.001” Make a Difference?

[ET]

For a sabot-less shooter it appears it does, so how about a sabot shooter?

Since I have been into some machining work I have gotten into using measurement instruments more often. Okay I should first take a look at my bore and see what I get.
After repeated measurements I get from land to land .500” and groove-to-groove .508”.
So now lets try some of my favorite sabot loads with 250SSt and 250SW. While trying to apply the same pressure at the same location area for each measurement I get readings between .504” and .505”. Okay I decided to separate these two groups and will watch for different results at the range. Now as I was doing these measurements I came across one that read .502”.
Where did this guy come from?
Definitely would be a flier in any group. So I decided to try a swap from another bullet say from the .504” group. Result was the same reading of .502”. My deduction is I got a sabot out of tolerance and it’s going in the recycle bin. One less wasted shot for sure.

In the future I plan to check each bullet/sabot combination like Richard started doing with his load experimentation. So for my question asked I will find an answer this year by paying more careful attention with my bullet/sabot load dimensions.

Of course Harley already set the bar standard now for me for powder measurement accuracy of loads.

Ed

[smokeeter]

Ed, I don't think the slight variation is as critical for saboted application as it is for sabotless. there should be some tolerance with the sabot. I not saying that one sabot won't produce a flyer, just that you can probably get away with more when using a sabot.

[rexxer]

Ed- I think you should take the out of tolerance sabots and put them a side. The next time you shoot see if they do indeed impact different. Then we all would know! Thanks in advance!!! ;D

[Richard]

Without even shooting, I would bet, that .002" to .003" (smaller)difference in diameter, will cause a loss of considerable velocity and result in a flyer and lower velocity!
Richard

[rexxer]

Richard=your probably right but it would be nice to prove!

[ET]

Smokeeter

I am inclined to partially agree. There may not be a lot of difference say between .504 & .505” fit for my bore size. But move to .506” such as with the hph-12 would give me a very noticeable difference in groups appearing. Here I am referring to using a 250SW or 250SST. Out of about 60-sabts with a trial fit 40 measured at .504” and about 18 measured at .505”
As for the .502” I did find another one tonight in a group size of about 60-sabots.
If I at least eliminate these I hope I may eliminate the odd flyer that appears now and then. As for finding if any difference actually exists, I just gots to know. ;D

Rexxer

I like many others have always just taken a sabot/bullet and shoved it down the bore thinking the fit should be perfect but when our groups start to do something out of the norm after carefully using a good wait time and keeping a bore reasonably clean as in my case I scratch my head wondering “What Happened?”
There may or may not be a noticeable difference as this might be an ideal range for fit to my bore and another factor that busts a good group periodically but will report my findings regardless of outcome.

Richard

I wouldn’t touch that bet as I already know. ;D


Ed

[jims]

I recall Tar12 mentioning he had some variances with the MMPs, an occasional flier then when shooting. I thought he shot Harvestors in his gun and it eliminated the problem.
I never measured the sabots assuming also they would be the same. Perhaps I need to do that and check some bullets also but I never heard much trouble with bullets.

[ET]

Do you ever feel there are some Idiot strands of DNA inside of you? ;D

Was starting some more sabot/bullet measurement checks this morning and being time consuming I thought there had to be a better way or approach to do this check. So took a coffee break and during this time a light came on. Why not try to make some gauges afterall I have equipment to do this.

Off to my other room and started up my tonka toy. ;D
Through experimenting with sizes I found a size within roughtly a .001 ( not less than .001" & not more than .0015") that actually works nicely. The larger diameter hole will allow the sabot/bullet to slide in easily with little or no effort and not leave any scuff marks on the petals. Where as the smaller diameter hole requires a slight effort to start the bullet/sabot in and scuffs the petals slightly.



Incase you are wondering why two different diameters on the gauges it is just to help quickly identify which end holds what diameter hole. Example, larger diameter hole is housed with larger diameter part of gauge. Now this checking chore of bullet/sabot combination is a quick breeze. Just need to make one up for the Harvester sabot combination that will be slightly smaller than HPH-24 sabot fit and I should have the range for checking fits covered.

Okay I am going to a lot of trouble to try and shrink my groups a little bit more if possible because my goal is best accuracy possible.

The next step is trying my hand at making sabots from a better polymer that is not just stronger but more heat resistant.
And the education goes on.

Ed

[jims]

I thought bowbender was doing something similar. Good ideas and it give you fun time on the lathe and makes a useful product.

[Richard]

Ed. Befor you know it, you will be buying a Bridgeport knee mill and a LaBlonde engin lathe ;D ;D
Glad your having fun!
Richard

[ET]

Jim

You're right about having fun and learning. Today was a windy and cool day so not much fun trying to do Spring chores outside.
Thought what the heck and take a spin at trying to make my first sabot jacket with current tooling. Even though my first attempt produced a poor start I now know what I need to do for better results. Definitely some better sharp tooling when the buget allows, like after tax return. ;D
First attempt is with 40-Cal 200-SW.



Richard

I am already looking for a mill machine. This machining is challenging and almost addictive as the 10ML-II can be. Wonder if they are related? ;D ;D


Ed

[bowbender6]

I redisned my sabot gauge and just made the first one a couple of weeks ago. I also have some intersting results using a .458 325ftx with N120 and MMP vs. BCR - tighter fit. Same load 60 fps faster. I'll post pic today or tommorow when I get time. The gauge works great (thanks Egde).