Question:

1)First shot is always high, second shot low, grouping gone. What would cause this ?
2)Bullets striking high at 200yrds like they did at 100yrds, no scope adjustment. How is that possible ?

Components and Pics below.... Thoughts or suggestions appreciated....


Components:
Shilen Barrel – 24”, 1:9
Caliber: 7x57
Bullet: 139gr SST
Powder: H4350 at 40gr @ 2200fps
Case: Norma

Went to the range today to do some work with the 7mm Mauser. I had previously sighted her in at 200yrds but had to do a little bench work so went back to the 100yrd and rechecked. Got a reasonable group of about ¾ inch and around 3 inches high – what I would have expected. Using a light load of powder just to get the initial work done. Barrel was fouled appropriately, no cleaning between groups.

Target 1
http://i1311.photobucket.com/albums/s670/shutter83dog/100yrdSightIn11072014_zpsd2823053.jpg

Having verified I was on paper I went back to the 200yrd and took some target practice, getting ready to test some rounds for bullet seating depth. I noticed some odd behavior. 1) The first shot was always high, the second one low and the others in between. Gone was the nice group at 100yrds. The other item… 2) I expected the bullets to strike the middle of the target (not at the top like on the 100ydr target)….. as you can see they are strung pretty high and I did not make any scope adjustment.

5 rounds with bullet seated on the lands 3.75 inch group at 200yrds
http://i1311.photobucket.com/albums/s670/shutter83dog/200yrds-TouchingLands11072014_zps280899a4.jpg

5 rounds with bullets seated .001 off the lands 2.63 inch group at 200yrds
http://i1311.photobucket.com/albums/s670/shutter83dog/200yrds-001OffLands11072014_zpsdf7c17a0.jpg

5 rounds with bullets seated .002 off the lands 1.79 inch group at 200yrds (Best)
http://i1311.photobucket.com/albums/s670/shutter83dog/200yrds-002OffLands11072014_zps57caf8b3.jpg

5 rounds with bullets seated .003 off the lands 4.15 inch group at 200yrds
http://i1311.photobucket.com/albums/s670/shutter83dog/200yrds-003OffLands11072014_zps32e5a1cf.jpg

I suspect the key is the "light load" you mention. All of your targets are showing vertical stringing. I would guess you are NOT moving the bullet fast enough to stabilize at longer ranges. I think you will need to get it up to 2500 to 2600 fps to stabilize it at 200 yards.

Doesn't look anyhting like a stability issue to me.

Light loads of slower burning powders don't ignite and burn with the consistency they will at higher pressures. Smokeless powders are progressive burning and that means the higher the pressure, the faster they burn and the faster they burn, the higher the pressure (and it's easy to see why it can get out of hand with an overcharge). But the bottom line is that a powder that is meant to operate at 50,000 psi isn't going to work consistently if the peak pressure is 20,000 psi. Not saying that's your pressure, just using dramatic extremes to make the point.

I'll go ahead and throw this out there..against my better judgement and I hope I'm not sorry.

There are nodes of accuracy at different ranges. What works well at 100 yards may not work so well at 200 or 300 yards. The benchresters, or at least some of them, have figured this out.

...and about POI being high at 200 like it is at 100, you need to just take a look at some trajectory charts. Take into account the height of your scope over the bore and think about it after you've looked at the charts.

It looks like a scope parallax problem to me.

I think RR and Geez are right about the powder choice for a reduced load. H4350 is slow burning and not the best choice for a reduced load, I would expect high extreme spread with it and that lite a powder charge. Might try H4895 or A5744 for that application. Both are faster burning and easy to ignite powders that lend themselves well for reduced loads.

Is the 2200fps measured or expected from some printed source. If measured what it the extreme spread? I would guess probably high and the further out the more dramatic the vertical stringing will be due to the high and low velocities.

Of course I could be wrong but if looking for a reduced load I look to the 2 powders above for good results.

Explain please ? I have a Leupold with adjustable objective (in this case set to 200yrds). And the bench work I mentioned above was an adjustment.

I am considering what RiverRider and Kmon1 are pointing out. When I am doing load workup, I always start low and work up but I've never seen a spread as bad as that before. My "go to" loads always end up at the higher end of the powder charge chart as a result of the testing though. Maybe I am wrong on this but the bullet seating that was .002 off the lands "seemed" to be the best - maybe this was because the pressure (not being on the lands) was in a relative sense more stable ? In any case the 40grs of H4350 is just my starting point. I don't expect I will stay there....

Kmon1 - the 2200fps is from the Hornady manual - not measured on the rifle. So, should I use the adjusted seating depth and continue up the charge weight scale ?

I usually work up in powder charge then play with seating depth once an accuracy node is found.

I think I would keep the best seating depth found so far and workup on the powder charge.

Hodgdon lists a starting charge of 43gr for a 139gr bullet and my guess is with that powder you will see accuracy/consistency improving as the powder charge is increased.

And this is why we should always check alternative data sources.... I am such a goof and I now have a ready source of fouling rounds... on the bright side, it also shows why checking loads at longer distances is meaningful. I like to shoot at 200yrds but had I stopped at 100yrds I likely would not have seen this.....

Thank you...

As I look at your targets, the most obvious difference between your 100 and 200 yard targets is vertical stringing. Vertical stringing is usually caused by inconsistent rifle bedding and barrel heating, but you had no such problem at 100 yards, so I would tend to eliminate that as the primary factor. 2200 fps is fairly low velocity, so I would expect to see more significant lateral variation due to wind than I would with a higher velocity round. I don't know what the conditions were like when you were shooting, so I can't make a definite observation on that factor. Another common cause of large variation in groups between 100 and 200 yards is thick cross hairs which can lead to an inconsistent sight picture. Again, I don't know anything about your scope, so I can't comment. Finally, the large variation in the vertical stringing, once we eliminate barrel heating, really looks like an inconsistent sight picture / cheek weld or incorrect scope parallax. Since you've got a nice group at 100, I would tend to eliminate the cheek weld as a factor and focus on either an inconsistent sight picture or parallax.

I don't think the problem is the rifle or the load. You might try changing targets to achieve a better sight picture with your existing scope, changing scopes as a test, or adjusting the parallax on your scope to give yourself the very clearest sight picture rather than simply setting it to 200 yards.

Thank you for your points....

The scope is a Leupold VX-III 4.5-14X40mm with fine duplex. The objective is adjustable as well. I have noticed in this scope more than the others I have (which are duplex) that this one seems to be a bit finicky on the parallax - one of the reasons she was back on the bench. However, the site picture is very good. I can see the fine lines on the target at 200yrds so a 1 inch circle is no issue.

The wind was from my back to the target and although breezy - not your typical Texas wind - kinda mild. And I had the same thoughts about the bedding and barrel touching when heated. Checked at the range and it was fine. I did extensive work on the stock and feel comfortable with it.

I think that for now, I am going to restart my load testing at 43grs of H4350 and continue to see if I can work the parallax. It is annoying and slows me down a bit...

Old saying about grouping: Up and down increase the charge, Left and right reduce the charge.

It seems to me that you are describing, in a round about way, a load/bullet stability issue.

2200 fps is pretty slow for 7x57. You need to get that baby going faster. Heck, my load for my 8x57 is 2650 with a 200 grain projectile.

Agreed

Yup. Feed the need for speed.

Yep - I'm going to jump it up a bit.... won't be able to shoot this weekend but will post-up with the faster loads.. I am sure the results will be better... What is interesting is that I have the target from 50yrds sight-in and then 100yrds... but 200yrds tells a whole different story.

.

No, not at all. I'm talking about consistent ignition, powder burn, and velocity.

If it was a bullet stability issue there should be some evidence of that on the target. If it's there, I don't see it.

With out a chart handy guessing the Projectile is going subsonic and turbulence disrupts trajectory. An external ballistic chart could verify that.

2 things.

1- if you just pick a charge weight out of the blue and run it, how do you know if the rifle likes this load or not. A rifle will string shots before and/or after an accuracy node. It can easily be a load that is right before or after a node. Plus, I don't think I can seat a bullet to within .001", .002" and .003" in groups. What is one thousandths of an inch? That's not near enough variable to know what the difference in shooting each test load. Tune it with the powder charge first, then work the seating depth if you want. But the 139 SST is not a seating depth sensitive bullet, so playing with the seating depth is not going to noticeably help, IMO.

2- The 40 grains is a reduced load. Like stated, you need to bump up your powder charges to reasonable levels with this powder.

^^^ Not correct. Starting out at 2200 fps at the muzzle and going to 200 yards will not go subsonic. Plus, the 139 SST has 9.6 degree boat tail, and even if it was going subsonic, it would still remain on it's flight path. This boat tail angle would not have the disturbance like the 13 degree or more boat tails would.




^^^ And not correct. If you run the stability of this bullet in a 1:9" twist, it has a stability factor of 2.10. That's a very stable bullet.
http://www.bergerbullets.com/twist-rate-calculator/

Just a quick note, the starting load of 40gr of H4350 was not “randomly chosen” . The Hornady Handbook of Cartridge Reloading – 9th Edition indicates that a starting load of 39.8gr of H4350 is sufficient to effectively launch a 139gr SST. The Hodgdon site indicates that for a 7x75 using a 140gr bullet and H4350, 43gr is the starting point. Sierra indicates that for 140gr bullet, 40.7 grains of H4350 is sufficient. Either way the choice wasn’t a guess. However, I did fail to compare these data sources as I think this would have helped.

Lessons Learned:
1) Compare data sources and ask questions…..
2) As the targets indicate, checking accuracy further out (200yrds in this case) is a valuable exercise. I normally shoot at this distance anyway but I see many folks stop at 100yrds and wonder why they miss further out…
3) I am bumping the charge…..

With regard to bullet seating, using an RCBS Precision Mic, you can determine where the ogive is in relationship to the lands and either seat on the lands or back in measured intervals by adjusting the seating die accordingly. Looking at my post I have indicated “touching the lands” and then off the lands by 001, .002 and .003. That should read, “touching the lands” and then off the lands by .010, .020 and .030. My mistake….. thank you.

This is good to know ==> But the 139 SST is not a seating depth sensitive bullet, so playing with the seating depth is not going to noticeably help, IMO.