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1/25/2018 7:38:29 AM
Posted: 2/10/2006 2:27:42 PM EST
Here are a couple pics of my "pre-owned" HK SR9TC. I installed a Tasco SS scope in 16x and took it to the range today. I shot 60 rounds of BH .308 BTHP and 40 rounds of Port 7.62x51 at 100 yards. I experienced good groups with both, but I found that the BH was keyholing 1-2 out 5 rounds and way off group. The Port didnt keyhole at all. The gun has an 18.5" polygonal bore barrel with a 1/14" twist rate. I cleaned and inspected the gun before shooting and found no wear in the barrel or the crown.

Here is the gun

Here is an example of my groups. This is 10 rounds of BH. See the key the 2 keyholed misses?

In all I had 9 keyholed missed rounds out of the 60 BH rounds. So far I really like this gun. Especially since it likes the cheaper surplus Port so much.

Link Posted: 2/10/2006 5:59:48 PM EST
[Last Edit: 2/10/2006 6:01:15 PM EST by advntrjnky]
1/14" is mighty slow to stabilize anything heavier than about 150 grain in .30 cal. what grain were the BH?

edit: most surplus .308 is in the 147-150gr weight.
Link Posted: 2/10/2006 6:21:57 PM EST
The BH is 168 grain. I estimated the twist rate by marking my cleaning rod and measuring how far it moved before the mark rotated once. So if I am correct on the twist rate, I should be shooting lighter weight rounds like the Port surplus?
Link Posted: 2/10/2006 9:22:30 PM EST
Link Posted: 2/11/2006 5:31:58 AM EST
generally the max gr for a 1/12" is in the 165-168 gr range, 1/10" is 173-175 for .308 bullets. there are a number of other factors involved also. the most important variable is bullet length. then probably bullet rpm out of the barrel. if you have longer barrel to get the bullet rpms up you can shoot a longer(ie...heavier) bullet in a slightly slower twist just fine. with your barrel only about 20" you don't get as much rpm from barrel length, so you have to match the bullet length/ weight more accurately. the "palma" bullet would be a good starting point, but IIRC they are fairly long for their grain weight (155 gr). try something with a lead core and/ or a flat base to get the bullet length shorter per grain weight. so, to finally answer your question the lighter weight bullets should give you better performance.
Link Posted: 2/11/2006 11:32:43 AM EST
I believe you're right about the twist rate being 1/11. I just rechecked it and I really screwed it up the first time. It came up 1/11 on the second check. Thanks for the help guys. BTW, I took off the handgaurd and checked the barrel. It is stamped "JA B8".
Link Posted: 2/11/2006 2:38:45 PM EST
i forgot to add that you have a very nice rifle!

not sure about the key holing. 1/11" should stabilize 168br BH HPBT just fine.
Link Posted: 2/11/2006 2:59:27 PM EST
1:11 should stabilize even 190's.

I suggest trying a box of Fed GM 175's, or some Georgia Arms 168gr match.

I've shot 175's in my 1:12 twist Springfield SAR3/8 with good results. Never saw a keyhole.

I shoot 175's in my Hart barreled Rem 700 and had no stability problems even at 1000 yards.

VERY nice rifle!

When I bought my SAR3, it was set up with the same goodies that come on the TC. I managed to sell the stock, grip, trigger pack and scope mount and only have $400 in the rifle.

I'd try some different ammo in it. Do you reload?
Link Posted: 2/11/2006 3:17:57 PM EST
Thanks for the advise and no I dont reload. I will try some different ammo next week. I figured it would like the BH cause my M1A loves it. But, what the hell, I have plenty of Port left for now. BTW, thank for the compliments. It sure got lots of attention at the range.
Link Posted: 2/11/2006 4:50:56 PM EST
Link Posted: 2/12/2006 11:05:07 AM EST
[Last Edit: 2/12/2006 11:19:12 AM EST by santino34]
Man, I hope no one would have cleaned this gun from the muzzle! It's way too easy to clean from the breach. Any way, I dont have access to the proper equipment to mic the bore at the muzzle, but to the naked eye it does not appear to have any wear. Also, it grips a round at the muzzle very tightly without coming near the casing.

I gave the bore a good cleaning and took the rifle to the range again today. I still havent bought anymore match ammo, but used some more Port surplus. Here is a pic of todays range session. This is 100 rounds of Port surplus at 100 yards. Not a single keyhole in the bunch!

I left the range with a smile on my face.
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