Switch to RS Powder: QL V's Actual results for .308 & .223

[exmarksman9870]

will try some tac powder also ..

[VarmLR]

I know it's a new barrel, but if you get no luck with the groups using various powders and after several different bullets it may be worth getting the barrel bore-scoped to see if there's any concerns raised there? It's not unknown for the odd new barrel to throw up a manufacturing issue that may help explain maters, but it would be unusual.

[snakeman]

double post

[snakeman]

exmarksman

 

I'm of the school of thought that this could end up costing you quite a lot of cash if you persist testing this bullet in an attempt to achieve tight groups..... you have only marginal stability of that 175g TMK bullet in your 1/12 twist - it will not be consistently good enough. The minimum barrel twist recommended for the 175g TMK, is 1/11)

It is true however that when one bullet doesn't stabilise in one rife it will indeed stabilise in another rifle BUT, looking at your own results, and the image below, clearly shows marginal stability. I'd be switching to the standard 175g SMK due its shorter length (1.240in)... which will be far more suitable for your 1/12 twist

 

Below image: 175g bullet with the TMK bullet-length data (1.352in), ... Although this is quite shallow data, it is enough to demonstrate your 1/12 will struggle to stabilise the 175g TMK consistently.

 

 

[exmarksman9870]

thanks for that snakeman...i will be trying other bullets..thanks for all the help troops..

[VarmLR]

That is marginal. 175 SMKs may be ok but yes, looking at the length of the TMKs, it looks like more of a lottery. As previously mentioned, I have seen them work further out with other 1/12 twist rifles, ( a case of stability returning with a drop in velocity?)but tend to agree with Snakeman seeing the stability analysis. If you need to offload the TMKs, I'd be happy to buy them from you if it helps fund a different bullet for you.

[exmarksman9870]

i will test what i loaded last night if the rain stops today... if no luck i will sell the rest ..anyone tried berger 175gn otm tactical...

[VarmLR]

i will test what i loaded last night if the rain stops today... if no luck i will sell the rest ..anyone tried berger 175gn otm tactical...

 

you may be ok with 175 matchings as they're given worst case stability factor of 1.48 and are very jump tolerant. They won't have the BC of the TMK. Alternatively, you could try loading the 155gr TMKs as they have an impressive BC and give those a try. You may be able to push those to 1000 yds?

[JSC]

i will test what i loaded last night if the rain stops today... if no luck i will sell the rest ..anyone tried berger 175gn otm tactical...

 

Yes and it was the best performer out of my Rem 700.

 

The top group here is 3 rounds... and note these were shot at 200yds.

 

[snakeman]

Never used the OTM bullet but all the stats show it looks good and will be stable ....and looking at JSC results only confirms it.

 

It will be down to you to find the load it likes..

 

But remember, we don't expect anything less than just the one perfectly cylindrical hole with five shots, this especially from an exmaksman

[VarmLR]

Never used the OTM bullet but all the stats show it looks good and will be stable ....and looking at JSC results only confirms it.

 

It will be down to you to find the load it likes..

 

But remember, we don't expect anything less than just the one perfectly cylindrical hole with five shots, this especially from an exmaksman

 

 

 

Absolutely....even if it means getting the pencil out and punching the holes yourself!

[BlueBoy69]

exmarksman

 

I'm of the school of thought that this could end up costing you quite a lot of cash if you persist testing this bullet in an attempt to achieve tight groups..... you have only marginal stability of that 175g TMK bullet in your 1/12 twist - it will not be consistently good enough. The minimum barrel twist recommended for the 175g TMK, is 1/11)

It is true however that when one bullet doesn't stabilise in one rife it will indeed stabilise in another rifle BUT, looking at your own results, and the image below, clearly shows marginal stability. I'd be switching to the standard 175g SMK due its shorter length (1.240in)... which will be far more suitable for your 1/12 twist

 

Below image: 175g bullet with the TMK bullet-length data (1.352in), ... Although this is quite shallow data, it is enough to demonstrate your 1/12 will struggle to stabilise the 175g TMK consistently.

 

 

Berger.jpg

 

I don’t use Berger’s program for calculating the stability of plastic-tipped and other bullets. This is because Berger’s program generally underestimates the value. It is fine for standard open-tipped match OTM) boat-tailed (BT) bullets though, just not good with the aforementioned plastic tipped, OTM or tipped flat-based bullets (they state this on their calculator page and pass you on to another page), pistol and cast bullets.

 

For plastic-tipped BT bullets, I use the web-based JBM stability program, as its calculations seem to be far more accurate. Well, far better at predicting stability that type of bullet than others.

The program can be found at the link below.

 

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

 

Putting exmarksman9870’s details into the JBM program, so: 308” calibre; 175 grain weight; its overall length 1.384” (details from an JBM web databases and QuickLOAD); its plastic tip 0.200” (as per the bullet); 2,500 fps MV; 1:12” twist; 18° temperature; and 1013.25 millibars standard sea-level atmospheric pressure – gives a stability factor (S_g) of 1.624, so quite stable! Putting the figures into Berger’s program, plus a G1 ballistic coefficient of 0.535 , gives an S_g factor of 1.21, so only marginally stable. Quite a difference.

 

Who’s truly right, well unless we have access to proper decent Doppler radar with spin analysis (the Labradar is OK, but its software and tracking range are limited), we aren’t going to be able to calculate accurate figures.

 

For further reading on the stability of plastic, and other bullets ballistics, try the papers or books listed below:

 

A Stability Formula for Plastic-Tipped Bullets - Part 1 (2014);

A Stability Formula for Plastic-Tipped Bullets – Part 2 (2014);

Aerodynamic Drag and Gyroscopic Stability (2014);

Computational Ballistics III (2007);

Gyroscopic Stability of Open Tipped Match Style Rifle Bullets (2014); and

The Aerodynamic Characteristics of 7.62 Match Bullets (1988).

 

If you can’t find them on the web, I can upload them, and any others on ballistics that you might like to read, to a folder on my Google Drive.

 

BB69

[JSC]

I should add the 175 OTMs at 2600-2640fps were excellent out to 1000 from my standard 700. I was using H4895.

[exmarksman9870]

thanks troops i will keep you all updated....i will swap otics and test on a rifle and load that i know is a shooter and the barrel is getting bore scoped on sat also... the tmk are nkw for sale 53 +17 pulled bagged seprate with no damage...

[snakeman]

BlueBoy

 

For exactly the reasons you describe I no longer use JBM...I had a few inconsistencies with a .223 a few years back on JBM so I use it only infrequently these days. The rule of thumb I use, is to use all calculator programmes as a rough guide only; mainly to save the cost of buying something that will not obviously stabilise.

 

The evidence I saw was on paper 5 weeks and 3 weeks ago respectively, when an experienced shooting buddy bought a box of 175g TMK, loaded them and, printed pretty much each five shot comparable to exmarksman groups..(all during load development) ....... This was through a CZ 550 Tacticool 1/12...The groups were so inconsistent and variable most would not even recognise them as 'groups', such was the dispersion of spread. It was more than obvious the bullet wasn't stable in his 1/12 twist, irrespective of the make or charge of powder.

 

Following seeing exmarksmans and my buddies groups, only confirms to me that if I should ever be in possession of a 1/12 twist .308 not to take the chance wasting money on buying the 175g TMK.... Incidentally, I could end up being in possession of a 1/12 twist that will actually stabilise it but, I'd prefer to purchase a bullet that I know will 9/10 be stable, without having to wrack my brain looking for a solution to a problem with all the other variables, that doesn't exist.

 

Over the years I have found the excellent stevespages more reliable than any online calculations.

 

http://stevespages.com/page8e.htm

 

ATB

[VarmLR]

Bit of a major thread drift this one...perhaps best to continue on a separate thread so that others perhaps wishing to share their thoughts on RS 50 for the .308 or .223 might like to contribute? Glad that so many have made suggestions though to try and help out exmarksman9870 and hopefully a load can be found which suits the rifle. The RS50 ought in theory to be very well suited at any rate.

 

I'll post a few more thoughts once I've had a chance to do a little more work with it including some 600 yd work with the 308.

[snakeman]

Bit of a major thread drift this one...perhaps best to continue on a separate thread so that others perhaps wishing to share their thoughts on RS 50 for the .308 or .223 might like to contribute? Glad that so many have made suggestions though to try and help out exmarksman9870 and hopefully a load can be found which suits the rifle. The RS50 ought in theory to be very well suited at any rate.

 

I'll post a few more thoughts once I've had a chance to do a little more work with it including some 600 yd work with the 308.

 

 

+ 1.... excellent investigation & analysis by the way, to start the thread off - very well done and helpful

 

Cheers

[exmarksman9870]

yep thanks for all the help guys.....i will update in a new thread my findings...