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rs50...175gn tmk update


exmarksman9870

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Hi troops..... A quick update with ref the tmk loads and findings so far with ref swapping optics ... on the .308 1/12 twist...

 

The first shot 4 shots was a cold barrel using a bushnel elite tactical.... the second group stated as warm was the pm2 the third group warm to hot barrel was also the pm2..all fired in quick succession im afraid as time was limited,,,,you can see the group started to open up when the barrel started to get hot... also between groups i worked the turrets and knocked the scope tube quite hard..trying to eliminate a faulty optic

 

I will now wait 24hrs and fire a 4 shot group with the pm2 with cold barrel then further 2 groups....

post-11466-0-12773300-1507046590_thumb.jpg

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Looks like a broadly similar pattern to before? Rising up and with the flier to the left.

 

At least you know it's not the scope. Cold barrel results best, so I'd probably look to make a little more time and allow the barrel to cool between shots for at least a minute with the bolt open as the rising dispersion to the left may be related to the barrel heating up. Seen it plenty of times with sporter profile barrels, not so much with heavier barrels. The 43gr load looks good and I wouldn't mind betting that if there was time left between shots, you may find you're shooting more of a ragged hole on that one. Speculation I know, but rushing through the shots may not help with anything conclusive if it is the barrel heating up and warping fractionally. Seems off that a fairly heavy barrel profile would do this after several shots though.

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yes i agree i should let it cool but i was in a hurry...hopefully will get back down to range tomo and see what results i get... it was very windy but no value as it was head on although the target may have had the odd wobble when shot was taken...

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Possibly better to wait for calmer weather and allow yourself plenty of time? Granny and eggs, I know but your groups could easily be halved with non-wobbly target! . It may also partly explain the vertical displacement of shots.

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Preferably it would be a x5 shot group....but seeing you're using 4 shots................

 

 

1. Determine your most accurate powder charge......(43g looks good...measure the powder accurately - 43.0g, no more, no less)

 

2. Shoot x4 round groups ....but allow one minute barrel cooling time between each of the four rounds you shoot in the group....(be disciplined about this)

 

3. Your barrel would have then warmed after your first x4 round group.....then leave it for five minutes (again be disciplined - have a cuppa).......and only then shoot your second x4 round group, this in exactly the same manner as you shot the first group.....by leaving it to cool for one minute between each shot, with bolt open to aid the cooling process and again the five minute interval(s) between each set of groups...and so on

 

Continue this method with all the bullets you have loaded...

 

 

P.S......A 'wobbly' target?...a faulty scope?...changing equipment???....Have you also attempted to drive a double-decker bus up to the top floor of a multi-story car park?

 

Please, do us all a favour?...make sure you use just the one, reliable and 'unfaulty' scope without bloody fiddling or 'knocking' it :)

 

ATB

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223 was a superb group :) .

 

Already mentioned that 43 gr looked the best group/node point and about leaving a minute between shots in the group, so agree with Snakeman on that. Swapping scopes, at least you can rule out the scope as the issue, so no harm done. I still think that bullet ought to be fine in your rifle. Discipline is the key, durng the reloading process and in the group testing ;). Perhaps parking the double decker bus so that it acts as a wind break would be a good idea :ph34r::D

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Right decision-there is no point in doing important testing in anything less than (very) good conditions.

Note that a head wind (or tail) will change bullet POI a little in the vertical plane,and that little will vary with the wind speed,just as does a variable horizontal wind vector.

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exmarksman

 

Why the rapid fire? - it's not a race and there's no prizes for the winner :unsure:

 

Clean your barrel and stop being concerned about 'variables' that do not exist - a clean barrel gives a clean shot ..(you're not shooting a rimfire here)

 

There's only one way now to be conclusive with your results - buy another box of he same bullet.. (this is the part I was referring to when I said it can become expensive)

 

The idea will be to repeat successively your right-hand group of x5 round....(discount the two flyers, if that's what they are?)

 

Shoot five groups, with each group being x5 rounds using the procedure described in post #7 ...for every round

.

Either that..or try the Berger you mentioned

 

ATB

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i know mate..i have a bit of pain in the prone position also now..back shoulder neck and sternum lol.. will be trying a few other bullets...just made some loads up for my .222 soon be out with the night vison so need that up an running again.... so next step i think is berger and 175smk...although i did read good reports in snipers hide of lapua scenar 155gn loads being a bit handy for a 1000y...

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If at first you dont succeed, pull your foreskin over your heed -

Infantry training staff Catterick Garrison

 

 

If at first you don't succeed, run around the drill square 20 times with your SLR held above your head -

 

Drill Sergeant - Le Marchant Barracks, Wiltshire!

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You could save a lot of time by getting a chronograph so you can find out where you are in terms of velocities and nodes.

 

That data from Swiss is fine and not far off what I've seen in Quickload using my own base data, but if you want these to work well out to 1000yds, you will want to be at the upper end of the scale i.e. around 2650fps which means high pressures, possibly compressed loads, sticky bolt lift and all the other things that go with pushing the boundaries.

 

Personally, I've found it much easier to develop loads by using the measured velocity and Quickload to get somewhere near the node and then fine tune from there with group testing. It means I can usually get within + or - 0.5 grain of the final powder charge by initially shooting no more than 20 or so rounds over the chrono and then moving to group testing at 1000yds preferably, where small load differences show up more and you can be sure the bullet is remaining stable.

 

The other thing I did which enabled me to get to 2644fps from my 700 with these bullets was to moly coat them so I could get to the MV I needed but keep the pressure in check when using the faster powders.

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Any reason for such a short COAL? SAAMI to mag length is 2.795 and the data above states a COAL of 2.767

 

The velocities look a little bit low to me. In a similar barrel length/tighter twist, I'm achieving around 50 fps more than those predictions for the Berger 175.

 

I agree with JSC. Buy, beg or borrow a chronograph. It's really an essential tool for LR load development.

 

I had no sticky bolt lift at the TMK 175gr 44.2gr load and that was measured at 2618 fps, more than enough for 1000 yds with it's BC. It may not be the same with the Berger though which may need more MV.

 

In fact, I loaded up to 2750 fps before pressure signs warned me to back off a little (15 thou off land though for that load).

 

One thing QL is good for is to predict barrel time. How accurate it is I don't know but when you eventually settle on a node and take the measured MV and loads used, it gives you some useful markers for barrel time which you can make a note of for your DOPE when looking to develop future loads

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One thing QL is good for is to predict barrel time. How accurate it is I don't know but when you eventually settle on a node and take the measured MV and loads used, it gives you some useful markers for barrel time which you can make a note of for your DOPE when looking to develop future loads

 

It can be very accurate, but you need to know which variables you need to tweak in order to make the predicted results get close to your real life results.

 

Once I got the hang of it I was able to tell a shooter buddy of mine what powder charge he was using to within 0.1 of a grain, by him telling me the MV, OAL and bullet/powder combination of the best load he'd worked up to after a lot of grouping tests on the range. That proved to me that QL and barrel timing theory works once you input correct data.

 

Once you've done it a few times it's really easy to get close to an ideal load for a different barrel and/or bullet just with a few test shots to tune the burn rate in QL and essentially calibrate the system.

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