1/7 twist and 55 grain rounds

[chp5]

Is there any loss of accuracy if you shoot 55 grainers out of a 1/7 twist barrel?

[DRich]

I've never noticed a difference in group size when shooting M193 through a 1:7, 1:9, OR 1:12 barrels. However, none of these barrels would be considered match-grade...just plain-jane gov't profile units.

[C4IGrant]

Typically, 1/7 barrels shoot 55gr VERY well out to about 100-110yds. After that accuracy tends to degrade somewhat.



C4

[chp5]

I've never noticed a difference in group size when shooting M193 through a 1:7, 1:9, OR 1:12 barrels. However, none of these barrels would be considered match-grade...just plain-jane gov't profile units.

The most accuarate barrel I have with 55's is an old A1 pencial barrel - 1/12. Incredible accuracy with the right loads.

[USMC03]

Typically, 1/7 barrels shoot 55gr VERY well out to about 100-110yds. After that accuracy tends to degrade somewhat.



C4

Grant,


Can you define "somewhat" (ie. degrades by a couple inches, a couple feet, ???).

I shoot 1/7 barrels using 55gr ammo (XM193, Q3131A, Black Hills Blue Box, IMI, etc) on a very regular basis out to 425 yards shooting 12 - 24" steel gongs, steel poppers, LaRue's, etc. and have no problem hitting the target when I do my part.





Semper Fi,
Jeff

[gunny]

We shoot Federal TRU 55gr SP from our duty rifles & AE 55gr FMJBT for training. Twist rates vary from 1/9 on our issue entry guns & 1/12 on our issue patrol rifles. I use 1/7 CMMG medcon on my own entry/patrol rifle with no accuracy issues at 100yds. Beyond that I cannot advise since I've not yet shot that far with the CMMG using the TRU 55grs. All twists have shot very well using the 55grs. All bores & chambers mentioned are chrome lined. There are several individual officers that have a mixture of CL & non CL on their own rifles.

[C4IGrant]

Grant,


Can you define "somewhat" (ie. degrades by a couple inches, a couple feet, ???).

I shoot 1/7 barrels using 55gr ammo (XM193, Q3131A, Black Hills Blue Box, IMI, etc) on a very regular basis out to 425 yards shooting 12 - 24" steel gongs, steel poppers, LaRue's, etc. and have no problem hitting the target when I do my part.





Semper Fi,
Jeff

Typically if I am getting half inch groups at 100yds, I will see groups open up by about .25 around the 110-130yd mark.


C4

[royta]

Typically if I am getting half inch groups at 100yds, I will see groups open up by about .25 around the 110-130yd mark.


C4

That's a considerable jump in just 10 to 30 yards. Any measurements taken at the 300 yard mark?

[Yojimbo]

I have shot plenty of 55gr, XM-193 out of my 1-7 barrels and I have no problems getting COM hits on a IDPA target at 300 yards.

Average accuracy is about 1.5-2.5 MOA at 100 yards if you do your part. Since, XM-193 is not loaded to match ammo specs I'm very satified with those results.

[C4IGrant]

That's a considerable jump in just 10 to 30 yards. Any measurements taken at the 300 yard mark?

Yes. It looks somewhat like a pattern to me instead of a group. I have only run this test using one type of ammo (might have had a bad lot). Generally a 1/7 twist barrel will over stabilize a 55gr bullet.

I will try and shoot some other 55gr ammo at 100yds and 300yds to see how the groups open up.


C4