[GeeBee]

Is there a chart available that shows the ranges a locking piece is good for?
For example:
Stock 45 degree is good for bullet weight of xxx-xxx at velocities of xxxx-xxxx.
#17 36 degree is good for bullet weight of xxx-xxx at velocities of xxxx-xxxx.
How much of a difference does going from a twist of 1:12 to 1:10 make in back pressure when it comes to choosing? (assuming same round used)
Last question, while people claim that changing the angle of the locking piece changes felt recoil, does anyone have empirical evidence of that?

 

[AndrewJackson]

As far as charts go, there's this one:
Small Arms Review Guide to HK Locking Pieces

I know it's not exactly what you were looking for.

There's also some Physics behind it.

Angle of the locking piece, and size of the rollers can affect function. Maybe someone more knowledgeable can speak to the how & why.

Hope this helps.

 

[jdonovan]

Is there a chart available that shows the ranges a locking piece is good for?

I've got one that has all the data that I've been able to find. None of them have any references to bullet weight/velocity except for the 10mm/40S&W guns, and that is limited to higher/lower power rounds.

How much of a difference does going from a twist of 1:12 to 1:10 make in back pressure when it comes to choosing?

NONE

Last question, while people claim that changing the angle of the locking piece changes felt recoil, does anyone have empirical evidence of that?

People make all kinds of claims. I've never found a felt recoil change, unless I had a badly over functioning LP installed and the carrier was hitting the stock.

 

[columrick]

New rifle. 25 rounds of factory ammo was used to break it in following PTRs instructions. I did check the bolt to carrier gap, and it was right at .019 before I took it to the range (Yes, hammer was down before taking measurement).

Only mod to PTR91 GI has been an updated buffer and the snap on brass deflector.

Couple questions regarding the locking piece, the recoil spring, and deflector.

One, I found HKparts has a #9 LP in stock. The visual dimensions appear different than the unit in the rifle. Same with the #17. Do the 9 and 17 function properly in the PTR bolt and carrier?

IMHO, some of the perceived recoil may be reduced or better controlled with a higher rate recoil spring. Not a lot, something like, say 5%. The rifle cycled 150 factory well, but was noticeably snappier with 168 gr factory ammo. I don't see a manufacturer/distributor offering anything like that.

Third, the deflector may/may not be doing its job. The port already had a small flare at the back of the port, and I installed the snap on piece as close to the port as possible. The cases still ejected at 2 oclock, and had slight dents on them. The flutes left only light marks on the brass.

Thanks for the help.

The windage was spot on. Only shot at 25 yards, but groups were very good.

 

[AndrewJackson]

In terms of managing recoil, I love Bill Springfield's Enhanced Buffer

 

[columrick]

That's what I'm running. I'm also considering trying out the 21e butt pad. Recoil was more than manageable. I'm really asking about the locking pieces and if there's a higher rate recoil spring.