob